Seasonal Differences in the Composition of Ogeechee River Benthic Communities in Response to Temporal and Environmental Factors

The Ogeechee river is a free-flowing blackwater river rising in the Georgia piedmont before flowing into the coastal plain. Benthic macroinvertebrate communities in the river experience seasonal variation of physicochemical variables due in part to winter and spring floods. In combination with temporally driven life history traits, these factors can alter community composition over the course of the year. To examine how they influence invertebrate assemblages, quarterly benthic and physicochemical sampling was performed at six sites along the Ogeechee River within the coastal plain. Invertebrates were collected using a 20 jab method and a 200-invertebrate sub-sample was identified to genus or lowest practical taxonomic level. Resemblance based analyses of community structure suggest some degree of separation between communities by season. Discharge, temperature and pH vary seasonally and appear to be major drivers of differences in community structure. The prominence of these variables supports the role of seasonal changes in climate and hydrology in governing benthic biota in the lower portion of the river