Plastic pollution in the marine environment and the marine food web 0

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Table of ContentsAbstract................................................................................................................................................2

Keywords.............................................................................................................................................2

Introduction..........................................................................................................................................2

Plastic pollution in the Earth’s oceans.............................................................................................3

How much plastic is there?..............................................................................................................4

What are microplastics?.....................................................................................................................6

Bioavailability of plastic pollution in the marine ecosystem........................................................8

Physical/Environmental impacts of macro/microplastic on the marine ecosystem........................9

Trophic relationships and the ingestion of Microplastics............................................................11

Apex predators and the effects of plastic pollution....................................................................12

Conclusion.........................................................................................................................................14

References..........................................................................................................................................15

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Plastic pollution in the marine environment and the marine food web.

Karl S. Jaeger

Abstract.Marine pollution has become a threat to the oceans of the world. Plastic

contamination has found its way into every area of the world’s oceans and has begun affecting the ecosystem. From general plastic waste to small particles of plastic now known as microplastics, these contaminants are beginning to accumulate and become a possible source of harm to the marine environment. (Andrady 2011) (Avio 2015)

This review outlines the current studies on the effects of plastic pollution in the marine environment and the possible deleterious effects of their presence in the marine food web. Topics covered in this review are the types of plastics found in the environment, the pathways they take to reach the water systems of the world, the formation of microplastic and the effects of the presence of plastic contamination in the marine food web and the organisms affected by them. (Derraik 2002) (Eriksson 2003)

Keywords Microplastic Biofouling Bioavailability Bioaccumulation Biomagnification Ecosystem Pollution

Introduction.Since the introduction of plastic into the industrialised world more than a century ago,

the accumulation of plastic pollution has become a growing concern. The increasing threat to the marine ecosystem by plastic pollution was brought to the scientific communities attention in the early 1970’s by E. J. Carpenter and K. L. Smith, with their findings from research into the effects of plastic pollution in the marine ecosystem. (Carpenter 1972)

Then when the Marine pollution (MARPOL) convention began the initiative to increase the worlds governmental involvement in controlling marine pollution by bringing to light the effects of plastic pollution, and by increasing the number of those involved in research. In doing so created an opportunity of the Environmental sciences to begin answering the questions of What types of plastics are involved? How much is there? Where is it coming from? Where is it located? and, What are the effects? It was then that the global community was introduced to the increase in the presence of plastic pollution. (Ryan 2009) The MARPOL convention along with other strategies such as the US National Marine Debris Monitoring Program (USMDMP), United Nations Environment Program, Algalita Marine Research Foundation and more recently the Marine Strategy Framework Directive (MSFD) in 2008, (Baztan 2014) (Kalogerakis 2015) have all begun addressing the presence of plastics in

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the world’s environment and what forms of monitoring and control need to be utilised. (Ryan 2009) The use of plastics in all aspects of manufacturing processes coupled with the advent of biodegradable forms of plastic to aid in the degradation process, have created a new form of plastic pollution which possibly presents a great threat to the marine ecosystem. (Kalogerakis 2015)

The increase in plastic pollution in the last ten years has been great, with an increase of approximately 40 million tonnes/year of plastic waste being produced during this period. (Thompson 2004) Microplastic is the term given to plastic particles ≤ 5mm, with plastic particles being found with diameters as small as 0.006mm (6µm). Microplastic pollution is what is left when modern starch and bioplastic based biodegradable plastic items break down leaving nonbiodegradable components behind as pellet like particles. (Thompson 2004) (Eriksen 2014) Microplastic pollution is relatively new and studies on the effects, location and types of material being found have begun piecing together an understanding of what the impacts of microplastics and general plastic waste on the worlds environments really are and where plastic pollution is doing the most damage. (Claessen 2013)

In this review I discuss the types of plastic found in the marine environment, and the fate of this plastic once it has entered the Earth’s environment, specifically the marine food web. Also the impacts of plastic pollution on the marine ecosystem, the different translocation vectors, effects of chemical interactions and the ingestion of this plastic by marine life are covered.

