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SFS Annual Meeting

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EFFECTS OF TEMPERATURE AND LIGHT GRADIENTS ON ALGAL STIMULATION OF LITTER-ASSOCIATED MICROBIAL HETEROTROPHS

Recent studies have provided compelling evidence that periphytic algae can stimulate litter-associated microbial heterotrophs in the presence of light, but few studies have tested how this stimulation varies with environmental gradients such as light and temperature. We grew natural periphyton communities on submerged Typha litter, and then manipulated temperature (15, 20, 25, and 30°C) and light (0, 25, 53, 123, and 388 µmol m-2 s-1 PAR) while simultaneously quantifying rates of algal and fungal productivity in the laboratory. Michaelis-Menten saturation curves were used to examine the effects of light on algal production and exudation as well as fungal production. As expected, increasing light stimulated periphytic algal production and exudation rates (P<0.001) on Typha litter, with the greatest light half-saturation constants for photosynthesis and maximal photosynthetic rates at 25°C. Likewise, fungal production rates were also significantly stimulated by light gradients (P<0.001), but only at the two highest temperatures. These data suggest algae can stimulate litter-associated decomposers in both a light- and temperature-dependent manner. These findings advance our understanding of autotroph-heterotroph interactions on plant litter, improving prediction of directions and strengths of algal priming effects on decomposition across environmental gradients.

Cody Pope (Primary Presenter/Author), University of Southern Mississippi, Cody.pope@usm.edu;


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


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


Steven Francoeur (Co-Presenter/Co-Author), Eastern Michigan University, sfrancoeu@emich.edu;


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