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EXAMINING SPATIAL CONCENTRATIONS OF
MARINE MICRO-PLASTICS ON SHORELINES
IN SOUTH PUGET SOUND, WASHINGTON
by
Nathaniel Ebi Gilman
A Thesis
Submitted in partial fulfillment
of the requirements for the degree
Master of Environmental Studies
The Evergreen State College
June 2013
©2013 by Nathaniel Ebi Gilman. All rights reserved.
This Thesis for the Master of Environmental Studies Degree
by
Nathaniel Ebi Gilman
has been approved for
The Evergreen State College
by
________________________
Erin Ellis
Member of the Faculty
________________________
Date
ABSTRACT
Examining spatial concentrations of marine micro-plastics
on shorelines in South Puget Sound, Washington
Nathaniel Ebi Gilman
The spatial distribution and density of marine micro-plastics (5.6 mm - 0.3 mm)
on 12 shorelines within three isolated finger inlets in South Puget Sound,
Washington were investigated during the winter of 2013. The mean density of
buried marine micro-plastics in Budd, Totten and Eld Inlets was 89, 2.1 and 2.3
items/ m2 respectively. Budd Inlet contained 45 fold more micro-plastics/ m2 than
Eld and Totten Inlets. Within each inlet an area was located where micro-plastic
concentration was significantly higher relative to other locations within the inlet.
Single locations in Budd, Eld and Totten comprised 98%, 68% and 59% of the
total micro-plastics collected within each respective inlet indicating that the
spatial distribution of micro-plastics is not even between inlets, or among inlets,
in South Puget Sound. The micro-plastics were divided into two size classes that
ranged from 5.6mm-1.0mm and 1.0mm-0.3mm. A strong positive correlation
between the two size classes was observed (R2 0.96, p=0.0001). A strong positive
correlation was also observed between the areas of high micro-plastic abundance
and the population density of the inlets (R2 0.74 p=0.0001). Study sites with a
south aspect in South Puget Sound accumulated more micro-plastics than study
sites that faced other directions, and this is believed to be driven by interaction
with the predominate Southwesterly wind. The findings of this study suggest that
spatial distribution between the inlets is driven by a combination of anthropogenic
factors, while the spatial variability within the inlets is driven by physical factors.
Table of Contents
LIST OF FIGURES .............................................................................................vi
LIST OF TABLES ...............................................................................................vii
LIST OF APPENDICES ......................................................................................ix
ACKNOWLEDGEMENTS .................................................................................x
INTRODUCTION ...............................................................................................1
LITERATURE REVIEW ....................................................................................4
Introduction ..............................................................................................4
Uses of Plastic ..........................................................................................5
Plastics in the Marine Environment .........................................................5
Micro-plastics ..........................................................................................7
Trends of micro-plastics in the marine environment ...............................7
Degradation of Plastics ............................................................................10
Marine Micro-plastics as a Vessel for Chemicals and Trace Metals .......13
Impacts of Marine Micro-plastics on Marine Wildlife and Ecosystems .15
Micro-plastic Sinks and Sampling Methods Development .....................19
Summary of Past Buried Marine Micro-plastic Shoreline Studies ..........20
Theories for Explaining Marine Micro-plastic Spatial Distribution ........22
Conclusion ...............................................................................................28
MATERIALS AND METHODS .........................................................................30
Overview of Puget Sound Circulation Patterns .......................................30
Description of study sites within South Puget Sound Basin ....................33
Factors affecting Circulation in South Puget Sound ................................35
Surface Circulation Patterns in South Puget Sound.................................37
Site Selection ...........................................................................................40
iv
Field Methods ..........................................................................................41
Laboratory Methods .................................................................................43
Data Analysis Methods ............................................................................47
ArcGIS Analysis Methods ...........................................................47
Statistical Methods .......................................................................47
RESULTS ............................................................................................................49
Overall......................................................................................................50
Variability of Micro-plastic Density (items/ m2) within Inlets ................52
Variability of Micro-plastic Density (items/ m2) within Sites .................53
Overall Distribution of types of Plastic Collected ...................................54
Overall Correlation between Size Classes ...............................................55
Correlation between Weight and Items....................................................57
Micro-plastic Accumulation Zones within Inlets ....................................57
Comparison of Accumulation Zones across the Inlets ............................58
Comparison of Non-Accumulation Zones across the Inlets ....................58
Watershed Demographics ........................................................................59
DISCUSSION ......................................................................................................60
Spatial Variability between the Inlets ......................................................61
Spatial variability within Inlets ................................................................65
Further Implications .................................................................................69
CONCLUSION ....................................................................................................72
FURTHER WORK RECOMMENDATIONS ....................................................72
INTERDISCIPLINARY STATEMENT .............................................................74
WORK CITED.....................................................................................................75
v
LIST OF FIGURES
Figure 1. Global Wind Driven Surface Currents ...............................................27
Figure 2. Map of Puget Sound, Washington State .............................................31
Figure 3. Map of South Puget Sound, Washington State ..................................32
Figure 4. Map of Budd, Eld and Totten Inlets ...................................................33
Figure 5. Map of Tidal current circulation patterns for
Budd, Eld and Totten Inlets ...............................................................36
Figure 6. Map of Drift Card Release Points in Budd Inlet ................................37
Figure 7. Map of Drift Card Pathways from Budd Inlet ....................................38
Figure 8. Map of Air Dropped Drift Card Release Points in
Budd, Eld and Totten Inlets ...............................................................39
Figure 9. Map of Accumulation Zones of Drift Cards Released in
Budd, Eld and Totten Inlets ...............................................................40
Figure 10. Map of Study Sites .............................................................................41
Figure 11. Sampling Transects ............................................................................43
Figure 12. Laboratory Methods ...........................................................................45
Figure 13. Micro-plastic categories .....................................................................46
Figure 14. Map of Spatial distribution of Micro-plastic Pieces/ m2....................49
Figure 15. Distribution of categories of micro-plastic .........................................55
Figure 16. Correlation of the two size classes of micro-plastics .........................56
Figure 17. Correlation of relationship between items of micro-plastics/ m2
and the weight of the micro-plastics in grams/ m2 ............................56
Figure 18. Map Micro-plastic Accumulation zones in each finger inlet .............58
Figure 19. Distribution of total micro-plastics Items/ m2 in each inlet ................62
Figure 20. Distribution of micro-plastics categories............................................64
vi
Figure 21. Wind direction in South Puget Sound, Washington State ..................66
vii
LIST OF TABLES
Table 1. Study Site Sample Date and High Tide .................................................42
Table 2. Density of micro-plastic by various size classes (items/ m2).................50
Table 3. Means of milligrams of micro-plastic/ m2 ............................................51
Table 4. Past studies examining micro-plastic density along shorelines .............70
viii
LIST OF APPENDICES
Appendix 1. Micro-plastic (number of items/ m2) collected from in
Budd Inlet......................................................................................... 85
Appendix 2. Micro-plastic (number of items/ m2) collected from in
Eld Inlet ............................................................................................ 86
Appendix 3. Micro-plastic (number of items/ m2) collected from in
Totten Inlet ....................................................................................... 87
Appendix 4. Variability of micro-plastic density (items/ m2) within Sites
in Budd, Eld and Totten Inlets ......................................................... 88
ix
Acknowledgements
I would like to thank everyone who has helped shape or contribute to this project
in any way. I would especially like to thank, Dr. Erin Ellis for her tireless help,
direction and inspiration on this project. Dr. Martha Henderson for always
believing that there was light at the end of the tunnel for me and Gail Wootan for
ensuring that I saw the light Martha was always seeing. Brittany Gallagher for
continuing to push me in the right direction, Dr. Skip Albertson for his guidance
about the physical oceanography of South Puget Sound as well as help creating
figures. I would also like to thank Julie Masura at the University of Washington
Tacoma for her guidance and work continuing to push the understanding of
marine micro-plastics both locally and globally. Lastly I would like to thank my
family for putting up with my new grey hairs created by this project as well as my
friends for keeping me motivated and on track, even when I wanted to pull out
that grey hair.
x
INTRODUCTION
The annual global production of plastics has increased from ~1.7 million tons in
1950 to ~280 million tons in 2011, at a rate of approximately 9% growth per year
(Plastics Europe 2012). While the benefits of plastics have helped to transform society,
plastic is also contaminating many parts of our environment. Discarded plastics are found
all over the marine world; from heavily populated areas to the most remote beaches in
Antarctica (Eriksson et al. 2013).
Micro-plastics which range from 5 mm to 0.3 mm, are either manufactured as
small pieces of plastic (primary) or they are created when larger pieces of plastic degrade
into smaller pieces (secondary) once disposed of in the landfill or in the natural
environment (Betts 2008). Eliminating marine micro-plastics pollution is one piece of
creating a healthy marine eco-system as the potential for negative environmental impacts
from micro-plastics has been established in the literature. The small size of micro-plastics
is believed to create a hazard to organisms through ingestion (Baird and Hooker 2000;
Boerger et al. 2010; Davison and Asch 2011; Derraik 2002; Fossi et al. 2012; Graham
and Thompson 2009; Kociubuk in press; Laist 1997; Murray and Cowie 2011).
The quantity, rate and locations that plastic is accumulating in different
environments, such as the ocean, is not understood, thus limiting clean-up efforts. Microplastics were initially recognized in the marine environment in 1972 (Carpenter and
Smith 1972). Since that time, with the rise in global plastic production, the quantity of
plastics found in the marine environment is believed to be increasing as well (Plastics
Europe 2012; Thompson et al. 2004).
1
Puget Sound is the second largest estuary in the United States and is located in
Washington State (Gaydos 2008). Research on marine micro-plastics in Puget Sound is
not existent in the published literature. This is the first study to examine marine microplastics in South Puget Sound. South Puget Sound is the furthest point away from the
entrance of Puget Sound. This location was selected because South Puget Sound’s
isolated location, similar wind and current patterns in combination with differences in
population between the smaller finger inlets located in the most southerly section of
South Puget Sound, create conditions in the field that are very close to a controlled
experiment and allow exploration of the drivers of spatial distribution of marine microplastics and establish baseline data to track if micro-plastics are increasing over time
locally. Thus, it advances the scholarly literature by creating a baseline from South Puget
Sound and identifies the primary physical and anthropogenic drivers of marine microplastics spatial distribution.
Aside from eliminating the source of micro-plastics, the best way to reduce
marine micro-plastic pollution and their subsequent impacts to wildlife is to remove the
plastic from the marine environment and dispose the plastic pollution properly. Once
micro-plastics have entered the marine ecosystem, there are four locations that they are
believed to be accumulating in. The sea surface, open ocean floor, near coastal sediment
and shorelines (Ryan et al. 2009a). Thus the easiest location to collect and remove plastic
pollution is from shorelines. Understanding the spatial distribution of marine microplastics along shorelines can facilitate focused clean-up efforts to increase cleanup
efficiency. Identifying the physical factors that are driving the spatial distribution in a
specific area creates the potential for isolating the source locations of micro-plastics.
2
Understanding how population and physical factors drive the spatial distribution
of marine micro-plastics is the key to facilitating both effective education programs to the
public about reducing inputs as well as coordinating efficient shoreline cleanup efforts. In
the marine environment, the small pieces of degraded plastic are thought to be
accumulating in the same areas, primarily the sea surface and shorelines that marine
organisms inhabit, thus creating the potential to negatively impact the health of the entire
marine ecosystem. Plastics have been demonstrated to accumulate persistent organic
pollutants and trace metals (Ogata et al. 2009; Teuten et al. 2009; Teuten et al. 2007).
Emerging work has demonstrated that Polybrominated diphenyl ethers (PBDEs) were
transferred into the tissues of Short tailed Shearwaters from pieces of micro-plastic that
they ingested (Tanaka et al. 2013)
3
LITERATURE REVIEW
Introduction
Plastic is one of the most prevalent materials in the world. Annual global
production of plastics has increased from ~1.7 million tons in 1950 to ~280 million tons
in 2011, at a rate of approximately 9% growth per year (Plastics Europe 2012). While the
benefits of plastics have helped to create the current world we live in, discarded plastic is
also contaminating many parts of our environment. The quantity and rate at which plastic
is accumulating in different environments, such as the ocean, is not understood.
Plastics begin to degrade into smaller pieces once disposed of in the landfill or in
the natural environment. In the marine environment small pieces of degraded plastic are
thought to be accumulating in the same areas that marine organisms inhabit, thus creating
the potential to negatively impact the health of the entire marine ecosystem (Ryan et al.
2009a). The degradation of plastic into smaller pieces creates a hazard to organisms
through ingestion. Furthermore, persistent organic pollutants and trace metals have been
demonstrated to accumulate in plastics. Marine organisms such as lobsters, oysters and
blue mussels have been observed with marine micro-plastics in their gut contents, in the
field as well as in laboratory experiments (Kociubuk in press; Murray and Cowie 2011;
von Moos et al. 2012).
