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MISSION SYNOPSIS Research Location The research will be conducted at three sites: at Wilkinson Basin in the Gulf of Maine, in the shallow shelf/slope water of Georges Bank and in the deep water of Oceanographer Canyon. Sampling Approach The focused, quantitative approach of this project will define the predation habits of Nanomia cara, a deep-living, but vertically migratory siphonophore. Of particular interest is the potential for colony predation on several species of ecologically important copepods resident within the Gulf of Maine. Diapausing (over-wintering) 
life history stages of copepod prey are concentrated in the deep waters of the Basin and the Canyon.
To overcome problems associated with traditional collection methods damaging to gelatinous animals, Nanomia will be captured with special chambers that are attached to the JOHNSON SEA-LINK (JSL) manned research submersible. A new, high-resolution digital video camera and recorder will be used to videotape in situ the feeding, locomotory, and migratory behaviors of these tentaculate predators. Researchers will also consider how the size and in situ behaviors of prey species may alter predation rates. Prey contained within the gastrozooids (functional stomachs) of colonies will be identified, and the contents will be compared to prey available within the environment. These comparisons will serve to determine the degree of prey selectivity by Nanomia. The research team suspects that copepod species will make up the bulk of the diet. The investigation will also seek to ascertain if seasonal shifts in the abundance and diversity of prey are reflected in the siphonophore diet. Spatial and temporal variables that can influence prey consumption will also be investigated, e.g., depth of the water column, stratification, circulation, and diel changes in light. Significance of Research Seasonal and interannual variability in siphonophore abundance, the abundance, diversity, and distribution of its prey, and various environmental features (e.g., thermohaline interfaces, fronts, eddies) will provide a basis for modeling the feeding habits of Nanomia cara.  Moreover, the multi-year, multi-seasonal design of the project will allow testable predictions about
predation rates in ecologically distinct sectors of the region.
"Siphonophore predation on over-wintering copepods at depth may be important in determining the availability of these prey populations for the young of cod and other commercially important fish species later in the year," notes Dr. Youngbluth. "Knowledge of these specific relationships should contribute significantly to predictive models for predator-prey dynamics, especially if copepod populations are predator-controlled and not food-limited."  |  |
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