2022/12/02 by Garcia, Nicole, Narwold, Benjamin, Barnett, Whitney
#discharge #hydropsychids #macroinvertebrates #stream diversions #stream hydrology
paper · doi:10.21973/n3v37r
Hydrological and sediment characteristics of streams are key determinants of aquatic macroinvertebrate community assemblages. Large-scale diversions are responsible for both reducing discharge and increasing rock embeddedness downstream, which reduces food and habitat for filter-feeding macroinvertebrates. Hydropsychidae, an abundant filter feeder family important for stream ecosystem functioning, prefer higher discharge and reduced rock embeddedness — however, we do not know how small-scale diversions influence these variables and consequently hydropsychid abundance. In this study, we sampled three diversion sites along Convict Creek at the Sierra Nevada Aquatic Research Laboratory in Mammoth Lakes, CA, USA to see how position relative to the diversion, discharge, and embeddedness are influencing hydropsychid and macroinvertebrate community abundances. Discharge (m3/s) was higher above diversions than below them. However, hydropsychid abundance was 61.9% higher and macroinvertebrate community minus the hydropsychids abundance was 18.4% higher below diversion compared to above. Furthermore, discharge and rock embeddedness exhibited no relationship with either macroinvertebrate group, contradicting what has been found in previous diversion-focused research. The magnitude of the difference in populations above and below the diversions demonstrates that hydropsychid abundance is directly impacted by more important abiotic or biotic factors that we did not consider, such as in-stream vegetation. It is possible study scale was a determinant of the results and that small-scale diversions do not affect macroinvertebrate communities to the same extent larger diversions do. Future research on macroinvertebrate abundances and small-scale stream diversion in terms of riparian vegetation habitat, coupled with discharge and stream embeddedness, could elucidate the relative importance of factors influencing macroinvertebrates in this system.