This literature review addresses what is currently known about the broad topic of
marine micro-plastic pollution. Micro-plastics which range from 5 mm to 0.3 mm, are
either manufactured as small pieces of plastic (primary) or they are created when larger
pieces of plastic degrade into smaller pieces (secondary) once disposed of in the landfill
or in the natural environment (Betts 2008). Initially the uses of plastics, the creation of
4
micro-plastics and how long those micro-plastics are believed to remain in the marine
environment is discussed. Next the sorption of toxic chemicals and trace metals as well as
the negative impacts that micro-plastics have on wildlife is examined. The current
sampling methodology along shorelines is examined to demonstrate that the methods
employed in this thesis are consistent with that which is established in the literature. The
results from past shoreline micro-plastic studies that have used this common
methodology and exploration of the theories that drive the spatial distribution of these
results is the final topic that is examined.
Uses of Plastic
The term plastic applies to many different materials that are derived from
petrochemicals produced from oil or gas (Thompson et al. 2009). Based on volume,
plastics are one of the most used materials in the United States both industrially and
commercially (Society of Plastics Industry 2012). 50% of annual plastic production is
used in single-use disposable applications, such as packaging, agricultural coverings and
disposable consumer items. Thus the majority of plastic products has very short useable
lifespans and is designed to be thrown away. In the United States, 31 million tons of
plastic waste was generated in 2010, which is approximately 12.4% of the total municipal
solid waste for the nation (Environmental Protection Agency 2012).
Plastics in the Marine Environment
Micro-plastics were initially recognized in the marine environment during
oceanographic research cruises in 1972 (Carpenter and Smith 1972). Since that time,
5
global plastic production has increased by approximately 9 percent per year and the
quantity of plastics found in the marine environment is believed to be increasing as well
(Plastics Europe 2012; Thompson et al. 2004). Multiple research studies have found
varying densities of marine micro-plastics around the globe. Marine micro-plastic
pollution has been found in every ocean and on isolated shorelines, such as Antarctica,
midway atoll in the middle of the Pacific Ocean and on the Fernando de Noronha
Archipelago in the middle of the South Atlantic Ocean, making marine micro-plastic
pollution a global issue (Barnes 2002; Cooper and Corcoran 2010; Costa et al. 2010; Ivar
do Sul et al. 2009; McDermid and McMullen 2004; Moore et al. 2002).
Pathways for plastics to enter the marine environment
Plastic enters the ocean through a variety of sources. Plastics can be delivered into
the marine environment through disposal of ship waste, spills of feedstock pellets into
water bodies and rivers, delivered through sewer systems and waste water treatment
plants’ outfall pipes, washed into the ocean by storm water drains and runoff, blown into
the ocean from land or simply left on the shoreline by beach goers (Ryan et al. 2009a).
An addition input of plastics are microscopic scrubbers which have replaced natural
exfoliating materials used in many household cleaners, body washes and facial scrubs
(Fendall and Sewell 2009; Gregory 1996). Once these microscopic scrubbers are used,
they are washed down the drain where they pass through waste water treatment plants
and are discharged into waterways.
In 2007, it was estimated that two-thirds of the Earth’s population lived within
100 miles of a coastline and this number is expected to increase (Coastal Hazards 2007).
6
With the large amount of disposable products being produced globally and the large
number of people living close to the coasts the potential for plastic waste to enter into the
marine system from land is high. Andrady (2011) estimated that 80% of the plastic that
enters the marine environment comes from land based sources. However, the quantity of
plastics that enter into the marine environment has not been reliably estimated (Andrady
2011).
Micro-plastics
Much of the research examining the distribution of plastics in the ocean has
focused on micro-plastics because of suspected increases in abundance and microplastic’s similar size to food sources of many marine fauna. Micro-plastics have been
recently defined as plastic that ranges from between 5 mm and 0.3 mm (Betts 2008), but
historically definitions have ranged between less than 20mm and .001 mm (Hidalgo-Ruz
et al. 2012). For the purpose of this literature review, the former definition will be used.
Micro-plastics can be manufactured as small pieces of plastic, such as plastic
production pellets, plastic beads for bead blasting, or micro scrubbers for facial washes
and dish soap (Fendall and Sewell 2009; Gregory 1996). Micro-plastics can also be
created by the degradation of larger pieces of plastic discarded in the marine
environment.
Trends of micro-plastics in the marine environment
The direction of long-term trends of micro-plastics accumulating in the marine
environment are unclear. Different studies have found that plastics are accumulating,
7
staying steady or not accumulating (Goldstein et al. 2012; Gregory 2009; Law et al. 2010;
Thompson et al. 2004). The changes in these trends could be influenced by changes in the
way people are disposing plastics globally.
Thompson et al. (2004) re-examined zooplankton samples from neuston trawls
that dated back to the 1960’s from the North Sea for micro-plastics. Examination of those
samples allowed the authors to see an increase in micro-plastic abundance over the last
50 years which was in concert with the increases in plastic production worldwide
(Thompson et al. 2004). Similarly, in the North Pacific micro-plastics are believed to
have increased by 2 orders of magnitude from 1972 to 2010 (Goldstein et al. 2012). The
authors note that although they believe micro-plastic abundance is increasing, they note
that sampling was not conducted from 1987 to 1999 allowing the potential that the
temporal pattern found could have more variation due to shifting wind and current
conditions during the study years.
In contrast, one of the longest running continuous studies (1986- 2008) on marine
micro-plastics, Law et al. (2010) found micro-plastics in 68% of the 6136 tows, but found
no spatial or temporal trends in the abundance of micro-plastics in the western Atlantic
and Sargasso Sea, with the density of micro-plastics observed in each neuston tow
remaining the same (Law et al. 2010). Finally, a study conducted over a similar period
examining pre-production plastic pellets (nurdles) on shorelines in Bermuda, eastern
Canada and New Zealand from the 1970’s to the mid 2000’s found a slight decline in the
abundance of nurdles on the shorelines sampled (Gregory 2009).
These differences in trends of micro-plastics, demonstrate the variability of not
only the marine system that is being studied, but also reflect the varying methodologies
8
being used between studies. For example, Gregory (2009) was only looking for preproduction plastic pellets (nurdles). During the time frame of his study, reduction of spills
was a major priority of manufactures and this reduction could be what is reflected in his
data. More benefit would have come from Gregory (2009) if all the plastic litter on
shorelines was examined. Thus, the decline observed by Gregory (2009) could be simply
due to the fact that he looked at nurdles, whereas the other studies examined other types
of plastic. The author notes that the decrease in abundance of nurdles could be due to
changes in the handling and transport. Examining all micro-plastic debris on the
shorelines would have allowed the author to see if their observations were in line with
increases in production of plastic products.
Another example as to how potential discrepancies in study design could affect
temporal trends is Thompson et al. (2004). They reanalyzed zoo-plankton samples that
were collected over 50 years, but little is known about the collection methods and if the
people who initially analyzed the zooplankton samples ever discarded micro-plastics
when identifying the zoo-plankton.
Aside from the potential discrepancies in methodology, the differences in these
trends could be attributed to different anthropogenic influences. Just as the reduction of
nurdle spills from industrial applications was seen as a reduction in marine micro-plastics
by Gregory (2009) the lack of trend in the density of plastics in the North Atlantic over
22 years by Law et al. (2010) could be attributed to increased recycling and
improvements in waste disposal that may cancel out the increase in the global production
of plastics.
9
Goldstein et al. (2012) and Thompson et al. (2004) both demonstrate opposite
trends from Gregory (2009) and Law et al. (2010). Both Goldstein et al. (2012) and
Thompson et al. (2004) observed increases in the abundance of micro-plastics in the
North Pacific and the North Atlantic respectively which they believe indicates that the
global increase of plastics is creating more plastic pollution in the oceans. Thus, although
a review of the academic literature suggests that there does not appear to be consistent
temporal trend in micro-plastic abundance, the presence of marine micro-plastics in the
water and the potential threat these small pieces pose to wildlife.
Whether the abundance of micro-plastic is constant or increasing, the processes
that create micro-plastics are becoming more understood by academia. The sorption of
toxic chemicals and the impacts to wildlife has been demonstrated but to be able to fully
understand the temporal and spatial variability, the factors that produce micro-plastic
need to be understood.
Degradation of Plastics
The processes creating micro-plastics from larger pieces of plastic are believed to
be a combination of physical degradation from wave action and chemical weathering
from the sun. Plastics are believed to be initially susceptible to photodegradation and
physical processes (Andrady 2005; Cooper and Corcoran 2010; Webb et al. 2012). The
process of photodegradation is the deconstruction by UV based processes, breaking down
molecules into lower molecular weight fragments (International Union of Pure and
Applied Chemistry 1996). Photodegradation causes the plastics to become brittle, then
10
physical processes such as wave action, cause the plastics to break into smaller pieces in
the marine environment (Webb et al. 2012).
On land the complete mineralization of polymers has been observed. After break
down from photodegradation, thermo-oxidative degradation is the next step that occurs
quickly, when heat and oxygen accelerate the breaking of the polymer chains that created
the plastic. Once photodegradation and thermo-oxidation have occurred, bacteria
degradation can consume the remaining polymer chains (Shah et al. 2008; Zheng et al.
2005). However, this process has not been observed in the marine environment largely
due to the long time scales it takes to breakdown plastics in the marine environment.
Current estimates for mineralization, the complete reduction of a polymer to inorganic
components, of plastics in the marine environment range from hundreds to thousands of
years (Andrady 2005; Barnes et al. 2009). Once plastics have entered the marine
environment they are believed to be a long lived hazard. However, there is debate on the
time frame for full mineralization of the polymer chains back into water and carbon
dioxide.
The time frame for full mineralization is hard to generalize as each additive to a
plastic product changes the durability of the product. It has also been found that identical
products will break into smaller pieces at many different speeds depending on the
environment they are left in (A.C. Albertsson, Personal Communication, January 25th,
2013). Cooper and Corcoran (2010) believe that the degradation of plastics to microplastics and eventually to unseen particles via mechanical and chemical weathering will
create microscopic plastic particles that will remain in Earth’s marine environment
indefinitely.
11
The time frame that plastics are re-mineralized is believed to be slower in the
marine environment than on land. The cold temperatures of the oceans and the lower
oxygen concentration in the deep oceans are believed to slow the degradation rates of
plastics (Andrady 2011). The growth of marine organisms on plastic is called fouling.
Fouling is also believed to slow the degradation rate by blocking the UV light and thus
slowing photodegradation and the process of re-mineralization even further.
A 2008 study examined the degradation rates of polyethylene bags. The study
found that after 40 weeks in the water less than two percent of the surface area of the
polyethylene bags was lost. All samples had been fouled by organisms and the presence
of these organisms is believed to slow their degradation times by blocking sunlight
(O’Brine and Thompson 2010).
O’Brine and Thompson examined the breakdown of the plastic bags in sea water
to micro-plastics, but they did not examine the mineralization of the materials. Roy et al.
(2011) examined the complete degradability of polyethylene sheets and the recent
development of biodegradable polyethylene. Polyethylene is the most common plastic in
use today and the primary component in packaging and common plastic bags. They found
that polyethylene bags disintegrate into pieces invisible to the naked eye, but still harmful
to marine organisms. The bags did not completely remineralize over a time frame, though
that time frame was not stated, that would avoid negative impacts to the marine
environment (Roy et al. 2011).
Cooper and Corcoran (2010) found that polyethylene appears to be more
conducive to degrading from a combination of chemical and physical processes while
12
polypropylene appears to degrade from physical processes first (Cooper and Corcoran
2010).
Because mass production of plastics began within the last 60 years, no long-term
studies in terrestrial or marine environments have been conducted to estimate the actual
time frame for which plastics will be remineralized and incorporated into biomolecules
(Andrady 2011; Roy et al. 2011; Webb et al. 2012).
Dr. Ann-Christine Albertsson, a leader in plastic degradation studies and the head
of the Polymer Technology Department at KTH in Stockholm, Sweden explains that
there are thousands of materials with very different chemistry that can be called plastic.
There are many types of plastic and each type contains different additives. These various
plastics are being used and discarded in different surroundings, making their interaction
with the environment very complex. For example, very simple plastics may stay for
thousands of years in a landfill but disappear quickly in the next surrounding (A.C.
Albertsson, Personal Communication, January 25th, 2013).
Marine Micro-plastics as a Vessel for Chemicals and Trace Metals
Common micro-plastics are less dense than water allowing them to float near the
surface of the water. This characteristic of plastic is believed to be the reason that microplastics are initially found on the surface of the sea. Persistent Organic Pollutants,
hydrophobic compounds and trace metals, have also been found accumulating in the seasurface micro layer as well. Concentrations of toxic chemicals and trace metals have been
found up to 500 times greater in the sea-surface micro-layer, than concentrations in the
water underneath (Ogata et al. 2009; Teuten et al. 2009; Teuten et al. 2007). As such,
13
micro-plastics and Persistent Organic Pollutants are present in the same micro layer, thus
causing micro-plastics to be vectors for organic pollutants, as will be discussed below.
