A retrospective assessment of primary productivity on the Bering and Chukchi Sea shelves using stable isotope ratios in seabirds

Thesis (M.S.) University of Alaska Fairbanks, 2000 Recent declines of marine mammal seabird populations in the Bering Sea have raised the question of whether the changes are caused by fishing pressure or a decrease in ecosystem carrying capacity. Stable carbon (¹³C⁾ and nitrogen (¹⁵N⁾ isotope ratios...

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Bibliographic Details
Main Author: Abromaitis, Grace Elizabeth
Other Authors: Schell, Donald, Castellini, Michael, Springer, Alan
Format: Thesis
Language:English
Published: 2000
Subjects:
Bering Sea
Chukchi Sea
Fairbanks
bowhead whale
Chukchi
thick-billed murre
Alaska
Online Access:http://hdl.handle.net/11122/4944
Description
Summary:Thesis (M.S.) University of Alaska Fairbanks, 2000 Recent declines of marine mammal seabird populations in the Bering Sea have raised the question of whether the changes are caused by fishing pressure or a decrease in ecosystem carrying capacity. Stable carbon (¹³C⁾ and nitrogen (¹⁵N⁾ isotope ratios in Thick⁻billed Murre muscle and feathers were used as indicators of changing seasonal primary production. ¹³C values in phytoplankton vary directly with growth rates and are passed up the food web to consumers. Muscle and feather ¹³C values decreased over the period 1976-1998 suggesting a decline in Bering/Chukchi continental shelf primary production. Carbon isotope ratios in murres were correlated with bowhead whale baleen isotope ratios and to some climate indices. In contrast, ¹⁵N values in the birds showed no significant change indicating no concurrent shifts in trophic status.

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