Phytoplankton production in the Corpus Christi Bay estuary.
The Texas Gulf coast is characterized by a number of subtropical estuaries which have great economic and ecologic value in that they support important regional fisheries through production of new organic matter by phytoplankton photosynthesis. One of these estuaries, the Corpus Christi Bay ecosystem, was studied for a three-year period to define temporal and spatial variability in its primary production and to elucidate environmental factors important in regulating production. Mean annual phytoplankton production at the various sampling sites increased with distance from the riverine influence of the estuary. This pattern was most closely associated with deeper, less turbid waters at the oceanic end of the estuary that provided a greater euphotic zone. Variability in measured primary productivity rates between sites was most influenced by water column nutrients in January and July and more significantly correlated to salinity changes in April and October. From the three years of data, annual phytoplankton production was estimated to be 174.1 g C/m2/yr, which represented 52% of total new organic production in this estuary. In contrast, macrophytes and tidal flat algae comprised the remainder of new organic carbon production. Annual production was found to be most significantly affected by freshwater input from either river flow or rainfall, depending upon where production measurement were made in the estuary. High turbidity of this estuarine ecosystem was thought to limit production in contrast to other north American estuaries. It was concluded from the study results that long-term maintenance of primary production in this estuary is accomplished through nutrient recycling while acute changes from both meteorological and hydrologic forcing cause short-term increases in the production that sustain steady-state and replenish lost materials to the system.