Carbon cycling in coastal sediments: Estimating remineralization in Buzzards Bay, Massachusetts

Accurately estimating rates of remineralization of organic matter in sediments (early diagenesis) is a prominent problem for benthic ecologists as well as organic geochemists. McNichol et al. (1988) employed a novel approach to the problem by separating CO{sub 2} produced by respiration from CaCo{sub 3} dissolution, thus theoretically eliminating the need to measure the reduction of terminal electron acceptors in respiration (O{sub 2} NO{sub 3}, SO{sub 4} etc.). Pioneered by Emerson et al. (1980) and Sayles (1981) for deep-sea sediments, this method employs measurements of Ca{sup 2+} in porewater to differentiate between carbonate dissolution and respiration. McNichol et al. (1988) were able to plot metabolic CO{sub 2} profiles over the surface 20 to 30 cm of sediment over an annual cycle at a single station in Buzzards Bay, MA. They used the carbon dioxide profiles in a vertical exchange and reaction model to estimate total organic carbon remineralization per year. Lower Buzzards Bay where McNichol et al. (1988) worked is well studied because of its proximity to the research institutions in Woods Hole. It is the authors intention in this paper to compare the results of these older benthic metabolism studies in Buzzards Bay with those inferred from the model of the porewater carbon dioxide profile. The published data from three studies have been converted from mL O{sub 2} M{sup {minus}2}H{sup {minus}1} to millimoles and plotted over a 12-month period, thus illustrating the seasonal change in total benthic oxygen demand. The temperature data available at the sites plotted over the year have a somewhat similar patter, and as expected the oxygen demand correlates reasonably well with the temperature.