Relationships between phytoplankton standing crop and physical, chemical, and biological gradients in the Suwannee River and Plume region, USA

The Suwannee River (USA) is an amber stained, nutrient rich, blackwater riv er which hows into relatively clear oceanic waters resulting in the formati on of a coastal region with unique physical, chemical, and biological gradi ents. The intent of this study was to describe the spatial and temporal var iability of phytoplankton as it relates to these gradients. Ten stations al ong a transect ranging from 5 km up river to 31 km offshore, were sampled d uring four different flow regimes. All four sampling periods included in ou r study of the Suwannee River and plume region exhibited a simiIar pattern of phytoplankton abundance; low phytoplankton biomass in the Suwannee River and offshore stations with an area of elevated biomass seaward of the Suwa nnee River outflow. The results of our analysis of light and nutrient Limit ation in the region support the hypothesis that this spatial pattern of phy toplankton abundance is strongly influenced by color dependent light Limita tion in the river and outflow area, combined with nutrient Limitation offsh ore, Our results suggest that both light and nutrient availability control abundance and composition of phytoplankton in this coastal area.