The ecology of <Emphasis Type="Italic">Pediastrum</Emphasis> (Chlorophyceae) in subarctic lakes and their potential as paleobioindicators |
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Authors: | Kaarina Weckström Jan Weckström Linda-Marie Yliniemi Atte Korhola |
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Institution: | 1.Department of Quaternary Geology,Geological Survey of Denmark and Greenland (GEUS),Copenhagen,Denmark;2.Department of Biological and Environmental Sciences, Environmental Change Research Unit (ECRU),University of Helsinki,Helsinki,Finland |
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Abstract: | Subarctic and arctic lakes are the focus of many paleolimnological studies, as they are still among the least impacted lakes
by humans. Hence they provide an excellent setting for studies on long-term climatic variability without the overriding effects
of direct anthropogenic perturbation. On the other hand, these ecosystems are highly vulnerable to even moderate anthropogenic
influence like long-distance airborne transport of nutrients and pollutants. The paleolimnological studies conducted in these
areas usually include a multitude of different proxies, but so far only few have used the green algal group of Pediastrum Meyen. These algae, however, preserve well in sediments and can be identified to species level, which lends them potential
as a paleo-proxy. In this study we analysed the present Pediastrum assemblages from surface-sediments of 16 subarctic lakes in Finnish Lapland as well as bottom samples from the same sediment
cores, which are “spot” samples from the recent past. We found a total of 14 Pediastrum taxa, five of which occurred at moderate to high relative abundances. The majority of the taxa showed distinct relationships
to environmental variables measured. Of these, pH and dissolved organic carbon (DOC) explained most of the variance in the
distribution of Pediastrum and generally summarised the main environmental gradients in our data set well. Five of the studied lakes lacked Pediastrum taxa altogether, and Pediastrum occurred at low abundances in four additional lakes. All of these nine lakes have extremely low nutrient concentrations and
generally lowest pH and DOC in the data set and were defined by barren catchment areas and scarce lake macrophyte growth.
According to a top–bottom analysis of sediment cores, the Pediastrum assemblages of the study lakes have changed moderately, suggesting changed environmental conditions in the lakes. Although
these changes appear to be climate-related, more studies are needed to confirm this hypothesis. |
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