Journal
JOURNAL OF PALEOLIMNOLOGY
Volume 65, Issue 3, Pages 335-352Publisher
SPRINGER
DOI: 10.1007/s10933-021-00175-z
Keywords
Diatoms; Recent climate change; Mercury; Lake sediment cores; Human impact
Funding
- Projekt DEAL
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The study found that even remote lakes, such as Lake Bolshoe Toko in eastern Siberia, are susceptible to the effects of climate change and human-induced pollution. Warmer air temperatures and shorter periods of lake-ice cover have led to pronounced thermal stratification in the lake. Mercury concentrations have increased as a result of atmospheric fallout, and an acidification trend has been observed.
Industrialization in the Northern Hemisphere has led to warming and pollution of natural ecosystems. We used paleolimnological methods to explore whether recent climate change and/or pollution had affected a very remote lake ecosystem, i.e. one without nearby direct human influence. We compared sediment samples that date from before and after the onset of industrialization in the mid-nineteenth century, from four short cores taken at water depths between 12.1 and 68.3 m in Lake Bolshoe Toko, eastern Siberia. We analyzed diatom assemblage changes, including diversity estimates, in all four cores and geochemical changes (mercury, nitrogen, organic carbon) from one core taken at an intermediate water depth. Chronologies for two cores were established using Pb-210 and Cs-137. Sedimentation rates were 0.018 and 0.033 cm year(-1) at the shallow- and deep-water sites, respectively. We discovered an increase in light planktonic diatoms (Cyclotella) and a decrease in heavily silicified euplanktonic Aulacoseira through time at deep-water sites, related to more recent warmer air temperatures and shorter periods of lake-ice cover, which led to pronounced thermal stratification. Diatom beta diversity in shallow-water communities changed significantly because of the development of new habitats associated with macrophyte growth. Mercury concentrations increased by a factor of 1.6 since the mid-nineteenth century as a result of atmospheric fallout. Recent increases in the chrysophyte Mallomonas in all cores suggested an acidification trend. We conclude that even remote boreal lakes are susceptible to the effects of climate change and human-induced pollution.
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