Stoichiometric effects of stream water source on nutrient change during leaf decomposition

M.J. DeOcampo, W.O. Lamp, and L.C. Alexander. Department of Entomology, University of Maryland, College Park, MD. 20742

Stoichiometric effects caused by elemental variation in leaf material, the primary nutritive source for headwater lotic habitats, are important factors in understanding freshwater communities. In lotic systems, understanding the initial elemental inputs of various species of leaves is complicated by the colonization of periphyton during decomposition, which alters the nutrients available to lotic organisms as a food source. The rate and amount of periphyton growth may also depend upon the source and elemental variation of the stream water in which they are decomposing. An experiment was conducted to measure the stoichiometric changes exhibited by leaf species as decomposition occurs in various sources of stream water. Tree leaves from sweet gum, red maple, and black walnut were incubated in the laboratory in water from four different stream sources. At 0, 7, 21, and 35 days, percent leaf C, H, N and P and mass lost were determined and compared between stream sources and leaf species. These results demonstrate the effect of ambient stream water on the nutritional quality of the main food source for headwater streams.