Toxicity of Microplastics to Aquatic Organisms

245 Pages·2017·1.33 MB·English

by  Sarah Au

Clemson University
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5-2017
Toxicity of Microplastics to Aquatic Organisms
Sarah Au
Clemson University, [email protected]
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TOXICITY OF MICROPLASTICS TO AQUATIC ORGANISMS
A Dissertation
Presented to
the Graduate School of
Clemson University
In Partial Fulfillment
of the Requirements for the Degree
Doctor of Philosophy
Environmental Toxicology
by
Sarah Au
May 2017
Accepted by:
Dr. Cindy M. Lee, Committee Chair
The late Dr. Stephen J. Klaine
Dr. Peter H. Adler
Dr. William S. Baldwin
Dr. Peter van den Hurk
Dr. John E. Weinstein
ABSTRACT

Plastic is used in products that span from cutlery to the main components in
automobiles, and airplanes. Both municipal solid waste streams and marine debris are
comprised of largely plastic products, and as annual global plastic production and use is
unlikely to decrease, the presence of plastic in the environment will likely increase.
Microplastics (MPs) are plastic fragments that have at least one dimension that is less
than 5 mm, and have been found throughout water bodies around the world. MPs are in
the same size fraction as most sediment particles and microorganisms, allowing them to
be easily ingested by a variety of organisms. The potential for MPs to alter the
bioavailability of contaminants, and whether MPs and adsorbed contaminants can
undergo trophic transfer, have been investigated in very few studies. Fluoranthene (FLU)
is one of the US Environmental Protection Agency’s 16 priority polycyclic aromatic
hydrocarbons; and its hydrophobic nature allows it to sorb easily to sediment and organic
matter, which suggests FLU will sorb to the hydrophobic surfaces of most MPs. While
most studies conducted have focused on acute MP exposures to marine organisms, little
is known regarding the toxicological chronic effects of MP exposures. Recent studies
have demonstrated that MP concentrations in freshwater water bodies are comparable to
those found in the ocean; even less information is available regarding MP toxicity to
freshwater organisms.
The first objective of my research was to characterize the physical toxicity of MPs
to aquatic invertebrates and fish. After establishing a baseline for acute MP toxicity, the
second objective focused on the determination of whether fluoranthene that is adsorbed to
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MP surfaces is bioavailable to aquatic invertebrates and fish. Finally, the third objective
evaluated whether MPs and the adsorbed fluoranthene can undergo trophic transfer
between prey and predatory organisms in both freshwater and marine ecosystems.
My results demonstrated that acute exposures to polyethylene spherical MP do
result in mortality at environmentally relevant concentrations. Specifically, 10- and 7-
day LC s of approximately 4.6 x 104 and 7.9 x 104 MPs/mL for spherical polyethylene
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MPs were quantified for amphipods and copepods, respectively. No mortality was
observed for either fathead minnows or mummichogs at MP exposures used during these
bioassays. Interestingly, polypropylene MP fibers were more toxic to exposed
amphipods than the polyethylene MP spheres, where mortality was observed at
concentrations as low as > 22.5 MPs/mL. When polyethylene spherical MPs are
contaminated with FLU, acute exposures can result in an increase in FLU bioavailability
to both fish and invertebrates. Chronic polyethylene spherical MP exposures resulted in
significant growth reductions in both Hyalellla azteca and Amphiascus tenuiremis, and
decreased reproduction in exposed H. azteca. In comparison to polyethylene spherical
MPs, fibrous polypropylene MP exposures to H. azteca resulted in significantly greater
mortality and reductions in both growth and reproduction. Exposure to FLU-
contaminated MPs resulted in an increase in FLU bioavailability to invertebrates and fish,
where more than 90% of the invertebrate FLU body burdens were due to MP exposure.
Finally, my results demonstrated that FLU that was adsorbed to MP surfaces can undergo
trophic transfer using both freshwater and marine invertebrates and fish. Approximately
1.5 mg fluoranthene was bioavailable to fathead minnows and mummichogs that had
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ingested amphipods, and copepods that had been pre-exposed to fluoranthene-
contaminated MPs, respectively. Hybrid striped bass that has consumed fathead
minnows that were pre-exposed to fluoranthene-contaminated MPs resulted in an average
bile concentration of approximately 1.3 mg fluoranthene. MPs represent another route of
exposure for ubiquitous persistent organic pollutants in the environment for lower and
higher trophic level organisms.
My research provided a platform on which the acute and chronic toxicological
effects due to MP exposures of freshwater and marine invertebrates and fish can be
compared because similar methods were used in all the bioassays. Generating data that
resulted from the use of similar exposure methods allows the scientific community to
make cross-species comparisons that are difficult to determine with the currently
available microplastic toxicity data. My results demonstrate that microplastics can have
both acute and chronic toxicological effects on aquatic organisms, and that the presence
of microplastics in the environment needs to be taken into consideration when evaluating
the exposure to environmental contaminants.

