HYDROLOGIC SIGNIFICANCE OF OSTRACODE SPECIES DIVERSITY IN APPALACHIAN SPRINGS

Springs of the forested Appalachians are remarkably varied in their lithologic settings and species diversity, yet are also characterized by small size, relatively short flow paths, low total dissolved solids, and small catchments. In a comparative study of 20 springs in Ohio, Pennsylvania and West Virginia, ostracode species, major ion hydrochemistry, and stable isotopes were analyzed. In the unglaciated areas, ostracode assemblages in each of the springs show little overlap with each other, despite the springs’ similar hydrochemistries. The distinctive assemblages indicate long established local and separate groundwater catchments and flow paths. In contrast, in glaciated areas, the ostracode species assemblages showed lower species richness, more overlap with each other, and a higher number of cosmopolitan species. Common species in the springs developed in glacial till include Cypridopsis vidua, Potamocypris pallida, Cypridopsis okeechobei, and Physocypria globula, all widely distributed cosmopolitan taxa. By comparison, species in unglaciated, karst settings of the forested Appalachians include Candona wegelini, Candona sigmoides, Bradleystrandesia sp., as well as Nanocandona and Schellencandona sp., both aquifer taxa. Hydrochemistries of these dilute systems are similar throughout the dataset, with d18O and dD values of the spring water indicating rapid response to precipitation. These conditions suggest that age of these springs plays an important role in species richness, with the unglaciated region supporting more diverse assemblages.