Marine Debris in the Indian Ocean: Why Care?

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Iron Age, Bronze Age, and now the Plastic Age?
The multitude of lasting human-induced changes to natural environments since the Industrialisation of the 1950s has led to the suggestion that we have now entered the Anthropocene. Yet, another term is gaining more and more popularity – that of the Plastic Age (Corcoran et al., 2014). From toothbrush to footwear and mobile phones, all our daily routines are becoming more and more dependent on plastic. Many of the plastic products we use every day, we throw away after just a single use, for example drinking straws and shopping bags. Yet some single use plastics are less obvious in our daily lives. Did you know for example, that some of the most popular producers of face scrubs, body wash and even toothpaste use hundreds to thousands of microscopic plastic per bottle? So we have a good idea of where all the plastic comes into our lives, but where does it go after? Recklessly discarded plastic can be blown or flushed out to sea by winds and rain. Other plastic finds its way into the sewage system of towns and cities and then into the waterways. Even the most efficient sewage treatment plants cannot filter micro plastic out of our wastewater and it will ultimately get dumped into the ocean too. Once at sea the big plastic pieces undergo fragmentation, chiefly due to UV light breaking chemical bonds and waves and shorelines causing mechanical breakdown. Each broken piece contributes to numerous smaller pieces of plastic, all floating around the globe for decades to come.

You may wonder what harm a little piece of plastic can really do in the vastness of the ocean. In fact, in the threats are numerous. Many marine organisms, mammals, fish and bird species ingest these small fragments leading to a blockage of the intestines and ultimately starvation. Entanglement can also lead to suffocation. Where it interferes with their metabolic pathways and by selective consumption of plastic based on age-class or genera, plastic pollution may lead to altered assemblages of marine communities. Unfortunately, this is not the only way marine debris harm the ecosystem. Bigger pieces are ideal for biofouling, enabling hitchhiker organisms to travel beyond its natural geographical range, and become invasive species in marine environments lacking natural predators. Another harmful aspect of marine plastic is leaching of harmful chemicals used in its making, such as endocrine disrupting bisphenols or plasticisers. If this is not enough to concern you yet, plastic debris also provide a sorption surface for toxic persistent organic pollutants (POPs) already in the marine environment and helps concentrate those. Through ingestion of microscopic plastics in the lowest trophic levels these toxins can move up the food chain and become more and more concentrated through bioaccumulation. With a global demand for and dependency on marine food resources, marine plastic pollution is now becoming a major threat to human health – what goes in the ocean, goes inside us.

Global status, Indian Ocean
In the global oceans the Great Pacific Garbage Patch (GPGP) is the most infamous and well-studied hotspot of marine plastic pollution. The North Atlantic and Mediterranean Basin are rapidly following suit in terms of research efforts both from Europe and North America. Global collaborative efforts such as the International Pallet Watch exist but the southern oceans and the Indian Ocean (IO) in particular are still understudied. A recent report summarises the list of countries from where the most mismanaged plastic enters the oceans (Jambeck et al., 2015). Half of the top-20 countries in that list are the IO-rim countries. With all of the countries surrounding the Bay of Bengal (BoB) having made onto the list, a hotspot for marine debris accumulation similar to the GPGP in the BoB would be unsurprising. In fact, model estimations for plastic dispersal have identified the BoB as a hotspot for marine debris - both by number and by weight despite the paucity of field measurements (Eriksen et al., 2014). Another hotspot can be expected in the southeast Indian Ocean off the southwest coast of Australia due to the overall convergence of the Indian Ocean Gyre. Overall many of the Indian Ocean rim-countries are amongst the least developed or fastest growing economies. As such their dependence and on marine ecosystems for food security is particularly high. Plastic consumption and management skills in this area will determine the state of the marine plastic pollution in the Indian Ocean and beyond for decades to come.

Author: Dr Nimit Kumar, Scientist (ISG), Indian National Center for Ocean Information Services (INCOIS), Hyderabad.

References (Tip: search for these on Google Scholar!):

Corcoran, P.L., Moore, C.J. and Jazvac, K., 2014. An anthropogenic marker horizon in the future rock record. GSA Today, 24(6), pp.4-8.

Eriksen M, Lebreton LCM, Carson HS, Thiel M, Moore CJ, Borrero JC, Galgani F, Ryan PG, 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 9(12): e111913. doi:10.1371/journal.pone.0111913.

Friendly Floatees consignment incident: https://en.wikipedia.org/wiki/Friendly_Floatees

Jambeck JR, Geyer R, Wilcox C, Siegler TR, Perryman M, Andrady A, Narayan R, Law KL. Plastic waste inputs from land into the ocean. Science. 2015 Feb 13;347(6223):768-71

(Acknowledgement: A version of this article was originally published for scientific community in the Indian Ocean Bubble newsletter in collaboration with Sara Hajbane, doctorate student from School of Civil, Environmental and Mining Engineering, and UWA Oceans Institute, The University of Western Australia.)