Benthic remineralization and burial of biogenic SiO2, CaCO3, organic carbon, and detrital material in the Southern Ocean along a transect at 170 degrees West

We investigated the composition, recycling, and mass accumulation rates of sediments along a transect in the Southern Ocean located from 66 degreesS to 57 degreesS at 170 degreesW. This transect also corresponds to the location of a sediment trap mooring line. The sediments at the seven sites studied range from largely terrigenous material to nearly pure (> 90%) biogenic silica. CaCO3 is a minor but persistent component at most sites. Mass accumulation rates have been determined on the basis of excess Th-230 in the sediments, i.e., Th-230-normalized accumulation rates. The influence of redistribution of sediments on the sea floor has been estimated from C-14 analyses. The recycling of material delivered to the sediments has been characterized on the basis of pore water studies that make extensive use of both in situ sampling and shipboard extractions. The influence of the highly variable rates of input of particulate matter that characterize much of the Southern Ocean upon pore water gradients and fluxes across the sediment water interface has been considered. We find only poor correspondence between BSiO2 burial fraction (=burial/particulate flux), a quantifiable measure of preservation efficiency, and BSiO2 particulate rain along the transect. However, preservation does appear to be closely linked to a combination of sedimentation rate and particulate rain. The burial fraction of BSiO2 is small relative to benthic rain (5-19%). Despite the small fraction buried, burial flux normalized to (sedimentation rate)(1,2) appears to provide a very consistent means of predicting benthic particulate rain over a large range of rain rates, including data from a number of different studies and environments. At sites with BSiO2 rain greater than or equal to 250 mmol m(-2) yr(-1) the average difference between predicted and observed rain is 25-30%. Such rain rates occur in many marine areas, particularly the Southern Ocean, with the result that this relationship potentially provides za means of estimating BSiO2 benthic rain over prolonged periods in the past on the basis of readily measured sediment parameters.