Are our seas now a snowglobe of microplastic?
Marine microplastics are posing increased risk to both ocean and human health, yet production and use of plastics is still growing exponentially. Public driven change is one of the most powerful mitigation tools and global awareness is key.
Written by Ellen McArthur
As a third year undergraduate in Marine Biology, the prospect of finishing university was daunting, I felt lost within my scientific field and lacked passion for any specific niche I had studied within it. Signing up for a Master’s degree was partly because I wasn't ready to face postgraduate life, but also because I wanted the opportunity to find my forte, a speciality, within which I could direct my energy. This was the main reason I chose to study Marine Biology in the first place. Without trying to sound overly cliché, this choice allowed me to produce work of which I am most proud, meet people I will continually aspire to and gain knowledge that both astonished and empowered me, fuelling my desire to share it with whoever may listen.
A general overview of Microplastics
Understanding the history and background of microplastics, what they are, where they originate and how they come into contact with marine life, is essential for us to comprehend their ecological impacts as well as determine methods to mitigate their harm to the environment.
Microplastics are commonly described as ‘ubiquitous’ within the ocean, a term meaning ever present. This is due to their presence within every marine environment, from the great depths of the Mariana Trench, to the shores of the Caribbean Sea. The ocean is contaminated by many different pollutants: oil, noise and light, however the most substantial is now marine plastic, and microplastics specifically are believed to account for 92% of this pollutant. Marine plastic can be categorised as either macro or microplastic. Macroplastics are items over 5mm in size, whereas microplastics are items smaller than 5mm, commonly those between 1-5mm. To date, over 800 species of marine life have been detrimentally affected by plastic. Microplastics in particular are generating growing concern over their impacts upon ecosystem health: their small size makes them easily eaten by a multitude of species and evidence of their adverse effects is becoming extensive.
Plastics are notably diverse in their looks, textures and characteristics. Microplastics can be categorised into 5 different groups (Foams, Fragments, Fibres, Sheets and Industrial Pellets) and these groups are directly linked to their original source. Marine microplastics come from both primary sources (plastics manufactured or released directly into the ocean at a size of less than 5mm) and secondary sources (marine macroplastics that have degraded into pieces less than 5mm in size through natural processes such as wind and weathering, UV exposure and wave action). Knowing the specific origin of a microplastic and how it reaches the ocean is an essential part of trying to reduce and prevent their transportation pathways to the sea. Poor waste management and prevention problems are currently the most common reasons as to why plastic is reaching our oceans.
“Microplastics can be categorised into 5 different groups: Foams, Fragments, Fibres, Sheets and Industrial Pellets”
Emily Duncan 2018
Many studies have reported widely differing levels of microplastic within sea floor sand, beach sand, the seawater and within marine animals themselves. These variations are likely to be due to the broad range of microplastic characteristics that contribute to differing movements within the ocean. Some microplastics float and their movement is subject to wind and waves, some sink and reside upon the sea floor and both are subject to currents that transport them.
Ecological impact
Following multiple worrying news articles highlighting the inadvertent consumption of plastic and its possible impact on human health, one of the first questions you probably want answering is “How they are starting to affect our health?” I will try and answer this for you a little later on in the article, because although critically important, it is vital to first understand how microplastic affects the ocean and the organisms within it, before we can better understand how microplastics can affect us.
Microplastic impacts on ocean wellbeing are fairly unknown. While research into this is increasing, major hurdles exist, for example, the vast number of methods by which microplastics can cause harm, as well as the thousands of different organisms and habitats they can affect and the dramatically different ways in which they all respond. As a result, trying to quantify (put a value to) the threat that microplastics pose is practically impossible. However, research over the last few years has well demonstrated that microplastics cause harm to almost every species and environment they come into contact with, in both a direct and indirect way.
The impact of microplastics is a particularly complex issue, but one I shall attempt to explain as best as I can. Their small size allows them to be easily swallowed by numerous marine animals and so taken into their body: a process called ingestion. This is probably the most common method by which microplastics come into direct contact with marine animals and usually occurs as the particles are mistaken for food or accidentally swallowed in the water along with their food. The way in which an animal feeds has been found to have the most effect on how much microplastic an animal will ingest. For example shellfish such as oysters feed by filtering water through their bodies, this mechanism has been found to cause very high amounts of particle ingestion.
