The dynamics of diatom blooms and silicon cycling in coastal waters of the southwestern Florida Shelf and northwestern Florida Bay

Diatom blooms dominated by Rhizosolenia sp. develop annually in northwestern Florida Bay. The annual cycle of diatom bloom development was analyzed in coastal waters of the southwestern Florida shelf during two years of contrasting precipitation. Spatial and temporal variability in the surface distributions of phytoplankton biomass were analyzed and nutrient sources to coastal waters were identified. Dilution-grazing experiments and nutrient bioassays investigated the dynamics of phytoplankton growth in inner shelf waters and in northwestern Florida Bay. Nutrient requirements were quantified and compared to the alongshore and riverine fluxes of nutrients. The role of advective processes in the transport of phytoplankton biomass and nutrients was investigated. The rate of exogenous supply of silicic acid to planktonic diatoms was compared to the rates of silicic acid regeneration measured in the water column and sediments. The turnover time for silicic acid was calculated. Silicon budgets were constructed to identify trends in the silicon cycle during three phases of a diatom bloom in northwestern Florida Bay and a conceptual model was developed to describe the temporal and spatial scales of evolution of an annual diatom bloom in coastal waters of the southwestern Florida shelf.