Late glacial and early Holocene climate and environmental changes in the eastern Baltic area inferred from sediment C/N ratio

We assessed the utility of using the sediment total organic carbon/total nitrogen (C/N) ratio as an indicator of paleoclimate changes in the eastern Baltic area during the late glacial and early Holocene. The C/N ratio in sediments from Lake Lielais Sve ̄tin ̧ u, eastern Latvia, was compared with other sediment variables that are used as proxies of past climate and environment. Analysis revealed that although the organic matter (OM) content in late glacial sediments was extremely low, the C/N ratio captured information about OM origin, and fluctua- tions in the ratio tracked climate oscillations. The C/N ratio was significantly positively correlated with pollen-inferred mean summer temperature. Therefore, C/N ratio was lower under colder conditions, indicat- ing a predominantly phytoplankton origin of OM, and was higher during warmer conditions, when there was more vegetation around the lake. A strong positive correlation between C/N ratio and the paleopigment beta carotene suggested that elevated phytoplankton production resulted from higher nutrient availability that was controlled largely by the input of terrestrial OM to the lake during warmer climate episodes. Thus, C/N ratio was a good indicator of paleoclimate changes, at least for the late glacial period, when generally cold conditions prevailed. This study also demonstrates the power of multi-proxy paleolimno- logical analyses for investigating past environmental changes in lakes and their watersheds.

This study was supported by the Estonian Ministry of Education and Research through institutional research funding (IUT1–8, IUT21–2, PUT1173), the Estonian Science Foundation (ETF9031) EBOR project and national basic funding for science project Y5-AZ03-ZF-N-110 ‘‘Dabas resursu ilgtspe ̄jı ̄ga izmantosˇana klimata pa ̄rmain ̧ u konteksta ̄’’ Nr. ZD2010/AZ03. This paper was revised by Elsevier Language Editing Services. Two anonymous referees and Co-Editor in Chief Mark Brenner provided helpful comments on the manuscript.