Sediment phosphorus fractionation in calcium carbonate sediments of northeastern Florida Bay

Different physiochemical processes control phosphorus storage in subtropical versus temperate estuaries; however, few studies are available on sediment phosphorus storage from the subtropics. In this study, solid-phase phosphorus pools of northeastern Florida Bay's sediments were examined by sequential chemical extractions, separating phosphorus into exchangeable, iron-bound, calcium-bound, and residual organic fractions. Calcium-bound phosphorus was the dominant fraction, accounting for approximately 60% of the total phosphorus and 93% of the inorganic phosphorus. Residual organic phosphorus was the second dominant fraction, accounting for 37% of the total phosphorus. In contrast to calcium-bound and residual organic phosphorus, the concentration of iron-bound phosphorus was low, indicating a limited role of iron in long-term phosphorus storage. The fine-grained carbonate sediments of Florida Bay probably account for the large pool of calcium-bound phosphorus, while the proximity of the mangroves to the northeastern section of the Bay may account for the high residual organic pool of phosphorus.