George L. Hunt

Mass and energy transfer to seabirds in the southeastern Bering Sea

It has been hypothesized that differentiation in food web structure occurs across the Bering Sea continental shelf as a result of seasonal differentiation of water masses. We tested this idea using an apex predator, pelagic birds. Seasonal abundance of birds in central Bristol Bay was estimated from counts made while underway between hydrographic stations. Prey and body mass were determined from birds collected at sea. Daily intake was estimated as an allometric function of body mass. Annual occupancy was estimated as the integral of a normal curve fit to seasonal data. Estimated carbon flux to seabirds in the middle domain was 0.12 gC m-2 y-1 in 1980, 0.18 gC m-2 y-1 in 1981. Carbon flux to seabirds in the adjacent waters of the outer shelf domain was 1.8 times higher than in the middle domain in 1980, 1.6 times higher in 1981. Carbon flux to seabirds in the inner domain was 1.2 times higher than in the middle domain in 1980, and 3.3 times higher in 1981. Carbon flux to seabirds in the outer domain was due primarily to non-diving species, principally northern fulmars (Fulmarus glacialis) during the summer and autumn, and Larus gulls in the autumn and winter. Flux to seabirds in the inner domain was due to diving birds, principally murres (Uria sp.) in the spring and shearwaters (Puffinus sp.) during the summer. The euphausiid Thysanoessa raschii was the primary food source of shearwaters in shallow waters of the inner shelf domain. A more diverse set of prey, including squid, jellyfish, hyperiids, and fish, was taken by shearwaters and fulmars in the deeper waters of the outer and middle shelf domains. This result suggests that prey diversity is higher in seasonally stratified waters of outer Bristol Bay than in mixed waters of inner Bristol Bay. Greater energy flux to diving species in shallow water, and greater energy flux to non-divers in deep water may be a function of topographic control of prey patchiness.

Overview of the Inner Front and Southeast Bering Sea Carrying Capacity Programs

Deep-Sea Research II 49 (2002) 6157–6168 Overview of the Inner Front and Southeast Bering Sea Carrying Capacity Programs Phyllis J. Stabeno a, *, George L. Hunt Jr. b a Pacific Marine Environmental Laboratory, NOAA, 7600 Sand Point Way NE, Seattle, WA 98115-6349, USA b Department of Ecology and Evolutionary Biology, University California, Irvine, Irvine, CA 92697, USA 1. Introduction During the 1990s, there has been a significant increase in our understanding of the Bering Sea ecosystem. Two programs, NOAA’s Coastal Ocean’s Southeast Bering Sea Carrying Capacity (SEBSCC) and the National Science Foundation- supported Inner Front Program (IFP), led the way in new findings. SEBSCC, whose focus was on the middle and outer shelves, and the slope, and IFP, whose focus was on the inner shelf, complemented each other. Several scientists, including the authors of this paper, were investigators in both programs. This resulted in close collaboration between the programs, a sharing of ship time, data, and ideas, and culminated in the compilation of this volume. Between 1995 and 2000, we had the good fortune to be studying the Bering Sea during a period of great variability. We were presented with the opportunity to study an extremely warm year (1997) and a cold year (1999). During the 1990s, there were other marked changes in the Bering Sea shelf ecosystem including extensive blooms of coccolithophores, increases in jellyfish, and the appearance of large baleen whales. We also observed a massive die off of shearwaters, the continued decline in northern fur seals (Callorhinus ursinus) and Steller sea lions (Eumetopus jubatus), and a sharp decrease in the number of salmon. *Corresponding author. Tel.: +206-526-6453. E-mail addresses: stabeno@pmel.noaa.gov (P.J. Stabeno), glhunt@uci.edu (G.L. Hunt Jr.). 0967-0645/02/

Increases in jellyfish biomass in the Bering Sea: implications for the ecosystem

- see front matter Published by Elsevier Science Ltd. PII: S 0 9 6 7 - 0 6 4 5 ( 0 2 ) 0 0 3 3 9 - 9 These changes in the ecosystem, together with advances in ocean technology, provided the opportunity to expand our understanding of this complex ecosystem. In this paper we summarize the major findings of the two programs, starting with the physical environment, progressing through primary production, and finally discuss- ing upper trophic levels. We then discuss a new hypothesis (Hunt et al., 2002) that links ecosystem function to climate. In closing, we pose several questions that remain unanswered and suggest directions for future research. 2. Decadal variability The Bering Sea is characterized by large year-to- year variability, but is also sensitive to climate changes on decadal and longer time scales (Over- land et al., 1999; Stabeno et al., 2001). It has been only within the last 10 years that significant research has been done on decadal-scale variability of climate and how it impacts the eastern Bering Sea ecosystem. The Bering Sea responds to two dominant decadal oscillations, the Pacific Decadal Oscillation (PDO) and the Arctic Oscillation (AO) (Overland et al., 1999). The PDO is the first mode of decadal variability in the sea-surface tempera- ture of the North Pacific and its major impact is in the North Pacific and the southern Bering Sea. Changes in fish populations and other ecosystem functions are correlated with oscillations in the PDO (Mantua et al., 1997; Hare and Mantua,