| Affiliation: | (1) Center for Biodiversity Studies and Department of Biology, Western Kentucky University, Bowling Green, KY 42101, USA;(2) Environmental Monitoring and Assessment Program, U. S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA;(3) Department of Biology, University of North Carolina-Greensboro, Greensboro, NC 27402, USA;(4) The Ecosystem Center, Marine Biological Laboratory, Woods Hole, MA 12543, USA;(5) Present address: Department of Ecology and Evolutionary Biology, Cornell University, Corson Hall, Ithaca, NY 14853-2701, USA |
| Abstract: | We tested whether increased phosphorus and nitrogen concentrations would affect a lake trout (Salvelinus namaycush) population in a small oligotrophic lake with a benthically dominated food web. From 1990 to 1994, nitrogen and phosphorus were added to Lake N1 (4.4 ha) at the arctic Long-Term Ecological Research site in Alaska. We used mark/recapture methods to determine the lake trout population size, size structure, recruitment, and individual growth from 1987 to 1999. Data were also collected on water chemistry and food availability. Fertilization resulted in increased pelagic primary productivity, chlorophyll a, turbidity, snail density, and hypoxia in summer and winter. Lake trout density was not affected by the manipulation however growth and average size increased. Recruitment was high initially, but declined throughout the fertilization. These results suggest that lake trout were affected through increased food availability and changes to the physical characteristics of the lake. During fertilization, hypoxia near the sediments may have killed over-wintering embryos and decreased habitat availability. Although lake trout responded strongly to increased nutrients, loss of recruitment might jeopardize lake trout persistence if arctic lakes undergo eutrophication. |
