Composition and Diversity of Intertidal Microphytobenthos and Phytoplankton in Chesapeake Bay

Microphytobenthic communities have long been recognized as significant components of aquatic systems and often treated as singular functional elements of benthic habitats. Recent evidence suggests that these communities are phylogenetically diverse, with varying physiological characteristics. Considering their capabilities of nutrient regulation, sediment stabilization, and position in aquatic food webs, characterization of microphytobenthic structure is an important aspect in understanding these communities. This study represents a 2-year survey of taxonomic composition of microphytobenthic communities associated with Chesapeake Bay, with comparisons made to adjacent phytoplankton communities. A total of 142 algal taxa were identified (124 phytoplankton; 95 benthos). Microphytobenthos were dominated by diatoms and cyanobacteria. Seasonal average benthic microalgal biomass ranged from 60 to 229 mu g C/cm(3). Within the phytoplankton, diatoms dominated the biomass in all but one season. Phytoplankton biomass was significantly lower than the benthos (p < 0.0001), and seasonally ranged from 0.44 to 2.20 mu g C/ml. Composition differed between habitats, with phytoplankton more diverse than microphytobenthos. Both communities exhibited seasonal patterns, though plankton was most influenced by salinity, whereas benthic algal populations were driven by sediment grain size. These results provide evidence for microphytobenthos as complex, diverse communities significantly different than neighboring phytoplankton populations.