Seasonal variation of the carbonate system in Florida Bay

Abstract

The carbonate system has been studied in the Florida Bay from 1997 to 2000. Measurements of pH, total alkalinity (TA) and total inorganic carbon dioxide (TCO 2 ) were made from 20 stations in the bay and used to calculate the partial pressure of carbon dioxide (pCO 2 ) and the saturation states of aragonite (Ω Arg ) and calcite (Ω Cal ), The results were found to correlate with the salinity. The pH was low and the pCO 2 was high for the freshwater input from the mangrove fringe due to the photochemical and biological oxidation of organic material. The TA and TCO 2 for the freshwater input are higher than seawater due to the low values of pH and Ω, The pH was high and the pCO 2 was low in November in regions where the chlorophyll is high due to biological production. During the summer when the salinity is the highest the normalized values of TA and TCO 2 were lower than average seawater, due to the inorganic precipitation of CaCO 3 caused by the resuspension of sediments or the biological loss by macroalgae. A transect across the mangrove fringe near the outflow of Taylor Slough shows that PO 4 and TA increases as the freshwater enters the Bay. This is thought to be due to the dissolution of CaCO 3 in the low pH waters from the bacterial and photo oxidation of plant material.