Resource Ecology & Ecosystem Modeling (REEM) Program
Ecosystem Indicators
Hydrographic structure is a dynamic feature that profoundly affects patterns in distributions, productivity, and interactions among species over the eastern Bering Sea (EBS) continental shelf. The depth-temperature profile during the spring-summer warming season over the EBS shelf represents an integration of mixing and stratifying forces.
Depth-temperature profile data have been collected annually over the EBS shelf since 1982 during the EBS bottom trawl survey conducted by the AFSC’s RACE Division. From each depth-temperature profile we are calculating statistics that describe potentially important habitat characteristics of the hydrographic structure. These characteristics are generally related to nominal temperatures, strength of stratification, and layering of the water column, which in turn help define types of water masses, fronts between them, and pelagic habitat.
We are investigating possible relationships between species distributions and interactions with respect to these water column characteristics.
In addition, we felt that some of these descriptive statistics would lend themselves to the creation of annual indices of water conditions integrated over the EBS shelf (Fig. 3 below), with the caveat that survey timing differs somewhat among years.
Figure 3. Examples of the types of indices that were calculated from water depth-temperature profiles over the eastern Bering Sea continental shelf (volume of water < 2°C, volume of the mixed surface layer, and the average of the maximum thermocline at each profile). Values are shown relative to their mean across all years.
By Troy Buckley, Angie Greig, and Jennifer Boldt
Seabird Interactions
Figure 4. AFSC researcher Dr. Ann Edwards cuts a 1-mg piece of primary feather for stable isotope sampling from an incubating Laysan albatross breeding on Midway Atoll.
Dr. Ann Edwards, National Research Council postdoc with the AFSC, completed field work on Laysan albatross at Midway Atoll in the Hawaiian Leeward Islands in coordination with the U.S. Fish and Wildlife Service (USFWS) (Fig. 4). The goals of the research were to sample feathers (for delta-15N analysis as an index of diet) in such a way as to link foraging patterns (inter-annual and intra-annual variation) and diet (specifically a “fisheries-associated” diet indicated by elevated delta-15N values) primarily to reproductive success.
Secondary goals were to link foraging and diet to age, breeding status, gender, and relative influence on reproductive success of a mate’s diet. Edwards sampled birds from USFWS reproductive plots (150 albatross), from pre-breeders (30 birds), and from older breeders outside of the reproductive plots (43 birds). Based on work completed for her Ph.D. research at the University of Washington, molting patterns and feather growth rates and genetic sequence are known for Laysan albatross. By taking small feather clips from several different feathers and different locations on a single feather and conducting stable isotope analysis, the trophic level that birds were feeding at can be determined up to several years in the past. Samples are currently being analyzed.
