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SFS Annual Meeting

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THE EFFECTS OF LIGHT AND TEMPERATURE GRADIENT EXPOSURE ON ENZYME ACTIVITY OF LEAF LITTER-ASSOCIATED MICROBIAL DECOMPOSERS

Algae, bacteria, and fungi develop complex litter-associated biofilms during decomposition of plant litter in aquatic ecosystems, and recent studies suggest algae can alter heterotrophic decomposition of organic matter in the presence of light by exuding photosynthates (labile carbon) via the priming effect. To better understand this stimulation of fungi and bacteria by algae, we quantified decomposition rates and degradative enzyme activity from Typha domingensis litter pieces exposed to dark, photosynthetically active radiation (PAR), or PAR + Ultraviolet light under contrasting temperatures (7, 14, 21, 28?C) conditions in aquatic mesocosms. Temperature significantly affected all enzyme activities and decomposition rates (P<0.001) with the highest rates consistently observed at 28?C. B-glucosidase, phosphatase, and leucine aminopeptidase activities were all significantly affected by light (P<0.05). Carbon-acquiring B-glucosidase activity was higher in the dark treatment, while nutrient-acquiring phosphatase and leucine aminopeptidase activities were higher in the PAR+UV and PAR treatments. Although there were only weak light effects on decomposition, these enzyme patterns suggest decomposition rates could differ longer-term. Broadly, the differences in enzyme activity suggest algal exudates alleviate heterotrophic carbon limitation, but competition with algae may exacerbate nutrient limitation of heterotrophic microbes during litter decomposition.

Stephanie Koury (Primary Presenter/Author), University of Southern Mississippi, steph.koury@gmail.com;


Halvor Halvorson (Co-Presenter/Co-Author), University of Southern Mississippi, Halvor.Halvorson@usm.edu;


Kevin Kuehn (Co-Presenter/Co-Author), The University of Southern Mississippi, kevin.kuehn@usm.edu;


Steve Francoeur (Co-Presenter/Co-Author), Biology Department, Eastern Michigan University, steve.francoeur@emich.edu;


Joel Bonney (Co-Presenter/Co-Author), Eastern Michigan University, jbonney@emich.edu;


Robert Findlay (Co-Presenter/Co-Author), University of Alabama, rfindlay@ua.edu;