DIDYMOSPHENIA GEMINATA STUDY IN RAPID CREEK, SOUTH DAKOTA

Rapid Creek is a spring fed perennial oligotrophic cold water stream that rises in southwestern South Dakota, in the Black Hills National Forest in the Black Hills in Pennington County (Carter et. al., 2002). In 2002, a massive algal bloom was observed in Rapid Creek. This bloom was due to excessive growth of a diatom Didymosphenia geminata. Algal blooms are typically associated with nutrient rich waters, often attributed to anthropogenic activities that pollute surface waters. It is paradoxical that D. geminata blooms under conditions where nutrient availability can be apparently growth limiting. Nutrient analyses on Rapid Creek confirm low concentration of dissolved nutrients. Yet the algal mats harbor relatively higher nutrient concentrations. While the surface water nutrient concentrations do not vary significantly over a 6 mile stretch of the Rapid Creek, D. geminata blooms are spotty. Observations show these stations differ in stream velocity, which may be an important factor in regulating the bloom of D. geminata in this stream. This paper presents how nutrients availability and stream flow rate at different sites contribute to the growth of D. geminata.

References

Carter J. M., Williamson J. S., Teller R. W. (2002): ‘The 1972 Black Hills-Rapid City Flood Revisited’, USGS Fact Sheet FS-037–02.