Under Gause's principle two species cannot indefinitely occupy the same niche. The north and south arms of Great Salt Lake are separated by a rail causeway, resulting in salinity differences and color variation between the arms. Farmington Bay is also separated from the south arm by a vehicular causeway to Antelope Island. These causeways allow examination of competitive exclusion of cyanobacteria in the hypersaline environment of the Great Salt Lake. Cyanobacterial distributions partially map salinity, with Aphanothece halophytica proliferating in the north arm, and Nodularia spumigena in the south arm. I hypothesized that cyanobacterial species abundant north of the railway causeway are competitively excluded from the south by other species, and that cyanobacterial species that thrive and bloom south of the Antelope Island causeway cannot grow in the high salinity of the north. To test these hypotheses, 129 flasks of autoclaved water from the north and south sides of each causeway were inoculated with Great Salt Lake water samples from the north and south sides of the causeways. Four genera of cyanobacteria, Aphanothece, Oscillatoria, Phormidium, and Nodularia were identified and counted from the culture flasks using comparative differential interference contrast, fluorescence, and scanning electron microscopy. Counts of the cyanobacteria found in each flask were totaled and two way Analysis of Variance tests as well as exact tests were performed. Rankings of median abundances were also calculated. These data support the first hypothesis because Aphanothece halophytica was found in all inocula, but appears to be suppressed by the presence of Nodularia spumigena, which periodically blooms. The second hypothesis is also supported by the data because N. spumigena was found only in inocula from the less saline waters south of Antelope Island causeway, and apparently cannot survive the high saline waters north of the railway causeway.



College and Department

Life Sciences; Plant and Wildlife Sciences



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cyanobacteria, competitive exclusion, Great Salt Lake