Factors controlling the rate of CaCO3 precipitation on Great Bahama Bank

Measurements by Langdon et al. [2000] in the man-made mesocosm coral reef a t Biosphere 2's ocean reveal a strong dependence of calcification rate on t he degree of supersaturation of CaCO3 in seawater. A similar trend was prev iously encountered on the Bahama Banks, where Halimeda and other calcifiers are likely responsible for aragonite precipitation [Broecker and Takahashi , 1966]. In this paper we compare these two sets of results and conclude th at the dependence on saturation state is significant but less strong in the Bahamas. However, it must be kept in mind that to some extent, the reducti on in CaCO3 precipitation on the Bahama Banks may be due to impact of highe r salinity on the growth of the calcifying algae. However, if, as many sedi mentologists are convinced, the precipitation of CaCO3 on the Bahama Banks is inorganic [Macintyre and Reid, 1992; Milliman et al., 1993], then the co mparison of the Bahamas and Biosphere 2 results for dependence of calcifica tion rate on saturation state is telling us something quite different.