GLOBEC: Applying Molecular Organic Tracers to Determine Age Structure, Nutritional Status and Possible Trophic Transfer in Euphausiids Euphausia Pacifica and Thysanoessa Spinifer

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This research project addresses the population age structure and nutritional status of the two primary target organisms for GLOBEC, the euphausiids Euphausii diapacifica and Thysanoessa spinifera. Using recent advances in quantifying biochemical markers of metabolism (lipofuscins), the researchers will determine the population age structure of both zooplankton in the California current system with particular emphasis on populations separated by physical zonation off the central Oregon. Lipid analysis in subsets of the same populations will provide a measure of nutritional status and feeding history. Sampling in conjunction with the current GLOBEC long term monitoring program (L-TOP) will provide information on physical structuring of each population together with measures of nutritional status over seasonal and interannual time scales to better predict their production, recruitment and thus importance in salmonid growth and survival. The research objectives include:1. Application of recent advances in biochemical methods to determine the age structure in populations of the two major euphausiid species Euphausia pacifica and Thysanoessa spinifera and the effects of mesoscale dynamics on maintenance or disruption of cohort populations seasonally and interannually.2. Examine the effects of physical zonation in shelf waters on the nutritional status and thus reproductive potential in juvenile and adults euphausiids (and eggs) using lipid classes; seasonal and interannual measures will be used provide information on the potential effects of changing nutritional status on subsequent recruitment and variations in abundance.3. To combine age structure information with lipid analysis in sets of the same individuals to understand the impact of nutritional status on age structure in field populations of E. pacifica and T. spinifera over seasonal and interannual time scales.4. To investigate individual lipids in euphausiids and other zooplankton as molecular markers of diet and their potential as markers of trophic transfer to their predators.