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Research article2009Peer reviewed

Atmospheric nitrogen-deposition may intensify phosphorus limitation of shallow epilithic periphyton in unproductive lakes

Liess, A.; Drakare, S.; Kahlert, M.

Abstract

1. We tested whether increasing atmospheric nitrogen (N) deposition along a north–south gradient intensifies epilithic phosphorus (P) limitation in oligotrophic Swedish lakes from the north to the south. We examined the epilithic community at a shallow depth from seven northern and six southern Swedish lakes, and also compared the results with a lake located geographically between the two groups. We determined lake nutrient state, epilithic nutrient ratios and epilithic algal composition, as well as grazer N : P ratios, grazer-epilithon N : P imbalance, and N : P cycling ratios. 2. Epilithic communities appear to be generally more N-limited in the northern lakes and more P-limited in the southern lakes. Lake water total N (Tot-N) and epilithic N : P ratios were lower in northern than in southern lakes and the proportion of N2-fixing cyanobacteria was higher in northern than in southern lakes. 3. Gastropod grazers had lower N : P imbalances and cycled less N relative to P in northern than in southern lakes. 4. Atmospheric N-deposition showed a strong positive correlation with lake water Tot-N and a much weaker positive correlation with epilithon N : P ratios. Atmospheric N-deposition also correlated negatively with the proportion of N2-fixing cyanobacteria. 5. There are indications that increased atmospheric N-deposition towards the south might intensify P-limitation of epilithic algae and invertebrate grazers, although more studies are needed to show the strength and generality of our findings

Keywords

benthos; latitudinal gradient; nitrogen-deposition; nutrient cycling; nutrient limitation

Published in

Freshwater Biology
2009, Volume: 54, number: 8, pages: 1759-1773