Pinchuk, A. I.. Institute of Marine Science, email@example.com
Coyle, K. I.. Institute of Marine Science, firstname.lastname@example.org
INTERANNUAL DIFFERENCES IN THE DISTRIBUTION AND ABUNDANCE OF EUPHAUSIIDS AND COPEPODS AT THE STRUCTURAL FRONT OF THE SOUTHEASTERN BERING SEA DURING A TWO YEAR PERIOD OF CLIMATIC EXTREMES
Euphausiids are an important component of the inner shelf planktonic ecosystem in the southeastern Bering Sea. They are a primary food for a variety of fishes and seabirds, including shortail shearwaters, which migrate from the southern hemisphere to forage in the Bering Sea during summer. Euphausiids are therefore a major link in the transfer of energy from primary producers to apex predators. During summer of 1997, the weather was unusually calm, temperatures were elevated, stratification was intense, nutrients were exhausted throughout the water column, production was low and an intense coccolithophorid bloom was observed. Under the above conditions, the plankton biomass was dominated by Calanus marshallae, euphausiids made up less than 10% of the total biomass and no euphausiid scattering layers were observed. The above conditions coincided with a massive die off of shearwaters, apparently from starvation. In contrast, the weather during 1998 was stormy, stratification was weaker and the spring bloom delayed. Extensive euphausiid scattering layers were observed near Dillingham, Cape Newenham and Nunivak Island. The layers contained adult and late juvenile stages of Thysanoessa raschii, which dominated the zooplankton biomass. The above observations suggest a possible link between unusually warm conditions and a disruption of energy flow through the euphausiid component of the planktonic food web to apex predators.
This research is part of a cooperative program involving University of Alaska Fairbanks, University of California Irvine, Pacific Marine Environmental Laboratory and University of New England.
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