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Zahra Siddique
Professor Mullins
UNIV 200
16 November 2015
The Invasion of Microplastics: Conquering Marine Food Chains
Lucy, who is currently going through her freshman year of college, has been
struggling to keep up with a number of activities including schoolwork, cross country, and
her Environmental Defense club. Due to this load of stress, she has developed acne that can
only be eliminated with certain cleansers. Recently, her new favorite cleanser is one that
doubles as an exfoliator, leaving her skin feeling clean and smooth. This cleanser contains
tiny plastic bits, known as microplastics, which are marketed to customers such as Lucy as
exfoliating microbeads. While many other cleansers on the market do not contain
microbeads, these particles have become so popular that they are becoming a regular store
item, being incorporated into popular and easily accessible beauty brands, such as
Neutrogena and Olay. Toothpaste, body wash, and facial cleansers are all products that can
carry these harmful microbeads. Accessible through everyday drugstores, such as CVS and
Rite Aid, microbead products are taking off amongst the beauty world.
While this may sound merely like a product description ad, microbeads are a flawed
product in that they pose a threat to the environment. Unbeknownst to Lucy, yet
undeniably important to her Environmental Defense interests, is that microbeads, though
an exciting improvement for skin care products, yield a danger to the environment that is
not prevalent in the mind of the average consumer while browsing through store aisles.
However, these shoppers, if clearly given information on the matter, can take a more
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conscious decision to what they are buying. These microbeads are so small that they have a
tendency to leak into the ocean. Since these microplastics are so small, many believe that
they are not a threat to the environment, and that other animals that are higher on the food
chain must be better studied and protected because they are key to certain lower keeping
species at bay from overproduction. However, recent research has revealed that due to
their size, microplastics are liable to enter the ocean by accident whenever someone uses a
product that contains them by bypassing water filtering systems in pipes (Fendall 1225), or
by natural factors crumbling larger pieces of plastic into smaller particles, eventually
causing microplastics to be available to smaller organisms.
Plastic, among other waste, is recorded to be the highest pollutant of Earth’s oceans. In
2006, the United Nations Environmental Programme estimated that there are 46,000 pieces of
plastic afloat in the ocean every square miles (UNESCO). The area of the world ocean is
approximately 139.7 million square miles. These statistics mean that if the United Nations
estimates are taken into account, then the ocean would contain about 6.43 million square miles of
litter. Comparing that area to a country, the area in which trash takes up in the ocean is almost
equal to the total area of Russia, which is about 6.6 million square miles. Think about it – if all
the trash that has accumulated within Earth’s ocean is collected, an area the size of an entire
continent could be produced, larger than that of Europe or Australia, made of only garbage. Over
time this plastic waste will degrade, bringing with it absorbed toxins and producing particles that
can clog internal organs of organisms. As these plastics degrade, they erode, similarly to how
rock is eroded into sediment, and become smaller particles known as microplastics, which are
defined as pieces of plastic 5mm or smaller. In some cases, the particles are broken down to such
a degree that they can be called nanoplastics.
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People argue that we do not need worry about microplastics due to their small size in
relation to the ocean, but that is precisely why they are a threat to communities of living
organisms known as ecosystems. Size does matter. There is sufficient evidence that proves
microplastics are a threat to ecosystems due to their small size. Specific organisms, known as
plankton, are in the direct line of danger posed by microplastics, which inevitably impacts the
entire marine biome - or large region home to various plants and animals, in this case the ocean thus effecting ocean ecosystems. As planktonic organisms are introduced to plastic particles at an
increasing rate, these microplastics will negatively impact the plankton, eventually leading to
decreased growth and population sizes. Ocean currents will push microplastics all around the
ocean, thus allowing these particles to invade every type of ecosystem of the ocean biome. With
no natural barriers within the ocean, plankton species around the world will no doubt encounter
microplastics as long as humans continue to expel a copious amount of plastic into bodies of
water around the world. Although plankton are keystone species of the ocean, their
population is in danger by the accumulation of microplastics, which due to their small size
and lack of ability to degrade over time, will negatively impact the future population of
plankton. Because plankton is the base of the marine food web, it is detrimental to preserve
their living spaces as efficiently as possible. Once plastic contamination is introduced to an
ecosystem, the harmful invader can be consumed by various trophic levels, which is the
position organisms occupy on the food chain, depending on the size of the particle and
spread its way up the food chain, eventually ending with the top predators – mainly
humans. Although humans will be greatly effected by marine plastic pollution, they are also
the cause of this problem.
