Nutrient limitation of benthic primary production in the upper Florida Keys

Spatial patterns in seagrass stoichiometry from the Florida Keys suggest that benthie community responses to eutrophication may significantly differ from nearshore habitats to the offshore reef tract. A 14 month in-situ nitrogen and phosphorus fertilization experiment was carried out to assess the consequences of coastal nutrient enrichment in the upper Florida Keys. The responses of benthic communities to nitrogen and phosphorus enrichment varied appreciably between nearshore and offshore habitats. Offshore seagrass beds were strongly limited by nitrogen, as suggested by highly significant increases in seagrass morphology, biomass, abundance, and growth rates in response to added nitrogen but not to phosphorus. Nearshore sites were affected by simultaneous nitrogen and phosphorus addition, where significant increases were found for seagrass abundance and growth, macroalgae abundance, epiphyte loads, and sediment microalgae. This investigation emphasized the importance of nutrient supply in determining benthic community composition in the upper Florida Keys