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Nitrate-depleted conditions on the increase in shallow northern European lakes

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Nitrate-depleted conditions on the increase in shallow northern European lakes

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WEYHENMEYER, Gesa A., Erik JEPPESEN, Rita ADRIAN, Lauri ARVOLA, Thorsten BLENCKNER, Thomas JANKOWSKI, Eleanor JENNINGS, Peeter NỠGES, Tiina NỠGES, Dietmar STRAILE, 2007. Nitrate-depleted conditions on the increase in shallow northern European lakes. In: Limnology and Oceanography. 52(4), pp. 1346-1353. eISSN 0024-3590. Available under: doi: 10.4319/lo.2007.52.4.1346

@article{Weyhenmeyer2007Nitra-7200, title={Nitrate-depleted conditions on the increase in shallow northern European lakes}, year={2007}, doi={10.4319/lo.2007.52.4.1346}, number={4}, volume={52}, journal={Limnology and Oceanography}, pages={1346--1353}, author={Weyhenmeyer, Gesa A. and Jeppesen, Erik and Adrian, Rita and Arvola, Lauri and Blenckner, Thorsten and Jankowski, Thomas and Jennings, Eleanor and Nỡges, Peeter and Nỡges, Tiina and Straile, Dietmar} }

2007 Blenckner, Thorsten Nitrate-depleted conditions on the increase in shallow northern European lakes First publ. in: Limnology and Oceanography, 52 (2007), 4, pp. 1346 1353 We determined relative nitrate nitrogen (NO3-N) loss rates in 100 north mid-European lakes from late spring to summer by using the exponential function N2 = N1e -k(t2 - t2), where N1 and N2 are NO3-N concentrations at<br />the beginning (t1) and the end (t2) of the time interval, respectively, and k is the specific NO3-N loss rate. We found that k decreased with increasing lake depth. Adjusting k to the lake depth (k adj), we observed that k adj was<br />positively related to spring NO3-N concentrations, but this relationship became insignificant at mean lake depths exceeding 12.5 m. A relationship between k adj and spring NO3-N concentrations in lakes shallower than 12.5 m implies that changes in spring NO3-N concentrations influence the NO3-N loss rate and thereby summer NO3-N concentrations. Time series from one Estonian, one German, and 14 Swedish lakes shallower than 12.5 m since 1988 revealed that May to August NO3-N concentrations have decreased over time everywhere, and the number of time periods exhibiting a NO3-N depleted condition, i.e., NO3-N levels below 10 mg L21, in these lakes has tripled since 1988. We explained the decreasing NO3-N concentrations by a reduction in external nitrogen loading including atmospheric deposition, and by changes in climate. The observed prolongation of NO3-N depleted conditions might be one possible explanation for the increasing occurrence of nitrogen-fixing cyanobacteria in a variety of lake ecosystems. eng Weyhenmeyer, Gesa A. Adrian, Rita Weyhenmeyer, Gesa A. Arvola, Lauri Jennings, Eleanor Nỡges, Tiina Nỡges, Peeter Straile, Dietmar Adrian, Rita Jankowski, Thomas 2011-03-24T17:32:36Z Nỡges, Tiina Blenckner, Thorsten 2011-03-24T17:32:36Z Jennings, Eleanor application/pdf Jeppesen, Erik Jankowski, Thomas Jeppesen, Erik Nỡges, Peeter Straile, Dietmar Attribution-NonCommercial-NoDerivs 2.0 Generic Arvola, Lauri

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