Nutrient limitation in southwestern Greenlandic lakes
Nutrient limitation in aquatic systems has important implications for ecosystem processes and resistance to perturbation. While nutrient limitation, especially by nitrogen and/or phosphorus, is relatively well understood in temperate systems, arctic systems, especially those in the eastern North American arctic, remain understudied. We examined the role of lake morphometry, community composition, and landscape position on phytoplankton nitrogen and phosphorus limitation in nine kettle lakes near Kangerlussuaq, Greenland. We used in situ microcosms spiked with nitrogen, phosphorus, neigther, or both.
We found that lake summer stratification contributed to phytoplankton nitrogen limitation in two lakes. Some lakes' phytoplankton also exhibited rapid phytoplankton release when isolated from grazers in microcosms. For our systems, these results show that the physical processes and top-down control are two most important factors governing phytoplankton concentrations. These results also demonstrate that dominating ecosystem forces may be very different in lakes that are relatively close to one another in the arctic.