The effects of substrate, predators, and variations in flow on the drift of a lotic Heptageniidae mayfly.

Abstract

Stream conditions have undergone and are likely to continue to experience drastic changes as a result of human-induced climate change and manmade dams. These conditions can have an enormous impact on benthic macroinvertebrates, which are an essential component of stream ecosystems. Drifting is the main method of movement between habitat patches for many macroinvertebrates, including mayflies. In this experimented, I studied the effect of an abrupt increase in flow, different stream substrates, and presence of predators on drift rates of the Heptageniidae mayfly from artificial stream channels. I found that substrate and predators have a significant effect on drift, with more insects drifting from sand than gravel, as well as more from no predators than predators. An increase in flow rate did not change drift rate relative to a flow rate that remained constant. There was a significant interaction effect between sand and absence of predators, with sand substrate increasing drift rates from streams with no predators.