The biogeochemistry of carbon in continental slope sediments: The North Carolina margin
The responses of the continental slope benthos to organic detritus deposition were studied with a multiple trace approach. Study sites were offshore of Cape Fear (I) and Cape Hatteras (III), N.C. (both 850 m water depth) and were characterized by different organic C deposition rates, macrofaunal densities (III>I in both cases) and taxa. Natural abundances of {sup 13}C and {sup 12}C in particulate organic carbon (POC), dissolved inorganic carbon (DIC) and macrofauna indicate that the reactive organic detritus is marine in origin. Natural abundance levels of {sup 14}C and uptake of {sup 13}C-labeled diatoms by benthic animals indicate that they incorporate a relatively young component of carbon into their biomass. {sup 13}C-labeled diatoms (Thalassiorsira pseudonana) tagged with {sup 210}Pb, slope sediment tagged with {sup 113}Sn and {sup 228}Th-labeled glass beads were emplaced in plots on the seafloor at both locations and the plots were sampled after 30 min., 1-1.5 d and 14 mo. At Site I, tracer diatom was intercepted at the surface primarily by protozoans and surface-feeding annelids. Little of the diatom C penetrated below 2 cm even after 14 months. Oxidation of organic carbon appeared to be largely aerobic. At Site III, annelids were primarily responsible for the initial uptake of tracer. On the time scale of days, diatom C was transported to a depth of 12 cm and was found in animals collected between 5-10 cm. The hoeing of tracer from the surface by the maldanid Praxillela sp. may have been responsible for some of the rapid nonlocal transport. Oxidation of the diatom organic carbon was evident to at least 10 cm depth. Anaerobic breakdown of organic matter is more important at Site III. Horizontal transport, which was probably biologically mediated, was an order of magnitude more rapid than vertical displacement over a year time scale. If the horizontal transport was associated with biochemical transformations of the organic matter, it may represent an important but nearly invisible diagenetic process.
- Research Organization:
- Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695-8208; Marine Life Research Group, Scripps Institution of Oceanography, La Jolla, CA 92093-0218 (US)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER), Ocean Margins Program; NOAA National Undersea Research Program at Wilmington, N.C.; National Science Foundation (US)
- DOE Contract Number:
- FG02-95ER62082
- OSTI ID:
- 765318
- Report Number(s):
- NSF Grant OCE 93-11711; NSF Grant OCE 93-01793; NSF Grant OCE 93-11711; NSF Grant OCE 93-01793; TRN: AH200105%%164
- Resource Relation:
- Conference: 1998 Organism-Sediment Interactions Symposium/Workshop, Columbia, SC (US), No conference date provided; Other Information: PBD: 1 Dec 1999
- Country of Publication:
- United States
- Language:
- English
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