Poster Presentation Freshwater Sciences 2023

The effect of flow manipulation on invertebrate communities and ecosystem function in a region experiencing long-term landscape  change (#619)

Sean Atkinson 1 , Leon Barmuta 2 , Bridget White 2 , Belinda Robson 1
  1. Murdoch University, Murdoch, WA, Australia
  2. University of Tasmania, Hobart, TAS, Australia

Streams are often subjected to short term disturbances such as rapid flow change from intense storms, water abstraction and environmental water releases. They also experience longer-term disturbances such as catchment clearing for agriculture, which dramatically alters stream ecosystems and their invertebrate communities. The way in which long-term disturbances influence the effects of short-term disturbances on ecosystem function and invertebrate community responses remains poorly understood yet is important for understanding ecosystem change and responses to management interventions. Ecological theory suggests that streams not influenced by catchment clearing and agriculture will recover more quickly from short-term disturbances than streams impaired by agricultural development. We tested this prediction by simulating a pulse flow disturbance (short-term increase and decrease in flow speed) in two groups of streams: those with > or < 30% of the catchment cleared for agriculture (threshold determined by pilot sampling). To simulate a pulse-disturbance, we constructed temporary in-stream weirs in eight stream reaches (n = 4 in each catchment type) downstream of a control reach. These partial weirs created adjacent regions of increased and decreased streamflow. Invertebrates, FPOM, leaf litter, cotton strip assays and physiochemical conditions were sampled before weir installation and twice afterwards over a period of three weeks. Weirs were then removed to allow normal streamflow to resume, and sampling continued to track recovery. Multivariate analyses showed that invertebrate communities in highly cleared catchment were less spatially and temporally variable than those in reaches with less clearing and the