Water Quality and Planktonic Communities of the Blackwater Satilla River


Water Quality and Planktonic Communities of the Blackwater Satilla River


Blackwater rivers in the southeastern U.S. have naturally low dissolved oxygen (DO) levels during the summer months. How can we recognize when we are observing naturally low DO levels or when we are observing low DO levels caused by various point and non-point influences? Are there planktonic organisms that can indicate excess nutrients, high turbidity, or low DO? To answer this, we must first understand the basic planktonic community composition in blackwater rivers. This study examined differences between two locations on the Satilla River (Woodbine and Burnt Fort) in relation to physiochemical parameters (e.g., DO, pH, salinity, conductivity, temperature, and secchi disk depth) and plankton communities (taxa richness, evenness, and diversity). Both Woodbine and Burnt Fort showed mean DO levels that fell below the state standard of 4.0 mg/L, even though only Woodbine is classified, using Georgia state standards, as a part of a DO-impaired segment. Results indicated that Woodbine had lower DO, higher turbidity, higher temperatures, and a greater salinity influence than Burnt Fort. Woodbine also had a greater number of plankton taxa, but the taxa were not as evenly distributed as at Burnt Fort, which therefore had a greater diversity index. The average total abundance of phytoplankton differed significantly between the two sites as well as the relative abundance of five other subgroups; these should be further studied to better understand how plankton abundance and diversity change with the influx of nitrates, phosphates, and organic matter.

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