Calcite Production Rates in the Arabian Sea

作为美国JGOFS计划的一部分，该项目将解决相对于阿拉伯海有机生产的钙化程度。地质和地球化学证据表明，方解石在这个非常多产的地区主导着碳的埋藏。然而，在与标准光合作用测量相容的时间尺度上，没有对钙化的直接估计。基于碱度和TCO2垂直变化的间接估计表明，在东南季风期间，与1-2 gC m-2d-1的初级生产相比，泛光带的钙化率将在0.3-0.4 gC m-2d-1左右。基于沉积物积累速率的间接估计给出了非常相似的预测。然而，就碳埋藏而言，有机碳优先再矿化，因此区域有机碳沉积为2.65x10 5吨C -1，不到阿拉伯海北部方解石埋藏3.6x10 6吨C -1的十分之一。这种对方解石产量的间接估计需要广泛的假设，而这些假设需要用经验数据进行验证。钙化的直接同位素估计对于理解方解石产量的大小至关重要，测量的时间尺度与标准的初级生产测量相一致。同样重要的是将钙化的估计与程序中其他人所作的地球化学估计进行比较。＊＊＊

9311077 Balch This project will address the magnitude of the calcification relative to the organic production in the Arabian Sea as part of the U.S. JGOFS program. Geological and geochemical evidence points to calcite dominating the burial of carbon in this very productive region. However, no direct estimates of calcification exist at time scales compatible with standard photosynthesis measurements. Indirect estimates based on vertical changes in alkalinity and TCO2 suggest that euphotic zone calcification rates will be on the order of 0.3-0.4 gC m-2d-1 during the SE monsoon as compared to primary production of 1-2 gC m-2 d-1. Indirect estimates based on sediments accumulation rates give very similar predictions. In terms of carbon burial, however, the organic carbon is preferentially remineralized such that the regional organic carbon deposition is 2.65x10 5 tonnes C yr-1, less than a tenth of the calcite burial of 3.6x10 6 tonnes C y-1 over the northern Arabian Sea. Such indirect estimates of calcite production require broad assumptions which need to be validated with empirical data. Direct isotope estimates of calcification are essential to understanding the magnitude of the production rate of calcite, measured on time scales compatible with standard primary production measurements. Equally important will be the comparison of the estimates of calcification with geochemical estimates made by others in the program. ***