The oceans have long accumulated the waste products of civilization. Dumping at sea is banned, but to protect the marine environment we must also monitor litter on coastal lands and rivers.
(More)

 When first setting their eyes on the 7km-deep Cayman Trough in the Caribbean Sea in February 2013, Jon Copley and his colleagues discovered that, poignantly, a beer bottle had got there first1. That beer bottle is not alone. Human-made rubbish has been found in the world’s most remote oceans —and there is more and more of it. For example, repeated photographic analyses of the sea floor at Fram Straight2, the deepest entrance to the Arctic Ocean, showed that the amount of litter there doubled between 2002 and 2011.

Expanding shipping routes and more sea-borne traffic could be partly to blame for the large volumes of discarded human products, such as ship paint and fishing equipment, in remote places. Furthermore, locations at high northern latitudes such as Fram Strait are affected by climate warming, another human impact: receding sea ice opens new paths for human-made debris into the deep sea.

More at above link.