Responses of microbial phototrophs to late-Holocene environmental forcing of lakes in south-west Greenland
1. The biological structure of arctic lakes is changing rapidly, apparently in response to global change processes such as increasing air temperatures, although altered nutrient stoichiometry may also be an important driver. Equally important, however, are local factors (e.g. landscape setting, hydr...
| Main Authors: | , , , |
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| Format: | Text |
| Language: | unknown |
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DigitalCommons@University of Nebraska - Lincoln
2013
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| Online Access: | https://digitalcommons.unl.edu/geosciencefacpub/384 https://digitalcommons.unl.edu/context/geosciencefacpub/article/1388/viewcontent/Fritz_FB_2013_Responses_of_microbial__DC_VERSION.pdf |
| Summary: | 1. The biological structure of arctic lakes is changing rapidly, apparently in response to global change processes such as increasing air temperatures, although altered nutrient stoichiometry may also be an important driver. Equally important, however, are local factors (e.g. landscape setting, hydrological linkages and trophic interactions) that may mediate responses of individual lakes at the regional scale. Despite general acknowledgement of the importance of local factors, there has been little focus on among-lake variability in the response to environmental change. 2. Sedimentary pigments, organic carbon and nitrogen, and biogenic silica (BSi) in 210Pb and 14C-dated sediment cores from three contrasting lakes in the Kangerlussuaq area (c. 67°N, 51°W) of south-west Greenland were used to reconstruct algal and phototrophic bacterial ecological change during the late-Holocene. Water chemistry for the individual lakes varies in terms of conductivity (range: 30– 3000 μS cm−1) and stratification regimes (cold monomictic, dimictic and meromictic), linked with their position along the regional climate gradient from the coast and to the present ice sheet margin. 3. Despite essentially similar regional climate forcing over the last c. 1000 years, marked differences among lake types were observed in the phototrophic communities and their temporal variability. Considerable short-term variability occurred in an oligosaline, meromictic lake (SS1371), dominated by purple sulfur bacterial pigments, most likely due to a tight coupling between the position of the chemocline and the phototrophic community. Communities in a lake (SS86) located on a nunatak, just beyond the edge of the present ice sheet shifted in a nonlinear pattern, approximately 1000 cal. years BP, possibly due to lake-level lowering and loss of outflow during the Medieval Climate Anomaly. This regime shift was marked by a substantial expansion of green sulfur bacteria. 4. A dilute, freshwater coastal lake (SS49) dominated by benthic algae was relatively ... |
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