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Since the introduction of micro-bead beauty products to the market, the
accumulation of microplastics has increased dramatically. Formerly known to originate
from weathered and eroded plastics, microplastics now are found in the form of
microbeads – tiny plastic balls that are meant to satisfy exfoliation of the skin. These beads
are made primarily of Polyethylene (PE), but can also be produced from other plastic
material, such as polypropylene (PP), Polyethylene terephthalate (PET), polymethyl
methacrylate (PMMA), and nylon (Fauna & Flora International et al). Lisa S. Fendall, a Biology
professor at the University of Aukland, notes that since the microbeads are so tiny, they
bypass the preliminary treatment screens on wastewater plants as they travel through city
wastewater systems – eventually entering the ocean (Fendall 1228). The particles
therefore pose a much greater threat because they easily enter the ocean at a forever
increasing rate – directly proportional to that of the boom of microbead product users.
With the increase of microbead skin care consumers, large bodies of water around the
world are being filled with microplastics, endangering animals of all sizes. The smallest of
these animals are the planktonic animals, mostly free-floating and small enough that they
can only intake tiny particles, such as microplastics. Although microbead cleansers are
popular at this point in time, human industry will continue to produce them in great
amounts until wide-spread damage is proven and accepted.
With the human population growing, the need for cheap and easy to make products is
rising. Stephanie L. Wright, a Biosciences professor at the University of Exeter, claims that “a
significant relationship between microplastic abundance and human population-density was
found (Browne et al., 2011). As the human population continues to increase, the prevalence of
microplastics will also most likely increase” (Wright 483). This assertion shows that human
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population and plastic presence are inherently linked. Britta Denise Hardesty of The
Commonwealth Scientific and Industrial Research Organization claims that humans like simple
materials that can easily be produced and replicated, both of which plastics qualify for, along
with durability and their lightweight bodies (Hardesty et al 5). With the imminent surge of
microplastic debris invading the Earth’s most important water sources we, as humans, the
cause of this danger, must understand the situation, then act on the problems before
microplastics go on to infect ecosystems from the energy producers upward across the
globe.
Plastics over time degrade into microplastics through the effects of environmental
forces such as “wave action, sand grinding, exposure to sunlight, and passing through the
digestion of other organisms” (Fendall 1228). As plastic particles break and form
microplastics, these units decrease in density and float to the surface of the water, exposing
themselves to the Sun’s UV rays. As UVB radiation persists, the microplastics become
fragile and break apart into nanoparticles, thus becoming available to the consumption of
smaller organisms. Since these particles are unable to degrade, they remain in constant
motion through the environment through either free floating or consumption and digestion
from low trophic level planktons up through the food chain, becoming more toxic over
time. Though undeniably harmful, UVB radiation is only a single type of chemical that can
be absorbed by plastics.
