Physicochemical drivers of managed river and agricultural drainage channel macroinvertebrate communities

Artificial channels are common features in lowland agricultural catchments, and are a potentially significant habitat for aquatic species. Recent studies have suggested communities in managed rivers and artificial channels are broadly similar, but with some compositional differences. However, because relatively few studies have considered how artificial channels may contribute to supporting aquatic communities, their physicochemical condition and suitability for aquatic fauna remain poorly characterised. Therefore, this study explores the role of physicochemical variables in driving macroinvertebrate community differences between intensively managed rivers and artificial channels in a highly arable catchment. Aquatic macroinvertebrates were sampled in intensively managed rivers and artificial channels. Physicochemical water quality variables were also recorded, and used to identify macroinvertebrate community responses. Both intensively managed rivers and artificial channels had spatiotemporally stable communities, with no significant differences in richness, abundance, effective diversity or Berger-Parker dominance detected between sampling months or channel types. Macroinvertebrate composition in intensively managed rivers and artificial channels was significantly different, and driven by the relative abundance of taxa present, not the number of taxa unique to each channel type. Compositional differences between intensively managed rivers and artificial channels were partially driven by conductivity, dissolved oxygen and temperature. Identifying remaining sources of compositional variance may support tailored management strategies that accentuate compositional differences between rivers and artificial channels, increasing overall diversity in intensively farmed arable catchments.