Resistance of headwater stream macroinvertebrates to flow pulses

Alterations to hydrological regime of running waters are one of the typical manifestations of current climate change. Small streams in particular are subject to both periods of critically low flow rates on the one hand and increased discharges at spates on the other. The response of macroinvertebrate assemblages to flow pulses following severe rainfall events was studied in two small highland streams. Benthic macroinvertebrates showed good resistance and resilience against the impacts of increased discharge rates caused by severe rainfall events not exceeding certain limits. No distinct changes were recorded in macroinvertebrate composition following discharge events in which current velocities increased by < 0.35 m.s; however, significant (p < 0.05) reductions in abundance was recorded following the spate where current velocity increased by > 1 m.s. Macroinvertebrate assemblages on gravel substrates were more resistant to the impact of sudden flow pulses than those on sandy substrates.