Successful recruitment of fish larvae to suitable juvenile nursery areas is a necessary condition for growth, energy storage, survival, and subsequently recruitment to adult populations. Climate variability, which may change existing meteorological and oceanographic conditions, will likely impact transport mechanisms between these areas. A better understanding of these transport pathways, larval behavior during the transport process, and delivery mechanisms (including settlement for flatfish) will help us predict the impact of changing climate conditions on recruitment success to adult populations.
We will study how growth, energy storage and metabolism interact to regulate the distribution and abundance of walleye pollock, Pacific cod and arrowtooth flounder in the Bering Sea. In order to recruit as adults, juvenile fish must survive multiple periods of energy depletion, which increases their risk of predation, starvation and disease. We will build models that relate the energy phenology of juvenile pollock, Pacific cod and arrowtooth flounder to seasonal changes in their distribution and abundance.
Microzooplankton do most of the “grazing” on phytoplankton in the Bering Sea and are an important link in the food web between phytoplankton and zooplankton, which are food for fish. Microzooplankton grazing also regulates phytoplankton blooms. This project will provide summer data on standing stocks of microzooplankton and their grazing activities. We will estimate abundance, biomass, size distribution, and composition of larger microzooplankton, and will measure grazing by microzooplankton on phytoplankton.
We hypothesize that seasonal and interannual variation in the timing and coverage of sea-ice and associated food resources will lead to differences in age structure, diet history and nutritional condition for euphausids, which ultimately translate into differences in product ion rates and availability as prey to higher trophic levels. We will quantify the age structure and diet history of important euphausids together with detailed information on their consumption and growth. We will also link field collections and analysis with laboratory rearing for age calibrations and shipboard feeding experiments to test the validation and retention of trophic lipid markers, as well as the quality and quantity of food resources.
We will analyze zooplankton (standing stock determinations and rate measurements) to determine relative microzooplankton and mesozooplankton grazing impacts. This project will provide size-fractioned chlorophyll-a concentrations as well as biomass stocks and rate measurements of grazing and growth for microzooplankton and mesozooplankton.
We will assess mesozooplankton populations during the spring and summer cruises during the field seasons outlined for BEST-BSIERP. We will measure total primary production, measuring the carbon chlorophyll ratios of the phytoplankton taxa and assess species composition, biomass and abundance of the phytoplankton, microzooplankton, mesozooplankton and micronekton (euphausiids) on the eastern Bering Sea shelf.
We will collect, quality control, analyze and distribute the core chlorophyll-a data on databases at PMEL, NODC, and AOOS. We will also use the biological data from this proposal combined with physical and chemical data collected on spring and summer BEST cruises, data from a September NPCREP cruise, and data from moorings and from satellite-tracked drifters to address the hypothesis that the marked difference between the more pelagic southern shelf and the more benthic northern shelf is a result of the position of the sea-ice edge during the transition from strong winter winds to milder summer conditions.