The modern era is witness to marked anthropogenic activities with rapid industrialisation, development and urbanisation. As a consequence the atmosphere, biosphere, hydrosphere and the lithosphere—all constituents of our earth, show increasing signs of pollution. While the atmosphere has shown a rise in the aerosol content and greenhouse gases, the land at most places is being turned into a barren wasteland with depleted groundwater and loss of soil nutrients.
Oceans are not only the last destination for rivers but also the final resting place for all the pollutants—physical and chemical, that rivers carry with them. Common manmade pollutants that reach the ocean include pesticides, herbicides, chemical fertilisers, detergents, oil, sewage and more. Among the wastes of different types, plastics are especially harmful. Its magnitude and the ill effects it causes to the marine ecosystem is unmatched. Plastic is a chemical substance that can never be completely eliminated. It can remain undegraded on the surface of the earth for years and incinerating it can increase the levels of many dangerous gases—carcinogenic fumes, in the atmosphere. Much of the avoidable wastes such as polythene bags, packing material for food items, water and soft drink bottles etc., openly discarded, find their way directly into the sea.
Estimating plastic waste in the oceans
As per a study (Eriksen et al, 2014), the North Pacific Ocean is the most polluted, containing approximately 38 per cent of plastic particles and 35.8 per cent of plastic mass. The oceans of northern hemisphere—North Atlantic and North Pacific—together contain 55.6 per cent of the plastic particles and 56.8 per cent of the plastic mass. In the southern hemisphere, however, the South Atlantic and the South Pacific Oceans contain less plastic particles and mass than the Southern Ocean and the Indian Ocean. According to the Environment Report of World Economic Forum of 2016 , the oceans will have more plastics than fishes by the year 2050 (World Economic Forum, 2016). Global annual plastic consumption has now reached over 320 million tonnes (MT) with more plastic produced in the last decade than
The Great Pacific Garbage Patch located between Hawaii and California accounts for most of the plastic and marine litter accumulated in the ocean. This Pacific Patch contains a total of 1.8 trillion plastic pieces weighing 79,000 tonnes, comprising debris categorised in four size classes: micro-plastics (0.05–0.5 cm), meso-plastics (0.5–5 cm), macro-plastics (5–50 cm), and mega-plastics (>50 cm). Researchers have collected 1,136,145 items and 668 kg of floating debris by trawls and found that more than 99.9 per cent of it is plastic material. It is estimated that an area of 1.6 million sq km holds ocean plastic concentrations ranging from tens to hundreds of kg per sq km. It was further outlined that only 1 per cent of the plastic floats above the water, while the remaining 99 per cent of it sits on the ocean floor or is swallowed by marine life such as fishes, turtles and other organisms. Through the sea creatures, plastic enters the food chain of birds and mammals (Leberton et al, 2018). Also, approximately 12,000 to 24,000 tonnes of fishes die annually in the North Pacific Ocean due to the swallowing of plastic.
As per one estimate, about 1 million seabirds (United Nations, 2017), 100,000 mammals and other marine creatures die each year by eating plastics or getting trapped in plastic wires and ropes. On February 27, 2018, a 10 m long sperm whale was found dead on the Cabo de Palos beach in Spain. About 29 kg of plastic and several kg of other garbage was found in her stomach. Similar cases are being reported from across the world. According to another estimate, scientists studied 233 fishes in a polluted area off the northwest Atlantic at depths of up to 600 m and found the presence of plastic particles in almost three quarters of fishes (Wieczorek et al, 2018). Similarly, the World Wildlife Fund (WWF) report published on World Ocean Day—June 8, 2018, reveals that the Mediterranean Sea, compared with open seas elsewhere in the world, had record levels of micro-plastics, with most waste coming from Turkey and Spain, followed by Italy, Egypt and France.
It is evident that anthropogenic intervention is especially responsible for the process of transporting plastic from human to sea creatures through the food web. Due to its durability, strength and low price, plastic has found wide usage in daily life in practically all segments of society. Plastic production on a global scale has increased from 100 MT in 1989 to 355 MT in 2016 (Statista, 2018), most of which is used in shopping bags, food packaging industries, bottled water and beverages, packaging of medicines, light machinery parts, computer parts and as accessories in the construction industry (PVC pipes, conduits for wires).
An article published in Science (Jambeck et al, 2015) revealed that in 2010 about 275 MT of plastic was produced in approximately 192 countries around the world—of this about 4.8 to 12.7 MT of plastic waste reached the oceans. Huge amounts of plastic waste have been discovered by environment scientists in the Pacific, the Indian and the Atlantic Oceans. The mound of giant waste floating in the sea between Guatemala and Honduras in the Caribbean Sea is currently a reason for tension between the two countries. In 2017, a ‘trash emergency’ was announced in Indonesia on Bali’s Noosa Penidah Island and some other beaches (Oliphant, 2017).
