Geology Department Colloquium, Jan. 31st

Speaker: Maria Prokopenko, Pomona College and USC

Title: “Being a walrus in the warming oceans – Using oxygen triple isotopes and O2/Ar ratios to determine factors controlling carbon export production in spring blooms on the Bering Sea shelf”

Please join us: Thursday, January 31st @ NOON in Edmunds 130

Abstract:  The ongoing climate change and decline in sea-ice cover observed over the last few decades have been implicated in driving large scale changes in high-latitude ecosystems. It has been proposed that on the eastern Bering Sea shelf, which hosts one of the world’s most productive biological ecosystems, the decline in the winter ice extent and duration weakens benthic-pelagic coupling, driving the decline of benthic biomass, and affecting bottom dwelling communities. However, mechanistic understanding of environmental factors driving the observed changes is currently lacking.

To address this issue, we constrained the rates of Net Community and Gross Photosynthetic Production in spring phytoplankton blooms in the marginal ice zones on the Bering Sea shelf using O2/Ar supersaturation and oxygen triple isotope composition of the dissolved O2. Linking the observed rates of biological production to water column hydrography we found that the depth of the mixed layer exerts direct control on the biological carbon export efficiency of the algal blooms on the Bering Sea shelf.

The depth of the mixed layer has been previously linked to the extent of winter ice cover and the timing of ice retreat, thus the relationship between the rates of Net and Gross biological production and the mixed layer depth observed in our study provide a possible missing link between the seasonal ice dynamic and the carbon flow through the eastern Bering Sea shelf ecosystem.