The Belmont Desalination Plant Ecosystem Monitoring Program was designed to establish a baseline and post‑commissioning framework to assess potential impacts of planned offshore desalination operations on the receiving marine environment. The program applies a multiple Before–After–Control–Impact (mBACI) design incorporating marine water and sediment quality, benthic infauna, fish, plankton and reef communities. This paper focuses on baseline surveys completed between 2023 and 2025.
Marine water quality was assessed at 17 sites, including the intake, existing wastewater outfall and the broader project area, using seasonal sampling and post‑rainfall events. Ecological surveys included seasonal sureys of multiple investigation and reference sites. Fish communities were assessed using baited remote underwater video (BRUV), underwater visual census (UVC) and environmental DNA (eDNA). Reef habitats were surveyed using diver‑collected photoquadrats analysed via Coral Point Count (CPCe), while plankton communities were sampled using plankton nets and taxonomic identification. Eight years of benthic infauna and sediment data monitoring program were also incorporated as baseline, with recent datasets analysed using both morphological and eDNA methods.
Results indicate spatial and temporal variability in baseline datasets, driven by regional hydrodynamics, seasonal upwelling and rainfall. Integrating traditional survey techniques with emerging tools, including eDNA, improved overall detection and interpretability of baseline conditions.