Abstract
Atmospheric deposition of nitrogen (N) is a well recognised environmental problem. N is a higly important nutrient that together with phosphorus (P) regulates growth of phytoplankton in lakes. Increased N loading due to atmospheric deposition has not been treated as an eutrophication process since P is generally regarded as the prime-limiting factor in freshwaters. However, there are growing evidence that natural oligotrophic lakes, in areas with low input of atmospheric N, are N-limited. This project therefore aims to test if there are regional differences in nutrient limitation of phytoplankton growth in Swedish lakes and if such differences can be related to the atmospheric input of N to lakes. Thus, this project aims to test if N limits phytoplankton growth in areas with low N-deposition, if lakes are N+P limited in areas with moderately enhanced N-deposition, and if phytoplankton growth is P-limited in areas with high N-deposition. In addition, the studies will also investigate if N-deposition has caused eutrophication of naturally N-limited lakes in southern Sweden where N-deposition is enhanced, and if enhanced atmospheric N-loading affects the species composition and the succession of phytoplankton in Swedish lakes. Lake sampling and nutrient enrichment enclosure experiments will be conducted in large number of lakes in different parts of Sweden.
Sweden