C33F-07
Decadal changes in carbon fluxes at the East Siberian continental margin: interactions of ice cover, ocean productivity, particle sedimentation and benthic life
Wednesday, 16 December 2015: 15:25
3007 (Moscone West)
Antje Boetius1, Christina Bienhold2, Janine Felden3, Mar Fernandez Mendez4, Manuela Gusky1, Pamela E. Rossel5, Andrey Vedenin6 and Frank Wenzhoefer1,2, (1)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany, (2)Max Planck Institute for Marine Microbiology, Bremen, Germany, (3)MARUM - University of Bremen, Bremen, Germany, (4)Norwegian Polar Institute, Tromsø, Norway, (5)Alfred Wegener Institute Helmholtz Center for Polar (AWI) and Marine Research and Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, Oldenburg, Germany, (6)P.P. Shirshov Institute of Oceanology, Laboratory of ocean bottom fauna, Moscow, Russia
Abstract:
The observed and predicted Climate-Carbon-Cryosphere interactions in the Arctic Ocean are likely to alter productivity and carbon fluxes of the Siberian continental margin and adjacent basins. Here, we compare field observations and samples obtained in the nineties, and recently in 2012 during the sea ice minimum, to assess decadal changes in the productivity, export and recycling of organic matter at the outer East Siberian margin. In the 90s, the Laptev Sea margin was still largely ice-covered throughout the year, and the samples and measurements obtained represent an ecological baseline against which current and future ecosystem shifts can be assessed. The POLARSTERN expedition IceArc (ARK-XXVII/3) returned in September 2012 to resample the same transects between 60 and 3400 m water depth as well as stations in the adjacent deep basins. Our results suggest that environmental changes in the past two decades, foremost sea ice thinning and retreat, have led to a substantial increase in phytodetritus sedimentation to the seafloor, especially at the lower margin and adjacent basins. This is reflected in increased benthic microbial activities, leading to higher carbon remineralization rates, especially deeper than 3000 m. Besides a relative increase in typical particle degrading bacterial types in surface sediments, bacterial community composition showed little variation between the two years, suggesting that local microbial communities can cope with changing food input. First assessments of faunal abundances suggest an increase in polychaetes,holothurians and bivalves at depth, which fits the prediction of higher productivity and particle deposition rates upon sea ice retreat. The presentation also discusses the controversial issue whether there is evidence for an Arctic-wide increase in carbon flux, or whether we are looking at a spatial shift of the productive marginal ice zone as the main factor to enhance carbon flux to the deep Siberian margin.
