SUMMARYIn the summer of 1959, temperature, Eh, pH, chlorinity and alkalinity of sea and interstitial water were measured in the westernmost part of Great Bahama Bank and in Florida Bay (Fig. 1).Boring organisms, especially algae, grazing snails and inorganic processes are deepening solution basins there (Fig. 2, 3, 5, 6). Carbonate balance in the Bimini lagoon is influenced by the activity of grass (Fig. 8), algae and animals with carbonate tests and shells, and physicochemical differences between day and night, high and low water. Inorganic precipitation of calcium carbonate seems to be small compared with the losses due to incorporation into organisms. In Florida Bay saturation is partly influenced by plants also. Supersaturation can be high and wind action stirs up countless small carbonate particles (Fig. 7). This suggests that inorganic precipitation must occur. Calcium carbonate precipitation as outlined by Smith(1940) was observed on Great Bahama Bank even in the mixed waters of the westernmost parts and in the interstitial water of moving oolitic sand.