(2004) Bull Shoals Lake, MO-AR - Spatial Distribution and Seasonal Dynamics of Plankton


Despite several decades of existing research on eutrophication in lakes, changes in reservoir plankton communities are poorly understood.

This study examined spatial patterns and dynamics of algae and zooplankton in an oligo-mesotrophic main-stem reservoir - Bull Shoals Lake, Missouri/Arkansas - which was threatened by rapid development in upstream reservoirs.

Eighteen sites were sampled for one week in the summer, and the seasonal dynamics of algae and zooplankton were then followed at two of the sites.

The lake showed strong spatial patterning in transparency, concentrations of phosphorus and chlorophyll-a, and densities of algae and zooplankton. Algal composition varied substantially among sites, with cyanobacteria most abundant in up-reservoir and tributary sites. Although cyanobacteria were most abundant in late summer, appreciable densities were found throughout the year. Zooplankton were dominated by rotifers and cladocerans, which showed large oscillations in density over time. Abundance peaks occurred earlier in an up-reservoir sites as compared with down-reservoir sites, with a time delay of about a month for algae and four months for zooplankton. The plankton composition was consistent with the oligo-mesotrophic status of Bull Shoals Lake, but high densities of cyanobacteria at some tributary sites and in upstream reservoirs indicated localized enrichment and the threat of eutrophication in this clear Ozark lake.