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• 1. [Article] Phytoplankton productivity and response to altered nutrient content in lakes of contrasting trophic state

  Lakes Findley, Chester Morse and Sammamish, Washington, are characterized by one major outburst of phytoplankton productivity and biomass (mainly diatoms) with usually no or low fall activity. Vernal outbursts ...

  Citation × Citation Citation Abstract Copy Title: Phytoplankton productivity and response to altered nutrient content in lakes of contrasting trophic state Author: Rock, C. A., U.S. International Biological Program. Coniferous Forest Biome, Hendrey, George R., Welch, E. B. (Eugene B.), University of Washington Lakes Findley, Chester Morse and Sammamish, Washington, are characterized by one major outburst of phytoplankton productivity and biomass (mainly diatoms) with usually no or low fall activity. Vernal outbursts were often delayed in some lakes and years probably by unfavorable climate (snow cover and cloudy rainy conditions). Mean spring-summer productivity ranged from 270 mgC/m² day in the most oligotrophic lake, Findley, to nearly 1000 mgC/m² day in mesotrophic-eutrophic Lake Sammamish. The range in mean Chlorophyll a content was 0.8 to 10 ug/l for the same lakes respectively. Mean biomass within and between the lakes was related to winter phosphorus content but not to nitrogen. However, nitrogen (N) and phosphorus (P) were simultaneously limiting productivity increase in the three lakes in summer. Carbon assimilation in response to added P showed increasing half-saturation constants for the natural phytoplankton progressing from oligotrophy to eutrophy. While diversion of over 1/2 the phosphorus from nearby Lake Washington during 1963-1967 was followed by reduction in winter mean P content and a rapid shift from eutrophy to mesotrophy (Edmondson 1970), mean winter P content and measured characteristics of plankton response have not changed significantly in Lake Sammamish following a diversion of similar magnitude. P availability in the water column (winter mean content) appears to be controlled by precipitation with Fe to a greater extent than in Lake Washington. Title: Phytoplankton productivity and response to altered nutrient content in lakes of contrasting trophic state Author: Rock, C. A., U.S. International Biological Program. Coniferous Forest Biome, Hendrey, George R., Welch, E. B. (Eugene B.), University of Washington Lakes Findley, Chester Morse and Sammamish, Washington, are characterized by one major outburst of phytoplankton productivity and biomass (mainly diatoms) with usually no or low fall activity. Vernal outbursts were often delayed in some lakes and years probably by unfavorable climate (snow cover and cloudy rainy conditions). Mean spring-summer productivity ranged from 270 mgC/m² day in the most oligotrophic lake, Findley, to nearly 1000 mgC/m² day in mesotrophic-eutrophic Lake Sammamish. The range in mean Chlorophyll a content was 0.8 to 10 ug/l for the same lakes respectively. Mean biomass within and between the lakes was related to winter phosphorus content but not to nitrogen. However, nitrogen (N) and phosphorus (P) were simultaneously limiting productivity increase in the three lakes in summer. Carbon assimilation in response to added P showed increasing half-saturation constants for the natural phytoplankton progressing from oligotrophy to eutrophy. While diversion of over 1/2 the phosphorus from nearby Lake Washington during 1963-1967 was followed by reduction in winter mean P content and a rapid shift from eutrophy to mesotrophy (Edmondson 1970), mean winter P content and measured characteristics of plankton response have not changed significantly in Lake Sammamish following a diversion of similar magnitude. P availability in the water column (winter mean content) appears to be controlled by precipitation with Fe to a greater extent than in Lake Washington. Close