Carbon dioxide daily variations and atmospheric fluxes over the Great Bahama Bank using a novel autonomous measuring system

A novel autonomous measuring device that acquires the partial pressure of CO2 (pCO2) by
equilibration and several other parameters is described. This device, the Floating Equilibrator System (FES)
was tested in field conditions for the first time in the Great Bahama Bank, in December 2000. We successfully
carried out two 24 h cycles in Norman’s Pond, one in front of the Caribbean Marine Research Centre (CMRC)
and another one near Bock Cay. Over-saturation of CO2 with respect to atmospheric equilibrium was observed
systematically at the three sites, although significantly more marked at Norman’s Pond. The higher
values of pCO2 and atmospheric CO2 fluxes obtained at Norman’s Pond, than in the adjacent open waters of
the Great Bahama Bank, suggest a comparatively stronger heterotrophy at Norman’s Pond. This is most likely
related to the organic carbon inputs to the water column and sediments from the dense mangrove forest
surrounding Norman’s Pond. The larger amplitude of pCO2 daily variations observed, during the Norman’s
Pond 24 h cycles, is probably due to higher biological activity than in the adjacent open waters of the Great
Bahama Bank. This is corroborated by a tentative estimation of Gross Primary Production based on simple
computations. We speculate that calcification could also contribute to some extent to different amplitude of
the pCO2 daily variations between the mangrove pond and the open waters of the Great Bahama Bank.