Benthic nutrient remineralization and oxygen consumption in the coastal area of Hiroshima Bay

Abstract

In situ and laboratory measurements of nutrient fluxes across benthic sediments and the sediment oxygen demand (SOD) rates were made and compared in a shallow, eutrophic coastal area of Hiroshima Bay. The difference in the SOD rates was sarcely noticed between the two methods, but the nutrient fluxes from in situ sediments were about 2 times higher than laboratory measurements. The SOD rates in the coastal area of Hiroshima Bay were in the range of 0.20–0.61 g/m 2/day. On the other hand, the in situ values of the benthic fluxes of nitrogen and phosphorus across the surface sediments were in the ranges of 3.7–53.7 g N/m 2/day and −0.9 to 17.2 g P/m 2/day, respectively, and showed higher value, 10 times greater in summer than in winter or spring. It became clear from comparing the sedimentation rates of particulate matter suspended in the water with the benthic fluxes that 60–70% of the particulate nitrogen and phosphorus which settled on the sediments might return again to the water column.