Carbon and nitrogen burial in a plateau lake during eutrophication and phytoplankton blooms

Organic carbon (OC) buried in lake sediment is an important component of the global carbon cycle. The impact of eutrophication on OC burial in lakes should be addressed due to worldwide lake eutrophication. Fourteen Pb-210- and Cs-137-dated sediment cores taken in Dianchi Lake (China) in August 2006 (seven cores) and July 2014 (seven cores) were analyzed to evaluate the response of the organic carbon accumulation rate (OCAR) to eutrophication and algal blooms over the past hundred years. The mean value of OCAR before eutrophication occurred in 1979, 16.62 +/- 7.53 (mean value +/- standard deviation), increased to 54.33 +/- 27.29 gm(-2) yr(-1) after eutrophication. It further increased to 61.98 +/- 28.94 g m(-2) yr(-1) after algal blooms occurred (1989). The accumulation rate of organic nitrogen (ONAR) is coupled with OCAR. The high loss rate of OC and organic nitrogen (ON) leads to a long-termburial efficiency of only 10% and 5% of OC and ON. However, this efficiency can still lead to an increase in OCAR by a factor of 4.55 during algal blooms in Dianchi Lake. Dianchi Lake stored 1.26 +/- 0.32 Tg carbon and 0.071 +/- 0.018 Tg nitrogen, including 0.94 +/- 0.23 TgOC and 0.32 +/- 0.14 Tg inorganic carbon, 0.066 +/- 0.018 Tg ON, 0.002 +/- 0.001 Tg nitrate nitrogen (NO3-N) and 0.003 +/- 0.001 Tg ammonium nitrogen (NH4-N) between 1900 and 2012. (c) 2017 Elsevier B.V. All rights reserved.