Riverscape structure and ecological processes

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Landscape ecology has drawn attention to the close linkages between landscape structure (e.g. topography, land use) and ecological function (e.g. photosynthesis). In large rivers, tributaries constitute a key landscape element affecting attributes of the main stem of the river (e.g. flow rate, sediment load) and causing gradients in environmental conditions such as organic matter content and the underwater light climate. We here propose a 'riverscape' approach to the St.Lawrence River (SLR) where underwater spectral composition ("water color") represents an integrative variable for characterizing the structural properties of the riverscape, and which in turn determines key autotrophic ecological functions. The overarching goal of this research proposal is thus to resolve how river ecosystem structure (based on underwater spectral properties) is determined by the connectivity (transfer of matter) between habitats, and how it affects key ecological functions of the SLR such as phytoplankton primary production, respiration and biodiversity and the trophic transfer from phytoplankton to primary consumers. Furthermore, this riverscape approach will allow a broad scale perspective of process-based autotrophic functions because of the strong relationship between surface color observations from remote-sensing and measured in situ underwater spectral composition, as we have recently demonstrated for the SLR. This finding now provides a new perspective for latitudinal comparisons of large rivers. The proposed research will also contribute to a general understanding of production mechanisms and biodiversity in human-impacted, flowing water ecosystems by providing important baseline information and approaches for monitoring future environmental change (e.g. global warming or toxic waste discharge). This program will provide outstanding opportunities for graduate student training. It will involve five graduate students: two PhD, three MSc, nine summer and three part time BSc students. Through this coupled set of research projects, my laboratory will provide advanced training in limnology with emphasis on large river ecology, hydrology, bio-optics, microbial ecology and ecophysiology.