Investigating the effects of river regulation and water quality on macroinvertebrate communities in the Goulburn basin during the millennium drought

Macroinvertebrates are essential components of the aquatic ecosystem, and their assemblages are influenced by a variety of abiotic and biotic factors. The effects of water quality parameters on macroinvertebrate assemblages were studied in regulated and unregulated reaches of the Goulburn River, Australia. Analysis of similarities (ANOSIM) revealed significant differences in macroinvertebrate community compositions between river reaches and revealed that regulation plays a vital role in the composition of macroinvertebrates. SIMPER analysis was conducted to determine the contribution of each species to the average similarity between unregulated reach R1 and regulated reach R2, which is influenced by hydropeaking. The results show that Psephenidae, Eustheniidae, and Synthemistidae play a significant role in the observed differences between the two reaches. Redundancy analysis (RDA) and threshold indicator taxa analysis (TITAN) identified the water quality parameters and their associated indicator species, and the appropriate response threshold was determined. The results show that dissolved oxygen is the most important water quality parameter influencing macroinvertebrate community assemblage in unregulated reaches, whereas total suspended solids and ammonia nitrogen influenced community structure in regulated reaches. This research provides insight into the relative effects of water quality parameters on macroinvertebrate assemblages and their resilience to anthropogenic disturbance.