“Their small size allows them to be easily swallowed by numerous marine animals and so taken into their body: a process called ingestion”
https://www.ecosia.org/images?q=ocean+microplastics+#id=EE8B65F9D31CCCCBB3F7DE0D7C7044C67EF2A9CE
To any animal that has ingested microplastic, these particles hold no nutritional value, yet they frequently take up a large proportion of their digestive system. This would be like us, without realising, replacing a large percentage of our daily diet with celery, a vegetable with next to no nutritional value. After a while this would start to cause us some problems right? We’d start loosing weight and lacking energy? That’s just using celery as an example, an organic vegetable we are able to digest naturally. For these marine animals, they’re consuming foreign, artificial objects and the body’s natural reaction is to try to remove it. This is done through the energetically costly process of egestion, which not only removes the microplastic but also, at the same time, eliminates a proportion of much needed nutrients.
So now you have an idea of how the process of accidentally ingesting microplastics can have significant, detrimental consequences for marine animals. The list of species confirmed to have microplastic present within them is increasing. Between 2017 and 2018, 29 studies found microplastic within 90 different species including the iconic animals; seals, dolphins, whales, sharks, seabirds and sadly all marine turtle species.
Photo: Gumbo Limbo Nature Center, Inc.
“Between 2017 and 2018, 29 studies found microplastic within 90 different species including the iconic animals; seals, dolphins, whales, sharks, seabirds and sadly all marine turtle species”
Scientific research is dominated by studies confirming ingestion in different species, however, further research is needed to understand the effects of microplastic exposure (its presence within an organism or its environment) as it has been recognised that such exposure has many highly detrimental effects and our present understanding and knowledge of them is currently only scratching the surface. These effects are behavioural, physical and toxicological (the adverse effects of chemical substances on living things), which I shall briefly explain using examples from recent research.
Reduced swimming and movement is a behavioural effect of particle exposure and is found in many animals from fish to crustaceans. This reduced movement influences an individual’s ability to survive by decreasing its ability to catch prey as well as increasing its chance of being predated upon. Physical effects of exposure have been found in the form of increased stress response, leaving affected individuals more susceptible to sickness and infection. Toxicological impacts from microplastic exposure are probably the least well understood and you’ll see why in a moment. I’ve previously explained that microplastics differ vastly in their characteristics; this is also reflected in their chemical composition. Plastics contain thousands of variations of chemical additives such as plasticisers and flame-retardants. The combination of these chemicals is what gives each type of plastic its desirable characteristics e.g. flexibility, rigidity, hardwearing, non degrading, the list is endless, as are the combination of chemicals. As macroplastic breaks down within the ocean into microplastic and then microplastics themselves degrade, these chemicals escape through a process known as leaching.
“I’ve previously explained that microplastics differ vastly in their characteristics; this is also reflected in their chemical composition. Plastics contain many thousands of variations of chemical additives such as plasticisers and flame-retardants”
The diversity of plastics
Photo: archive.theplastiki.com
Photo: https://cartoondealer.com/image/53657929/vector-bacteria-virus-icons-set.html
Microplastic particles are also found to attract pollutants via chemical attraction, this is the result of the composition of the particles. These pollutants include heavy metals, PCBs (polychlorinated biphenyls) and PAHs (Polycyclic aromatic hydrocarbons), all of which are known to be harmful to life. These are classed as “adhered” pollutants. Finally, microplastic particles themselves provide a new habitat within the ocean, one that can be utilised by pathogens (bacteria, viruses and fungi). These can live on the surface on the microplastic particles, therefore as microplastic particles move within the ocean so do the pathogens allowing them to invade new marine environments and animals. So the toxicological impacts of microplastics are far reaching, they leach harmful chemicals, they attract pollutants and they transport invasive pathogens. When ingested by marine animals, the chemicals, pollutants and pathogens associated with the plastic particles hold potential to cause serious damage. This has been demonstrated in a variety of species e.g. fish and is manifested as neurotoxicity (adverse effects on the nervous system), lipid oxidative stress (cell damage as a result of an imbalance of electrons in the body) and erratic abnormal behaviour.
“So the toxicological impacts of microplastics are far reaching, they leach harmful chemicals, they attract pollutants and they transport invasive pathogens”
These pollutants, chemicals and pathogens have the ability to act synergistically, in combination, to cause significantly higher damage than if acting individually. The combined cumulative effect of these pollutants also decrease the affected organism’s ability to cope with further environmental stressors such as increased sea water temperatures or noise pollution. This is particularly worrying for warm water coral species that are already suffering from increasing sea temperatures and invasive species. Research now shows that microplastics are lowing their immunity and tolerance to these stressors, as well as providing new stressors such as pollutants and pathogens. In January 2018 the European Chemical Heath Agency called for an urgent evaluation of the risk that microplastic cause to both the environment and human health: the diverse and complex ways that microplastics are threatening all oceans and many of the organisms within them provides a bleak outlook for species already suffering from environmental changes.
