An ecological study of algal communities in the Jackson River (Covington, VA): Spatial and temporal trends in the taxonomic composition of algal assemblages

K. Sachen^1,2, C.A. Firth^2,3, N.E. Saxe², C.A. Flinders², F. Acker², and D.F. Charles². ¹Department of Biology, Michigan State University, Lansing, MI, 48825, ²Patrick Center for Environmental Research, Academy of Natural Sciences, Philadelphia, PA, 19103, ³Department of Marine Science, University of Texas at Austin, Austin, TX, 78712

The Jackson River (Covington, VA) is a regulated river which experiences constant flows June-November and high benthic algal biomass (200-1600 mg chl a/m², > 6.27 x10⁶ µm/m²) downstream of nutrient-enriched effluent. Algal communities were analyzed (species composition and biovolume) to evaluate impacts on community composition and identify potential remediation measures. Samples were collected from a phosphorus-limited reference site upstream of the facilities and several nitrogen-limited sites at varying distances downstream of the facilities during 2000 (Aug-Dec) and 2001 (Apr-Dec). During 2000, algal biovolume was greatest during the fall months, especially October. Community trends in 2001 were less consistent with peak biovolumes being site and date dependent although higher biovolumes typically occurred in the fall. Non-filamentous diatoms and green alga were dominant at the reference site in 2000 and blue-green taxa dominant in 2001. During both years, filamentous diatoms were the most important taxa group, accounting for the greatest component of algal biomass at sites downstream of the facilities. The filamentous diatoms, Pleurosira laevis and Melosira varians, contributed the largest portion to overall algal biovolume at downstream sites. Results will aid in developing a model of periphyton-oxygen dynamics and be applied in efforts to reduce nuisance algae in the Jackson River.