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Clare Reimers, CEOAS, OSU

Benthic Exchange Dynamics on the Oregon Shelf

Thursday, April 26, 2018 3:30 PM - 4:30 PM

 

Mid-shelf sediments off the Oregon coast are characterized as fine sands that trap and remineralize phytodetritus leading to the consumption of significant quantities of dissolved oxygen. Sediment oxygen consumption (SOC) can be delayed from seasonal organic matter inputs because of a transient build-up of reduced constituents during periods of quiescent physical processes. Between 2009 and 2018, measurements of benthic oxygen exchange rates have been and are being made using the non-invasive eddy covariance (EC) method on the Oregon shelf. Ancillary measurements have included in situ microprofiles of oxygen at the sediment-water interface, and concentration profiles of pore water nutrients and trace metals, and solid-phase organic-C and sulfide minerals from cores. Sediment cores are also incubated to derive anaerobic respiration rates. At one 80 m station, EC measurements in different seasons yielded average benthic oxygen flux estimates that varied between -2 and -15 mmol m-2d-1. The EC oxygen fluxes were most highly correlated with bottom-sensed, significant wave heights (Hs).  The relationship with Hs was used with an annual record of deep-water swell heights to predict an integrated oxygen consumption rate for the mid-shelf of 1.5 mol m-2 for the upwelling season (May-September) and 6.8 mol m-2y-1.  The annual prediction requires that SOC rates are enhanced in the winter because of sand filtering and pore water advection under large waves, and it counters budgets that assume a dominance of organic matter export from the shelf. Refined budgets will require winter flux measurements and observations from cross-shelf transects over multiple years.


OSU Hatfield Marine Science Center
Guin Library Seminar Room
2030 SE Marine Science Drive
Newport
OR
cinamon.moffett at oregonstate.edu
Hatfield Marine Sci Ctr
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