“In January 2018 the European Chemical Heath Agency called for an urgent evaluation of the risk that microplastic cause to both the environment and human health.”
Trophic transfer of microplastic
Photo: Sarah Nelms 2018
The final blow and one that is highly important with regards to the impacts of microplastic on human health, is that of trophic transfer: If an organism at the bottom of the food chain ingests microplastic, lets say a crab, and this crab is then eaten by a fish, the fish will have indirectly eaten plastic. If this fish is then caught and consumed by us, then we ourselves have inadvertently eaten microplastic. Now you might be thinking, yes, I’ve eaten a fish that may have microplastic within it, but a fish fillet doesn’t contain its stomach or intestines so I wont have eaten the plastic. But this is where scientists are becoming more concerned. It has now been found microplastic particles less than 1mm are more easily transported across the lining of the gut and taken into the cells and tissues of an organism during digestion. Microplastic particles are therefore no longer confined to just the digestive system of marine organisms.
Photo: bigthink.com
A particular study I want to draw your attention to is one that looked into the presence of microplastic and artificial materials in mussels from both UK waters and supermarket imported sources. Artificial material was discovered in 100% of all samples and microplastic accounted for 50% of this. Furthermore 40-60% of the microplastic found was of a size small enough to be taken into human tissue cells from the gut. The microplastic levels and sizes identified in these mussels for consumption suggest that food safety management measures should be implemented. This is probably the study that shocked me the most during my research. These statistics branded themselves into my brain and I think they really put into perspective how personal this marine microplastic problem is becoming.
If you’re still unconvinced, then another study investigating microplastic contamination of sea salt in Turkey found particles in all supermarket stocked brands and estimated that on average a citizen could consume 248-302 particles of microplastic from sea salt alone. Another European study estimated the average seafood consumer could ingest up to 11,000 particles a year from shellfish alone. Microplastic contamination is now encroaching upon an increasing range of consumable produce, from seafood and sea salt, to bottled water, sugar, honey and even beer!
”The average seafood consumer could ingest up to 11,000 particles a year from shellfish”
It’s not all doom and gloom
I apologise for this bombardment of worrying facts and figures. I appreciate ignorance can be bliss, especially in our day and age of overwhelmingly bleak outlooks across so many aspects of our world. But there is good news and positivity to be shared too! The last few years have shown that increased public awareness and support is successfully driving positive change alongside scientific research and subsequent understanding. I strongly support this view: In 2017, our beloved Sir David Attenborough captured our hearts and our minds with his documentary Blue Planet II. The final episode focused on the impacts of marine microplastics and reached over 37 million people in the UK alone. 62% of the surveyed audience stated they wanted to make changes to their daily life to help reduce plastic impact in our oceans. On top of this, in 2018 the Collins dictionary announced the word of the year to be “single use” in reference to single use plastics. I read well over 300 scientific research papers during my masters year at Exeter University and one aspect that was mentioned more times than I can count was how successful the public are at driving positive change. Public awareness has resulted in improved waste management and the banning of plastic production in locations all over the world. I strongly believe that increasing our knowledge can equip us to make more informed choices and through my writing, I hope to promote better understanding.
“In 2017, our beloved Sir David Attenborough captured our hearts and our minds with the documentary Blue Planet II. The final episode focused on the impacts of marine microplastics and reached over 37 million people in the UK alone”
A call to action
No one can make drastic changes overnight. In this day and age living plastic free is almost impossible, especially if living on a budget; why are 3 x peppers wrapped in a plastic pack significantly cheaper than 3 loose peppers? I will never understand! Despite now knowing so much more, I admit that I am nowhere near close to living plastic free, but I like to think the most important thing is that I am making a daily effort to reduce the plastic I buy. I now peruse the supermarket isles and question whether I need a plastic wrapped 3 pack of peppers or a cling film wrapped plastic punnet of mushrooms on offer, or, would I survive with just two loose peppers and a handful of loose mushrooms for the same price? The answer is yes, and I like to think my food tastes better for it! Swapping plastic for paper bags, plastic for glass bottles and plastic for tin cans is definitely feasible.
Living by the coast and working as a RNLI beach lifeguard in Pembrokeshire National Park during the summer, I have witnessed first hand large amounts of marine plastic washed up on my beaches. It has also given me the opportunity to collect and dispose of it before it’s swept back out to sea. I like to think I’ve set a good example to the public and encouraged people to join me. Helping the environment can be done in any capacity, whether it’s a 2 minute beach clean as you walk your dog each morning, signing up to be a Big Blue Ocean Clean up ambassador (https://www.bigblueoceancleanup.org/become-an-ambassador) or reducing your plastic usage, it all makes a difference.