It has been found through various studies that Persistent Organic Pollutants are
attaching to plastics through sorption. Bisphenol A (BPA), chlordanes,
dichlorodiphenyltrichloroethane (DDT’s), dischloroethene (DDE’s),
hexachlorocyclohexane (HCH), nonylphenol, polychlorinated biphenyls (PCBs),
Polycyclic aromatic hydrocarbons (PAHs), and Polybrominated diphenyl ethers (PBDEs)
have all been found to achieve sorption into plastics in the marine environment (Bakir et
al. 2012; Endo et al. 2005; Hirai et al. 2011; Ogata et al. 2009; Teuten et al. 2009; Teuten
et al. 2007; Van et al. 2012). When micro-plastics were analyzed for trace metals they
were found to contain Aluminum, Copper, Chromium, Cobalt, Cadmium, Iron,
Manganese, Nickle, Lead and Zinc (Ashton et al. 2010; Holmes et al. 2012). These initial
studies demonstrate the potential for metals as well as POP’s to be transported into the
food chain through the consumption by marine organisms where they would not have
originally appeared.
Plastics are initially produced to be biochemically inert materials that do not
affect the endocrine system because of their large molecular size which does not allow
them to penetrate through cell membranes. Additives within plastic products are believed
to be disruptive and create the potential for new plastic products to carry chemicals that
can disrupt the endocrine system (Teuten et al. 2009). As plastic products degrade in the
marine environment, their molecular weight decreases (Andrady 2011). Plastics with
lower molecular weight have higher rates of sorption of chemicals than plastics with
larger molecular weights (Teuten et al. 2009).
14
The potential for chemicals and trace metals to sorb into wildlife has been
demonstrated in the laboratory. Tanaka et al. (2013) is the first study to find that
chemicals from marine micro-plastics are accumulating in marine wildlife. All the Short
tailed Shearwaters studied contained from 0.04 g-0.59g of micro-plastics in their
stomachs. The Shearwaters tissue was examined for the chemical compounds found on
the micro-plastics from their stomachs. Polybrominated diphenyl ethers (PBDEs) was
found in all the Shearwaters tissues (Tanaka et al. 2013).
Although the potential for micro-plastics to be a vector for the sorption of toxic
chemicals and trace metals in marine organisms is beginning to be understood, further
work is needed to understand the full scope of the issue and what the biological
implications are for the sorption of chemicals from micro-plastics. Micro-plastics threat
to certain species through ingestion has already been well documented.
Impacts of Marine Micro-plastics on Marine Wildlife and Ecosystems
The potential for plastics to harm ecosystems is high and potential mechanisms by
which they could do so are through the transport of invasive species and toxic chemicals,
and being ingested by wildlife and entangled in marine debris (Baird and Hooker 2000;
Bakir et al. 2012; Barnes 2002; Boerger et al. 2010; Davison and Asch 2011; Derraik
2002; Endo et al. 2005; Fossi et al. 2012; Graham and Thompson 2009; Gregory 2009;
Laist 1997; Murray and Cowie 2011; Ogata et al. 2009; Teuten et al. 2009; Teuten et al.
2007; Williams et al. 2011). However, actual documentation of harm to marine species
has only been demonstrated for ocean going seabirds (Colabuono et al. 2009).
15
Direct Impacts (Primary consumers in the food chain)
Marine organisms have the potential to consume micro-plastics. Laist (1997) was
the first study to compile a list of species that interact with marine debris. Laist found
over 100 animals that either ingested or were entangled in marine debris (Laist 1997).
Papers have emerged since the original 1997 census taken by Laist (Baird and
Hooker 2000; Boerger et al. 2010; Davison and Asch 2011; Derraik 2002; Fossi et al.
2012; Graham and Thompson 2009; Kociubuk in press; Laist 1997; Murray and Cowie
2011; Williams et al. 2011). It has now been shown that most marine organisms are
indiscriminant eaters and will consume anything that passes by that resembles a food
source including micro-plastic. Large mammals such as Baleen whales down to Oysters
all have the potential to ingest marine micro-plastics.
Williams et al. (2011) conducted a study off of the north end of Vancouver Island
in the Eastern Pacific looking at the relationship between marine mammals and plastic
marine debris. Marine mammals were present in the same areas that accumulations of
plastic marine debris were found. Williams et al. (2011) found that micro-plastic
abundance off the North End of Vancouver Island was similar to those found in more
urban areas suggesting that the potential for ingestion by marine mammals was present
even in isolated areas (Williams et al. 2011).
Many of the studies that examine consumption of micro-plastics are based on
theoretical models and laboratory experiments. However, a few studies examining
myctophids and lobsters used direct methods from samples collected at sea. They found
micro-plastics were ingested by both species (Boerger et al. 2010; Lusher et al. 2013;
Murray and Cowie 2011). The potential for micro-plastics to disrupt food webs has been
16
exhaustively explored but the work done in the field to truly measure in just beginning to
emerge. Seabirds are the most studied consumer of marine micro-plastics.
Procellariiformes (albatross, shearwaters and petrels) are commonly found
deceased with micro-plastic pieces in their stomachs. It is believed that procellariiformes
are the most affected bird from marine micro-plastic pollution. This is thought to be a
result of the combination of feeding habits, collecting zoo-plankton from the ocean’s
surface, and regurgitating the food for chicks on land. Marine micro-plastics have been
observed filling the stomachs of various procellariiformes species as well as getting
lodged in the ventriculus making ingestion of other food difficult (Colabuono et al. 2009)
Procellariiformes are not the only birds affected by marine micro-plastics. The
most common sea bird in Puget Sound, Glaucous-winged Gulls, were examined for
consumption of marine micro-plastics by a team from the Port Townsend Marine Science
Center. 12% of the boluses examined contained plastics. The most common type of
plastic found within the Gulls bolus was films, which were similar to disposable plastic
bags and wrappers (Lindborg et al. 2012).
With many species on the lower levels of the food chain thought to be consuming
plastics, the ingestions of those organisms by predators further up the food chain can be a
mechanism by which higher trophic level species ingest plastics. Many micro-plastic
studies hint to the idea of micro-plastics making their way up trophic levels, but do not
collect samples to support their hypothesis.
Eriksson and Burton (2003) is the main study that found micro-plastic has the
potential to move up trophic levels through ingestion. Scat samples from the carnivorous
fur seals on Macquarie Island were collected from 1991 and 1997. In the laboratory they
17
found that 4% of the scat samples collected contained pieces of micro-plastic. Fur seals
eat a variety of fish including the most abundant species of fish, myctophids. Eriksson
and Burton believe that the plastic particles were consumed by the myctophid species E.
subaspera which in turn was eaten by the fur seals (Eriksson and Burton 2003).
Indirect Impacts (Changes to the Marine Ecosystems)
The most commonly used and produced plastics have densities that are lighter
than sea water (Morét-Ferguson et al. 2010) and have the potential to float in the ocean
over long distances. This allows locations that have had no inputs of marine plastics to be
invaded by foreign marine debris and the associated organisms that have attached
themselves along the way. Both macro-plastics and micro-plastics have been implicated
in changing the marine environment.
Pieces of plastic regardless of size are commonly colonized by many different
species of barnacles, tubeworms, foraminifera, coralline algae, hydroids and bivalve
mollusks. Large pieces of floating plastic such as polypropylene rope can provide cover
for planktonic organisms similar to Sargassum (Gregory 2009).
Pieces of plastic have been found all over the world from remote parts of
Antarctica to isolated islands in the south Pacific. Barnes (2002) explores the transport of
invasive species to some of the last pristine places on Earth. Barnes found that plastic
marine debris was washing up in many places but the biotic communities on the foreign
marine debris were still limited by environmental conditions such as temperature in the
Artic (Barnes 2002). He concluded that with changes in climate patterns these barriers
18
could be weakened and invasions of biota could occur on plastic debris to some of the
last pristine places on Earth in the near future.
Changes in abundance of floating substrate available in the oceans due to
increased micro-plastic abundance has also allowed marine organisms that depend on
substrate for breeding, to increase in population. Goldstein et al. (2012) found that the
Halobates population in the North Pacific is increasing and they attribute that rise to the
increased in marine micro-plastic (Goldstein et al. 2012). Whether micro-plastic is
ingested by zooplankton, a seabird or a marine mammal it has the potential to impact the
lifecycle of that organism and thus, the entire marine ecosystem. The introduction of
foreign species by micro-plastics has the potential to be devastating to ecological
communities. Micro-plastics are another anthropogenic threat to the marine ecosystem.
Micro-plastic Sinks and Sampling Methods Development
The main findings from the 2008 International Research Workshop on the
Occurrence, Effects, and Fate of Microplastic Marine Debris were that, “Data that
conclusively demonstrate negative impacts of micro-plastics on the marine environment
are not available. This is probably the largest and most critical gap to fill. Research into
collection methods, species impacts, and removal methods should focus on potential
micro-plastics hotspots” (Arthur et al. 2009). Thus, interest is high in assessing where
micro-plastics are accumulating, with an emphasis on shoreline locations.
There are four locations that micro-plastics are believed to be accumulating. The
sea surface, open ocean floor, near coastal sediment and beaches (Ryan et al. 2009a).
Because shorelines are the most accessible sink locations, beach surveys have been
19
conducted more often than the other locations (Browne et al. 2010; Browne et al. 2011;
Claessens et al. 2011; Cooper and Corcoran 2010; Corcoran et al. 2009; Costa et al. 2010;
Eriksson et al. 2013; Frias et al. 2010; Ismail et al. 2009; Ivar do Sul et al. 2009; Kusui
and Noda 2003; Martins and Sobral 2011; McDermid and McMullen 2004; Rees and
Pond 1995; Rosevelt 2011; Ryan et al. 2009b; Van et al. 2012; Velander and Mocogni
1999; Zurcher 2009).
The majority of shoreline sampling for micro-plastics has occurred along sandy
shorelines. The highest tide line of a beach is the most common place for sampling to
occur because the debris deposited is likely from the most recent tide (Martins and Sobral
2011; Velander and Mocogni 1999).
Summary of Past Buried Marine Micro-plastic Shoreline Studies
A protocol has been adopted by a few studies examining buried marine microplastics. One m2 quadrats are placed along the highest tide line, sediment samples are
taken from the top 2 cm of the beach. These samples are processed using saltwater to
float out the micro-plastics which have low specific densities. The micro-plastics are
identified visually or with the aid of a dissecting microscope. The use of this similar
protocol has allowed comparisons of micro-plastic density along shorelines across the
world (Claessens et al. 2011; Costa et al., 2010; Ivar do Sul et al. 2009; Kingfisher, 2011;
Kusui & Noda, 2003).
20
Density and distribution in previous shoreline studies
Results from these previous studies demonstrate great spatial variability. The
densities range from 2610 pieces of micro-plastic per m2 along Japan’s coast to 9 pieces
micro-plastic per m2 along the shorelines of the island Fernando de Noronha in the
Equatorial Western Atlantic (Ivar do Sul et al. 2009; Kusui & Noda, 2003). These studies
further illustrate that marine micro-plastic pollution placed in one location has the
potential to be not only a local problem but a global on as well.
The spatial variability in types of plastics is different across the global locations
that have been surveyed using the similar protocol as well. This indicates that people are
using and discarding plastics in different ways in different parts of the world. The
samples from north Puget Sound and Japan have higher abundance of foamed plastics.
This could suggest that an activity associated with foamed plastics is performed more
often near shorelines than along the central California Coast where an even split of
polystyrene and other plastic pieces is found (Kingfisher 2011; Kusui and Noda 2003;
Rosevelt 2011).
The most common micro-plastic found in the Puget Sound is polystyrene
followed by a much lower concentration of plastic fragments and very few virgin pellets
(Kingfisher 2011). On Russian and Japanese shorelines 87.1% of the plastic found was
polystyrene followed by 10.6% plastic fragments and 1.8% plastic pellets (Kusui and
Noda 2003).
In Belgium and Fernando de Noronha, very low numbers of polystyrene were
found but high numbers of plastic fragments and pellets were observed (Claessens et al.
2011; Ivar do Sul et al. 2009). This suggests that people may be discarding larger pieces
21
of plastic into the marine environment, an alternative hypothesis is that both locations
perform as sinks for micro-plastics coming from the Atlantic Gyres.
The factors that drive that spatial variability are a combination of physical and
anthropogenic drivers working in concert to create the spatial variability across locations
as well as the variability in the types of plastics that are collected.
Theories for Explaining Marine Micro-plastic Spatial Distribution
Spatial variability is a common theme in published micro-plastic studies, both
documenting variability between the studies and variability within the studies themselves.
Physical and anthropogenic factors are attributed as explanations for locations having
different densities of micro-plastics. Physical factors used to explain the variability
include the effect of wind, global currents, local currents and tidal currents.
Anthropogenic factors used to explain the variability include population density around
the study area and proximity to recreational use. The presence of industrial areas is
described in studies but no quantification is conducted to measure the effect on microplastic density. No studies have examined the affect that impervious surfaces have on
micro-plastic density.
