Investigating the effects of climate change on aquatic insects

Climate change has the potential to alter patterns of precipitation and temperature, which in turn could have effects on benthic macroinvertebrates. Many studies have compared macroinvertebrate assemblages among sites with different flow and thermal regimes, but few studies have examined changes in macroinvertebrate assemblages over long periods of time to address the impacts of climate change. We seek to quantify the effects of stream temperature and flow on benthic macroinvertebrates over a 13-year period at West Brook in Whately, MA. Specifically, we asked whether interannual variation in benthic macroinvertebrate assemblages could be explained by temperature or flow. Macroinvertebrates have been collected annually in late June since 2003, from three sections (approximately 300-400 m apart) using a Surber sampler. Stream temperature was recorded every 2 h with a Hobo data logger (Onset Corp., Bourne, MA, USA) placed at the downstream end of the reach. Depth was recorded every 2 hours with a pressure transducer (Onset Corp.) and converted to discharge (m3s-1) using a stage discharge relationship. We calculated several streamflow and temperature metrics related to frequency, duration, magnitude, timing, and variation of events. Macroinvertebrates were identified to genus (except Chironimidae), where possible, and used to calculate metrics including taxa richness, Shannon diversity index, abundance, % abundance of EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa, and % abundances of cold water and rheophilic taxa. Multiple linear regression analysis was used to determine the strength of the relationships between macroinvertebrate assemblages, streamflow, and temperature. We expect that in years of low flows and high temperatures, macroinvertebrates will have lower richness, Shannon diversity indices, abundance, and % abundance of sensitive EPT taxa, and that by altering patterns of precipitation and temperature, climate change could have direct effects on macroinvertebrates. Brook trout populations in the West Brook have been intensively studied since 1997 and these macroinvertebrate data may be additionally used to investigate the relationships between macroinvertebrates and brook trout growth, mortality, and recruitment.