“I have first hand witnessed large amounts of marine plastic wash up on my beaches. It has also given me the opportunity to collect and dispose of it before it’s swept back out to sea”
For anyone inspired to make such efforts and changes after learning a little more about marine microplastic and the risks they are posing to our oceans, I thank you!
If you have any questions you would like to ask me please get in touch and email: ecm220@exeter.ac.uk
If you’re interested in the studies I have mentioned in this article, please take a look at the reference list of scientific papers.
Journal Papers referred to:
Title: Ecotoxicological effects of polystyrene microbeads in a battery of marine organisms belonging to different trophic levels
Author: Gambardella
Journal: Marine Environmental Research
Link: https://www.sciencedirect.com/science/article/pii/S0141113618301533
Title: The Mediterranean Plastic Soup: Synthetic polymers in Mediterranean surface waters
Author: Suaria
Journal: Scientific Reports
Link: https://www.nature.com/articles/srep37551
Title: Persistent marine litter: small plastics and cigarette butts remain on beaches after organized beach cleanups
Author: Loizidou XI
Journal: Environmental monitoring and assessment
Title: Do microplastics affect marine ecosystem productivity?
Author: Troost
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X18303965
Title: Presence of microplastics in benthic and epibenthic organisms: Influence of habitat, feeding mode and trophic level
Author: Bour
Journal: Environmental Pollution
Link: https://www.sciencedirect.com/science/article/pii/S026974911832712X
Title: Contamination of table salts from Turkey with microplastics
Author: Gündoğdu
Journal: Food Additives and Contaminants
Title: Monitoring plastic ingestion by the northern fulmar Fulmarus glacialis in the North Sea
Author: Van Franeker
Journal: Environmental Pollution
Link: https://www.sciencedirect.com/science/article/pii/S0269749111003344
Title: A critical perspective on early communications concerning human health aspects of microplastics
Author: Rist
Journal: Science of the total environment
Link: https://www.sciencedirect.com/science/article/pii/S0048969718301128
Title: Distribution and importance of microplastics in the marine environment. A review of the sources, fate, effects, and potential solutions
Author: Auta
Journal: Environment International
Link: https://www.sciencedirect.com/science/article/pii/S016041201631011X
Title: The true depth of the Mediterranean plastic problem: Extreme microplastic pollution on marine turtle nesting beaches in Cyprus
Author: Duncan
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X18306581
Title: Microplastics in mussels and fish from the Northern Ionian Sea
Author: Digka
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X18304685
Title: First data on plastic ingestion by blue sharks (Prionace glauca) from the Ligurian Sea (NorthWestern Mediterranean Sea).
Author: Bernardini
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X18305009
Title: On some physical and dynamical properties of microplastic particles in marine environment.
Author: Chubarenko
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X16302600
Title: Factors influencing the microplastic contamination of bivalves from the French Atlantic coast: Location, season and/or mode of life?
Author: Phuong
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X17309001
Title: Screening for microplastics in sediment, water, marine invertebrates and fish: Method development and microplastic accumulation.
Author: Karlsson
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X17305799
Title: Single and repetitive microplastics exposures induce immune system modulation and homeostasis alteration in the edible mussel Mytilus galloprovincialis
Author: Détrée
Journal: Fish and Shellfish Immunology
Link: https://www.sciencedirect.com/science/article/abs/pii/S1050464818305540
Title: Characterization of microplastic litter in the gastrointestinal tract of Solea solea from the Adriatic Sea
Author: Pellini
Journal: Environmental Pollution
Link: https://www.sciencedirect.com/science/article/pii/S0269749117332062
Title: Microplastics contamination in molluscs from the northern part of the Persian Gulf
Author: Naji
Journal: Environmental Pollution
Link: https://www.sciencedirect.com/science/article/pii/S0269749117328439
Title: Retention and characteristics of microplastics in natural zooplankton taxa from the East China Sea
Author: Sun
Journal: Science of the Total Environment
Link: https://www.sciencedirect.com/science/article/pii/S0048969718319600
Title: Plastic debris contamination in the life cycle of Acoupa weakfish (Cynoscion acoupa) in a tropical estuary
Author: Ferreira
Journal: ICES Journal of Marine Science
Link: https://academic.oup.com/icesjms/article/73/10/2695/2647104
Title: First detection of plastic microfibers in a wild population of South American fur seals
Author: Perez-Venegas
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X18306374
Title: Capture, swallowing, and egestion of microplastics by a planktivorous juvenile fish
Author: Ory
Journal: Environmental Pollution
Link: https://www.sciencedirect.com/science/article/pii/S0269749117338599
Title: Investigating microplastic trophic transfer in marine top predators.