Plastic pollution in the Earth’s oceans.Pollution in the world’s oceans has developed into a major concern. Since the

discovery of plastic over a century ago, the waste created by modern industry has increased to 265-300 million tonnes/year worldwide (2009-2012). (Derraik 2002) (Hirai 2011) The waste from this accounts for around 60-80% of the pollution found in the marine environment with estimates made of around 268,940 tons afloat at sea. (Eriksen 2014) Today plastic is now thoroughly integrated into everyday society, from the food industry, vehicle manufacturing, packaging, science and now can be found in any home, and can be found in many different forms (Figure 1). (Claessen 2013) The structure and chemical composition affects the types of uses the materials will have. (O'Brine 2010)

With the advent of society’s understanding of pollution and the demands to create more readily degradable material, the production of materials such as polyethylene (PE), polyethylene terephthalates (PET) and recently the production of bio-degradable plastics such as Polylactic acid (PLA) and plastic containing TDPA a oxygen/UV activated bio-degradable plastic additive and starch based materials have increased dramatically. It is these plastics and their fate once they have entered the marine ecosystem is the focus of the topics to follow. (Moore 2008)

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Acrylonitrile butadiene styrene (ABS): Cases for electronics such as computers and monitors

High impact polystyrene (HIPS): Vending machine cups, food packaging, refrigerator liners

High-density polyethylene (HDPE) plastic #2: Beverage containers, cleaning product containers, shopping bags, cabling, pipes, wood composites

Low-density polyethylene (LDPE) plastic #4: Produce bags, flexible food containers,

shrink wrap, lining for cardboard, wire coverings, toys

Melamine formaldehyde (MF): Cookware and dishes, moldings, toys

Phenolics (PF) or (phenol formaldehydes): Insulation for electronics, lamination for paper, molding alternatives

Polyamides (PA): Nylon materials, car moldings, fishing line, toothbrushes

Polycarbonate (PC) plastic #7: Beverage bottles, DVDs and CDs, eyeglasses, traffic lights, lenses

Polyester (PES): Textiles Polyetheretherketone (PEEK): Medical implants, aerospace parts

Polyethylene terephthalate (PET) plastic #1: Beverage bottles, food film, microwaveable packages

Polylactic acid (PLA): Biodegradable beverage bottles and dishes

Polymethyl methacrylate (PMMA): Light diffusers for vehicles, contact lenses, Plexiglas

Polypropylene (PP) plastic #5: Large and small appliances, food containers, auto parts, pipes

Polystyrene (PS) plastic #6 :Foam products, food containers, CD and DVD cases, plates and cups

Polytetrafluoroethylene(PTFE): Coatings for fry pans (Teflon) and water slides

Polyurethanes (PU): Foam products for furniture and coatings

Polyvinyl chloride (PVC) plastic #3: Toys, pipes, shower curtains, flooring, windows, food films

Urea-formaldehyde (UF): Adhesives for wood, casing for electrical switches

Table1: Types of plastics found in marine debris.

How much plastic is there?The manufacture of plastics has increased approximately 150 fold since the early

1950s, from approx. 1.5 million tonnes in 1950 to 265-300 million tonnes in 2009-2012, with an estimated 6 million tonnes making its way into the marine environment every year. (Ivar doSul 2014) (Eriksen 2014) The sources of these plastics vary but can be traced back to any number of industries, also plastic debris from all populated areas can find its way into the marine ecosystem simply by accident. Discarded plastics in the forms of containers, bottles, bags, even fibres from clothing and more recently plastic beads found in modern cosmetics are finding their way into the sea. (Table 1) (Howell 2012)

The pathways of these plastics vary almost as much as the materials involved, with plastics making their way to the marine environment from inland locations and urban and coastal communities alike. Poor waste management in industry has allowed plastics to pollute inland river systems, creating a vector for plastic pollution to be carried to the oceans. (Howell 2012) Plastic refuse and discarded materials find their way to storm water runoff and