Population density
People are responsible for the inputs of marine micro-plastics. Examining the
relationship between population density and micro-plastic density can provide evidence
to guide clean-up efforts. Population density as an indicator of micro-plastics present was
used by Browne et al. (2011). In the 18 locations sampled worldwide, a positive
22
correlation was found between population density around the sample location and the
quantity of micro-plastics that were discovered (Browne et al. 2011). The study only
examined one sample from each location and did not look at any local variability. The
initial findings display that population density could be an explanatory variable in the
spatial distribution of micro-plastics but local spatial variability was not taken into
account.
Population density was also used as a possible explanatory variable for the spatial
distribution of micro-plastics found at different shoreline locations along the Japanese
and Russian coast. Kusui & Noda (2003) found that micro-plastic density was higher
along the Japanese coast where the population was much higher. They found that foamed
polystyrene was much higher along Japanese shorelines and was responsible for the
majority of the differences in micro-plastic density between the two coasts.
In north Puget Sound, there was a very weak negative correlation between the
number of plastic items collected and the distance from a population center (Kingfisher
2011). The weak correlation could be because other factors were not eliminated first
when selecting site locations such as isolation and circulation. Surface water in the North
Puget Sound has a very short residence time, 20 days or less, suggesting that locations
where micro-plastic inputs occurred were different from where accumulation zones were
located due to wind and tidal currents dispersing the micro-plastics.
Proximity to Recreational Use
Claessens et al. (2011) found that shoreline study locations within an enclosed
inner harbor where 2000 moorings were located had the highest density of micro-plastics
23
within their study area as compared to shoreline study locations located along the open
ocean. The geographic characteristics of the inner harbor being confined was also thought
to be a cause of the higher density found in the inner harbor (Claessens et al. 2011).
Ismail et al. (2009) also found that the quantity of plastic pellets along the shorelines in
Malaysia were higher in areas that were used for recreation (Ismail et al. 2009). The
increase was very slight, no statistical tests were performed and the sample size was
small, but the pattern was visible.
Rosevelt et al. (2013) found that no relationship between accessibility and the
density of plastic debris that was found on beaches in Monterey Bay California. The
authors believe that other factors such as currents and wind could be driving the density
along beaches in Monterey Bay (Rosevelt et al. 2013). In the tidal estuary Firth of Forth
located in Scotland, the density of plastic debris was also not dependent on the
accessibility of the beach itself (Storrier et al. 2007). Storrier et al. (2007) believe that
storm conditions combined with tidal current patterns are the most likely explanation for
areas of increased density on shorelines in the estuary.
Only at locations where physical geography creates a way to keep micro-plastics
near their area of input can the influences of anthropogenic uses be seen. Because
anthropogenic influences are responsible for the inputs of marine micro-plastics to the
marine environment the simple process of tracking them becomes much harder. Once
micro-plastics have entered the marine environment wind and currents disperse them
creating the spatial variability that is seen worldwide.
24
Wind Driven
Browne et al. (2010) found that the location of the site in relationship to the
prevailing wind had an effect on the quantity of micro-plastics. Locations that were
downwind had higher levels of micro-plastics than locations that were up wind. Dense
micro-plastic was found at higher quantities than less dense and expanded polystyrene
foam at the downwind locations. The study was conducted along the Tamar Estuary in
the United Kingdom, where the combination of strong winds and flat shorelines are
believed to be one explanatory variable for the low abundance of foamed polystyrene
which is less dense. It is believed that the wind blows the foam polystyrene out of the
water, up the shorelines and off the beaches into the near shore environment. The near
shore environment was not sampled, so this remains a theory to explain the low numbers
of foamed polystyrene at this time.
In the Artic and the middle of the Equatorial Atlantic a beaches aspect in relation
to the prevailing wind has been demonstrated as an explanatory variable of the spatial
distribution found within local study locations. On the Fernando de Noronha
Archipelago, in the western side of the South Atlantic, beaches on the eastern side of the
islands had significantly higher densities of micro-plastics (Ivar do Sul et al. 2009). The
prevailing winds around the Fernando de Noronha Archipelago, blow from east to west.
Eriksson et al. (2013) conducted daily surveys of two islands in the Antarctic. Marine
debris accumulation was greater on the western side of the islands which both intercept
the Antarctic circumpolar current (Eriksson et al. 2013).
Ivar do Sul et al. (2009) hypothesize that the higher density of micro-plastics on
the eastern beaches could be explained by the beaches interception of the prevailing
25
wind. Ivar do Sul et al. (2009) also believe that the location of the Fernando de Noronha
Archipelago in the path of the South Atlantic Ocean anticlockwise gyre could be an
alternative cause of the higher micro-plastic concentrations on the eastern side of the
archipelago (Ivar do Sul et al. 2009). The location of a shoreline in relation to the
established currents has also been demonstrated as a driver for spatial variability of
marine micro-plastics on shorelines worldwide.
Surface Current Based Studies
Surface currents carry large amounts of water around the world. The global
surface current pattern is clockwise in the northern hemisphere and counter-clockwise in
the southern hemisphere (Figure 1). These surface currents carry any floating debris
placed in the water. For example, a piece of plastic washed into the ocean from an
individual in San Diego can be carried by the California Current south and eventually by
the North Equatorial Current to be washed on the eastern shoreline of Kauai.
Heavier accumulations of micro-plastics were found on the eastern side of Kauai
Island in Hawaii that were influenced by the current from the North Pacific sub-tropical
Gyre and currents traveling around the island (Cooper and Corcoran 2010; Corcoran et al.
2009).
Martins & Sobral (2011) found the location and the orientation of the beaches
sampled in Portugal to be the cause of the extremely high density of micro-plastics. The
north orientation of beaches places them in the path of the North Atlantic Gyre, which is
known for high densities of micro-plastics and the authors believe promote higher rates
of accumulation (Martins and Sobral 2011).
26
Figure 1. Global wind driven surface currents taken from NASA’s Ocean Motion and surface currents
(American Meteorological Society 2005).
These studies demonstrate the importance of understanding the physical factors
that drive the surface movement of the water, be that by the wind or currents. Locations
that intercept the prevailing wind or currents coming from areas with high anthropogenic
influence will likely have higher densities of micro-plastics on their shorelines.
Previous Studies Examining Marine Micro-plastic Spatial Distribution Summary
Examination of the previous results indicates that more than one factor is driving
the variability found within each study. Utilizing a combination of factors including
wind, currents, proximity to areas of high population and recreational use is believed to
be the best explanation of the spatial variability in micro-plastic density within studies.
Understanding the physical geography of the study location, the prevailing wind and the
currents within the study area is key to understanding the local spatial variability. Once
27
these factors have been understood the larger issues of anthropogenic influences can be
examined and sources of micro-plastics be traced back to their sources via the physical
factors.
Thus, South Puget Sound is an excellent location to study the combination of
anthropogenic and physical factors driving the spatial distribution of marine microplastics. South Puget Sound is the furthest point away from the entrance of Puget Sound.
South Puget Sound’s isolated location, similar wind and current patterns in combination
with differences in population between the smaller finger inlets located in the most
southerly section of South Puget Sound, create conditions in the field that are very close
to a controlled experiment and allow exploration of the drivers of spatial distribution of
marine micro-plastics and establish baseline data to track if micro-plastics are increasing
over time locally. Thus, it advances the scholarly literature by creating a baseline from
South Puget Sound and identifies the primary physical and anthropogenic drivers of
marine micro-plastics spatial distribution.
Conclusion
Plastic production is believed to continue to increase (Plastics Europe 2012). The
persistence of micro-plastics in the marine environment is not yet understood, but the
estimates are in the range of tens to hundreds of years (Andrady 2005; Barnes et al.
2009). Once these plastics enter the marine environment they begin to slowly break down
into smaller pieces. These small pieces pose a threat to marine organisms from ingestion,
transport of toxic chemicals and the transport of invasive species.
28
Micro-plastics are believed to be accumulating in three locations, the open ocean
floor, near coastal sediment and shorelines (Ryan et al. 2009b). The most accessible
locations that micro-plastics are believed to be accumulating are shorelines. Thus
shoreline surveys have been a popular way to establish baseline data for micro-plastic
densities. Local and global spatial variability along shorelines has been documented.
The localized spatial variability is believed to be driven by prevailing winds and
currents, while global trends in spatial variability are attributed to anthropogenic
influences such as population density or levels of recreational use in a region.
Understanding the local spatial variability allows a clearer picture to be drawn when
establishing baseline data for marine micro-plastic densities. Obtaining clear baseline
data allows the exploration of these areas again as the growth of plastic manufacturing
and consumption of plastic products continues to grow globally.
29
METHODS
This study used an established protocol for sampling marine micro-plastics in
sediment along shorelines, to investigate the spatial distribution of marine micro-plastics
in South Puget Sound, Washington USA. This protocol has been implemented locally in
North Puget Sound (Kingfisher, 2011) as well as internationally (Costa et al., 2010; Ivar
do Sul et al., 2009; Kusui & Noda, 2003; Martins & Sobral, 2011), hence this protocol
was selected for purposes of cross comparison.
This is the first study to examine marine micro-plastics in South Puget Sound.
South Puget Sound is the furthest point away from the entrance of Puget Sound. This
location was selected because South Puget Sound’s isolated location, similar wind and
current patterns in combination with differences in population between the smaller finger
inlets located in the most southerly section of South Puget Sound, create conditions in the
field that are very close to a controlled experiment and allow exploration of the drivers of
spatial distribution of marine micro-plastics and establish baseline data to track if microplastics are increasing over time locally.
Overview of Puget Sound Circulation Patterns
Puget Sound is the second largest estuary in the United States with approximately
2,500 miles of shoreline. The net flow within the Puget Sound is towards the entrance at
the Strait of Juan de Fuca, with this flow being driven by surface freshwater inputs from
rivers, creeks and groundwater runoff pushing the surface water toward the entrance. Sea
water, which is denser, enters the system at depth running in the opposite direction and
draws its source from the Pacific Ocean. The flow is further influenced by wind strength
30
and direction (Gaydos 2008). Driven by these variables, the residence time of water in the
entire Puget Sound Basin is approximately 90 days, but it ranges from 20 to 120 days in
the different Puget Sound basins.
This circulation pattern is further modified by three underwater sills, left by
glaciers during the last ice-age. The sills are located at the head of Admiralty Inlet to the
North, the mouth of Hood Canal to the west and the Tacoma narrows to the south
(Gaydos 2008).
Four distinct water bodies are created by the sills in Puget Sound: Hood Canal,
North Puget Sound, the Main Basin and South Puget Sound (Figure 2).
Figure 2. Four main water bodies created by underwater sills in Puget Sound, Washington State USA. A.
North Puget Sound is the water to the north of the sill at Admiralty Inlet; B. The Main Basin is the largest
water body in Puget Sound; C. Hood Canal is the water to the southwest of the sill at the mouth of Hood
Canal; D. and South Puget Sound is the water body south of the Tacoma Narrows. Dotted lines indicate
underwater sills.
North Puget Sound is the water body north of the sill at Admiralty Inlet, North
Puget Sound is closest to the ocean and contains a mix of high and low population
31
density. Central Puget Sound also referred to as the Main Basin is the water body south
of Admiralty Inlet and north of the sill at the Tacoma Narrows. The Main Basin of Puget
Sound has the highest population density and two major cities are located on its east
shorelines, Seattle and Tacoma. The population density for the east side of the Main
Basin is 2,924 people/ km2 (United States Census Bureau 2013).
Figure 3. South Puget Sound, Washington State USA.
Finally, South Puget Sound, which is the basin examined in this study, is the
water body south of the Tacoma Narrows. This basin is a complex and interconnected
system of straits and fjord-like bays (Albertson et al. 2007) (Figure 3). South Puget
Sound’s location as the furthest basin from the ocean creates the greatest tidal range, 14.4
feet on average, in the Puget Sound (Ebbesmeyer et al. 1998). South Puget Sound is less
densely populated than the Main Basin, with 1,056 people/ km2 residing in the most
populated area at the south end of Budd Inlet (Thurston Regional Planning Council 2012;
United States Census Bureau 2013).
32
Description of study sites within South Puget Sound Basin
Within South Puget Sound the three most southerly inlets, Budd, Eld and Totten,
were selected as study locations (Figure 4). These three inlets were selected as study
locations because of their similar geographic locations, differences in population, and
differences in land use. They are the furthest points from the Pacific Ocean in Puget
Sound allowing the exploration of the influence that localized wind and current patterns
have on the spatial distribution of micro-plastics. The differences in population density
and differences in land use between the inlets allow the exploration of the influence that
population density and impervious surfaces have on the spatial distribution of microplastics as well.
Figure 4. Budd, Eld and Totten Inlets located in South Puget Sound, Washington State USA.
Budd Inlet is the most populated watershed in South Puget Sound. As of 2010, the
population density within the Budd Inlet watershed is approximately 1186 people/ km2
33
(U.S. Department of Commerce 2010). The land within the Budd Inlet watershed had an
estimated 8% of impervious surfaces as of 2005 (Thurston County Regional Planning
Council 2006). The residence time of water in South Puget Sound Basin is approximately
8-12 days (LOTT 2000). Budd Inlet has been the most studied inlet of the three finger
inlets due to the metropolitan center of Olympia, being located at the south end of the
inlet. The surface circulation and currents were studied as part of the recertification
project for the Lacey, Olympia, Tumwater and Thurston County sewage treatment plant
during 1996-1997 (Aura Nova Consultants et al. 1998) (see below).
