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Carbon Cycling in the Bering Sea

Moran reports on changes in Bering Sea carbon cycling at Ocean Carbon and Biogeochemistry Workshop

Bering Sea Project investigator Bradley Moran presented some research findings at this year's Ocean Carbon and Biogeochemistry Workshop, held in July 2010 at the Scripps Institute of Oceanography. Together with co-PI Mike Lomas, Moran is focused on two projects within the benthic focal area of the Bering Sea Project: Carbon Export in the Eastern Bering Sea Water Column and The Impact of Changes in Sea Ice Extent on Primary Production, Phytoplankton Community Structure, and Export.

carbon cycling hypotheses Moran et al.The team hypothesizes (right) that changes in sea-ice extent shift the autotrophic community between:

  • Open-water blooms, which are characterized by lower biomass, flagellate blooms, low pelagic export, and reduced pelagic-benthic coupling; and
  • Marginal ice-zone (MIZ) blooms, which are characterized by high biomass, diatom-dominated blooms, high pelagic export and tighter pelagic-benthic coupling. See larger image

Moran presents early findings

The Arctic was one of the themes in this year's OCB workshop. Moran summarized carbon cycling in the lower trophic levels from data obtained from cruises that occurred in spring and summer of 2008 and 2009.  Specifically, he reported on seasonal and interannual changes in primary productivity, phytoplankton community composition, particulate organic carbon export, net community composition, and sediment oxygen utilization in the Bering Sea Project study region. 

Early results indicate that primary production and export seem to vary with changes in the autotrophic community structure between the ice edge and open water conditions. Download Moran's presentation (PDF, 7.4MB)

What does it mean for this ecosystem?

Recent ice coverage was much more extensive compared to 2001-06. The old saying "spring ahead" seems to apply here -- ice retreat was later than expected at the outset of this project; indeed, the ice had only just retreated by the summer cruises in July.

changing sea ice extentChanging sea ice extent has a potentially large impact on the Bering Sea ecosystem, as evidenced by decreasing seasonal sea ice extent in the Bering Sea from 1976-2009 (right; graphic by Sigler et al). See larger image

This is an important development in the Bering Sea, one of the world's most productive ecosystems:

  • The Bering Sea is the source of half the U.S. fish landings annually (pollock, salmon, crab).
  • Over past several decades, shifts have occurred in pelagic and benthic ecosystems, decreasing the abundance of commercially important organisms. This shift has been partly linked to global climate change, decreasing sea ice extent, and related physical forcing mechanisms.
  • Climate change could also be affecting lower trophic levels and food web structure, and it turn feeds back to higher trophic levels.

Download Moran's presentation (PDF, 7.4MB)