Possible effect of lower phosphorus concentrations on the phytoplankton in Onondaga Lake, New York, U.S.A.

Abstract

Onondaga Lake is a heavily polluted, saline lake near Syracuse, New York. Since completion of a detailed study of this lake in 1969, lake conditions, including phytoplankton populations, have been monitored. A ban on phosphorus in detergents in Onondaga County (1971) and throughout New York State (1972) resulted in reduction of inorganic phosphorus concentrations in the surface waters of Onondaga Lake by approximately 50 %. A change in the summer phytoplankton was observed in 1972 and the next 2 years. Prior to 1972 flagellates and diatoms were common in spring. During summer green algae (Chlorococcales) and blue-green algae were dominant in the lake. Before 1972 nitrogen and phosphorus were present insufficient quantities to support observed growths of phytoplankton. Silica was depleted during diatom blooms. During 1972 to 1974 green algae persisted in large numbers throughout the summer, and blue-green algae were absent or rare. Absence of blue-greens probably did not result from direct limitation of their growth by low phosphorus levels.