In 2025 South Australia experienced an unprecedented harmful algal bloom (HAB) event with high concentrations of Karenia spp. in Gulf St Vincent (GSV) and Spencer Gulf (SG). These gulfs support abundant and diverse benthic habitats that provide critical ecosystem services, support iconic biodiversity and underpin key fisheries. To assess the impact of the HAB on benthic habitats, tow camera video transects were completed across both gulfs in October 2025 to describe the abundance, distribution and condition of key habitat types. Surveys were completed prioritising sites >10m depth which are more difficult to access and monitor and where impacts are less obvious. Crucially, pre-HAB survey data were available to assess broad habitat impacts where 2025 surveys were compared with existing footage from October 2024 (GSV) and September 2021 (SG) for before and after comparison. Benthic surveys reveal spatially variable impacts that could be representative of exposure time. High epiphyte loads and benthic detrital layers were also present in areas with high chlorophyll at the time of survey. It is possible that lag effects exist for large-scale stress events such as HABs and time-critical archived benthic habitat footage will be useful for ongoing monitoring.