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waste water drains that lead to the inland river systems and in the case of some coastal areas, directly into the oceans. (Galgani 2014) Industries such as fishing and merchant shipping contribute greatly to marine pollution, with studies showing yearly estimates of 135,400 tonnes of fishing gear being discarded directly into the oceans, with observations of more debris being added to that by recreational fishermen. (Baulch 2014) Merchant shipping vessels create an estimated 639,000 tonnes of plastic pollution consisting of mainly plastic containers. (Howell 2012) More general plastic pollution such as packing materials, cups and containers make up some 23,600 tonnes in some studies. (Derraik 2002)

In Australia alone we use 1.3 million tonnes of plastic/year, with an estimated 50% of this making it to the ecosystem. (Reisser 2013) The presence of marine plastic debris in the oceans has presented a problem in the form of accumulation of masses of garbage, plastics making up 60-80% of these gyres created due to the ocean currents (Figure 3). (Eriksen 2014) These gyres can be found in each of the major ocean basins at intersections of oceanic currents, it is here that the most of the marine plastic debris can be found. (Ryan. 2014) It is these gyres that have become a major source of the plastic pollution found in the oceans of the world. Through the processes outlined in table 2 the plastic material is broken down into smaller pieces and begins its journey it the marine ecosystem. (Boerger 2010) (Eriksen 2014)

As there is very little data in relation to the amount of plastic found in the marine ecosystem, recent studies have made an attempt to quantify the amount by sampling the world’s oceans. A study headed by Marcus Eriksen has conducted sampling of all of the five Gyres and has trolled for samples from coastal Australia, Bay of Bengal, the Mediterranean sea as well as the North and South Pacific and Atlantic oceans. (Figure 2-3) This study was under taken with the help of institutions such as The Five Gyres project, Washington Fish and Wildlife, eCoast limited and the University of Western Australia. (Eriksen 2014) This study was conducted in an attempt to map the distribution of plastic pollution in the worlds marine environment and has revealed a disturbing result, with estimate made of 5.25 trillion pieces weighing up to 268,940 tons afloat in the world’s oceans. (Figure 2-3) (Eriksen 2014)

Figure 1: Locations of the five gyres (Eriksen 2014)

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Figure 2: Locations of sampling areas. (Eriksen 2014)

Figure 3: Distribution of plastics in the world’s oceans (size in mm) (Eriksen 2014)

What are microplastics?Microplastic pollution is classified as any plastic ≤ 5mm in diameter, although studies

have termed plastics that are capable of passing through 500µm-6µm sieve (0.500mm-0.006mm) are true microplastics (Figure 2-6) (Andrady 2011). Any samples ranging from >500µm-5mm as mesoplastics and samples <6µm are termed nanoplastics. This type and size of plastic pollution first came into recognition in the 1970s when researchers E. J. Carpenter and K.L. Smith found small particles of plastic in their studies into marine pollution in the North Atlantic. (Carpenter 1972) From the early 70’s to present date studies have identified the presence of microplastic in all of the world’s oceans, even as far as the Arctic and Antarctic regions. (Eriksson. 2013) (Carpenter 1972)

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Figure 4: Submicroscopic particles of PVC (shown via electron microscope).

The formation of microplastic is due to the effects of weathering, wave action, and abrasion of larger plastic against harder materials as the plastic makes its way to the oceans. (Table 2). Other forms of degradation include UV radiation acting upon the plastics and breaking them down over longer periods of time. (Table 2) (Hollman 2013) (Eriksen 2014)

Recent studies in Australian waters estimate there are around 500-24000 pieces of microplastic/km² (Figure 5). (Reisser 2013) Other global studies have put the estimate at around 46,000/1.6km², with some findings in the extreme scale of 100000/m². (Derraik 2002)

Biodegradation: Process of degradation by microbial organisms.

