I live in a beautiful tropical valley, with a river, near to it, that flows into the sea when there is heavy rainfall. It is planted in avodcados mangos bananas ect and I know it is chemically fertilized. I know this area for 25 years and have noticed that all living things have nearly vanished close to shore, the water is crystal clear but nothing alive. There used to be abundance of octopus, shrimp, sea horses, squid, scools of all kinds of fish and many things that lived on the bottom like crabs and flying fish. What I want to know can the nitrates from fertilizer accumulate in the silt near shore and destroy the habitate or might it be somthing else? If this is the cause and it was stopped how long would the sea take to recuperate? Do the nitrates fall to the bottom or are they in suspension? This is only a agricultural area no chemical waste of any type or factory are dumped into the sea. I saw a film on BBC about Fiji that had a problem with nitrates from fertilizer killing the coral reefs. They buildt retention ponds with plants that ate the nitrates and reduced the pollution to replant corral reefs.