Factors Regulating the Presence and Abundance of the Invasive Alga, Didymosphenia geminata, in the Upper Tennessee River Watershed
Hix LA. 2015. Factors Regulating the Presence and Abundance of the Invasive Alga, Didymosphenia geminata, in the Upper Tennessee River Watershed. Tennessee Technological University
ABSTRACT: Didymosphenia geminata is an invasive diatom that can form thick mats covering stream and lake bottoms altering benthic habitat structure and potentially altering community-level structure and function. The current range of D. geminata is expanding and there is limited knowledge of the factors that support colonization and mat growth. Twenty-four sites in the upper Tennessee River Watershed were sampled seasonally over one year to determine environmental factors that drive D. geminata presence, cell abundance and mat formation. Mats were only found in dam tailwaters and mat biomass decreased with distance downstream. Several environmental parameters correlated to cell and mat presence. Discriminant function analysis correctly classified 93 % of sites in regards to D. geminata state (i.e., absent, cells only, or cells-and-mats) based on water quality and habitat variables. The strongest discriminating variables among groups were SO42−, pH, temperature, Ca2+ and light availability. Variables that correlated with D. geminata presence were higher pH, lower temperature and higher light availability. The most important variables associated with mat formation were lower SO42− and higher Ca2+. There was also a strong relationship between water column cell abundance and pH (r2 of 0.94). To explore this relationship further I incubated D, geminata mats in recirculating chambers to determine the effects of pH on mat structure and function. There was significantly lower net primary production in acidic than neutral and basic treatments; thus the acid deposition and the underlying geology in the Southern Appalachian Mountains may be playing a role in limiting suitable habitat to D. geminata in areas such as in Great Smoky Mountains National Park. The distribution of D. geminata is currently limited to tailwater reaches in the upper Tennessee River Watershed and sites positive for D. geminata have substantially different habitat characteristics than are negative for D. geminata.
- Type
- Academic
- Authors
- Hix, Lucas
- Date of Issue
- 2015-12
- Publisher
- Tennessee Technological University
- Units
- GRSM
- Keywords
- Abrams Creek, acid deposition, acidification, algae, APHN, Appalachian Highlands Network, Calderwood, Cheoah, Chilhowee, Citico, Deep Creek, diatom, Didymo, Didymosphenia geminata, Fontana, Great Smoky Mountains National Park, GRSM, GRSM-01162, invasive, Little River, Middle Prong Little Pigeon River, Middle Prong Little River, Oconaluftee River, Raven Fork, rock snot, SER, Southeast Region, thesis