Author: Nelms
Journal: Environmental Pollution
Link: https://www.sciencedirect.com/science/article/pii/S0269749117343294
Title: Microplastic ingestion ubiquitous in marine turtles
Author: Duncan
Journal: Global Change Biology
Link: https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14519
Title: Uptake and transcriptional effects of polystyrene microplastics in larval stages of the Mediterranean mussel Mytilus galloprovincialis
Author: Capolupo
Journal: Environmental Pollution
Link: https://www.sciencedirect.com/science/article/pii/S0269749118303609
Title: Polystyrene microplastics alter the behavior, energy reserve and nutritional composition of marine jacopever
Author: Yin
Journal: Journal of Hazardous Materials
Link: https://www.sciencedirect.com/science/article/pii/S0304389418306708
Title: Negative effects of microplastic exposure on growth and development of Crepidula onyx
Author: Lo
Journal: Environmental Pollution
Link: https://www.sciencedirect.com/science/article/pii/S0269749117330452
Title: Macro- and microplastics affect cold-water corals growth, feeding and behaviour
Author: Chapron
Journal: Scientific Reports
Link: https://www.nature.com/articles/s41598-018-33683-6
Title: Toxicological effects of irregularly shaped and spherical microplastics in a marine teleost, the sheepshead minnow (Cyprinodon variegatus)
Author: Choi
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X18301279
Title: Responses of reef building corals to microplastic exposure
Author: Reichert
Journal: Environmental Pollution
Link: https://www.sciencedirect.com/science/article/pii/S0269749117329536
Title: Toxicities of polystyrene nano- and microplastics toward marine bacterium Halomonas alkaliphila
Author: Sun
Journal: Science of the Total Environment
Link: https://www.sciencedirect.com/science/article/pii/S0048969718322174
Title: Toxicities of polystyrene nano- and microplastics toward marine bacterium Halomonas alkaliphila
Author: Magni
Journal: Science of the Total Environment
Link: https://www.sciencedirect.com/science/article/pii/S0048969718308295
Title: Effects of microplastic exposure on the body condition and behaviour of planktivorous reef fish (Acanthochromis polyacanthus)
Author: Critchell
Journal: PLOS One
Link: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193308
Title: Occurrence of microplastics in surface waters of the Gulf of Lion (NW Mediterranean Sea).
Author: Schmidt
Journal: Progress in Oceanography
Link: https://www.sciencedirect.com/science/article/pii/S0079661117300484
Title: Occurrence and distribution of microplastics in marine sediments along the Belgian coast.
Author: Claessens
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X11003651
Title: Spatial variability in the concentrations of metals in beached microplastics.
Author: Vedolin
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X17308366
Title: Microplastics cause neurotoxicity, oxidative damage and energy related changes and interact with the bioaccumulation of mercury in the European seabass,
Author: Barboza
Journal: Aquatic Toxicology
Link: https://www.sciencedirect.com/science/article/pii/S0166445X17303776
Title: Microplastics increase mercury bioconcentration in gills and bioaccumulation in the liver, and cause oxidative stress and damage in Dicentrarchus labrax juveniles
Author: Barboza
Journal: Scientific Reports
Link: https://www.nature.com/articles/s41598-018-34125-z
Title: Impacts of macro - And microplastic on macrozoobenthos abundance in intertidal zone.
Author: Bangun
Journal: IOP Conference Series Earth and Environmental Science
Title: Marine microplastic: Preparation of relevant test materials for laboratory assessment of ecosystem impacts.
Author: Kuhn
Journal: Chemosphere
Link: https://www.sciencedirect.com/science/article/pii/S0045653518316850
Title: Microplastics in mussels sampled from coastal waters and supermarkets in the United Kingdom
Author: Li
Journal: Environmental Pollution
Link: https://www.sciencedirect.com/science/article/pii/S0269749118302197
Title: Microplastic contents from maricultured and natural mussels
Author: Renzi
Journal: Marine Pollution Bulletin
Link: https://www.sciencedirect.com/science/article/abs/pii/S0025326X18302571
Title: Anthropogenic debris in seafood: Plastic debris and fibers from textiles in
fish and bivalves sold for human consumption
Author: Rochman
Journal: Science Reports
Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4585829/
Title: The environmental effects of microplastics on aquatic ecosystems.
Author: Ha
Journal: Molecular and Cellular Toxicology
Documentary: Blue Planet II
Available from: https://www.bbc.co.uk/mediacentre/latestnews/2018/plastics-watch
Site: Collins Dictionary
Available from: https://www.collinsdictionary.com/woty