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THE INFLUENCE OF DIDYMOSPHENIA GEMINATA ON THE RESOURCE USE BY INVERTEBRATES AND FISH IN FRESHWATER STREAMS.

We used fatty acid methyl ester signatures to determine the effects of Didymosphenia geminata (Didymo) mat formation on food web dynamics and basal resource use in affected rivers. Invertebrates were collected from upstream areas with high Didymo levels and downstream areas with no concentrations in three Tennessee rivers. Lipid profiles of dominant macroinvertebrate taxa (Gammarus, Baetis, Chironomidae and Simuliidae) indicated a consistent reduction in the ratio of Omega-3 to Omega-6 fatty acids in upstream reaches. This change in fatty acid composition suggested a shift away from algal resources and a reduced reliance on biofilms in the presence of Didymo mats. Lipid profiles of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) showed a similar shift in fatty acid composition, most likely due to changes in composition of their food sources. However, brown trout showed an increase in DHA in the presence of Didymo, which was not seen in the invertebrates. This may reflect some level of Didymo consumption by these fish. Overall, our results indicate a dramatic shift in food web structure in the presence of Didymo mats.

Michelle Baskins (Primary Presenter/Author), Canisius College, baskinsm@my.canisius.edu;


Jonathan O'Brien ( Co-Presenter/Co-Author), Canisius College, obrien46@canisius.edu;


Natalie Knorp ( Co-Presenter/Co-Author), Tennessee Tech University, neknorp42@students.tntech.edu;


Justin Murdock ( Co-Presenter/Co-Author), Tennessee Tech University, jnmurdock@tntech.edu;