Paleoceanographic Productivity Reconstruction Using Marine Mammal Bone Collagen

Grant Winners

Dean

Abstract

Changes in primary ocean productivity play a key role in determining the structure and biomass yield of the North Pacific ecosystem. Are recent dramatic fluctuations in marine ecosystem productivity a function primarily of industrial and other anthropogenically induced changes or part of larger ecosystem scale processes? Archaeofaunal remains of pinnipeds and cetaceans from the Aleutian Islands, Alaska are used as a proxy for marine productivity changes over decade, century and millennial scales throughout the Holocene. Marine vertebrate remains from several previously excavated well-dated archaeological deposits on Unalaska Island span the period AD 1912-5500 BP. Stable carbon and nitrogen isotope ratios (d13C and d15N) derived from marine mammal bone and tooth and shell collagen provide information about changes in food web dynamics and marine productivity levels and, through inference, about ecosystem changes. The paleorecord of phytoplankton production, in response to changes in atmospheric and oceanic fluctuations, is reflected in the stable isotope composition of the skeletal remains of these animals. Our current understanding of the controls on production, and the time-scales over which these controls vary, is extremely limited. We are developing a time series of stable isotope signatures from these zooarchaeofaunal remains to assess changes in trophic dynamics related to changes in primary productivity. The results of this study will contribute to baseline data on marine productivity and how these data relate to recent declines in the carrying capacity of the Bering Sea and the northern Gulf of Alaska.