Competitive exclusion of Cyanobacterial species in the Great Salt Lake

The Great Salt Lake is separated into different salinity regimes by rail and vehicular causeways. Cyanobacterial distributions map salinity, with Aphanothece halophytica proliferating in the highly saline northern arm (27% saline), while Nodularia spumigena occurs in the less saline south (6-10%). We sought to test if cyanobacterial species abundant in the north are competitively excluded from the south, and if southern species are excluded by the high salinity of the north. Autoclaved samples from the north and south sides of each causeway were inoculated with water from each area. Aphanothece, Oscillatoria, Phormidium, and Nodularia were identified in the culture flasks using comparative differential interference contrast, fluorescence, and scanning electron microscopy. Aphanothece halophytica occurred in all inocula, but is suppressed in the presence of Nodularia spumigena. N. spumigena was found only in inocula from the less saline waters in the south, and apparently cannot survive the extremely hypersaline waters of the northern arm. These data suggest that both biotic and abiotic factors influence cyanobacterial distributions in the Great Salt Lake.