PRESERVATION EFFICIENCIES AND ACCUMULATION RATES FOR BIOGENIC SILICA AND ORGANIC C, N, AND P IN HIGH-LATITUDE SEDIMENTS - THE ROSS SEA

Rates of biogenic sediment accumulation (biogenic silica and organic C , N, and P) and pore water flux have been established for a variety of depositional environments in the Ross Sea, On the basis of C-14 measu rements in kasten cores, sediment accumulation rates ranged from 250 c m kyr(-1) in the coastal basin of Granite Harbor to 1-2 cm kyr(-1) in the shelf and slope environments of the northern and eastern Ross Sea. Burial of biogenic material was most rapid in the southwestern Ross S ea, where biogenic silica accumulation rates ranged from 2 to 31 g cm( -2) kyr(-1) and organic carbon accumulation rates ranged from 0.05 to 1.4 g cm(-2) kyr(-1) In the northern and eastern Ross Sea, biogenic si lica and organic carbon accumulation rates typically equaled 0.02-0.03 g SiO2 cm(-2) kyr(-1) and 0.002-0.004 g C cm(-2) kyr(-1). Flux core m easurements were used to estimate seated regeneration rates for biogen ic silica, organic carbon, and phosphorus. Pore water fluxes, in gener al, showed much less variability across the Ross Sea than did the biog enic accumulation rates. Pore water silicate fluxes in the study area ranged from 0.6 to 5.3 g SiO2 cm(-2) kyr(-1), whereas carbon fluxes ra nged from 0.1 to 1.2 g C cm(-2) kyr(-1) and phosphate fluxes varied fr om -0.006 to 0.012 g P cm(-2) kyr(-1). Seabed preservation efficiencie s were calculated for biogenic silica, organic carbon, and phosphorus by combining the solid-phase and pore water data. The seabed preservat ion efficiencies for biogenic silica (1-86%) were greater than for org anic carbon (1-71%) at all nine stations examined. The preferential pr eservation of biogenic silica relative to organic carbon also was appa rent in Ross Sea sediments because the biogenic silica/organic carbon ratio in the material buried in the seabed generally was 2 times great er than the ratio in sediment particles arriving at the sediment-water interface. Sediment accumulation rate correlated strongly with both t he biogenic silica and the organic carbon preservation efficiency data . P preservation efficiencies remained relatively high (24-65%) even w hen the accumulation rates were low (1-2 cm kyr(-1)) because of the ne ar-zero phosphate fluxes out of the seabed. Of the total P in the seab ed (0.04-0.09 wt. %), approximately 25% existed in the form of organic P. The total amount of biogenic silica accumulating on the Ross Sea s helf is similar to 2.3 x 10(12) g SiO2 yr(-1), which is approximately an order of magnitude less than the Ledford- Hoffman et al. [1986] est imate that was based on Pb-210 chronologies. Biogenic silica accumulat ion rates in the southern, central, and western Ross Sea increased dur ing the mid and late Holocene, reaching their maximum values during th e past 500 to 1000 years.