Animal-mediated organic matter transformation: aquatic insects as a source of microbially bioavailable organic nutrients and energy

1. Animal communities are essential drivers of energy and elemental flow in ecosystems. However, few studies have investigated the functional role of animals as sources of dissolved organic matter (DOM) and the subsequent utilization of that DOM by the microbial community. 2. In a small forested headwater stream, we tested the effects of taxonomy, feeding traits, and body size on the quality and quantity of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) excreted by aquatic insects. In addition, we conducted steady-state solute additions to estimate instream demand for labile C and compared it to the C excreted by invertebrates. 3. Individual excretion rates and excretion composition varied with body size, taxonomy, and feeding guild. The estimated average community excretion rate was 1.31 μg DOC· per mg insect dry weight (DW)-1·h-1 and 0.33 μg DON·mg DW-1·h-1 and individuals excreted DON at nearly twice the rate of 〖\"NH\" 〗_\"4\" ^\"+\" . This DOM was 2-5 times more bioa...