Plastic is able to absorb and store toxic chemicals for long periods of time, making it a
dangerous material to ingest. The toxins plastic absorb are known as persistent organic
pollutants, or POPs. Stephanie L. Wright, a Research Fellow at King’s College in London, and
part of the Division of Analytical and Environmental Sciences, provides that “microplastics are
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liable to concentrate hydrophobic persistent organic pollutants (POPs), which have a greater
affinity for the hydrophobic surface of plastic compared to seawater. Due to their large surface
area to volume ratio, microplastics can become heavily contaminated - up to six orders of
magnitude greater than ambient seawater with waterborne POPs (Hirai et al., 2011; Mato et al.,
2001)” (Wright 484). Plastic is a hydrophobic material, which means it is “water fearing,” or
resists contact with water. As POP’s are hydrophobic, they tend to be pulled to unsaturated
hydrophobic plastics, which will then absorb them and a high capacity. Both POPs and plastic
resist water, so it makes sense that the two have a tendency to merge. Depending on the type of
plastic, the microplastic can concentrate POPs at a rate 1,000,000 times greater than the
concentration of POPs calculated in ocean water. As told by Morgana Matus, Chelsea M
Rochman, a professor at the Department of Biology and Coastal and Marine Institute at San
Diego State University, conducted a test with other scientists that tested how long plastic would
soak in toxins for until capacity is reached. The scientists tested the five most common plastics,
including PET and PVC, which are common plastics used to manufacture microbeads. The other
three plastics were high-density polyethylene (HDPE), low-density polyethylene (LDPE), and
PP. The POPs that were used in this study were polychlorinated biphenyls (PCBs) and polycyclic
aromatic hydrocarbons (PAHs). Rochman’s study found that HDPE, LDPE, and PP consistently
absorbed a greater amount of toxins than did PET or PVC. One study calculated that HDPE
would only stop absorbing chemicals after 44 months of submersion (Matus). It has been
calculated that in 2007, HDPE, LDPE, and PP are responsible for 62% of all plastic produced
globally, while PVC and PET only constituted for about 19% (UC Davis). Along with PCBs and
PAHs, another prevalent toxin that is found in seawater is dichlorodiphenyltrichloroethane
(DDT). When toxins are absorbed by plastic particles, they are collected in a more concentrated
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amount, proving harmful to marine organisms that ingest them. It does not matter how small the
plastic is, it will absorb toxins, and it will always have the possibility of being consumed.
Another effect of the plastic particles floating to the surface, aside from being more
susceptible to absorbing surface toxins and UVB radiation, is that they are accessible by
euphotic organisms, such as plankton. Euphotic organisms are organisms that live within
the photic zone – also known as the euphotic zone, or sunlight zone – of the ocean, which is
the upper layer of the ocean where enough light penetrates as to allow photosynthesis to
occur. Euphotic organisms include animals such as planktons, many fish (including sharks
and rays), and jellyfish.
Much like how humans live in a hierarchical society, with the poor at the bottom of
the ladder performing grunt work, and the rich at the top consuming the spent energy of
those below them, the natural world also functions in a pecking order – producers provide
energy for the system, primary consumers eat and absorb the energy of the producers, then
the energy proceeds up the consumer scale to the top predator. Plankton are primary
producers of the ocean, so that means they are at the base of the food web, ready to provide
energy for the rest of marine animals. If their population is disrupted, the entire ocean
ecosystem will be in danger.
As planktonic organisms are introduced to plastic particles at an increasing rate, their
populations will deteriorate, as such simple organisms are prone to being harmed when foreign
acts are issued. This, in turn, will have an even bigger impact on the ocean ecosystem, as
plankton is responsible for about 95% of productivity in the ocean (Stewart). Plankton are split
into two categories. Phytoplankton, also largely known as algae, are single-celled primary
producers, as they contain chlorophyll and are able to perform photosynthesis in order to produce
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energy. Examples of phytoplankton are diatoms and dinoflagellates. Zooplankton, on the other
hand, can be both single-celled or multi-celled, as they are the smallest floating animals, many of
which are larval forms of larger animals, such as jellyfish (Stewart). Zooplankton eat
phytoplankton, so they are known as primary consumers. Plankton live in the upper level of the
ocean, known as the photic zone.
With the introduction of microplastics to the ocean, it has been proven that the planktonic
species are in danger. These microplastics, the defining ingredient in many popular skin
cleansers, are invading Earth’s precious waters and being ingested by the animals that live there.
Filter feeding animals, such as zooplankton, take in microplastics, mistaking them for other
zooplankton or phytoplankton, their main food sources. When this happens, their internal
structures are unable to digest the plastics. These organisms are so small that their body mass
cannot consume and store plastics, as many other larger animals do. In many autopsies of
seabirds and fish, plastic pieces are found clogging the stomachs. However, due to the small size
of zooplankton, their bodies are unable to withstand the weight or mass of microplastics, and the
organism slowly dies. Wright establishes that microplastics “may accumulate within organisms,
resulting in physical harm, such as by internal abrasions and blockages. In addition to the
potential physical impacts of ingested microplastics, toxicity could also arise from leaching
constituent contaminants such as monomers and plastic additives, capable of causing
carcinogenesis and endocrine disruption (see Oehlmann et al., 2009; Talsness et al., 2009)”
(Wright et al 484). Ingested plastic clogs and scrapes the insides of marine organisms, resulting
in cancerous areas and obstructions during excretion. While some animals, such as sea birds, are
commonly found to have plastic within them that ultimately lead to their deaths, it is important to
consider the effects of microplastic ingestion within even the smallest of organisms when
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thinking about the ocean ecosystem. Plastics and toxins are also introduced to the food web once
the animals that have ingested them have been consumed by a predator.
