Natural and plastic flotsam strading in the Indian Ocean

Over long periods of geological time the island rich NE Indian Ocean region has developed to be a region of high marine species richness but in the last few decades it has also become a generator of anthropogenic flotsam. Plastic proved such a success, it was disposable, and is now transforming ocean surfaces and shorelines. Sea voyages, coastal conservation and remote island visits started raising awareness of the problems of rubbish at sea in the Atlantic and Pacific Oceans. Household plastic items are now chiefly made in SE Asia and their use in that area where there is a very large human population density in contact with a large coastline results in disposable plastic items entering the surrounding seas. Surveys from Negombo in West Sri Lanka, Ari Atoll in the Maldives, Pemba Island in North Tanzania, Christmas Island, Cocos Island, Quirimba Island in North Mozambique, Rodrigues Island, Nosy Ve in South-West Madagascar and Inhaca Island in South Mozambique are reported. The accumulation of durable rubbish reaching even remote mid Ocean islands such as Christmas and Cocos islands is high and much of what was found stranded on shores was colonized by animals. The vast amounts of waterborne debris is almost certainly drastically changing opportunities for many marine organisms to travel and thus for exotic invaders to spread. Supralittoral hermit crabs on such remote Indian Ocean shores are even starting to use debris instead of the more usual gastropod shells as debris is so abundant. As in other oceans awareness of the problem and periodic clean up operations have grown but dumping at sea continues.

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