Pelagic C:N:P Stoichiometry in a Eutrophied Lake: Responses to a Whole-Lake Food-Web Manipulation
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Changes in the ecological stoichiometry of C, N, and P in the pelagic zone are reported from a whole-lake manipulation of the food web of Lake 227, an experimentally eutrophied lake at the Experimental Lakes Area, Canada. Addition of northern pike eliminated populations of planktivorous minnows by the third year (1995) after pike introduction, and in the fourth year after pike addition (1996), a massive increase in the abundance of the large-bodied cladoceran Daphnia pulicaria occurred. Accompanying this increase in Daphnia abundance, zooplankton community N:P declined, seston concentration and C:P ratio decreased, and dissolved N and P pools increased. During peak abundance, zooplankton biomass comprised a significant proportion of total epilimnetic phosphorus (greater than 30%). During the period of increased Daphnia abundance, concentrations of dissolved inorganic nitrogen (TIN) increased more strongly than dissolved phosphorus (TDP), and thus TIN:TDP ratios were elevated. Sedimentation data indicated that increased grazing led to greatly reduced residence times of C, N, and especially P in the water column during 1996. Finally, previously dominant N-fixing cyanobacteria were absent during 1996. Our results show that strong effects of food-web structure can occur in eutrophic lakes and that stoichiometric mechanisms play a potentially important role in generating these effects.
- Pelagic C:N:P Stoichiometry in a Eutrophied Lake: Responses to a Whole-Lake Food-Web Manipulation
Volume 3, Issue 3 , pp 293-307
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- Key words: ecological stoichiometry; cascading trophic interactions; carbon; nitrogen; phosphorus; plankton; nutrient cycling; food webs; ecosystem experimentation; cyanobacteria.
- Author Affiliations
- A1. Department of Biology, Arizona State University, Tempe, Arizona 85287 USA, US
- A2. Department of Ecology, Evolution, and Behavior, Unversity of Minnesota, St. Paul, Minnesota 55108 USA, US
- A3. Department of Biology, University of Texas at Arlington, Arlington, Texas 76019 USA, US
- A4. Freshwater Institute, Department of Fisheries and Oceans, Winnipeg, Manitoba R3T 2N6 Canada, CA
- A5. Department of Biology, University of Alberta, Edmonton, Alberta, T6G 2E9 Canada, CA