Much of the Southwestern United States is currently going through a prolonged drought which can cause stream drying, leading to a decrease in flow volume and loss of aquatic habitat. The objective of this study was to identify how decreasing flow levels and associated water quality factors impact aquatic insect populations. We sampled aquatic insects and measured water quality (conductivity, dissolved oxygen, pH, and temperature) in five stream reaches in the Chiricahua Mountains. At each site, we sampled a pool and a riffle when these habitats were present; however, two sites did not have a riffle due to lack of flow. In pools, we sampled for aquatic insects with a D-net 30 cm wide for ten seconds per square meter of surface area. At the three sites with riffles, we sampled riffles with an aquarium net 12 cm wide for ten kicks (total sampled area: 1,500 cm2). All invertebrate samples were placed in 500 ml containers with 100% ethanol and identified in the lab. We then conducted a multiple linear regression analysis to investigate the relationship between measured covariates and aquatic insect diversity.
Results/Conclusions
Cumulatively, we found 93 different aquatic species. We found that that flow volume (p = 0.022) was the only significant factor associated with aquatic species diversity. Flow volume demonstrated a positive linear correlation with aquatic insect diversity (β =1.77). Species most impacted by loss of flow included a mayfly (Fallceon), two caddisflies (Ochrotrichia and Hydropsyche), and two true flies (Thienemannimya and Larsia). As flow decreases due to climate change, worsened droughts, and stream drying, aquatic insects may be put at an increased risk for survival. As a primary food source for numerous fish species, this reduction in diversity has the potential to negatively influence the food web of aquatic desert ecosystems.