Once microplastics are ingested by planktonic animals, the particles and toxins that have
been absorbed by the microplastics, as they are unable to degrade and in most cases unable to be
egested from the organisms, are then added to the food web. Outi Setälä, a marine biologist at the
Finnish Environmental Institute, studied the impacts of microplastics on the marine food web by
conducting experiments on marine copepods. One of her studies found that “mesozooplankton
and mysid shrimps showed that particles may transfer within the food web. Mysid shrimps were
exposed to the microspheres not only directly, but also indirectly, which implies that there are
several alternate routes for microplastic transfer in the pelagic food webs” (Setälä et al 81). What
is important about her findings is the fact that these mysid shrimps were affected both directly
and indirectly by microplastics. Directly – meaning the mysid shrimp were the organisms that
initially ingested the microplastics, and indirectly – meaning the mysid shrimp had gained effect
from phytoplankton or zooplankton prey that had initially ingested the microplastics. By
mentioning the pelagic food web, Setälä is addressing the ocean zone that is not near the coast,
but out in the open ocean. By conducting this study, Setälä found that there are multiple routes
that microplastics can be introduced and can travel through the marine food web.
Just as microplastics are transfer agents of toxins to plankton, contaminated plankton are
transfer agents to the rest of the marine food web. The marine food web makes up many kinds of
ecosystems that are the home to all of the ocean’s inhabitants, so spreading toxins through the
food web is dangerous to all the oceans ecosystems. Alan W. White, a biologist at Fisheries and
Environmental sciences “conclude(s) [through various studies on marine fish, copepods,
barncales, and zooplankton] that there exists a fairly general mechanism for transmission of G.
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excavata toxins through herbivorous zooplankton to animals at a higher trophic level and that G.
excavata toxins can cause fish kills as a result of herbivorous zooplanktons acting as vectors”
(White). Paralytic toxins are found in protist excavates known as Gonyaulax excavate, which are
a type of dinoflagellate phytoplankton. While the dinoflagellates are known to absorb these
paralytic toxins, much like how microplastic absorbs ocean water toxins, zooplanktons consume
the G excavate phytoplanktons. As a result, the G excavates act as trajectories and pass on the
paralytic toxins to the zooplanktons. When fish consume these zooplankton, the zooplankton
then becomes the vector, and the fish then carries the paralytic toxins. While these toxins do not
originate from microplastics, it is important to recognize that plankton, as the base of the food
web, once introduced to microplastics, have the ability to transfer the toxins contained within
those plastics through the food web, acting as vectors to higher trophic level organisms, thus
sending harmful chemicals into the entire ecosystem.
Not only do plankton aid in the introduction of toxins to the food web, but also their
population, as primary subjects that ingest microplastics, is harmed by the harvested
microplastics. G.E. Walsh, a biologist at the Environmental Research Laboratory of the United
States Environmental Protection Agency, mentions that “when Burnett (1973) fed a marine
copepod, Tigriopus sp., phytoplankton exposed to DDE, growth rate and egg production were
reduced” (Walsh 268). DDE, or Dichlorodiphenyldichloroethylene, is a chemical compound
similar to DDT, except it lacks hydrogen chloride. DDE rarely excretes from the body, so it
accumulates within an organism over the course of its life. In the case of this experiment, the
DDE infected the phytoplankton, which was then passed onto to contaminate the copepod once
the copepod ingested the phytoplankton. The effects of DDE contamination caused a decrease in
both growth rate and egg production. When considering the chain effect through trophic levels of
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this chemical, three things can happen. First, the population size of each organism within the
hypothetical food chain would be infected with DDE, and in turn would most likely grow at a
slower rate while producing less offspring. Second, due to each consecutive organism
contracting DDE, the entire food web would then be infected, and the ecosystem it is a part of
could deteriorate due to the decline of certain organisms within the food web. Third, plankton, as
the base of the food web, plays the most important role as the primary energy producer. If its
numbers decrease, then less food is available for higher trophic levels, thus causing a decline in
the entire ecosystem, even before the toxin spreads.
