Biogeographic, Geochemical, and Paleoceanographic Investigations of Ostracodes in the Bering, Chukchi, and Beaufort Seas

• Main Author: Gemery, Laura
• Other Authors: Cooper, Lee W., Digital Repository at the University of Maryland, University of Maryland (College Park, Md.), Marine-Estuarine-Environmental Sciences
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2022
• Subjects: Paleoecology; Paleoclimate science; Paleontology; Arctic Ocean; Ostracoda; Arctic; Pacific; Chukchi; Sea ice; Subarctic
• Online Access: http://hdl.handle.net/1903/28711; https://doi.org/10.13016/ghjt-vau7

In this study, I investigated the continental shelf environments of the Bering, Chukchi, and Beaufort Seas using species of Ostracoda and their shell chemistry as indicators of oceanographic conditions and change. Ostracodes are bivalved Crustacea that secrete a calcareous shell commonly preserved in sediments in the Arctic. Because ostracode species have survival limits controlled by temperature, salinity, oxygen, sea ice, food, and other habitat-related factors, they are useful ecological indicators. A primary objective of my dissertation research was to establish how their ecology, biogeography and shell geochemistry is related to ocean variability in water mass properties and productivity at high latitudes. First, I examined community assemblages of ostracodes over several decades (1970-2018) in the northern Bering, Chukchi, and Beaufort Seas, and the main environmental factors that affect their biogeography. Results showed that large-scale south-to-north and small-scale nearshore-offshore gradients in ostracode community structure were tied to changes in water mass properties in combination with food sources and sediment substrate. Although the dominant species did not significantly change over the investigated period, the frequency of two cold-temperate species that are primarily and previously restricted to shallow North Pacific sediments off Asia has increased during the last decade. This suggests that these species are responding to recent increases in coastal and mid-shelf bottom water temperatures and/or carbon flux to the benthos. A second goal was to assess the feasibility of using stable oxygen isotopes (δ18O) of carbonate from ostracode shells as paleoceanographic proxies for water mass identification on Arctic and subarctic continental shelves. Through the use of regression analyses, I established that the δ18O values of carbonates from two species (of five investigated) can be reliable recorders of summer water mass changes in temperature and seawater δ18O content. The third part of the study ...