Photodegradation: Process of degradation by light (UV exposure).

Thermooxidative degradation: Slow process involving oxidative breakdown at moderate temperatures.

Hydrolysis: Reactions with water.

Table 2: Processes involved in the breakdown of marine debris. (O'Brine 2010) (Ryan. 2014) (Sivan 2011)

This sampling was conducted primarily in the euphotic and epipelagic region of the water column (figure 7), due in part to the plastics density allowing them to remain close to the surface in a salt water environment. (Derraik 2002) Microplastic has been reported in the mesopelagic region of the water column and in some studies samples have been taken from bottom sediments. (Moore 2008) Along with general plastic pollution being responsible for the formation of microplastic, facial cleansers, scrubs and other forms of cleaning products (figure 6) contain plastic particles that freely find their way into the marine ecosystem. (Fendall 2009)

Figure 5: Distribution of plastic pollution in Australian waters (Reisser 2013)

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Figure 6: Electron scanning microscopy image of microplastics extracted from shower gel. Photo Credit

A. Bakir and RC Thompson Plymouth University

Figure 7: Strata of the marine water column.

Bioavailability of plastic pollution in the marine ecosystem. Bioavailability is the term used to describe the presence of a specific element in an

environment and its availability to the biological system. A number of factors may influence the availability of plastic and the preferences marine organisms exhibit towards them. For example, the size (microplastics) and type of materials the fragments are made of (Table 1) can also influence the bioavailability of this pollution. The relative density of the plastic can affect the buoyancy of the plastic in seawater allowing the material to be spread throughout the water column (Figure 7). (Lobelle 2011) Other factors that can affect the bioavailability of plastic in the marine environment is the absorption of hydrophobic chemicals to the surface of the plastic. This process can change the relative density of materials in the aquatic environment by adding extra material to the particle. (Rochman. 2014) Recent studies have also shown that the accumulation of microbial colonies on the surfaces of plastic and the subsequent formation of biofilm, may contribute to the change of density of these materials. (Lobelle 2011)

This research has shown that the presence of microorganisms forming biofilms can cause changes in the relative buoyancy of the plastics allowing for a neutral buoyancy effect. (Lobelle 2011) This neutral aspect allows the plastics to move freely throughout the water column and once the microorganisms have completed their life cycle and begin to deplete in

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numbers, the plastic becomes buoyant and the cycle begins again. (Sivan 2011) Research into the colour of available plastics has revealed that there may be an effect on the availability macro/microplastic in the marine environment due to the varying range of colours in plastics that can often mimic the colours of the prey of visual predators, causing the plastics to be ingested as food. It is the bioavailability of microplastics in the marine environmental system that creates the opportunities for the ingestion of microplastics and facilitates the translocation into the marine food chain. (Baulch 2014)

Physical/Environmental impacts of macro/microplastic on the marine ecosystem.

Despite their small size, micro-plastics have been linked to a range of deleterious effects on marine species and their surrounding environment. (Avio 2015) (Rochman. 2014) The introduction of toxins formed by the degrading of these plastics have been found, and formation of biofilms created by microorganism attaching themselves to these plastic particles is now of interest to researchers. The presence of microplastics in the marine food web has raised questions of whether the plastics passing through the food chain are introducing the toxins commonly associated with plastic materials.

Recent studies into the ability of plastic materials to absorb and retain hydrophobic chemicals present in the marine environment as pollution have shown that microplastics can become a transmission vector for these hydrophobic chemicals. (Lee 2014) Studies involving experiments conducted under controlled conditions using materials commonly found in microplastics such as PE, PP, PS, LDPE and HDPE, as well as some heavy metal elements such as Cr, Co, Ni, Zn, Cu, Pb, Al, Fe and Mn have demonstrated that these materials have a high affinity for hydrophobic compounds. (Paul-Pont 2010) (Rochman 2014) These studies have determined that the materials found in microplastics have high sorption values that allow chemicals such as Polycyclic aromatic hydrocarbons ( PAH ), Hexachlorocyclohexanes ( HCH ) and Polybrominated diphenyls ( PBDE) and Chlorinated benzenes ( CB ) (figure 8) to bind to the surface of the microplastics and be transferred into the marine food web. (Bakir 2012)

