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Shannon Harris

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shharris@...



Globec


Shannon Harris | MSc Candidate


The response of phytoplankton populations to variability of their physical oceanic environment and the subsequent effect on marine resources


The Global Ocean Ecosystem Dynamics Program (GLOBec) will examine how and why living marine resources are affected by variability of their physical oceanic environment. More specifically, this project will determine the response of commercial fish and plankton populations off the western Canadian continental shelf and slope to variability of circulation and water properties at seasonal to decadal time scales. I will examine variations in phytoplankton primary production, biomass, and composition as mediated by physical transport and nutrient supply and how these variations affect food availability for salmon. Combined with time-series data sets from other locations this work will allow me to evaluate large scale coherence of year-to-year "anomalies" between various variables and between widely separate locations. This work is essential to provide input and validate data for the physical/plankton/fish model being developed for the western continental margin of Vancouver Island. This model will be used to forecast ecosystem production trends based on physical forcing of the lower trophic levels, and natural and anthropogenic forcing of the higher trophic levels.

Study Rational

Pacific coast fish and zooplankton communities undergo yearly and decadal fluctuations which are ecologically/economically significant in terms of production. Both steady-state fisheries models and increasing scientific evidence correlate stock collapse and extreme failures to major shifts in the marine climate rather than purely fishery harvests. Currently, several west coast fisheries are managed using various proxy indices of oceanic conditions based on correlations with convenient variables that incorporate minimal knowledge of the underlying mechanisms. These management indices based solely on hindcast correlations have a history of breaking down over time, either permanently or during specific oceanic events. Major errors in management advice resulting in both conservation and social crises and the loss of millions of dollars to the Canadian economy are conceivable. What is needed to make the indices more reliable is an understanding and quantification of the causal processes underlying these correlations. Specifically the processes that affect the growth and survival of early marine life stages, and the migration of adult stages will be addressed.

Study Area

This study will span the continental shelf and slope of the west coast of Vancouver Island from the Juan de Fuca Strait to Queen Charlotte Sound. This region is particularly interesting for study because it is characterized by several regions of intense wind-induced and topographically enhanced upwelling. It is also a primary migration corridor for west coast salmon stocks and is ecologically and economically productive. The historical information base is excellent and makes this one of the few Canadian ecosystems for which assessment of interdecadal variability is possible.

Project Status

I have recently completed the first of three cruises scheduled for the 1997 sampling season. My project will be based on analysis of data from two years - 1997 and 1998. Cruises are schedules to study the spring bloom, summer population, and the fall phytoplankton population transition.


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