ROV investigations of organic matter
mineralization in continental shelf benthic habitats
Clare E. Reimers, Ph.D.
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.
Next:Fluid circulation through the oceanic crust- The solution to
geochemical mass balances?
Last updated: December 19, 2000