GLOBEC: The Use of Molecular Organic Tracers to Determine Age Structure, Nutritional Status and Potential for Trophic Transfer in the Euphausiids Euphausia pacifica and Thysanioessa spinifera
H.R. Harvey [University of Maryland]
The project described in this proposal will addresses the population age structure and nutritional status of the two primary target organisms for GLOBEC, the euphausiids Euphausiidia pacifica and Thysanoessa spinifera. Using recent advances in quantifying biochemical markers of metabolism (lipofuscins), we 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. Our 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.
We hypothesize that differences in mesoscale circulation north and south of Cape Blanco will lead to differences in age structure and nutritional status for the two target organisms, and as a result differences in production rates which directly impact their availability as prey for salmon. As part of the LTOP monitoring program we will sample five times per year (February, April, July, September, and November) with emphasis on four stations (10, 15, 25, and 45 miles) along the Newport transect line at night to collect both adults and juveniles. Vertical net town using 70cm Bongo 333 m mesh nets will be used for juvenile and adult collections together with 1m2 MOCNESS with 333 m mesh over several depths strata. We will randomly collect approximately 50 individuals of each species from each station for a total of approximately 200 animals on each cruise in conjunction with planned activities which will investigate euphausiid population dynamics (B. Peterson - NMFW Hatfield Marine Science Center). Animals will preserved in LN2 for subsequent analysis in the shore based laboratory. Recent development in the use of biochemical methods to determine population age structure will be applied to animals collected together with parallel measures of nutritional status in subsets of the same individuals. Individual lipids will also be investigated to establish markers for dietary history of the two euphausiids in the hopes of addressing the known differences in cross-shelf zonation of the two species and controls on population dynamics.
To establish absolute age structure of target species, nauplii or larvae from an identified cohort will be collected at night by 1-meter net that samples the upper 10 m while the ship drifts on station. These animals will be returned to the laboratory and reared on a mixed phytoplankton diet during the first year for age calibration with field populations. On bi-monthly intervals 20 individuals will be sacrificed to quantify lipofuscin concentrations over time together with lipid class analysis used to confirm nutritional status. Information on age structure will allow the impact of physical zonation across the shelf habitat on potential recruitment to be determined. Field collections will be repeated in each of three years to document seasonal and interannual changes in age structure, nutritional status and potentially diet history of Euphausiidia pacifica and Thysanoessa spinifera in the northern California current and its relationship to physical oceanographic processes.
This page was last updated on
March 15, 2007.
Maintained by:
Hal Batchelder
College of Oceanic and Atmospheric Sciences
Oregon State University
Corvallis, OR 97331-5503
phone: 541-737-4500; FAX 541-737-2064