The greatest percentage of population and impervious surfaces are located at the
south end of Budd Inlet. The rest of the inlet is lightly populated and with much less
impervious surfaces (Thurston Regional Planning Council 2012). All of the inlets are
similar in their distribution of slightly denser populations along the shorelines that in the
interior of the watersheds.
The Eld Inlet watershed has less people than the Budd Inlet watershed, with 267
people/ kilometer2 and an estimated 4% of the land is covered with impervious surfaces
(Thurston County Regional Planning Council 2006; U.S. Department of Commerce
2010). The residence time of water in Eld Inlet is not known.
The Totten Inlet watershed is the least populated and has the least amount of
impervious surfaces. The Totten Inlet watershed has a population density of
approximately 84 people/ kilometer2 and an estimated 2% of the land is covered with
impervious surfaces (Thurston County Regional Planning Council 2006; U.S.
Department of Commerce 2010) The residence time of water in Totten Inlet is not
known.
34
Factors affecting Circulation in South Puget Sound
The water that enters South Puget Sound, and consequently Budd, Eld and Totten
inlets, comes from two sources. Dense salt water enters at depth through the Tacoma
narrows at the northern tip of South Puget Sound. Annually the approximate rain fall is
50 inches in the South Puget Sound region (United States Naval Research Laboratory
2008). This less dense freshwater enters the South Puget Sound from two freshwater
rivers fed by the Cascade Mountains, the Nisqually and Deschutes. Precipitation falls an
average of 185 days a year, allowing freshwater to enter South Puget Sound directly, and
as storm water runoff.
Though freshwater inputs contribute freshwater into the system, the circulation in
Puget Sound, and consequently South Puget Sound is driven by tidal pumping. Tidal
pumping is the movement of water created when the tide moves over and through
changes in bathometry (Gaydos 2008). The complex and interconnected system of straits
and fjord-like bays in combination with the single entrance and exit at the the Tacoma
Narrows makes the residence time of water in South Puget Sound Basin the longest in
Puget Sound at approximately 120 days (LOTT 2000).
The prevailing wind in South Puget Sound is from the southwest but wind
patterns are affected locally by the interactions with the main flow and local topography
(United States Naval Research Laboratory 2008). This southwest wind is a product of the
wind flowing around the southern end of the Olympic Mountains and up through the
Chehalis River Valley (United States Naval Research Laboratory 2008).
All inlets share the same input of salt water coming from Central Puget Sound
through the Tacoma Narrows. The tidal flow of salt water enters Budd Inlet on the west
35
side and proceeds to the south. The central gyre in the inlet rotates counter-clockwise and
the water exits along the eastern side of the inlet (LOTT 2000; McGardy and Lincoln
1977) (Figure 5).
Figure 5. Tidal current circulation patterns for Budd, Eld and Totten Inlets located in South Puget Sound,
Washington State USA. Budd Inlet circulation based on (LOTT 2000), Eld and Totten Inlet circulation
based on (McGardy and Lincoln 1977).
The tidal currents in Eld and Totten Inlets have only been briefly studied. The
main study of tidal currents in South Puget Sound was conducted using the University of
Washington’s Puget Sound model, using pieces of Styrofoam and a film camera
(McGardy and Lincoln 1977). The general circulation patterns were identified but the
detail that is available in Budd Inlet is not available for Eld or Totten Inlet.
Surface Circulation Patterns in South Puget Sound
36
The previous section described tidal circulation patterns at depth. However,
surface circulation may differ substantially from patterns observed at depth. Much of
what is known about circulation patterns in the South Puget Sound is from work
conducted by Aura Nova Consultants to evaluate the effects of increasing the capacity of
the sewage treatment plant located at the south end of Budd Inlet.
Figure 6. A. The fifteen drop locations drift cards were released in Budd inlet from October 1996 to
September 1997 taken from (Ebbesmeyer et al. 1998). B. Figure of a drift card used by the Aura Nova
Consultants in South Puget Sound taken from (Albertson et al. 2007)
Briefly, a drift card study was used to understand the surface circulation patterns
in South Puget Sound. From October 1996 to September 1997, 8,950 drift cards were
deployed by dropping them in 15 locations within Budd Inlet (Figure 6). These drift cards
are wooden, measure approximately 3" x 5", and were coated with orange, non-toxic
paint to render them readily visible to beachcombers. Each card carried a serial number
preceded by 'L' for LOTT, an address, and a 1-800 telephone number enabling
37
beachcombers to report recoveries. The recovery reports were tabulated within 1-mi
shoreline segments because most of the cards were found along short stretches of beach.
Fifty one percent of the drift cards were recovered, some were found as far as
Alaska (LOTT 2000). Of the recovered cards 31% were found within Budd Inlet
suggesting that not everything placed into the inlet will be washed out of the inlet
(Albertson et al. 2007). Less than 2% of the drift cards released in Budd Inlet were
recovered from the closest adjacent inlets, Eld and Totten (Figure 7).
Figure 7. Drift card pathways from Budd Inlet. Dotted lines represent divisions between water bodies in
South Puget Sound. Arrows represent drift card pathways and direction. Percentages shown are based on
the total number of cards recovered within each water body from those released within Budd Inlet from
October 1996 to September 1997. Data taken from (Ebbesmeyer et al. 1998).
38
Aura Nova Consultants conducted a secondary drift card study to ensure that
circulation patterns were responsible for the low recovery rates of drift cards from Eld
and Totten Inlets. In January, 1997 drift cards were released in Eld and Totten Inlets as
well as Budd Inlet by small plane (Figure 8). Similar detection rates (51.5%) were found
for the entire study area providing evidence that recovery rates were driven by the tidal
currents. This also demonstrated that the net direction of floating debris deposited within
the finger inlets is towards the ocean.
Figure 8. Drift card air drop drift card release sites. Twelve locations where drift cards were released from
a small airplane on January 22, 1997: site I-L in Totten Inlet; sites M-P in Eld Inlet: and sites Q-T in Budd
Inlet. Figure taken from (Ebbesmeyer et al. 1998).
Further examination of the drift card data suggests that drift cards accumulate in
certain regions of each inlet. Accumulation zones were identified as regions within each
inlet where a high quantity of drift cards were recovered. Non- accumulation zones,
locations where little to no drift cards were recovered, were identified from the drift card
data as well (Figure 9).
39
Figure 9. Accumulation and non-accumulation zones identified from the examining data collected for the
recertification of Lacey, Olympia, Tumwater and Thurston County Clean Waster Alliance’s waste water
treatment plant, conducted by Aura Nova Consultants. Percentages represent the quantity of drift cards
released in each inlet that were recovered at each location. Bold locations are accumulation zones. Data
collected from (Aura Nova Consultants et al. 1998)
The lower percentages in Budd Inlet are due to the higher number (1,429) of drift
cards recovered and released (8,950) over the period of one year (Ebbesmeyer et al.
1998). This created a more dispersed distribution of detection in relation to Eld and
Totten Inlets where 200 drift cards were released once, hence a smaller proportion of drift
cards (55 and 51 respectively) were collected to create higher relative percentages. Had
the drift card study been conducted for a longer time period with more drift cards the
results are believed by the author to more closely resemble Budd Inlet.
Site Selection
Twelve study sites were selected in the study area. Initial selection of two sites in
each inlet was based on the identification of accumulation zones from the Aura Nova
40
Consultants data. Two more sites in each were selected on the opposite side of the inlet
from the accumulation zones. The location of these sites was the same approximate
distance from the mouth of the inlet. These locations are referred to as non-accumulation
zones based on low detection rates of drift cards at these sites (Figure 10).
Figure 10. Twelve site locations in South Puget Sound. Bold locations are accumulation zones.
Field Methods
This study used an established protocol for sampling marine micro-plastics in
sediment along shorelines, to investigate the spatial distribution of marine micro-plastics
in South Puget Sound, Washington USA. This protocol has been implemented locally in
North Puget Sound (Kingfisher 2011) as well as internationally (Costa et al. 2010; Ivar
do Sul et al. 2009; Kusui and Noda 2003; Martins and Sobral 2011), hence it was selected
for purposes of cross comparison.
41
The field survey was conducted from January 16th, 2013 to February 6th, 2013
(Table 1). Sampling along the highest, high tide line took place during the day after the
most recent high tide had begun to recede. The survey purposely took place immediately
following the highest high tide of the year, 16.9 feet which occurred on January 14th
(Ecology 2013). The intention of this sampling design was to collect floating debris
deposited at the same time, by the same high tide across all sites.
Table 1. Study site locations and Sampling Dates. Tide data from (NOAA Tides and Currents 2013).
Inlet Sample Location
Sample Date
High Tide
(Feet)
Budd NE
January 16, 2013
16.51
Budd NW
January 22, 2013
13.21
Budd SE
January 16, 2013
16.51
Budd SW
January 29, 2013
15.8
Eld NE
January 23, 2013
13.18
Eld NW
January 22, 2013
13.21
Eld SE
January 23, 2013
13.18
Eld SW
January 29, 2013
15.8
Totten NE
February 1, 2013
15.94
Totten NW
February 6, 2013
14.43
Totten SE
February 6, 2013
14.43
Totten SW
February 1, 2013
15.94
42
At each site, ten quadrats were sampled along a one hundred meter transect
parallel to the water’s edge (Figure 11) and spaced 10 m apart from each other. Transects
were placed along the highest high tide mark, the highest line of floating deposited
material up the shoreline, as plastic is believed to accumulate in this zone (Martins and
Sobral 2011).
Figure 11. Transects were located along the highest high tide mark (upper wrack line) and were 100 meters
in length. Each 0.5-m2 quadrat was placed every 10 meters along the upper wrack line.
Within each 0.5-m2 quadrat, all large rocks and woody debris were removed.
Sediment was then removed to a depth of 2cm, which was subsequently placed into a 3.8
liter bag to be processed in the laboratory.
Laboratory Methods
Micro-plastics have been recently defined as plastic that ranges from between 5
mm and 0.3 mm in diameter (Betts 2008), but historically definitions have ranged
43
between less than 20mm and .001 mm (Hidalgo-Ruz et al. 2012). For the purpose of this
study, objects between 5.6 mm and 0.3 mm in diameter are considered micro-plastics.
The 5.6mm sieve was selected due to limitations of available equipment at the time of
sampling.
To isolate the micro-plastics from the sediment the beach samples were oven
dried at 75°C for 24 hours and weighed using a balance to the nearest gram. The sample
was then sieved, using a 5.6-mm sieve, and the portion of the sediment sample larger than
5.6-mm was discarded.
The remaining dry sediment was weighed using an analytical balance to the
nearest gram. The sample was subjected to density separation using 500-750ml of 5 M of
NaCl aqueous solution in a 1000ml beaker following the protocol of several previous
studies including Claessens et al. (2011), Costa et al. (2010), Ivar do Sul et al. (2010),
Kusui & Noda (2003) and Martins & Sobral (2011). The aqueous solution was vigorously
mixed by hand using a metal spatula to float out any portion of the sample that had a low
specific density.
44
Figure 12. A. The dry sample was sieved using a 5.6mm sieve. B. The remaining sample was vigorously
mixed in a 5M NaCl solution by hand using a metal spatula to separate floatable material C. The sample
was decanted into stacked 1.0mm and 0.3mm sieves. D. The sample was dried at room temperature for 24
hours then identified by category using a dissecting micro-scope.
The sample was then decanted for floatable material and passed through stacked
1-mm and 0.3-mm sieves. These sieve size classes were selected to allow comparisons to
be drawn with other Puget Sound studies (Baker et al. 2011). This process was repeated
until no floatable material was visible at the surface, generally 3 to 4 times (Figure 12).
The floatable material collected on the 1-mm and 0.3-mm sieves was air dried for 24
hours at room temperature. The floatable material collected on the sieves was visually
inspected using a microscope under 40x magnification to identify the different types of
the micro-plastic collected. The micro-plastic was collected using forceps and placed into
a pre-weighed 4ml vial. The collected micro-plastics were weighed using an analytical
balance to the nearest 0.001 mg.
45
For this thesis micro-plastics are identified as an object between 5.6 mm and 0.3
mm in diameter where no cellular or organic structures are visible. Types of microplastics were identified as follows: if fibrous the fibers should be equally thick
throughout their entire length. Fibers, foamed particles and fragments are a single and
homogeneous color (Hidalgo-Ruz et al. 2012). Recent studies have used five microplastic categories for identification which allow differences in anthropogenic uses of
plastics to be compared around the globe. The five categories are; plastic fragments,
foamed plastics, filaments (which are referred to as line balls in this study), films and preproduction pellets (also referred to as nurdles) (Figure 13). The first four categories of
micro-plastics are created by the degradation of larger plastic items while the
preproduction pellets are manufactured as micro-plastics.
