Environmental forcing of primary production in arctic and subarctic seas

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Boreal marine ecosystems are highly sensitive to climate change. Perturbations are most acute in the Arctic, where temperature increases steadily and the ice cover declines rapidly. Hemispheric changes in the circulation of oceanic water masses, the incidence of extreme weather events and the freshwater content of the upper ocean alter vertical mixing in surface waters and the long-range dispersal of nutrients and organisms. Through their effects on the growth conditions of phytoplankton, these changes are likely to affect food webs and the oceanic drawdown of atmospheric CO2 (which mitigates global warming). Our present knowledge of phytoplankton ecology in relation to climate variability and change is insufficient to assess the current and future state of northern marine ecosystems. The long-term objective of the proposed research is to quantify and predict the major effects of environmental forcing on primary production in Arctic and subarctic seas. Two fundamental questions will be addressed by the initial five-year plan: what controls the (1) species dominance and (2) magnitude of primary production? Data from ship-based process studies, in situ sampling observatories and controlled experiments with phytoplankton cultures will be combined to test the working hypotheses. A suite of key phytoplankton variables will be quantified with and without experimental manipulations of light, temperature and nutrients. Bloom-forming phytoplankton will be isolated and taken to the home laboratory to quantify their growth dynamics across gradients of light, temperature and nutrients. Collectively, the results are expected to increase our fundamental understanding of phytoplankton processes and provide the data necessary to parameterize models and simulations of environmental forcing. The benefit to Canada will be greater knowledge of critical ecosystem processes and, in the longer term, greater capacity to anticipate and manage change in climate and marine renewable resources.