SAN FRANCISCO, Feb. 6, 2013 -- Nitrogen in ocean waters fuels the growth of two tiny but toxic phytoplankton species that are harmful to marine life and human health, warns a new study published in the Journal of Phycology.
Researchers from San Francisco State University found that nitrogen entering the ocean -- whether through natural processes or pollution -- boosts the growth and toxicity of a group of phytoplankton that can cause the human illness Amnesic Shellfish Poisoning.
Commonly found in marine waters off the North American West Coast, these diatoms (phytoplankton cells) of the Pseudo-nitzschia genus produce a potent toxin called domoic acid. When these phytoplankton grow rapidly into massive blooms, high concentrations of domoic acid put human health at risk if it accumulates in shellfish. It can also cause death and illness among marine mammals and seabirds that eat small fish that feed on plankton.
"Regardless of its source, nitrogen has a powerful impact on the growth of phytoplankton that are the foundation of the marine food web, irrespective of whether they are toxic or not," said William Cochlan, senior research scientist at SF State's Romberg Tiburon Center for Environmental Studies. "Scientists and regulators need to be aware of the implications of both natural and pollutant sources of nitrogen entering the sea."
Nitrogen can occur naturally in marine waters due to coastal upwelling, which draws cool, nutrient-rich water containing nitrate (the most stable form of nitrogen) from deeper depths into sunlit surface waters. Pollution, including agricultural runoff containing fertilizer and effluent from sewage plants, is also responsible for adding nitrogen, including ammonium and urea, to ocean waters, but in most regions these types of nitrogen occur at relatively low concentrations.
In laboratory studies, Cochlan and former graduate student Maureen Auro found that natural and pol
|Contact: Elaine Bible|
San Francisco State University