Ecological processes influencing zooplankton productivity in highly dynamic estuarine transition zones

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Estuarine transition zones, were freshwater mixes with saltwater, are critical ecotones for entire river systems worldwide. These ecosystems have a high ecological value in terms of biological productivity which is strongly driven by physical properties such as estuarine re-circulation, tidal mixing and freshwater discharge. The St. Lawrence estuarine transition zone represents important retention and nursery zones for crustaceans and commercially important fishes. The high productivity and spatiotemporal heterogeneity of this highly energetic and complex estuarine ecosystem makes it an ideal site to study the influence of habitat interconnectivity on trophic relationships and biological processes. Even if it is recognized that population and community dynamics are regulated by trophic interactions and passive and active transport processes that determine environmental spatial complexity and interconnectivity (e.g., dispersion of resources, migration of organisms), the overall ecosystem significance of these processes in estuaries is not well understood. The objective of my research program is to understand the control mechanisms of secondary (zooplankton) productivity by considering intraspecific genetic diversity, trophodynamics and the degree of connectivity among discrete habitats of the estuarine seascape. I aim to significantly advancing our scientific comprehension of zooplankton secondary productivity patterns, as this knowledge is of crucial relevance to the conservation and sustainable utilization of marine resources and ecosystem health in an ecosystem-based management approach. At the same time, this knowledge is essential to complement our understanding of the trophic turnover from primary production to tertiary trophic levels, as zooplankton often represents the nutritional basis for upper trophic levels (e.g. fish). We will focuss on the most important estuarine species, such as copepods, mysids and fish larvae. We will determine links between the temporal and spatial variability in Eurytemora affinis secondary production, and genetic diversity and trophic interactions throughout the estuarine transition zone. We will estimate the degree of trophic interactions between E. affinis clades and mobile consumers (mysids, fish larvae). Results on E. affinis clade productivity and the strength of trophic linkages may help predicting larval fish recruitment in this important nursery zone. This will be of importance for the management of the re-introduced striped bass.