Bioremediation of waste
From Coastal Wiki
A significant amount of human waste settles on the seafloor, through wash off from land and through transport from rivers and estuaries. Waste settling on the seabed is stored, assimilated, diluted and recycled through chemical re-composition, processes which de-toxify and purify waste and are of critical importance to the marine environment. Marine organisms such as the polychaete worm, Nereis succinea, takes heavy metals through feeding on sediments.