Phosphorus (P) limits seagrass and phytoplankton growth in much of Florida Bay. Dissolved phosphate concentrations in bay waters are as low as a few nanomolar (Zhang and Chi, 2002). Sedimentary phosphorus represents the largest phosphorus reservoir as carbonate sediments in the bay strongly retains phosphorus. In November 2000, surface sediments were collected from 40 stations in Florida Bay, USA. The total sedimentary P (TSP) was determined by single-step high temperature combustion of samples at 550°C. An improved sequential extraction technique was used in a subset of samples to fractionate TSP into five different pools: (1) exchangeable inorganic and organic P, (2) iron bound inorganic P, (3) biogenic calcium carbonate bound inorganic and organic P, (4) apatite and (5) refractory organic P. The dataset also include surface reactive iron by selective reduction and percent of calcium carbonate (CaCO₃) in Florida Bay sediments. This dataset provides the first detailed spatial distribution of TSP and its partitioning in five chemically distinguishable pools in the surface sediments of Florida Bay. A strong gradient of decreasing TSP concentration was observed from the west (14.6 µmol g⁻¹) to east (1.2 µmol g⁻¹) across the central bay. Among the five pools, the authigenic carbonate fluorapatite, biogenic apatite and CaCO₃ associated phosphorus account for the largest fraction (45%) of TSP, of which inorganic P is the dominant form, and organic P accounts for about 30% in regions of relatively high productivity and less than 10% in other areas of the bay. The second largest pools are the refractory organic P (24% of TSP) and Fe-bound inorganic P (19% of TSP). Readily exchangeable adsorbed P accounts for 8% of TSP, of which organic P is 60%. Detrital apatite phosphorus of igneous or metamorphic origin represents the smallest fraction, only 5% of TSP. Combining all five pools, organic P accounts for 38% of TSP.
