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Atmospheric nitrogen (N) deposition to lakes and watersheds has been increasing steadily due to various anthropogenic activities. Because such anthropogenic N is widely distributed, even lakes relatively removed from direct human disturbance are potentially impacted. However, the effects of increased atmospheric N deposition on lakes are not well documented. We examined phytoplankton biomass, the absolute and relative abundance of limiting nutrients (N and phosphorus [P]), and phytoplankton nutrient limitation in alpine lakes of the Rocky Mountains of Colorado (USA) receiving elevated (>6 kg N·ha−1·yr−1) or low (<2 kg N·ha−1·yr−1) levels of atmospheric N deposition. High‐deposition lakes had higher NO3‐N and total N concentrations and higher total N : total P ratios. Concentrations of chlorophyll and seston carbon (C) were 2–2.5 times higher in high‐deposition relative to low‐deposition lakes, while high‐deposition lakes also had higher seston C:N and C:P (but not N:P) ratios. Short‐term enrichment bioassays indicated a qualitative shift in the nature of phytoplankton nutrient limitation due to N deposition, as high‐deposition lakes had an increased frequency of primary P limitation and a decreased frequency and magnitude of response to N and to combined N and P enrichment. Thus elevated atmospheric N deposition appears to have shifted nutrient supply from a relatively balanced but predominantly N‐deficient regime to a more consistently P‐limited regime in Colorado alpine lakes. This adds to accumulating evidence that sustained N deposition may have important effects on lake phytoplankton communities and plankton‐based food webs by shifting the quantitative and qualitative nature of nutrient limitation.
Knowledge graph centered on Nutrient availability and phytoplankton nutrient l with 29 nodes and 187 connections. Top connected: Rocky Mountain Biological Laboratory, Shifts in lake N:P stoichiometry and nutrient limi, Crested Butte, Pekania pennanti, Zooplankton.
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