Fast reaction of macroinvertebrate communities to stagnation and drought in streams with contrasting nutrient availability

AbstractSmall, permanent streams are at risk of becoming stagnant or intermittent because of hydrological changes induced by climate change, which can be further intensified by anthropogenic disruptions, such as water abstraction. Macroinvertebrate communities are vulnerable to such changes because they depend on stream hydromorphological regime. We conducted a fully controlled field experiment in 1 impacted and 1 unimpacted Danish lowland stream with contrasting nutrient availability. We used dams and diversions to create short-term (2–10 wk) stagnant and drought conditions, and we installed pools in the drought area to test their value as refugia for benthic macroinvertebrates. After 2 wk, community composition had changed significantly in all treatments in both streams. The abundance of Chironomidae increased and the abundance of mayflies (Baetis rhodani), stoneflies (Amphinemura standfussi, Leuctra nigra), caddisflies (Silo pallipes, Sericostoma personatum), the amphipod Gammarus pulex, and some Dipte...