WATER RESOURCES RESEARCH GRANT PROPOSAL
Project ID: 2003OK16B
Title: Algal-nutrient dynamics in fresh waters: direct and indirect effects of zooplankton grazing and nutrient remineralization
Project Type: Research
Focus Categories: Nutrients, Non Point Pollution, Surface Water
Keywords: nutrient-algal ecology, zooplankton, grazing, nutrient cycling, nutrient supply, water quality, freshwater reservoirs
Start Date: 03/01/2003
End Date: 02/28/2004
Federal Funds: $24944.00
Matching Funds: $51759.00
Congressional District: 4th
Principal Investigator: Hambright, K. David
Abstract: Although nutrients
in freshwater lakes are ultimately from the watershed and atmosphere, most
primary productivity is maintained by planktonic nutrient regeneration ( remineralization).
Few comparative studies are available, but it is believed that regeneration
efficiency decreases with increasing trophy (i.e., oligotrogphic systems should
be based on efficient regeneration, while eutrophic systems are likely more
inefficient, relying on inputs from the watershed). Previous research in my
lab has documented that this paradigm may not be supported in reality, as
I found that in eutrophic Lake Kinneret, planktonic regeneration of nitrogen
and phosphorous could be as high or higher than 100 times the annual external
nutrient load. These results bring into question the propensity for limnologists
and freshwater resource managers to focus on external loads and in-lake concentrations
of nutrients with respect to algal abundances. Rather, it is logical that
not only productivity, but algal abundances and species composition in lakes
and reservoirs may be regulated through nutrient regeneration by planktonic
consumers (mainly crustacean and protest zooplankton).
The objective of this proposed research is to examine the role and magnitude of planktonic consumer-driven nutrient regeneration in mesotrophic Lake Texoma. Using laboratory mesocosm experiments based on consumer-food encounter rate models, I will quantify grazing rates and nutrient remineralization rates by both macro and micro zooplankton assemblages.
Data generated from these experiments will further our understanding of algal nutrient ecology in lakes and reservoirs by providing a first step in a detailed analysis of planktonic grazing and nutrient regeneration and thereby enable lake managers to more informatively design and implement management measures, including, but not limited to, food web manipulation and runoff regulation.