Figure 13. Micro-plastic categories. All pictures taken on quarter to give scale A. Five Foamed Plastics
A1. Blue Foamed Plastic A2. White foamed plastics B1. Three Plastics Films C. Four Plastic Fragments
C1. Fibrous plastic Fragment C2. Blue Plastic Fragment C3. Light Green Plastic Fragment C4. Green
Plastic Fragment with little degradation present D. Four Pre-production plastic pellets (nurdles) D1. One
Large Nurdle D2. Three small nurdles E. Line Balls (not pictured)
46
Data Analysis Methods
This study used GIS to determine the watershed boundaries of the three finger
inlets and to determine the population density of Budd, Eld and Totten Inlets. ERSI
ArcMap 10 and Microsoft Excel 2010 were used for the GIS analysis.
GIS Analysis
Watershed
Using National Watershed Boundary (WB) vector shape file data set for
Washington State from the National Resource Conservation Service the watersheds of
Budd, Eld and Totten Inlets were identified. The smaller watershed units within each
inlet were merged to create a new ArcGIS layer for each inlet.
Population Density
2010 census block TIGER vector shape files were used for analysis, which were
provided by the Washington State Office of Financial Management. The Tiger data was
queried using select by location. Total population in watershed was calculated using the
ArcGIS summary statistics tool. Total square kilometers of each inlet watershed was
calculated using the measure tool. Population density was calculated using Microsoft
Excel 2010, total population within the watershed was divided by the total square
kilometers of the watershed.
Statistical Methods
Statistical analysis of the samples was conducted to establish if there was a
difference in micro-plastics density between the three finger inlets. JMP Pro 10.0.2
statistical package was used. Summary statistics for micro-plastic density for the total
47
micro-plastics collected, large micro-plastics (5.6mm-1.0mm) and small micro-plastics
(1.0mm-0.3mm) were conducted for each study site, each finger inlet and total study
area. Data is presented in items/ m2 and grams/ m2 ± the standard error of the mean.
Correlation between the large and small size classes were conducted to determine if the
density of items (i.e., items or grams/ m2) was correlated between the size classes.
Correlation was also performed on the relationship between population density of an inlet
and the total micro-plastics items/ m2 collected with the inlet.
The data was checked for normality using Shapiro-Wilk W test, for goodness of
fit to the normal distribution. The data was not found to be normally distributed, so nonparametric analyses were conducted. Using the Wilcoxon test of rank sums the total
density of total micro-plastics/ m2 collected within the three finger inlets, the total density
of micro-plastics/ m2 for the suggested accumulation zone locations across the three
finger inlets and the total density of micro-plastics/ m2 from suggested non-accumulation
zone locations in the three finger inlets were tested for statistical significance. These
Wilcoxon tests of rank sums were conducted to determine if a statistical difference was
present either between the inlets, between the accumulation zones or between the nonaccumulation zones.
48
RESULTS
1,872 pieces of marine micro-plastic were collected over the 60 m2 that was
surveyed. The composite weighed 1.9 grams and was collected in 189,747 grams of
sediment. There was great spatial variation in the density of items collected and the
weight of the items collect across the study area. One location, Budd NE, contained the
majority of the micro-plastic collected in the study area (Figure 14).
Figure 14. Map of spatial distribution of micro-plastic items/ m2 collected from January 16th, 2013 to
February 6th, 2013.
49
Overall
Overall Density of Items
An average of 31 ± 14 items/ m2 (including all size classes examined during this
study) was observed throughout the three finger inlets. Budd Inlet had the highest density
of micro-plastics with 89 ± 40 items/ m2. Eld and Totten Inlets had much lower densities
with 2.1 ± 0.8 and 2.3 ± 1.1 items/ m2 respectively (Table 2).
Table 2
Density of micro-plastic by various size classes (items/ m2) collected from January 16th, 2013 to February
6th, 2013.
Water Body
Summary statistics
Inlet
Variable
Mean
Std. Error of µ
Area Sampled (m2)
All Finger Inlets
Items (5.6 mm-0.3 mm)/ m2
31
13.7
Items (5.6 mm-1.0 mm)/ m2
25
11
Items (1.0 mm-0.3 mm)/ m2
6
2.4
Items (5.6 mm-0.3 mm)/ m2
89
39.8
Items (5.6 mm-1.0 mm)/ m2
73
32.1
Items (1.0 mm-0.3 mm)/ m2
16
7.8
Items (5.6 mm-0.3 mm)/ m2
2.1
0.8
Items (5.6 mm-1.0 mm)/ m2
1.3
0.7
Items (1.0 mm-0.3 mm)/ m2
0.8
0.3
Items (5.6 mm-0.3 mm)/ m2
2.3
1.1
Items (5.6 mm-1.0 mm)/ m2
2.2
1.1
Items (1.0 mm-0.3 mm)/ m2
0.1
0.1
120
Budd Inlet
40
Eld Inlet
40
Totten Inlet
40
50
Overall Weights
An average of 32 ± 13 mg of micro-plastics/ m2 was observed throughout the
study area, which reflects the weight of all the size classes. Budd Inlet had the highest
density by weight of micro-plastics with 91 ± 38.8 mg of micro-plastics/ m2. Eld and
Totten Inlets had much lower densities by weight with 1.5 ± 0.7 and 2 ± 1.0 mg of microplastics/ m2 respectively (Table 3).
Table 3
Means of milligrams of micro-plastic/ m2 collected from January 16th, 2013 to February 6th, 2013.
Water Body
Inlet
Variable
Summary statistics
Mean
Std. Error of µ
31.57
13.39
31.02
13.22
0.36
0.18
91.2
38.76
90.16
38.26
0.94
0.54
1.48
0.7
1.35
0.7
0.13
0.1
2.03
0.98
1.56
0.9
0.01
0.01
Area Sampled (m2)
All Finger Inlets
Milligrams (5.6 mm-0.3 mm)/
m2
Milligrams (5.6 mm-1.0 mm)/
m2
Milligrams (1.0 mm-0.3 mm)/
m2
Budd Inlet
Milligrams (5.6 mm-0.3 mm)/
m2
Milligrams (5.6 mm-1.0 mm)/
m2
Milligrams (1.0 mm-0.3 mm)/
m2
Eld Inlet
Milligrams (5.6 mm-0.3 mm)/
m2
Milligrams (5.6 mm-1.0 mm)/
m2
Milligrams (1.0 mm-0.3 mm)/
m2
Totten Inlet
Milligrams (5.6 mm-0.3 mm)/
m2
Milligrams (5.6 mm-1.0 mm)/
m2
Milligrams (1.0 mm-0.3 mm)/
m2
120
40
40
40
51
The overall standard error of the means of each inlet, for both density by number
of items and density by weight, were very high because of the spatial variability within
sites, between sites and between the inlets. For example, one site (Budd NE) contained
94% of all the micro-plastics found in this study. Hence the highest mean density of
micro-plastic was observed at Budd NE with 350 ± 131 items/ m2 and 91.2 ± 38.8 mg/
m2, whereas the lowest mean density of micro-plastic for a study location (Eld NE) was
0.2 ± 0.2 items/ m2 and 0 ± 0 mg/ m2.
Variability of micro-plastic density (items/ m2) within Inlets
Unless otherwise indicated, “mean density of total items” refers to the density of
items in both the large (5.6mm-1.0mm) and small (1.0mm-0.3mm) size classes. The
strong positive relationship found between number of items in the two size classes (R2 =
0.96) suggested that examination of both size classes together would be representative of
the sample in order to examine the factors driving spatial variability within inlets. This is
further supported by the strong positive relationship found between total number of items
collected and total weight (R2 = 0.98).
Budd Inlet
Budd Inlet contained 95% of the plastic collected during this study. Spatial
variation within the inlet was very high as the majority of micro-plastics collected within
Budd Inlet (98%) were located at the study site Budd NE. The mean density of total items
collected at Budd NE was 350 ± 131 items/ m2. 1% of the micro-plastics from Budd Inlet
were collected at Budd NW, where the mean density was 4 ± 1 items/ m2. Budd SW and
Budd SE contained less than 1% of the micro-plastics collected within Budd Inlet. The
52
mean density of total items collected at Budd SW and Budd SE was 2 ± 1 items/ m2 and 1
± 1 items/ m2 respectively (Appendix 1).
Eld Inlet
Eld Inlet contained 2.2% of the micro-plastic collected during this study.
Though Eld had a lower density of micro-plastic than Budd Inlet, spatial variability was
also great in Eld Inlet. The majority of micro-plastics collected within Eld Inlet (68%)
were located at the study site Eld SW, where the mean density was 6 ± 3 items/ m2. Eld
NW and Eld SE each contained 14% of the micro-plastics, with mean density of total
items being 1 ± 1 items/ m2 and 1 ± 0.5 items/ m2 respectively. Eld NE contained 2% of
the micro-plastics collected within Eld Inlet. The mean density of total items collected at
Eld NE was 0.2 ± 0.2 items/ m2 (Appendix 2).
Totten Inlet
Totten Inlet contained 2.5% of the micro-plastic collected during this study. The
majority of micro-plastics collected within Totten Inlet (59%) were located at the study
site Totten SW, where the mean density was 5 ± 4 items/ m2. Totten NW contained 24%
of the micro-plastics collected within Totten Inlet with a mean density of 2 ± 1 items/ m2.
Totten NE and Totten SE each contained 4% of the micro-plastics from Totten Inlet. The
mean density of total items collected at Totten NE and Totten SE was 1 ± 1 items/ m2 and
1 ± 0.5 items/ m2, respectively (Appendix 3).
Variability of micro-plastic density (items/ m2) within Sites
Spatial variability was present within the sites (Appendix 4) both in terms of the
variability of micro-plastic density, but also in the distribution of the small versus large
53
size classes. Sediment samples from Budd NE consistently contained both size classes,
and this site was the only site where micro-plastics were detectable in all of the ten
quadrats analyzed per site. The density of individual items was higher by 2 orders of
magnitude in the center of the Budd NE when compared to the edges. Similarly, sites
such as Budd NW, Budd SE, Budd SW, Eld SW and Eld NW contained both size classes
and the spatial distribution appeared to be focused at specific areas along the shorelines.
When micro-plastics were detected in Totten Inlet they were generally from the large size
class. Like the observations for Budd Inlet, but at a small spatial scale, one quadrat at
Totten SW contained the majority of the micro-plastics found in the inlet. Totten NW
was the only location where micro-plastics appears to a more uniform distribution across
an approximate 50 meter section of the beach. Finally, Eld SE was the only location
where the smaller size class of micro-plastics was exclusively found. The micro-plastics
found at Eld SE were in two quadrats 50 meters apart from each other along the
shoreline.
Overall Distribution of types of Plastic Collected
Micro-plastics were identified by five categories; foams, fragments, films, pellets
and filament balls. Of the five categories that the micro-plastics were identified by, foams
comprised 87.8% of all items collected in this study. Fragments of micro-plastic
comprised 11% of the total, while films 0.6%, pellets 0.3% and filament balls 0.3% were
the least dominant items (Figure 15).
54
Figure 15. Distribution of categories of micro-plastic collected from January 16th, 2013 to February 6th,
2013. A. Distribution of all micro-plastics collected. B. Same data set as Figure A. but axis has been
adjusted to better portray the data. Large (5.6 mm - 1.0 mm) and Small (1.0 mm - 0.3 mm).
Overall correlation between Size Classes
The size class 5.6 mm - 1.0 mm contained 81.7% of the total micro-plastic items
and 99.5% of the total weight that was collected during this study, whereas the size class
between 1.0 mm - 0.3 mm contained 18.3% of the total micro-plastic items and 0.5% of
the total weight. There was a strong positive correlation between the size classes 5.6 mm
- 1.0 mm and 1.0 mm - 0.3 mm for items/ m2 (R2 0.96, p=0.0001, n=120), indicating that
the same processes were causing the accumulation of both large and the small size classes
at a given site, although there are exceptions (i.e. Totten Inlet, where very small amounts
of the small size class is observed and Eld SE where no micro-plastics of the large size
class is observed). There was a weak positive correlation between the size classes large
and small when density was explored by weight (R2 0.05, p=0.0146, n=120) (Figure 16).
55
Figure 16. Correlation of the two size classes of micro-plastics collected from January 16th, 2013 to
February 6th, 2013. A. Correlation of total items of micro-plastic/ m2 between large (5.6 mm - 1.0 mm) and
small (1.0 mm - 0.3 mm) size classes. B. Correlation of total weight of micro-plastic/ m2 between large (5.6
mm - 1.0 mm) and small (1.0 mm - 0.3 mm) size classes.
Figure 17. Correlation of relationship between items of micro-plastics/ m2 and the weight of the microplastics in grams/ m2 collected from January 16th, 2013 to February 6th, 2013. A. Correlation of total items
of micro-plastic/ m2 and total weights of micro-plastics in grams/ m2. B. Correlation of items of microplastic/ m2 and weights of micro-plastics in grams/ m2 for the large size class.
C. Correlation of items of micro-plastic/ m2 and weights of micro-plastics in grams/ m2 for the small size
class.
