The flow regime has been considered the maestro of river ecosystem structure and function, influencing habitat availability, ecological processes, and the distribution of aquatic organisms. In Australia, natural flow patterns have been increasingly altered by water extraction, farm dams, and long-term climatic drying, potentially affecting stream biodiversity. Macroinvertebrates are widely used as indicators of ecological condition because they respond sensitively to environmental change and integrate habitat conditions over time.
This study investigated how hydrology influences macroinvertebrate assemblages across streams in the Mount Lofty Ranges, South Australia. The relationships between community composition and environmental variables were examined to identify the key factors associated with variation in macroinvertebrate communities. Species responses to flow velocity were assessed to determine how individual taxa are distributed along hydraulic gradients and whether community change occurs gradually or through distinct ecological thresholds. The influence of flow-regime characteristics on biodiversity was also evaluated using both taxonomic and functional measures of diversity. In addition, taxa were classified into hydraulic guilds based on shared velocity preferences to provide a functional framework for understanding responses to hydrological variation.
Together, these analyses provide a comprehensive assessment of the role of hydrology in structuring stream macroinvertebrate communities. By integrating community, species, and functional perspectives, the study improves understanding of ecological responses to flow variability and alteration in Mediterranean-climate streams. The findings contribute to the identification of hydrological characteristics important for maintaining aquatic biodiversity and provide a strong ecological foundation for environmental flow management and conservation planning.