This record provides an overview of the NESP Marine and Coastal Hub Emerging Priorities project "Assessing impacts of harmful algal bloom events on South Australian benthic habitats". For specific data outputs from this project, please see child records associated with this metadata. -------------------- In early 2025, South Australia experienced an unprecedented harmful algal bloom (HAB) dominated by Karenia species, with high concentrations in Gulf St Vincent and Spencer Gulf. These gulfs support diverse benthic habitats, iconic biodiversity, and important commercial and recreational fisheries. The rapid development of the bloom and challenges associated with accessing affected areas limited timely assessment of impacts to benthic ecosystem. This Emerging Priorities project will assess HAB impacts by repeating recent benthic surveys at impacted sites across both gulfs. The project will take advantage of existing pre-bloom baseline data, allowing robust before-after comparisons with minimal confounding by seasonal or inter-annual trends. The assessment will integrate towed-camera habitat imagery, stereo-BRUV fish assemblage surveys, benthic trawl data and environmental measurements. Towed-camera resurveys will provide post-bloom imagery, and visual and quantitative assessments of habitat condition. Repeat stereo-BRUV surveys will assess changes in relative abundance, richness and composition of fish and larger invertebrate communities across seagrass and sand habitats. The findings will inform the South Australian HAB Science Program, support development of HAB-related coastal habitat monitoring, and provide evidence for state and Commonwealth agencies to prioritise future monitoring, research and management actions. Outputs • Post-HAB benthic imagery [imagery] • Quantitative assessment of impacts on benthic habitat and fish communities [dataset] • Final technical report [written]