Pelagic C:N:P Stoichiometry in a Eutrophied Lake: Responses to a Whole-Lake Food-Web Manipulation

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• 作者：James J. Elser ; Robert W. Sterner ; Amy E. Galford ; Thomas H. Chrzanowski ; David L. Findlay ; Kenneth H. Mills ; Michael J. Paterson ; Michael P. Stainton and David W. Schindler
• 关键词：Key words ; ecological stoichiometry ; cascading trophic interactions ; carbon ; nitrogen ; phosphorus ; plankton ; nutrient cycling ; food webs ; ecosystem experimentation ; cyanobacteria.
• 刊名：Ecosystems
• 出版年：2000
• 出版时间：May 2000
• 年：2000
• 卷：3
• 期：3
• 页码：293-307
• 全文大小：439 KB

文摘

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.