Once these materials have found their way into the marine food web the desorption of the compounds into the biological systems of the organisms is a possible threat to the well being of marine organisms. (Baulch 2014) Studies have shown that the presence of one or more of the chemical compounds or elements mentioned before can possibly be translocated into the tissue of marine organisms. (Bakir 2012) Data was collected over two months in an experiment involving Japanese Medaka (Oryzias latipes). The fish involved in this experiment showed effects of Endocrine disruption with indicators such as down regulation of the hormones Choriogenin (Chg H), Vitellogenin (Vtg) and Estroer (Er α), with abnormal proliferation of germ cells in males. (Rochman 2014) The disruption of the Endocrine system may be attributed to the effects of chemical compounds used in the manufacture of plastics such as stabilisers, Phthalates and Nonylphenols which are known to have estrogenic and/or antiandrogenic properties.

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Figure 8: Examples of Poly Aromatic Hydrocarbons (PAH’s)

Further data pertaining to the possible effects of the desorption of chemicals into the systems of marine organisms has been collected from studies involving filter feeders such as mussels. (Schikorski 2013) Current research into the effects of microplastics on marine bird colonies has also revealed the presence of several of the chemicals mentioned above in the adipose tissue of the birds examined. Concentrations of higher Brominated cogeners such as BDE209 and BDE183 were found most likely to be the effect of exposure to PBDE, a chemical used as a flame retardant. Studies into the effects of this form of pollution have also shown that the release of these chemical compounds can be accelerated in the presence of surfactants similar to those found in warm blooded organisms such as stomach fluids under controlled conditions. These studies have indicated that warm blooded organisms may facilitate an increase in the desorption rate of these chemicals, this not only presents a risk to marine life but possibly all life that consumes sea life as food including humans. (Bakir. 2014)

As mentioned in the in the bioavailability Section 5, the presence of microorganisms on plastic pollution is of great interest to researchers. As chemicals bind to plastic surfaces so too can microorganisms. This relationship between microplastics and their surrounding environment is now of much interest to Environmental Microbiologists. The creation of biofilm can alter the plastic particles density and allow a neutral aspect to form, this can create an environment where microplastic can be located anywhere in the water column. (Lobelle 2011) The formation of these biofilms may to also present a health risk to the marine ecosystem. (Paul-Pont 2010) (Eriksen 2014)

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Although there is very little information of the effects of pathogens on microplastic, studies into the possibility that pathogenic organisms such as Vibrio bacteria specifically V. harvegi an aggressive marine pathogen and V. cholera a human pathogen are using microplastics as transport vector and can survive for quite some time without a host. These pathogens are regularly associated with mortality in fish, mussels and oysters farmed and wild. (Schikorski 2013) Further study into the effects of these pathogens on larger predators that consume these species is needed to further understand the possibility that these pathogens have any effect on humans. (Van Cauwenberghe. 2014)

Trophic relationships and the ingestion of Microplastics. Once the microplastic has entered the marine environment, it can be transferred from

species to species by simply being mistaken for prey. The risk of ingestion of plastics by marine animals is strongly influenced by the style of feeding of each particular animal. (Frias 2014) Zooplankton are typically found in the surface regions of the water column though some research has recorded findings at depths up to 25m.(Figure 7) Zooplankton can be divided into two main groups, holoplankton which include radiolarians, dinoflagellates, foraminifera, amphipods, and krill and the meroplankton which include most larval forms of sea urchins, sea stars, crustaceans, marine worms and most fish. (Setala 2014) The ingestion of microplastic at this level of the food chain can be attributed to the relative size and abundance of this material in the marine ecosystem. (Ivar do SulJ. 2013) The density of microplastic pollution increases in proximity to ocean gyres and it has been suggested these regions have become a source for the microplastic consumed by zooplankton. (Boerger 2010)

