The Relationship of Bioturbation, Macrobenthos and Seabed Radionuclides to the Flux and Fate of Organic Carbon Along the JGOFS Equatorial Pacific Transect

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In 1991-1992, the US JGOFS Equatorial Pacific program will study the production, flux and fate of organic carbon along a cross-equatorial transect at 140oW. From the equator northward, this transect traverses a steep gradient in particulate organic-carbon flux and burial at the abyssal seafloor. In order to elucidate the fate of organic carbon in these sediments, an understanding of bioturbation and seabed particle dynamics (as traced by naturally occurring radionuclides) is essential. The P.I.'s propose to test, along this carbon-flux gradient, four hypotheses of biogoechemical significance: (1) bioturbation rates and depths vary with annual particulate organic-carbon (POC) flux to the seafloor, (2) these variations have a significant impact on the mineralization and burial of organic carbon in the seabed, (3) macrobenthic standing crop and mean body size are correlated with annual POC flux, and (4) seabed inventories of excess 234Th, 228Th and 210Pb are correlated with POC flux on 100-d, 10-yr and 100-yr time scales, respectively.