Dark survival strategies in benthic diatoms from polar waters

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The highly productive microphytobenthos of polar shallow water zones is dominated by diatoms which have to cope with long periods of darkness between late autumn and early spring. Since the dark survival strategies of these organisms are almost unstudied, a comprehensive and precise evaluation of the underlying mechanisms will be carried out under controlled conditions in the laboratory with representative species abundant in the Arctic Kongsfjorden and the Antarctic Potter Cove. The mechanisms to be studied include the maximum survival period which will be determined using various cell biological markers (macromolecular composition, ultrastructure, viability, activity) as well as genetic markers (expression of functional genes involved in the degradation of chrysolaminaran and lipids). In addition, the capability to recover after re-irradiation by measuring growth and photosynthesis, and the effect of temperature on the dark survival potential will be evaluated. Arctic and Antarctic benthic diatoms will be compared to outline specific response patterns which are probably related to the different cold water history of both regions and hence to a different degree of adaptation to extreme low temperatures in the respective taxa. If environmental changes such as the observed Arctic warming are negatively affecting the dark survival potential of benthic diatoms, their ecological function as important primary producers in polar regions may be strongly reduced with consequences for all higher trophic levels.