The goal of BEST (Bering Sea Ecosystem Study), a large NSF-supported research effort, is to identify and quantify mechanistic links between climate and the ecosystem response. An ecosystem responds to changes in climate forcing by altering the abundance, biomass and species composition of its constituent populations. Without information on lower trophic level populations forming the base of the food web, it is impossible to determine the state of the system, estimate the direction or magnitude of change, if any, to validate or refute hypotheses or to adequately validate or parameterize lower trophic level models. In order to contribute to the assessment of the state and variability of the species composition, abundance and biomass of the populations forming the ecosystem of the Eastern Bering Sea Shelf during BEST and to estimate population trends, funds are provided to collect and process approximately 260 zooplankton samples from the eastern Bering Sea during each of two cruises per year and to analyze the resultant data.
The primary task of this project was to assess the amount of zooplankton on the Bering Sea continental shelf. Zooplankton are large and small animals, mostly invertebrates, which drift in the water. Information on zooplankton abundance is being used by the Bering Sea Ecosystem Project (BEST) to assess the health of the Bering Sea ecosystem and to aid in understanding the potential effects of global climate change on Bering Sea fisheries. Since the Bering Sea sustains large commercial fisheries and subsistence resources for native communities, understanding the potential effects of climate change on zooplankton and their associated fish populations will aid policy makers in planning for and mitigating climate-related impacts on the fishing and indigenous communities along the Bering Sea coast. The project resulted in 675 zoopalnkton samples collected and processed. The samples will be stored at University of Alaska for at least 20 years and made available upon request to future researchers. The data on zooplankton composition and surrounding environment, which were simultaneously collected using automated sensors during the tows, were uploaded into the BEST interdisciplinary database (www.eol.ucar.edu/projects/best/) to make them available for other researches and general public for current and/or retrospective analyses and interpretations. Ecosystem studies over the last decade revealed substantial declines in populations of large zooplankton during the warm period of 2002 – 2006. These declines were accompanied by declines in the survival of juvenile pollock, a major commercial fish on the Bering Sea shelf. Since large zooplankton are an important food for young pollock, the declines in large zooplankton are a potential reason for observed declines in survival of young pollock. In addition, large zooplankton are an important food for salmon, herring, capelin and other large fish species. In the absence of large zooplankton, other large fish were consuming juvenile pollock, thus lowering pollock survival and stock size. As fish stalks decline, the supply of fish to the fishery also declines, resulting in lower incomes and employment in the fishing communities. Colder temperatures in 2007-2010 were accompanied by a recovery of large zooplankton populations as assessed by the BEST project. Increases in abundance of large zooplankton during the recent cold period are further evidence that declines in zooplankton during the warm period were temperature-related. In addition to increases in populations of large zooplankton during the cold period of 2007 – 2010, large Arctic zooplankton species occurred in the samples. These arctic species had not been observed in the southern Bering Sea since the 1970s. Arctic species can be an important food source for seabirds and commercial fish, so their reappearance on the Bering Sea shelf is an indication that climate change can impact the Bering Sea ecosystem by changing the species composition of the constituent populations in addition to changing population size. The species composition and abundance of plant and animal populations in ecosystems are continuously changing in response to climate. Since climate warming is predicted to occur more rapidly in arctic and subarctic environment, these changes in species composition and abundance are likely to accelerate and increase in amplitude. Nevertheless, ecosystems are extremely complex and can change in unpredictable ways. Therefore, sound resource management in a changing world requires continuous assessment of the plant and animal populations to allow resource managers to modify management policies in a timely manner, to minimize the potential impacts of unexpected changes in fish and wildlife populations on the coastal communities which depend on these resources for subsistence and commercial harvests.
