Evolutionary adaptation of natural phytoplankton populations to warming

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Global warming is projected to alter temperature regimes across ecosystems. In the ocean, increased sea surface temperatures will affect marine organisms, with likely consequences for ecosystem functioning and biogeochemical cycles. Our present understanding of the biological consequences of ocean warming is primarily based on short-term experiments, while the potential for evolutionary adaptation is only slowly gaining attention. Fast reproducing planktonic organisms, such as phytoplankton, are particularly prone to respond to environmental change via evolutionary adaptation. The few laboratory selection experiments that have addressed evolutionary processes in phytoplankton suggest that adaptation can mitigate negative effects of climate change. However, the relevance of adaptation observed in the laboratory to natural populations remains to be resolved. One outstanding opportunity to investigate evolutionary adaptation in natural phytoplankton populations can be found in Swedish coastal waters where cooling water discharges from nuclear power plants have resulted in well documented local warming regimes. In these coastal areas the common diatom species Skeletonema marinoi forms locally restricted populations and genotypic changes can be followed over decades via resting stages preserved in the sediments. The proposed project aims to use these promising settings to assess the relevance of evolutionary adaptation to warming in two independent S. marinoi populations that have been similarly affected by warming over the last decades. A profound understanding of evolutionary processes will most likely be indispensable for reliably predicting biological responses to ocean change and is thus of pivotal relevance, not only to science, but also to policy makers and society.