A new study to be published in the academic journal Reviews in Fisheries Science recommends that efforts to restore the endangered California delta smelt and other declining pelagic fish should more sharply focus on reducing nutrient pollution to the species' native waters. The research indicates these fish populations would greatly benefit from reductions in the amount of nitrogen flowing into the Sacramento-San Joaquin Bay-Delta from wastewater treatment plants and balancing the ratio of nitrogen and phosphorus contained in the discharged water.
"While a great deal of emphasis has been placed on ensuring there is enough water for delta smelt, we also need to recognize that the water also has to have the right chemical balance," said Dr. Patricia Glibert of the University of Maryland Center for Environmental Science. "The research shows us that reducing the amount of nitrogen from Bay-Delta wastewater treatment plants should aid the recovery of the delta smelt population. The high nutrient loads are affecting the algae at the base of the food web, which in turn, affect the food supply for the fish. This has altered the ecology of the system over many years."
For her research, Dr. Glibert analyzed 30 years of water chemistry, river flow, plankton, fish population and effluent discharge data to determine possible linkages to the population of the delta smelt and other pelagic fish in the Bay-Delta system. The analysis reveals that declines in delta smelt population most closely coincide with effluent changes from the region's major wastewater treatment plant.
"The effect of nutrient loading on fish populations has been in debate for some time," said Dr. Glibert. "While the current rate of wastewater discharge is within established permit and nutrient criteria guidelines, the ecology appears to require environmental conditions more favorable than these guidelines. In this study, a broad-scale, long-term approach was taken to und
|Contact: Christopher Conner|
University of Maryland Center for Environmental Science