Working 9 to 5: Diurnal Variability in Terrestrial Invertebrate Activity Does Not Compromise Ecosystem Health Assessments in Dry Stream Channels

ABSTRACT Temporary streams are impacted by climate change and other anthropogenic pressures, but fluctuating water levels complicate ecological assessments. Terrestrial invertebrate communities may enable dry‐phase assessments, but their sampling can be resource intensive. We assessed diurnal variability in the capacity of two methods (hand searching and pitfall trapping) to rapidly characterise terrestrial invertebrate assemblages and their responses to environmental conditions when channels are dry. The methods provided comparable estimates of richness and abundance at any time of day (i.e., morning, midday and evening), and among sites with different dry‐phase durations, air temperatures and proportions of fine sediment. Differences in taxonomic assemblage composition were detected among sites with differing dry‐phase durations, air temperatures and proportions of fine sediment, suggesting that the effects of natural and human‐influenced environmental stressors can be detected despite intermittence. Assemblage composition differed between methods, but not among times of day, suggesting diurnal activity patterns need not hinder assemblage characterisation in dry streams. Taxon‐specific preferences for dry‐phase duration, silt and sand suggest that biomonitoring indices which distinguish the influence of drying from human impacts could be developed. Monitoring over shorter periods may provide managers, regulators and citizen scientists with opportunities to increase the representation of terrestrial assemblages in ecosystem health assessments for temporary streams.