Process Influencing Water Column Nutrient Characteristics and Phosphorus Limitation of Phytoplankton Biomass in Florida Bay, FL, USA:Inferences from Spatial Distributions

Abstract The concentrations of nutrients, dissolved and particulate organic matter, salinity and chlorophyll-α in the water column were measured over the period of June 1989 to August 1990 at a network of 26 sampling locations across Florida Bay. Florida Bay was hypersaline during this time period, with an average salinity of 41·4. Dissolved organic phosphorus was the dominant form of P in the water column, while soluble reactive P was generally less than 5% of the total P. Organic nitrogen forms dominated the N pool, and NH + 4 was the dominant form of dissolved inorganic nitrogen. Many of the measured parameters were correlated. Principal Components Analysis extracted three composite variables that described 90·3% of the variation in the original data set. PC I was highly correlated with total organic N, total N, total organic C and salinity. PC II was correlated with all measures of P and chlorophyll-α. PC III was correlated with measures of inorganic N. The spatial distribution of factor scores for these principal components indicate three processes acting independently to control the composition of the water column of Florida Bay: the evaporation-driven concentration of dissolved material in Florida Bay; the delivery of P to Florida Bay through water exchange with the Gulf of Mexico; and the delivery of freshwater with an excess of N with respect to P to Florida Bay. The phytoplankton biomass in the water column of Florida Bay is shown to be P-limited.