Nitrate nightmare

Published: Wednesday 15 September 2004

Oxygen deficit waters strangle (Credit: Naney Rabalais)A huge 'dead zone' of water has spread across 15,022 square kilometres (km) of the Gulf of Mexico. The dead zone is fed by rising use of nitrate-based fertilisers by farmers in the Mississippi watershed. The nitrates, carried into the gulf's waters by the river, feed algae blooms that use up oxygen and make the water uninhabitable.

A scientist at the Louisiana Universities Marine Consortium said measurements showed the area extended from the mouth of the Mississippi River in southeastern Louisiana 402 km west to near the Texas border. "Fish and swimming crabs escape (from the dead zone)," said Nancy Rabalais, the consortium's chief scientist for hypoxia, or low oxygen, research. "Anything else dies." Meanwhile, the situation has triggered a spate of shark bites along the Texas coast. Terry Stelly, an ecosystem biologist with the Texas Parks and Wildlife Department, said greater numbers of sharks have been found near the dead zone. Along with other factors, "chances are good they (sharks) were looking for higher dissolved oxygen in the water," he said.

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