MODELING THE ANNUAL PRODUCTION OF INTERTIDAL BENTHIC MICROALGAE IN ESTUARINE ECOSYSTEMS

The purpose of this study was to develop and validate a habitat-specific production simulation model to quantify annual benthic microalgal production in North Inlet estuary, South Carolina. Using hourly measurements of incident irradiance during 1990-1991 as the forcing function, the simulation model was used to obtain hourly estimates Of areal benthic microalgal gross primary production in five habitat types. The model, which was validated using actual measurements of production, showed good (r2 = 0.63, P < 0.001) agreement between observed and predicted production values. During the year, predicted microalgal production in the short Spartina alterniflora Loisel zone habitats showed the highest mean hourly production (61.1 mg C.m-2.h-1) while intertidal mudflats had the maximum hourly rate (166.9 mg C.m-2.h-1). Daily production was highly variable, primarily due to daily fluctuations in irradiance. Annual estimates of habitat-specific production were multiplied by the known area of each habitat type to determine total microalgal production for the estuary (3.423 x 10(9) g C.yr-1). Short Spartina zone habitats provided 45% of total microalgal annual production, followed by intertidal mudflats (22%), tall Spartina zones (18%), shallow subtidal (13%) and intertidal sandflat (3%) habitats. In this estuary, benthic microalgal production exceeds phytoplankton and macroalgal production but is less than Spartina production.