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DEDICATION

I dedicate my dissertation to my family and friends.
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ACKNOWLEDGMENTS
I cannot express how thankful I am to have had the opportunity to study under my
PhD adviser, Dr. Stephen J. Klaine. It is easy to say that he was a great teacher and
mentor, but it is a rare gift to be able to say that one’s adviser was also a friend, father-
figure, and colleague. The science that I learned from him will carry me through my
future career decisions, and the people I have met through him are not just professional
acquaintances, but are some of the most amazing friends one could ever have.
Professionally and personally, I am a better scientist, and person because of Steve Klaine.
Hopefully I am a little better at seeing one tree at a time, and not just the whole forest.
My committee members also deserve a round of applause. Everyone has
contributed to being a solid support system that I hesitate to think of what the last year
would have been like without them. I wholeheartedly thank Dr. Cindy M. Lee for being
an amazing mentor and friend. You have been a steadying presence in my life for the
past year, and I don’t think I could have finished my dissertation without your help.
Thank you for taking the time to correct all my writing errors. This may seem trivial, but
I “believe” I am a better writer now. Any future collaborator or correspondent will have
you to thank as well. I am grateful that through Sea Grant, and my dissertation work, I
was given the opportunity to collect microplastics in Charleston and Georgetown, SC,
with Dr. John Weinstein and his students. Getting a different perspective on microplastic
sampling techniques made me more aware of the various abiotic and biotic processes that
influence contaminant transport and fate in the environment. Thank you for your
guidance at my platform presentations. It is always good to have a friendly face around.
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A special thanks to Dr. Peter Adler for opening his lab to me, so that I could develop
better methods to image my invertebrates. I believe that our discussions on science as a
whole and how my work is influenced by other worldly events has given me a better view
on how to connect with individuals that do not have the same research background.
Thank you for taking the blinders off occasionally, and giving me a chance to truly reflect
on different aspects of my research. I am grateful that Dr. William Baldwin has also
opened his lab for me, so that I could explore different methods to better extract
fluoranthene from my tissue samples. Thank you for allowing me to use some of the
instruments in your lab. Finally, a special thank you to Dr. Peter van den Hurk for being
a mentor throughout my five years as a graduate student, and becoming a committee
member for me in my last year. Thank you for also opening your lab to me, and helping
me with method development.
I would like to acknowledge and thank Ron Gossett, Norm Ellis, and John Smink
for their assistance with animal culture and maintaining facilities at both the Institute of
Environmental Toxicology and Cherry Farm. None of my work could have been
accomplished without you because you were always helping us whenever an extra hand
was needed. ‘Thank you’ is a phrase that does not quite amount to the gratitude I feel.
I would also like to thank all past and present Klaine lab members. The research
projects that everyone had are so different, and I believe that I benefitted from having so
many types of methods and perspectives on toxicology surrounding me every day. Thank
you to Kim Newton, Austin Wray, Lauren Sweet, Anna Lee McLeod, Katherine Johnson-
Couch, Erica Linard, Lauren Stoczynski, Jason Coral, and Chad Mansfield for helping
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with fish culture, lab inspection cleanings, and giving me a support system throughout the
last five years. A special thanks to Lauren Sweet and Chad Mansfield for helping me
count copepods during a few bioassays.
I would also like to thank Dr. Tom Chandler and Emily Stewart at the University
of South Carolina for providing me with copepods to use in my toxicity bioassays.
Thank you, Paul Kenny, for assisting us in the collection of pluff mud and mummichogs
at the Belle W. Baruch Institute of Coastal Ecology and Forest Science. There are many
experiments that would not have been conducted if you had not helped me on so many
occasions. Thank you, Austin Gray, for helping me on countless field collection trips in
Charleston and Georgetown, SC. I am so glad that we were able to become both
colleagues and friends through these trips and various conference meetings. I would also
like to thank Dana Szymkowicz and Kaleigh Sims from Dr. Lisa Bain’s lab for helping
me with mummichog collection and embryo fertilization. Thank you, Drs. Lisa Bain and
Charlie Rice, for helping me develop methods for various experiments in the last few
years, and giving me advice regarding mummichog collection and culture.
Establishing the What’s in Our Water Jr. Program would not have been possible
without the help of Janine Sutter, Cathleen Reas, Laura Nash, and the numerous mentors
from Clemson University that helped make science fun for elementary students.
Participating in this program has given me a refreshing outlook on my research and a
different platform on which to relate my research to the interests of people in different
age groups and personal interests.
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Finally, a huge thank you to my mother, father, brother, and sister. Your patience
with my schedule has helped me get through the last few years and I am so glad to finally
be back in the Maryland-DC area so that the time between visits are not as long. Thank
you to all my friends that are scattered between the two coasts for taking the time to
maintain our friendships despite everyone having such crazy schedules. I would also like
to thank Jacob for making the multiple trips to South Carolina every year so that we can
explore various cities in the south. Thank you for listening to all my problems, and
helping me cope with all the stress. A general thank you to everyone I have met during
my five years at Clemson University. Your patience, guidance, and friendship though out
this whole experience has made this dissertation possible.

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