Monitoring Marine Environments

The oceans are the sink for many of man’s waste products and substances lost by accident. These quickly become enormously diluted, so that ocean dumping or discharging into estuaries or coasts provides a cheap and apparently safe method of disposal. Two factors can alter this. In some areas, polluted waters mix little with general ocean circulations. Pollutants in the relatively enclosed Baltic Sea and Mediterranean Sea can build up more rapidly than they would in the North Atlantic Ocean, causing local pollution problems. Secondly, a wide range of substances can be taken up by organisms and concentrated to many times the level found in the surrounding water (bioaccumulation). Seaweeds and marine invertebrates of many groups can concentrate some metals by factors of 10 000 to 100 000 times that found in seawater (Bryan, 1984). Further increases in concentration can occur as a result of biomagnification. That is, animals higher up the food chain may accumulate higher concentrations than found in their prey as a result of feeding on many prey organisms. Although biomagnification does not always occur, since higher animals can regulate levels of many substances in their bodies, top predators can often be exposed to pollutants several orders of magnitude more concentrated than might be expected from information on the rates of pollutant input into the sea.