Ecosystem function in changing environments: an integrative approach to modeling the control of genetic biodiversity and secondary productivity by hydrodynamic circulation

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Coastal environments are severely stressed ecosystems due to a combination of human activities and natural processes.  The St. Lawrence estuary (SLE) is Canada's largest and most heavily impacted estuary due to a suite of stressors including pollution and over-fishing.  The keystone feature underlying this ecosystem is the pattern of circulation - the combination of currents and tides that both create water masses of distinct characteristics and transport organisms living in the water column either permanently or temporarily (i.e., the larvae of benthic invertebrates).  Circulation patterns will thus have profound effects on the population structure of species both by creating a heterogeneous environment that can support genetic diversity and local population stability and by controlling the dispersal of individuals between populations.  Ultimately these effects will influence secondary production, a key ecosystem function in the maintenance of food web structure and energy flow.  Here we propose to examine the influence of coastal and off-shore circulation on the population structure and secondary production of three key invertebrates, an estuarine copepod, a marine copepod, and a marine mussel, that together form the basis of secondary production in the SLE.  In parallel, we will describe the genetic and demographic structure of these species, examine how any such structure corresponds to hydrographic structures of the SLE and document the effect of this structure on ecophysiological performance. We will then use this information to develop models capable of predicting the secondary productivity under different environmental scenarios, including those associated with climate change (e.g., altered freshwater discharge).  We anticipate circulation patterns will have large effects on population structure with concomitant effects on the secondary production, a consequence of key importance in identifying the spatial scales and temporal stability of management units, a vital process in the development of governmental environmental policies for protecting the health of Canadian ecosystems.