Monsoonal forcing of calcification in the Arabian Sea

This paper summarizes our results on the changes in pelagic calcification and the standing stock of calcium carbonate associated with the SW Monsoon and NE Monsoon (cruises TN049 and TN053 of the U.S. JGOFS study, respectively) in the northern portion of the Arabian Sea. Mean calcification was similar to 3X greater during the SW Monsoon than during the NE Monsoon. Calcification per coccolithophore was 7-10X higher, and the ratio of calcification to photosynthesis (C/P) was 40-45% higher during the SW Monsoon. The turnover time of PIC was not statistically different between the two cruises (similar to 4.5 d averaged over the euphotic zone). Turnover time of POC increased significantly between TN049 and TN053 (from similar to 3 to 6 d over the euphotic zone). We discuss vertical sections of coccolithophore: abundance, carbon standing stocks and carbon fixation. Coccolithophore calcification was usually about 1-5% of community photosynthesis. The ratio of calcification to photosynthesis spanned almost 2 orders of magnitude, and was not significantly different from the ratio of the PIC and POC standing stocks. We compare surface PIC and POC production rates to sediment trap fluxes from the same region. (C) 2000 Elsevier Science Ltd. All rights reserved.