Environmental factors of high phytoplankton beta-diversity across reservoirs

Background/Question/Methods

High beta-diversity is thought to help buffer local communities against environmental fluctuations, thereby increasing the reliability of related ecosystem services [i.e., potable water].  For example, high potential for species turnover is expected to foster species-rich local communities, which can suppress otherwise competitively superior cyanobacteria in nutrient-rich environments.  Therefore, it is of key importance to understand the environmental factors that best explain algal diversity in various ecosystems.  We examined the algal communities in twenty prairie reservoirs characterized along a gradient of moderate to high production, and analyzed beta-diversity that works to compare the species diversity between ecosystems along such environmental gradients. 

Results/Conclusions

At the local scale (among reservoirs), phytoplankton species diversity had a significant relationship with total phosphorus.  Redundancy Analysis (RDA) ordination of the algal data resulted in two significant axes, and identified high algal production concordant with a diverse population of cyanobacteria.  In contrast, species-rich algal communities dominated namely by phytoflagellates was consistent in reservoirs being nitrogen-rich [i.e., N:P > 15].  Our findings suggest that reductions in the dominance of cyanobacteria, with a more diverse assemblage of all other algal populations, can only be maintained based on the rates of diminished internal phosphorus loading in these reservoirs.