Studies conducted in the Baltic Sea show that zooplankton typically ingest plastic items around 1.7-30.6µm, but have also been observed to consume macro- particles up to

220µm. LDPE, PE and PP plastics are the most commonly recorded in zooplankton sourced from depths of up to 25m. Once ingested by zooplankton, controlled experiments have shown plastic items to be transferred to meso and macro-zooplankton within three hours. This would allow for the rapid accumulation of microplastic in macro-zooplankton before being consumed by a predator. (Baird 2011)

Filter feeders such as mussels, oysters and marine worms are being exposed to the effects of microplastic and there is possibly a risk to these organisms. Research into the ingestion of microplastic by Blue mussels (Mytilus edulis) and marine worms (Arenicola marina) have shown there was no significant change in the organisms ability to process nutrients, but changes in the animals metabolic rate were detected, this has been attributed to stress caused by the organism digestive process having to work harder once the plastic particles have been ingested. (Van Cauwenberghe L. 2015)

Under experimental conditions the samples of M. edulis were shown to have ingested an average of 0.200±0.300/g pieces of plastic and the marine worm A. marina consuming 1.200±2.800/g on average. (Van Cauwenberghe L. 2015) There was no significant change in the organisms ability to process nutrients, although the study does suggest that there is reason to consider the possible effect of chemicals desorbed by the plastic once the smaller particles are translocated to the circulatory system. Also the risk to human consumers of these marine species should be taken into consideration, as potentially a single shell fish can ingest 14000 pieces in its life time, this increases the chance of human consumption greatly. (Van Cauwenberghe. 2014)

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Oysters are consumed all over the world on a daily basis, an estimated 660000 tonnes/year of Cassotrea gigas are farmed, with studies showing that there is a possibility of oyster consumers being exposed to 11000 pieces of microplastics per year. (Van Cauwenberghe. 2014) Further research into the presence into of microplastic in aquatic filter feeders have revealed effects such as histological changes indicated by inflammatory responses, granulocytomas, lysosomal and gene transcription destabilisation with increased exposure times. (Avio 2015) Under experimental conditions levels of pyrene (a chemical used as a maker in experiments in translocation of PE and PS in filter feeders) have been found in the range of 126.000±35 ng/g to 244.000±52.000ng/g in the tissue of samples of M. edulis, C. gigas and M. gallopprovincialis, in the higher limit assays revealed gene disruption and other effects in the endocrine system. This is a good indication that chemicals that are being absorbed to plastics are being translocated into the tissue and circulatory systems of these filter feeder species. (Avio 2015)

Studies into the presence of microplastic being ingested by the fish population have revealed data similar to the zooplankton and shellfish research. (Carson 2013) Regions located in the areas of the gyres of the Earth’s oceans have seen increases in microplastic in a range of 300,000/km² in 1999 to 752,110/km² in 2008. (Boerger 2010) Studies carried out in the United States and the United Kingdom have shown that the species of fish sourced from off the west coast of the USA and from the English channel have had microplastic present in their gut.

The presence of this plastic in the Epipelagic and Mesopelagic regions (Figure 5) is again shown in reports of fish taken from these levels containing plastic material as well as zooplankton. (Lusher. 2013) Data from recent studies has also reported that the presence of LDPE, PET, PE, nylon and Styrofoam in the forms of granules and filaments consistent with discarded fishing gear and other forms of marine plastic pollution, with sizes in the range of 1-2.790mm with an average of two pieces per fish. (Lusher. 2013) From this position in the food chain microplastic has become a part of a larger sector of the prey predator food web, plastics can be transferred from fish species to larger species such as sharks, whales, seals, dolphins and seabirds. (Carson 2013)