56
Correlation between Weight and Items
There was a strong positive correlation between the weight of the micro-plastic
collected (summing both size classes) and the quantity of items (again summing both size
classes) collected for the overall study area (R2 0.98, p=0.0001, n=120). There was also a
strong positive correlation between the weight of the micro-plastic collected and the
quantity of items collected for the large size class (R2 0.98, p=0.0001, n=120), and a very
weak positive correlation between the weight of the micro-plastic collected and the
quantity of items collected for the small size class (R2 0.07, p=0.0027, n=120) (Figure
17). This weak correlation was due to the lower limits of the scale used for measuring
micro-plastics which made the weights of the small size class undetectable.
Micro-plastic Accumulation Zones within the Inlets
As described in the previous section, all three finger inlets studied had locations
where higher accumulation of micro-plastics occurred. For the purposes of this thesis,
accumulation zones are defined in this study as locations within an inlet that contain 50%
or more of the total number of micro-plastic items/ m2 collected in that inlet, which
indicated that each inlet contained one accumulation zone. The study site Budd NE
contained 98.1% of the micro-plastic pieces collected within Budd Inlet. Eld SW
contained 68.3% of the micro-plastic pieces collected within Eld Inlet, whereas Totten
SW contained 58.7% of the micro-plastic pieces collected within Totten Inlet (Figure 18).
57
Figure 18. Accumulation zones in each finger inlet. Percentage is the quantity of micro-plastic items/ m2
within each inlet Bold indicates an accumulation zone.
Comparison of Accumulation Zones across the Inlets
The wilcoxon test of mean ranks of the density of total micro-plastic (in units of
items/ m2) in the accumulation zone sites between the inlets was significantly different (p
= 0.0001). Tukey’s honest significance difference test was performed and Budd NE was
significantly different from Eld SW and Totten SW. Budd NE contained the majority of
the plastics collected within the study area.
Comparison of Non-Accumulation Zones across the Inlets
Wilcoxon test was performed between areas designated as non-accumulation
zones across the inlets to determine if one inlet had a higher density of total micro-plastic
items/ m2. The mean ranks of the non-accumulation zone sites between the inlets were
significantly different (p = 0.0484). The mean micro-plastic density for the non-sink
locations in Budd Inlet was 2.3 items of micro-plastic/ m2, while the non-sink locations in
58
Eld and Totten inlets were 0.9 and 1.3 items of micro-plastic/ m2, respectively. Wilcoxon
test were further performed between Eld and Totten inlets to determine if one inlet had
significantly higher micro-plastic density. The mean ranks of the non-accumulation zone
sites between Eld and Totten inlets were not significantly different (p = 0.91). This
suggests higher densities of micro-plastics were collected in both the sinks and non-sinks
of Budd Inlet.
Watershed Demographics
Demographically, the three inlets are very different. Budd inlet had a population
density of approximately 1186 people/ kilometer2, while Eld inlet has a population
density of 267 people/ kilometer2 and Totten inlet has a population density of 84 people/
kilometer2.
59
DISCUSSION
Micro-plastics have been demonstrated to pose a threat to wildlife through direct
ingestion (Baird and Hooker 2000; Besseling et al. 2012; Boerger et al. 2010; Colabuono
et al. 2009; Davison and Asch 2011; Graham and Thompson 2009; Lindborg et al. 2012)
and the sorption of toxic chemicals into wildlife from those plastics that were ingested
(Tanaka et al. 2013; Teuten et al. 2009). Micro and Macro-plastics are also dispersing
invasive species and have the potential to disrupt ecological communities (Barnes 2002;
Gregory 2009). Aside from eliminating the source of micro-plastics, the best way to
combat marine micro-plastic pollution and their subsequent impacts to wildlife, is to
remove the pieces of plastic from the marine environment and dispose the plastic
pollution properly. The easiest location to collect and remove plastic pollution is from
shorelines.
Understanding the spatial distribution of marine micro-plastics along shorelines
can facilitate focused clean-up efforts to increase cleanup efficiency. For example, microplastics have been demonstrated to accumulate in select areas of shorelines as a result of
different factors, including population density (Browne et al. 2011; Kingfisher 2011;
Kusui and Noda 2003), prevailing wind conditions (Browne et al. 2010; Eriksson et al.
2013; Ivar do Sul et al. 2009) and surface currents (Cooper and Corcoran 2010; Corcoran
et al. 2009; Martins and Sobral 2011). Once the spatial distribution and the physical
factors that are driving that distribution in a specific area are understood, the potential for
isolating the source locations from which micro-plastics originate is obtainable.
Accordingly, starting at locations with high micro-plastic density and tracing the physical
60
factors backwards to the location of the source is a valuable tool for combating cleanup
efforts.
Resources are limited for cleanup efforts as well as our current ability to trace the
source locations of micro-plastic pollution in Puget Sound. Kingfisher (2011) found little
relationship between proximity to population and micro-plastic density on shorelines.
While Baker (2011) found a higher densities of micro-plastics in surface waters near
urban locations than in remote locations, suggesting that population density is correlated
to micro-plastic density.
As such, this study examined the distribution of micro-plastics between Budd, Eld
and Totten inlets all located in the South Puget Sound. Budd inlet, which has the highest
population density of the inlets, contained the highest density of micro-plastics by one
order of magnitude. This suggests that anthropogenic factors are the main driver of
spatial variability between the inlets. Within the inlets spatial variability was also very
great suggesting that physical factors are the main driver of spatial variability within the
individual inlets. The findings of this study also suggest that when micro-plastic pollution
is present in South Puget Sound, it will accumulate in specific areas driven by physical
factors such as winds and currents, (see discussion below), thus suggesting that targeted
cleanup efforts should be devised in South Puget Sound.
Spatial variability between the Inlets (Anthropogenic Factors)
Budd Inlet as a whole contained 45 fold more micro-plastics/ m2 than Eld and
Totten Inlets (Figure 19). Further, it contained 95% of the total micro-plastics collected.
The spatial distribution between the inlets appears to be driven by a combination of
61
anthropogenic factors, including population density, the amount of land covered with
impervious surfaces, and marine utilization by recreational users.
Figure 19. Distribution of total micro-plastics Items/ m2 collected in the study area separated by inlet from
January 16th, 2013 to February 6th, 2013.
First, the population of Budd Inlet is much higher than that of the Eld and Totten
Inlets. The population density is approximately 1,186 people/ kilometer2 in Budd Inlet
while Eld and Totten have an approximate population density of 267 and 84 people/
kilometer2. As micro-plastics are only anthropogenically produced, this suggests that
population could be responsible for the high density of micro-plastics found in this inlet.
The density of micro-plastics found overall within the inlet, within the accumulation
zones (p = 0.0001) and within the non-accumulation zone locations (p = 0.0484) was
significantly higher in Budd Inlet compared to Eld or Totten Inlet.
A strong positive correlation between population density and micro-plastics/m2
was present (R2 = 0.98, p = 0.10), although there were only three inlets examined,
augmenting the p-value. Browne et al. (2010) as well as Kusui and Noda (2003) found a
62
similar relationship between population density and micro-plastic density. Browne et al.
(2010) sampled 18 shoreline locations around the world with varying populations, a
positive correlation was found between population density around the sample location
and the quantity of micro-plastics that were collected. Kusui and Noda (2003) found a
similar relationship between population density and micro-plastic density when they
compared Japanese shorelines with high population density to less populated Russian
shorelines.
The distribution of population and developed land is different between the inlets
which could also be influencing the differences in micro-plastic density between the
inlets. Sixty eight percent of the population in Thurston County lives in the incorporated
areas, along the shorelines population density is the highest within the Olympia city
limits. Olympia is located at the southernmost tip of Budd Inlet and the majority of
development is densely located within that area, which is demonstrated by the differences
in impervious surfaces. Impervious surfaces make up 25-40% of the land cover in the
southern tip of Budd Inlet, while 2-10% of the land cover in the middle and north section
of Budd Inlet contain impervious surfaces. The land use in Eld and Totten inlets closely
resembles (2-10% impervious surfaces) the middle and north end of Budd Inlet (Thurston
Regional Planning Council 2012).
However it is interesting to note that the highest accumulation of micro-plastics
was not found in the southern Budd inlet sites. The highest accumulation was found at
Budd NE, which is located at the end of Budd inlet on the eastern shoreline. The high
population density in the south end of Budd Inlet, in combination with the higher density
of impervious surfaces may create the opportunity for more plastics that are discarded to
63
enter the inlet and be transported by the prevailing southwest wind and surface currents to
the Budd NE study site and beyond (see discussion below in Physical Factors driving
Spatial Variability).
The inputs of micro-plastics from waste water treament plants was originally
hypothesized in this study to be a driver of micro-plastic density on shorelines in South
Puget Sound. Upon further investigation the majority of the micro-plastics collected were
foamed plastics and plastic fragments from the degradation of larger plastic pieces. The
micro-plastics of concern from waste water treatment plants are micro-beads which are
commonly used in facewash, tooth paste and dish soap (Fendall and Sewell 2009). Five
of the 1,751 pieces of micro-plastics collected at Budd NE were nurdles. Four of the five
nurdles collected were very small and blue in color, similar to the micro-beads found in
facewash and toothpaste.
Figure 20. Distribution of micro-plastics categories collected in the study area from January 16th, 2013 to
February 6th, 2013.
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There are four waste water treatment plants that input water into Budd Inlet, one
in Totten Inlet and none in Eld Inlet (Roberts et al. 2009). This suggests that the inputs of
the wate water treatment plants have the potential to become a source for micro-plastics
in the South Puget Sound, but larger plastic waste being discarded into the marine
environment is currently the major issue. Foamed plastics were the dominate microplastic collected within all inlets (Figure 20).
Foamed plastics are one of the plastics considered disposable. Common uses for
foamed plastics are to-go and carryout containers from restaurants as well as coolers for
beachgoers, recreational boaters and commercial fishermen. Foam was also used in the
construction of older floats and docks for marinas (Gregory 2013). Foamed plastics float
higher out of the water, than other plastics due to their construction with air pockets. The
compositional data suggests that these are likely sources of marine micro-plastic
pollution in South Puget Sound.
Spatial Variability within Inlets (Physical Factors)
This study found that locations within South Puget Sound inlets accumulate
floating debris non-uniformly. For example, the number of micro-plastics/ m2 collected at
the Budd Inlet North East site (Budd NE) was 158 fold that which was collected at the 11
other sites in the study, including three other sites found within Budd Inlet. Budd NE
contained 181 fold more foamed plastics, 122 fold more plastic fragments and 19 fold
more plastic films compared to the 11 other sites in the three finger inlets. The only
plastic pellets collected during the study were collected at Budd NE, though no line balls
were detected at the site. These observations beg the question as to what is causing the
65
preferential accumulation of micro-plastics at this site, relative to Budd Inlet as a whole
and the rest of the study area. In addition to being affected by higher population in Budd
inlet, the high density of micro-plastics collected at Budd NE could be attributed to a
combination of two physical factors: its geographical position and aspect relative to the
prevailing wind direction and the effects of localized currents.
Winds
Winds are likely to be a dominate factor in controlling the spatial distribution of
micro-plastics within the inlets. The prevailing wind in South Puget Sound is from the
southwest (United States Naval Research Laboratory 2008). During this study the
average wind direction was from the southwest (Figure 21).
Figure 21. Wind direction in South Puget Sound, Washington State USA during the duration of this study
(January 16th- February 6th, 2013). Data from (National Weather Service - NWS Seattle 2013). Reprinted
with permission from S. Albertson.
66
The micro-plastics that float higher in or on top of the water such as foamed
plastics would have the potential to be driven by wind alone. With strong southwest
winds during this study, foamed plastics were found in higher densities on shorelines that
have a southward aspect, such as Budd NE which faces west-southwest. This suggests
that downwind shorelines from population centers could have higher densities of microplastics.
Totten and Eld Inlets also contained locations where higher densities of microplastic items/ m2 were collected compared to the other sites within each inlet. Eld
southwest (Eld SW) and Totten southwest (Totten SW) are both located in the southwest
of their respective water bodies, which could have played a factor in the higher microplastic density found at each of these sites relative to the other study locations within
their respective inlets. Eld SW faces south while Totten SW faces south-southwest. Eld
SW and Totten SW both contained high percentages of foamed plastics, with 89% and
93% respectively. The high percentage of foamed plastics collected at the two sites could
be due to the way that foamed plastics float upon the water. The strong prevailing
southwesterly wind could have pushed discarded foam pieces up onto the Eld SW and
Totten SW beaches where they were broken apart into smaller pieces and mixed in with
the sediment by wind wave action.
Further evidence that wind may be a driving factor of the micro-plastic
accumulation in the South Puget Sound can be found by examining sites Eld northwest
(Eld NW) and Totten northwest (Totten NW). Both Eld NW and Totten NW face eastsoutheast, indicating these sites would intercept the southwesterly wind, these two sites
contained 14.6% and 23.9% of the micro-plastics collected within each inlet respectively.
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Foamed plastics were the only item collected at Totten NW while an even mix of plastic
fragments and foamed plastics was collected from Eld NW.
