Biogenic silica cycle in surface sediments of the Greenland Sea

In contrast to several investigations of biogenic silica (BSi) content and recycling in surface sediments of the Southern Ocean, little is known about the benthic cycle of BSi in high northern latitudes. Therefore, we investi gated the silicic acid concentration of pore water and BSi content of surfa ce sediments from the Greenland Sea. Low BSi contents of less than 2% were observed. High-resolution (2-5 mm) BSi profiles and comparisons to trap stu dies suggest that only relatively dissolution-resistant siliceous component s reach the seafloor. Pore water-investigations reveal BSi fluxes of more t han 300 mmol m(-2) a(-1) only for a few sites on the shelf. A statistically significant relationship between water depth and BSi rain rate reaching: t he seafloor was not observed. Sampling along a transect perpendicular to th e marginal ice zone (MIZ) revealed no enhanced rain rate of BSi reaching th e seafloor in the vicinity of the ice edge. Although the MIZ of the Greenla nd Sea is characterized by the enhanced export of biogenic particles from s urface waters, this feature is not reflected in the benthic cycle of biogen ic silica. The lack of such a relationship, which is in contrast to observa tions of shelf and continental margin sediments in the southern South Atlan tic, is probably caused by the enhanced dissolution of BSi in the water col umn and highly dynamic ice conditions in the Greenland Sea. (C) 2000 Elsevi er Science B.V. All rights reserved.