Apex predators and the effects of plastic pollution.The discovery of microplastics in the marine environment has raised concerns of the

effect of this pollution on the higher feeders, the prevalence of these plastics in marine bird populations has been well documented, studies have been conducted into the effects of microplastics on marine bird colonies all over the world. (Tanaka 2013) These studies have all revealed similar data involving the ingestion of plastics causing malnutrition morbidity and deaths in many of the birds that had show the presence of plastics in their systems. (Lavers 2014) As has been discussed previously, not unlike any other feeding organism in the marine food web the birds of the marine ecosystem have mistaken plastic pollution for prey. This type of vector has been proven to be the most common in marine food web and facilitates the transfer of the plastics from species to species. (Donnelly-Greenan 2014) Studies of sea birds have found plastics ranging in sizes from micro particles ( ≤ 5mm ) to larger macro particles with size of 5mm2 to pieces of 5cm in length in birds.

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Figure 9: A marine bird choked by plastic and an example of plastics found in the marine environment. (Greenpeace, 2015)

Studies into the effects of plastic pollution have shown that this transfer vector has increased the possibility of the bioaccumulation of plastics in the marine food web and has proven to be a cause of mortality in marine bird colonies. (Donnelly-Greenan 2014) Research involving apex predators such as marine birds suggests that this bioaccumulation has become a concern as it facilitates the biomagnification of the toxins that have been introduced into the food web. Studies have shown that these effects not only occur in bird populations but in larger members of the marine ecosystem, with seals, whales, dolphins and marine reptiles being affected by the transfer of toxins through predator prey relationships. Some recent studies have shown that in bird populations the passing of plastics and related toxins through the parental vector to young can cause malnutrition leading to morbidity and mortality in the early stages of life. (Rodriguez 2012)

Apex predators are possibly the most at risk in regards to the deleterious effects of microplastic pollution, as the bioaccumulation of the plastics and toxins in prey target species increases the chances of larger predators being affected by the presence of these elements becomes more prevalent. (Lavers 2014) The seal populations of the world have become a focus point in the research of microplastics and general marine plastic pollution with studies carried out in the populations of Seals in Australia and Netherlands (Bravo Rebolledo 2013).

The vectors in which this plastic travel can lead to the accumulation of microplastic in prey species and subsequently find their way to the apex predators at the top of their respective food chains. (Eriksson 2003) The presence of plastic pollution in large marine mammals such as seals can be seen as an indication that the entire food web is being contaminated by plastic pollution. Studies involving seal populations around the world have shown that there has been an increase in the presence of plastics in the seal’s food web, with results from Netherlands showing the presence of plastic particles in the range of 4-8 pieces/stomach with masses averaging 1.423g in a range of 0.082-1.967g totals of 11.2% in the seals examined, with the most common material being found PP and PE plastics. (Bravo Rebolledo 2013)

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Research based on Macquarie Island in the sub-Antarctic waters off the southern coast of Australia has shown a presence of micro and macro plastics in the seal colonies of those waters, with a study revealing the presence of 164 pieces found in 145 scat samples taken over several years. (Eriksson 2003) From the samples collected 1990/91, the 45 samples contained 1 piece of plastic per sample analysed. The 100 samples taken in 196/97 85% contained 1 piece per scat, 12% had 2, 2% had 3 and 1% 4. The materials found were consistent with the common varieties of marine pollution such as PP, PE and other assorted materials like PVC and nylon, with sizes ranging from 2-5mm with some plastics up to 30mm found. Material found <2mm was not kept in this example, but was recorded. (unpubl) Colours of materials varied, with blue, red, yellow and green etc, items being detected. (Eriksson 2003)

