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Limnetic Herbivory: Effects on Phytoplankton Populations and Primary Production
- Bergquist, A. M., Carpenter, S. R.
- Ecology 1986 v.67 no.5 pp. 1351-1360
- algae, alkaline phosphatase, biomass production, chlorophyll, grazing, herbivores, lakes, nutrient deficiencies, phytoplankton, primary productivity, zooplankton, Michigan
- Population—level and ecosystem—level responses of phytoplankton to grazing by zooplankton were determined in nutrient—enriched and unenriched enclosures in Peter Lake, Michigan. Species—specific net growth rates were determined, and chlorophyll a, primary production (PPR), and alkaline phosphatase activity (APA) were determined for each of three size categories of phytoplankton: <22 μm, 22—75 μm, >75μm. Thirteen of 16 dominant algal taxa were nutrient limited. Zooplankton reduced APA, an indicator of nutrient deficiency. Growth rates of grazed, nutrient—limited algae (< 30 μm) increased at low levels of zooplankton μμm) nutrient—limited algae increased or did not change as zooplankton biomass increased. These species—specific responses resulted in four— to fivefold changes in chlorophyll concentration and PPR. Overall, the stimulatory effect of nutrient regeneration by zooplankton overrode losses due to grazing, and caused net increases in phytoplankton biomass and productivity.