Set in a wider context, the dolphin mortalities may be just one sign of a slow collapse of coastal environments.

In some parts of the USA, lobsters and crabs are covered with mysterious 'burn holes'. Nearly a third of Louisiana's oyster beds are routinely closed because of pollution and half the shellfish beds in Galveston, Texas, are off limits to fishermen.

In 1988-89, some 18,000 harbour seals died in the North Sea, a death toll that accounted for approximately 60 per cent of each colony. The primary agent responsible is believed to be a new virus of the morbillivirus group which resembles the virus that causes canine distemper. Morbilliviruses suppress the body's immune system and allow secondary infections to proliferate but many scientists believe that pollution may have effected the extent and severity of the die-off.

between 28 November, 1987, and 3 January, 1988, for example, 14 humpback whales were found dead on the beaches along Cape Cod and northern Nantucket Sound in Massachusetts. The whales were reported to have died after eating Atlantic mackerel which contained saxitoxin, another naturally occurring poison associated with red tides.

The countries which border the North Atlantic and other northern seas are some of the most heavily populated and highly industrialized in the world. The ocean is not only being depleted of its natural resources, it is also being used as a 'sink' for the waste products of millions of people and countless industries. Illustrating the magnitudeof the problem, Dutch marine mammal scientist, Dr Peter Reijnders, recently reported that only one per cent of existing PCBs has so far reached the world's oceans, and that an additional 40-50 per cent is likely to make its way there in the future.

It is possible that red tide themselves are becoming more frequent, because of the increasing amounts of nutrients from fertilizer and sewage which are reaching the sea. These feed the micro-organisms responsible for red tides, causing them to multiply at explosive rates. Climatic change and atmospheric degradation may also play a role in this.

Dolphins are at the rop of the marine food chain, and their health is an indicator of the condition of the entire aquatic environment. Perhaps the dolphin 'die-off' was a sign that, after decades of over-exploitation and abuse, the marine ecosystem simply cannot take any more.

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