Currents
In addition to winds, surface current rotation and tidal pumping are likely to be a
secondary factor in controlling the spatial distribution of micro-plastics in this study. The
counter-clockwise rotation of surface and sub-surface currents in Budd Inlet suggest that
debris could be picked up from the higher populated south end of the inlet and deposited
at the entrance to the inlet at the Budd NE site (Aura Nova Consultants et al. 1998;
Roberts et al. 2009).
The currents in Eld and Totten inlets have not been studied as extensively in Budd
Inlet. However, higher levels of micro-plastics were collected in levels indicated as
accumulation zones in data on Totten and Eld inlets surface currents obtained from Aura
Nova Consultants. The areas predicted to be accumulation zones by the recertification
project for the LOTT contained much higher densities of micro-plastics than the other
locations, suggesting that currents as well as wind are playing a role in accumulating
micro-plastics on shorelines.
Another driver of surface water in the South Puget Sound is freshwater inputs.
The net flow within any estuary is toward the entrance; this flow is primarily driven by
tidal pumping in Puget Sound but the addition of fresh water on the surface does aid in
this movement. The Deschutes River enters Budd Inlet at the inlets southernmost tip, and
contributes to the net surface flow toward the entrance of the inlet. Though freshwater
inputs have some effect on the circulation and net flow of the surface water in Puget
68
Sound, tidal pumping has been demonstrated to be the major driver of surface flow in
South Puget Sound and Budd Inlet (LOTT 2000).
Conclusion of driving factors
A combination of local currents and prevailing wind appear to be the main drivers
of the spatial distribution of micro-plastic densities within the finger inlets in South Puget
Sound. The same physical processes that drove the location of accumulation zones were
also responsible for the lower densities of micro-plastics at the other locations. The
predominant southerly wind would have blown micro-plastics away from Budd northwest
(Budd NW), Budd southeast (Budd SE), Budd southwest (Budd SW), Eld northeast (Eld
NE), Eld southeast (Eld SE), Totten northeast (Totten NE) and Totten southeast (Totten
SE). These same locations were also indicated as non-accumulation zones in the 1998
LOTT study, with the exception of Budd SE. This suggests that both current and winds
created the conditions for lower micro-plastic densities on these shorelines.
Further Implications
The overall results for micro-plastic density of items/ m2 are similar to other
shoreline micro-plastic surveys. When examined per inlet the results for Budd Inlet are
on the higher end of the spectrum (89 pieces of micro-plastics/m2) while the results for
Totten (2.3 pieces of micro-plastics/m2) and Eld (2.1 pieces of micro-plastics/m2) are the
lowest reported numbers.
69
Table 4
Previous studies examining micro-plastic density along shorelines. Mean density is presented.
Weight/ m2
Author
Location
Kusui & Noda (2003)
Japan
13.6 g
Russia
8.8 g
Portugal
36.4 g
South Puget Sound
0.003 g
Brazil
Equatorial Western Atlantic
North Puget Sound
2.46 g
Martins & Sobral (2011)
Gilman (2013)
Costa et al. (2010)
Ivar et al. (2009)
Kingfisher (2011)
Pieces/ m2
2610 Pieces
31.3 Pieces
185.1 Pieces
31 Pieces
29 Pieces
9 Pieces
The milligrams/ m2 of micro-plastics found during this study was much lower
than any other study that examined buried marine micro-plastics (Table 4). This can be
explained by the other studies not isolating micro-plastics when creating total weights for
their studies. Kusui & Noda (2003) included rubber, glass and metals in their estimates
for marine debris on shorelines. Martins & Sobral (2011), included plastics larger than
greater than 10mm which accounted for 89.6 percent of the weight collected during their
study. The distribution of plastics that they collected during their survey was dominated
by polyethylene, polyester and then polystyrene. Products made of polyethylene are
commonly dense and weigh more than products made of foamed polystyrene which is
created using air pockets in the foam.
The values found by Kingfisher (2011) were only reported in terms of weight so
comparisons are difficult. The net flow of surface currents in Puget Sound is toward
ocean so higher numbers would be expected in the North Sound than the South Sound as
well. The population density on the east side of northern and central Puget Sound metro
area was 2,930 people per km2 in relation to the population density of South Puget Sound
metro region was 1,058 people per km2 (United States Census Bureau 2013). The
70
cumulative effect of the population all along the shorelines adds to help create the larger
numbers in the North Sound.
The lower denisty of micro-plastic pieces/ m2 found in this study are due to
sampling at the head of the 120km long estuary in isolated inlets with lower relative
population denisty. The drivers of micro-plastic density in South Puget Sound appear to
be a combination of anthropogenic factors; higher total population at possible source
areas and high percentage of impervious surfaces allow the micro-plastics to enter the
system. Once micro-plastics have entered the system the prevailing Southwest wind in
combination with the surface currents driven by tidal pumping and riverian sources push
north. Shorelines that are oriented south within the inlets accumulated the majority of the
micro-plastics that were collected during this study.
71
CONCLUSION
Micro-plastics are present on all of the shorelines surveyed across the three South
Puget Sound finger inlets Budd, Eld and Totten. Two orders of magnitude more microplastic pieces/ m2 were collect in Budd Inlet than Totten or Eld Inlets. The spatial
distribution between the inlets is due to anthropogenic factors. Once the micro-plastics
have entered the inlets, physical drivers control the spatial distribution. In South Puget
Sound, wind appeared to be the primary driver of spatial distribution. This study creates
baseline data for South Puget Sound as well as locating sites that would be ideal for
further research studying temporal accumulation rates of micro-plastics for shorelines in
South Puget Sound. Further work should be conducted examining other areas that microplastics are believed to be accumulating in. Further research into the temporal distribution
of marine micro-plastic density will allow future trends to be understood. Selecting
locations for future work where circulation is understood and little mixing between
isolated sites allows other issues such as the impact of population density to be
understood.
FURTHER WORK RECOMMENDATIONS
Further research on the spatial distribution of marine micro-plastics in South
Puget Sound is recommended in three areas; the role of impervious area, the role of
recreational boating and the role of bathymetry on smaller scale spatial distribution.
Total impervious area was positively correlated to micro-plastic pieces/m2 in the
inlets (R2 = 0.89, p = 0.21), though the high p-value is likely due to the small sample size.
The total percentage of impervious surfaces was also higher in Budd Inlet. Eight percent
72
of the land within the Budd Inlet watershed is covered with impervious surfaces, which
can contribute to greater levels of storm water runoff. Storm water runoff can carry
pieces of plastic and micro-plastic into the inlet. An estimated 4% of the land within the
Eld inlet watershed is covered with impervious surfaces, while an estimated 2% of the
land in the Totten Inlet watershed is impervious surfaces. The combination of high
population density and high percentage of impervious area creates a situation where more
plastics and micro-plastics can be washed into an inlet by storm water water runoff
though this relationship has been studied very little.
In addition to factors on land, more recreational boaters are using Budd Inlet than
Eld or Totten Inlets (personal observation). Budd Inlet is also the only inlet of the three
studies that contains recreational marinas (Discover Boating 2013). The combination of
anthropogenic factors may create a situation where more micro-plastics are accumulating
within Budd Inlet due to coolers and plastic pieces falling off of boats.
Spatial variability of micro-plastic density, pieces/ m2 within the sites was also
present. Six of the twelve sites appeared to have patterns of areas along the shoreline that
accumulated more than others. At the other six sites the spatial distribution appears
sporadic. The spatial distribution at the smaller level is believed by the author to be due
to changes in localized bathymetry. But further work understanding the small scale
spatial distribution would contribute to the ultimate goal of tracking the sources of microplastics at the source.
Understanding the role that these additional factors play in the spatial distribution of
marine micro-plastics will further advance knowledge in the ability to identify point
sources of the pollution as well as informing organizations working on beach cleanups.
73
INTERDISCIPLINARY STATEMENT
More and more people live close to coastlines, creating more and more waste.
Plastics persist in the marine environment for much longer than we had thought about,
and accumulation is believed to be increasing. The use of cleanup efforts along beaches is
one pathway to combat the growing problem of marine debris and marine micro-plastics.
This study identified the presence of locations with higher density of micro-plastics than
other locations, suggesting that beach cleanup efforts can have a large effect at localized
areas. These findings suggest that beach cleanup efforts in South Puget Sound should be
targeted at locations with a high abundance of visible micro-plastics. Targeted cleanup
efforts will likely have a large impact on reducing micro-plastic pollution in South Puget
Sound.
This study found that foamed plastics were the most prevent form of plastics in
our marine waters. The same high quantities of foamed plastics was found in shoreline
surveys conducted in the Northern region of Puget Sound (Kingfisher 2011). A possible
source of foamed plastics could be marina floats. Marinas in Puget Sound are required to
convert from foam plastic docks to concrete docks in order to obtain the Clean Marina
Certification from Puget Soundkeeper Alliance (Gregory 2013).
Recycling programs for foamed plastics are now in place in Thurston county as
well as efforts to educate the public on alternatives to foamed plastics (Dodge 2009). In
Thurston County 0.83 percent of the solid waste by weight were foamed plastics. Efforts
to reduce, reuse and recycle should be continued but work should also be conducted to
isolate the principle uses of foamed plastics to identify the points of entry into the marine
eco-system.
74
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APPENDICES
Appendix 1.
Table Budd
Micro-plastic (number of items/ m2) collected from January 16th, 2013 to January 29th, 2013 in Budd Inlet.
Standard error of the mean is reported as (SEM).
Inlet
Sample Location
Variable
Budd Inlet
Budd NE
Summary statistics
Items (5.6mm-0.3mm)/ m2
350
131.8
Items (5.6mm-1.0mm)/ m2
286
105.2
63
27.3
Items (5.6mm-0.3mm)/ m2
4
1.4
Items (5.6mm-1.0mm)/ m2
3
1.2
2
1
0.5
Items (5.6mm-0.3mm)/ m2
1
0.5
Items (5.6mm-1.0mm)/ m2
1
0.4
2
1
0.3
Items (5.6mm-0.3mm)/ m2
2
0.6
Items (5.6mm-1.0mm)/ m2
1
0.4
2
1
0.4
Items (1.0mm-0.3mm)/ m
Budd NW
Items (1.0mm-0.3mm)/ m
Budd SE
Items (1.0mm-0.3mm)/ m
Budd SW
Items (1.0mm-0.3mm)/ m
Mean
2
Std. Error of µ
% within Inlet
98.1%
1.0%
0.4%
0.5%
85
Appendix 2.
Table Eld
Micro-plastic (number of items/ m2) collected from January 22nd, 2013 to January 29th, 2013 in Eld Inlet.
Standard error of the mean is reported as (SEM).
Summary statistics
Inlet
Sample Location
Variable
Eld Inlet
Eld NE
Mean
Std. Error of µ
Items (5.6mm-0.3mm)/ m2
0.2
0.2
2
0.2
0.2
Items (1.0mm-0.3mm)/ m2
Eld NW
0.0
0.0
Items (5.6mm-0.3mm)/ m2
1.2
0.5
2
0.6
0.4
Items (1.0mm-0.3mm)/ m2
Eld SE
0.4
0.3
Items (5.6mm-0.3mm)/ m2
1.2
1.0
2
0.0
0.0
Items (1.0mm-0.3mm)/ m2
Eld SW
1.2
1.0
Items (5.6mm-0.3mm)/ m2
5.8
2.9
2
4.4
2.6
Items (1.0mm-0.3mm)/ m2
1.2
0.4
Items (5.6mm-1.0mm)/ m
Items (5.6mm-1.0mm)/ m
Items (5.6mm-1.0mm)/ m
Items (5.6mm-1.0mm)/ m
% within Inlet
2.4%
14.6%
14.6%
68.3%
86
Appendix 3.
Table Totten
Micro-plastic (number of items/ m2) collected from February 1st, 2013 to February 6th, 2013 in Totten
Inlet. Standard error of the mean is reported as (SEM).
Inlet
Sample Location
Variable
Totten Inlet
Totten NE
Items (5.6mm-0.3mm)/ m2
Items (5.6mm-1.0mm)/ m2
Items (1.0mm-0.3mm)/ m2
Totten NW
Items (5.6mm-0.3mm)/ m2
Items (5.6mm-1.0mm)/ m2
Items (1.0mm-0.3mm)/ m2
Totten SE
Items (5.6mm-0.3mm)/ m2
Items (5.6mm-1.0mm)/ m2
Items (1.0mm-0.3mm)/ m2
Totten SW
Items (5.6mm-0.3mm)/ m2
Items (5.6mm-1.0mm)/ m2
Items (1.0mm-0.3mm)/ m2
Summary statistics
Mean
Std. Error of µ
% within Inlet
0.8
0.8
0.0
0.53
0.5
0.0
8.7%
2.2
1.8
0.4
0.7
0.6
0.4
23.9%
0.8
0.8
0.0
0.4
0.4
0.0
8.7%
5.4
5.4
0.0
4.3
4.3
0.0
58.7%
87
Appendix 4.
Variability of micro-plastic density (items/ m2) within Sites in Budd, Eld and Totten Inlets
Figure Budd
88
Figure Eld
89
Figure Totten
90
