 |
Thursday, May 29, 2008 - 3:00 PM
576
Biological stoichiometry of prokaryotic hetertrophs: Implications for nutrient recycling in periphyton and ecosystem production
J. Thad Scott1, Timothy M. LaPara2, and James B. Cotner1. (1) Ecology, Evolution, and Behavior, University of Minnesota, 100 Ecology, 1987 Upper Buford Cir, St Paul, MN 55108, (2) Civil Engineering, University of Minnesota, 500 Pillsbury Drive S.E., Minneapolis, MN 55455
The microbial loop hypothesis suggests that bacteria are primarily nutrient sinks within aquatic food webs and that nutrient recycling is generally dominated by organisms that prey upon bacteria. This idea assumes that bacteria are nutrient rich relative to their resources. Our recent work has indicated that bacterial communities may not be as nutrient rich as previously thought and that individual bacterial populations may regulate their elemental composition homeostatically. This suggests that nutrients may be recycled directly by bacteria under certain conditions. In order to understand when and how bacteria are likely to regenerate nutrients, we must understand how they regulate their own chemical composition in variable environments. Here we present data on the chemical composition (C:N:P) of bacteria isolated from aquatic environments and grown in chemostats under varying C:P ratios (10 to 5000). Results suggest that bacteria regulate C:P homeostatically, but homeostasis is stronger in organisms that are more P rich. Based on this evidence we present a conceptual model that demonstrates how bacterial nutrient regeneration could explain recent patterns observed in algal-bacterial coupling in stream epilithon. Furthermore, we demonstrate how bacterial nutrient regeneration may drive benthic primary production in nutrient poor systems and contribute to increased ecosystem production efficiency.
Web Page: bacteria, ecological stoichiometry, biofilms