This study will focus on the effects of multiple, climate related stressors on arctic lake ecosystems in three geographical regions (Northeast Siberia, Northwest Finland, Northeast Canada), which are showing diverse response to global warming. In many arctic regions, global warming is expected to lead to higher loads of organic matter entering lakes from catchment areas. This organic matter affects light attenuation and thereby mediates lake productivity. The effects of temperature, terrestrial organic matter (in the form of dissolved organic carbon, DOC) and UV-radiation on planktic and benthic algae and bacteria will be studied, combining means of data gathering, experiments and paleolimnology. In addition, the adaptive responses of algae to changes in UVR will be evaluated by measuring the existence of phototrophic pigments. Because also water level changes are expected, resistance of benthic algae to drying and freezing will be studied in the laboratory. In each region, three lakes with varying DOC concentrations will be studied for basic limnology, optical properties as well as pelagic and benthic biomass and production of algae and bacteria. Additionally, historical changes in fossil algal pigments and organic carbon will be analysed from lake sediments. This information enables the estimation of past changes in water column transparency, mainly regulated by colored organic carbon originating in catchment area vegetation and soil. Experimental set up will be conducted in situ in each region using full factorial design in which each stressor (DOC, temperature, UV) will be tested at two levels. In the experiment, the response of benthic and pelagic algae and bacteria for individual stressors as well as for their combined effects will be analysed by measuring changes in community structure, biomass and productivity. This study will give new insights on the role of arctic lakes in the global carbon cycle, especially on the possible changes in their level of net heterotrophy or autotrophy with regards to changes such as increasing loads of organic material entering lakes. By including benthic algae and bacteria a more realistic concept of lake functioning will be achieved, since a substantial part of photosynthesis often occurs in benthos in shallow arctic lakes.
|Gällande start-/slutdatum||01/01/2011 → 31/12/2013|
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