<P> In addition to land runoff, atmospheric anthropogenic fixed nitrogen can enter the open ocean . A study in 2008 found that this could account for around one third of the ocean's external (non-recycled) nitrogen supply and up to three per cent of the annual new marine biological production . It has been suggested that accumulating reactive nitrogen in the environment may have consequences as serious as putting carbon dioxide in the atmosphere . </P> <P> One proposed solution to eutrophication in estuaries is to restore shellfish populations, such as oysters . Oyster reefs remove nitrogen from the water column and filter out suspended solids, subsequently reducing the likelihood or extent of harmful algal blooms or anoxic conditions . Filter feeding activity is considered beneficial to water quality by controlling phytoplankton density and sequestering nutrients, which can be removed from the system through shellfish harvest, buried in the sediments, or lost through denitrification . Foundational work toward the idea of improving marine water quality through shellfish cultivation to was conducted by Odd Lindahl et al., using mussels in Sweden . </P> <P> Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean . Eighty percent of marine debris is plastic--a component that has been rapidly accumulating since the end of World War II . The mass of plastic in the oceans may be as high as 100,000,000 tonnes (98,000,000 long tons; 110,000,000 short tons). </P> <P> Discarded plastic bags, six pack rings, and other forms of plastic waste which finish up in the ocean present dangers to wildlife and fisheries . Aquatic life can be threatened through entanglement, suffocation, and ingestion . Fishing nets, usually made of plastic, can be left or lost in the ocean by fishermen . Known as ghost nets, these entangle fish, dolphins, sea turtles, sharks, dugongs, crocodiles, seabirds, crabs, and other creatures, restricting movement, causing starvation, laceration, infection, and, in those that need to return to the surface to breathe, suffocation . </P>

Discuss several negative effects of water pollution. read more