Recent studies into the diet and feeding habits of seals have shown that these apex predators will travel distances of up to 200km in search of food. The diets of larger mammalian species such as Arctocephalus spp have wide variety of prey, with species like Cephalopods, ranging from Arrow Squid, Nototodarus gouldi and Calamari, Redbait (Emmelichtys nitidus), Barracouta (Thyrsites atun), Red Cod (Pseudophycis bachus), Jack Mackerel (Trachurus declivis) and Leatherjackets (Family Monocanthidae). (Kirkwood 2008) In these two examples of studies into the presence of plastic pollution in seal populations it was determined that the plastics could not have been consumed directly by the seals themselves but have made their way into the seal population by the vectors discussed previously in this review, again confirming that the presence of micro and macro plastic pollution can be found throughout the marine food web and the effects of bioaccumulation and biomagnification are quite clearly present. (Eriksson 2003)

ConclusionPlastic pollution in general the world over is now of great concern as it presents a

threat not only to the marine environment but the global ecosystem. It was the aim of this review is to discuss the presence of a genuine threat to the well being of the marine ecosystem and all those that depend on the condition and wellbeing of it. As is discussed in this review the presence of microplastic pollution in the marine food web and its effect on marine life is a relatively new field of study and little research exists on the real effects of this pollution on the organism that have contact with it. (Rochman 2014)

Recent studies have clearly shown that plastic pollution in all its forms presents a possible threat to the marine environment, as discussed in this review the extent of this pollution can been seen to be effecting the marine ecosystem in many areas, and it is only through further education of the global governments and their communities that we can begin to develop a better understanding of the increasing problems created by plastic pollution. (Kalogerakis 2015) (Eriksen 2014) Initiatives like the original MARPOL convention and recently the MSFD will make aware the increasing need to develop further research programs to be used to begin to control the increasing effects of plastic pollution in the marine ecosystem, if not in general the world’s ecosystem. (Kalogerakis 2015)

It is the field of Biotechnologies obligation to the global community to continue developing the necessary methods to deal with the ever increasing threat to the Earths ecosystem. (Kalogerakis 2015) As is discussed in this review studies have shown that there is a presence of micro/macro plastic pollution in the marine food web, that has shown to have

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possible deleterious effects on the organisms that have contact with it. (Lusher. 2013) From lower feeders such as zooplankton species and filter feeders like mussels/oysters through to higher Apex feeders such as seals, birds and fish etc, studies mentioned in this review have shown that there is reason for great concern as to the physical impacts to not only marine animals but to the marine environment in general. (Andrady 2011) (Lavers 2014) (Galgani 2014)

Further research into the physical effects of plastic pollution in the marine environment and the development of new methods of control and identification are necessary. In 2008 the MSFD outlined the recommendations of the areas of study that could greatly benefit the process of controlling this problem. Development of early warning systems using Biotechnological methods such as the use of biomarkers as a way of monitoring the wellbeing of marine organisms by providing an early detection method to assist in the monitoring of the general condition of the marine environment. (Kalogerakis 2015) Biosensors can become tools used to monitor the presence of biotoxins, contaminants and as mentioned in this review the disruption of transcription and translation in genes caused by the possible effect of pathogenic organisms or the desorption of chemicals carried by the microplastics. (Kalogerakis 2015) (Avio 2015)

The use of marine organisms to aid in the degradation process of plastics is a relatively new avenue of study in Environmental Biotechnology/Microbiology. Organisms such as Alkanivorax and Cycloclasticus species typical to the marine environment have shown a strong ability to breakdown HC compounds, others have displayed an anaerobic reduction reaction that can possibly aid in the dechlorination of toxic PCB plastics and compounds. (Kalogerakis 2015) These processes could then be utilised in the decontamination of plastic, marine pollutants such as hydrocarbon base materials and with further research the brake down of plastic material all together.

In conclusion there is sufficient evidence that there is need for concern for the presence of marine plastic pollution. The possible effects of this pollution not only present a threat to the plant and animal life of the marine ecosystem, but to all those that are dependent on it including humans (Van Cauwenberghe L. 2015). The studies mentioned in this review also present evidence that there is a need for continued research into the prevalence of and the physical effects of macro/micro plastic pollution in the marine food web.

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