Pollution in Oceans | Plastic eating organisms
In 2015-16, researchers at the Stanford University, California and Beihang University, Beijing, China jointly found new types of plastic eating worms which can feed on polystyrene foam. It was found that several plastic eating worms like wax worms—the larvae of Indian meal moths, have special bacteria in their guts that can biodegrade polyethylene. Researchers found these insects can consume 34 to 39 milligrams of polystyrene per day (Jordan, 2015).
In April 2017, a similar research emerged from the University of Cambridge where a beetle-eating caterpillar that could also eat plastic was discovered. Scientists found that this caterpillar, Galleria melonella, had the ability to break the chemical composition of plastic. During the experiments, researchers found that just a few of these caterpillars could consume about 92 milligrams of plastic in just 40 minutes. These creatures not only ate plastic but also converted it into degradable substances (Bombelli and Howe, 2017).
In another interesting research published in April 2018, scientists from US, UK and Japan discovered an enzyme that has the ability to easily decompose plastic waste (Reuters, 2018). According to scientists of the US National Renewable Energy Laboratory and Portsmouth University of Britain, this enzyme—Ideonellasakaiensis, 201-F6 is able to digest polyester or polyethylene terephthalate (PET). However, the enzyme does not destroy the plastic, instead digests it to a benign waste.
Climate change and oceans
It is not only plastic but also global warming that is causing irreversible damage to the oceans and the marine life therein. Weiqi Yao et al (2018) have opined that “Though the consequences of global warming for fisheries are not well understood, but the geological record demonstrates that carbon cycle perturbations are frequently associated with ocean deoxygenation”. During the Palaeocene-Eocene Thermal Maximum (PETM), the CO2 emission scenario was similar to the recent Intergovernmental Panel on Climate Change projections. The sulphur isotope data from their study suggest that “during PETM significant parts of the ocean must have become sulphidic. The toxicity of hydrogen sulphide will render two of the largest and least explored ecosystems on earth, the mesopelagic and bathypelagic zones, uninhabitable by multi-cellular organisms. This will affect many marine species whose ecozones stretch into the deep ocean”
The need of the hour is to educate people about the damage plastics are causing. There is a need to develop an international agreement to reduce dumping of plastic waste in the sea and clear up the mess already created. Governments of all the countries should bring together legislations to boost recycling, ban single use plastics and phase out the use of micro-plastics in detergents and cosmetics. However, it is pertinent to note that most of the research discussed above is still in its nascent stages and it would be incorrect to consider these as a sufficient countermeasure for pollution from plastic—which is growing at a much faster rate than a panacea being developed.
Bombelli P. and C. Howe, 2017. Caterpillar found to eat shopping bags, suggesting biodegradable solution to plastic pollution, University of Cambridge, April 24.
Eriksen M., C.M. Lebreton, H.S. Carson, M. Thiel, C.J. Moore, J.C. Borerro, J. Reisser, 2014. Plastic Pollution in the World’s Oceans: More than 5 Trillion Plastic Pieces Weighing over 250,000 Tons Afloat at Sea, PLOS ONE, DOI: 10.1371/journal.pone.0111913
Jambeck J., R. Geyer, C. Wilcox, T. Siegler, M. Perryman,…and K. Law, 2015. Plastic waste inputs from land into the ocean, Science, 347 (6223): 768-771.
Jordan B., 2015. Plastic-eating worms may offer solution to mounting waste, Stanford researchers discover. Stanford News. September 29.
Lebreton L., B. Slat, F. Ferrari, B.S. Rose, J. Aitken, R. Marthouse,… and J. Reisser, 2018. Evidence that the Great Pacific Garbage Patch is rapidly accumulating plastic, Nature: Scientific Reports, 8(4666).
Oliphant R., 2017. Bali declares rubbish emergency as rising tide of plastic buries beaches. The Telegraph. December 28.
Reisser J., 2014. Plastic Pollution in the World’s Oceans: More than 5 Trillion Plastic Pieces Weighing over 250,000 Tons Afloat at Sea, PLOS ONE.
Reuters Staff, 2018. Plastic-eating enzyme holds promise in fighting pollution. Reuters, April 17.
Statista, 2016. Global plastic production from 1950 to 2016 (in million metric tons), Statista: The Statistics Portal.
Strange H., 2018. Sperm whale washed up on Spanish coast was killed by plastic pollution, The Telegraph, April 6.
United Nations (UN), 2017. The Ocean Conference Factsheet: Marine Pollution: UN. Available at: https://bit.ly/2BhCeM1
Wieczorek A., L. Morrison, P. Croot, A. Allcock, E. MacLoughlin, O. Savard…and T. Doyle, 2018. Frequency of Microplastics in Mesopelagic Fishes from the Northwest Atlantic, Frontiers in Marine life, 5:39.
World Economic Forum (WEF), 2016.The New Plastics Economy Rethinking the future of plastic: World Economic Forum. Available at: https://bit.ly/1Ou5wDU
World Wide Fund (WWF), 2018. Out of the Plastics Trap Saving the Mediterranean from Plastic Pollution:WWF. Available at: https://bit.ly/2Mb67Ph