Zooplankton species diversity in the temporary wetland system of the Savannah River Site, South Carolina, USA
Zokan, Marcus Alexander
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Understanding how diverse species communities develop and how the species within them coexist is one of the central questions in community ecology. The temporary wetland system occurring on the Savannah River Site near Aiken, South Carolina is home to the most species rich temporary wetland zooplankton assemblage known in the world. While previous research has documented this remarkable diversity, there has been little study directed at understanding how diversity is distributed at the landscape and local scales or on investigating potential mechanisms of what has led to the high richness of this system. The collection of studies presented here examine diversity patterns in the zooplankton community, links these patterns to spatial and temporal variation, experimentally tests the effects of two important environmental factors on diversity, and describes two new species. Results indicate that long hydroperiod lengths were associated with high species richness. Wetlands with similar species assemblages were generally closer together, suggesting the importance of dispersal. Over the course of a year, diversity increased during the spring and summer months and declined toward the fall, these changes were associated with low pH, low conductivity, and high water temperature. Vegetated areas within wetlands had greater diversity than did unvegetated areas, and diversity was particularly low in areas of decaying vegetation. Temporal comparisons provide evidence for distinct seasonal communities that arise every year. Experimental tests of the impact of hydroperiod length on diversity found that shorter hydroperiods resulted in reduced species richness, and communities dominated by just a few species. Predation was found to have no effect on diversity or community composition. During investigation of the diversity of these wetlands, two new species of the genus Chydorus were discovered and described. These two species differ from congeners both in morphology and phylogenetically. Together these studies describe how environmental variation can impact the diversity of the zooplankton communities within temporary wetlands and show how hydroperiod limits the richness of these systems. The results presented here provide insight into the forces that may lead to diverse communities in temporary wetlands, providing direction for future research into these dynamic ecosystems.