While it can be argued that plankton are more important than other organisms to ocean
ecosystems when considering microplastics entering a food chain, some people argue that we
must focus our attention to the top predators, or highest point of a food chain that consume all
lower tiers. As presented by Bjorn Carey, Neil Rooney of Canada’s University of Guelph
mentions that top predators act as a regulator to food chains – they keep the populations of their
prey in check. If a top predator is wiped out, then the lower consumers of the food chain will
become overpopulated, causing problems for the entire food chain as then certain animals will
populate out of control, while others will become overeaten (Carey). Top predators are an
important presence in food webs, yet they do not face the same threat that producers, such as
plankton, do when microplastics are introduced to their food chains.
Top predators may not normally directly consume microplastic particles often, unless the
top consumer, through the process of ingesting its prey first, then ingests the microplastic. While
microplastics have such a huge impact on plankton, it is important to consider the effects they
have on the entire food chain. If plankton is in danger by microplastics and toxins leached form
then, every other animal on the food chain will be as well, and each consumer organism will be
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in danger of decreased population growth and production. If the lower trophic levels dwindle in
population size, then the top predators would not have enough prey to hunt, ultimately causing
the top predator population to also decline, even without the introduction of microplastics to the
top predator’s body.
Microplastics have the ability to cause harm to the plankton that consume them,
lowering growth rate and population size, due to the ability plastic has to absorb toxins
while free floating debris, and then transfer these contaminants to their host organisms.
Animals can ingest and live their whole lives with plastic in their guts, the entire time in a
state of sickness while being leached contaminants from the plastics. Since plankton are at
the bottom trophic tier, if they ingest toxic microplastics, every animal later on in the food
chain will then be effected by the toxic material. Plastic doesn’t degrade – it remains a
constant and ever increasing dangerous invader in the natural world.
Many types of POPs, such as PCP and DDT are transmitted through manmade plastic
materials, such as PCE, PET, and LDPE to living organisms. These chemicals are foreign
invaders that pose a threat to marine life that are known to POPs pose a serous threat to
marine life, however the actual magnitude of their impact on marine food webs is still being
studied. It is vital to realize that plankton are key to the foundation of the oceans
ecosystems, as zooplankton regularly intake plastic particles thinking the particles are
phytoplankton. If us humans, the top predators of the marine food chain, make an effort to
retract microbead products from stores and regulate plastics efficiently, then hopefully in
the future the primary producers of the ocean food web, plankton, may have a safer, less
toxic, home to live and grow in.
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Although plankton are the ocean’s energy producers, which arguably name them the
most vital character of the marine world, there is still very little research concerning their
interactions with ocean pollution. Since their numbers are so large, yet since they are
microscopic organisms, it has been difficult for scientists to conduct studies with accuracy
in a given area. Many studies that involve plankton and microplastic interaction provide
estimations as to how much plankton is impacted, but no solid numbers are given for
targeted specimens. So far, microplastics have been studied extensively in relation to sea
birds and bony fishes, as it is a simple task to collect these animal corpses, then dissect
their stomachs as a way to measure plastic consumption. Researchers must find new ways
in measuring planktonic activity in order fully understand the impact microplastics have on
these specific organisms. Once foundation research is established for planktonic organisms,
scientists will be able to better understand the impact microplastic has on marine
ecosystems as a whole.
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Works Cited
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"International Campaign Against Microbeads In Cosmetics." Beat the Microbead. Plastic
Soup Foundation, 2015. Web. 15 Nov. 2015.
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Microplastics in Facial Cleansers." Marine Pollution Bulletin 58 (2009): 1225-228.
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Matus, Morgana. "Ocean Plastics Absorb Other Toxins, Become Even More Dangerous To
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Stewart, Robert R. "Marine Food Webs." Ocean World. Texas A&M University, 3 Aug. 2009.
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pag. Stanford. Web. 3 Oct. 2015.
White, Alan W. "Marine Zooplankton Can Accumulate and Retain Dinoflagellate Toxins and
Cause Fish Kills." Limnology and Oceanography 26.1 (1981): 103-09. American Society
of Limnology and Oceanography. Web. 14 Nov. 2015.
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