ROV investigations of organic matter mineralization in continental shelf benthic habitats

Clare E. Reimers, Ph.D.
Rutgers University

Monday, September 28, 1998
3:00 p.m.—Pacific Forum

The sediments on most continental shelves are relict sands with very low organic contents and high permeabilities. Paradoxically, microelectrode measurements indicate that dissolved oxygen concentrations typically go to zero within a few millimeters of the sediment-water interface at such sites within the Middle Atlantic Bight (water depths 17-50 m), and these gradients are accompanied by a corresponding decline in pore-water pH. Microelectrode measurements were made in August and October 1996, June 1997 and June 1998, in situ and in real-time, using a Remote Operated Vehicle (ROV) with close-up video capabilities. The ROV also carried equipment for Mn2+, Fe2+ and sulfide microelectrode measurements by voltammetry, but these species could only be detected when measurements were made at muddy sites.

It will be concluded that oxygen fluxes at the sandy seabed of the inner shelf are many times greater than has been estimated using benthic flux chambers. This is because rapid bacterial mineralization of organic matter is fueled by the advection of organic substrates and oxygen through the upper millimeters-centimeters of the sediment.

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