The offshore renewable energy (ORE) sector is rapidly developing in Australian waters to support national carbon emission targets. However, new marine infrastructure can introduce additional risks to threatened species. The eastern Indian Ocean pygmy blue whale (Balaenoptera musculus brevicauda) was identified by the Australian Government as a priority species for assessing potential ORE impacts. This subspecies ranges from the Subtropical Convergence (~40-45°S) to Southeast Asia (~2°S), with much of its documented distribution occurring within Australia’s Exclusive Economic Zone. Its distribution overlaps with multiple anthropogenic activities, indicating likely exposure to existing and emerging pressures. This dataset compiled available spatial information to quantify the full distribution and foraging distribution of pygmy blue whales, and to assess exposure to individual and cumulative threats across the species’ range. The threat exposure analysis incorporated expert elicitation to estimate the probability of exposure arising from spatial overlap between pygmy blue whale distribution and anthropogenic pressures, with particular focus on areas undergoing ORE development. The cumulative exposure assessment indicated relatively low exposure of pygmy blue whales to existing threats within Australian waters, including within declared ORE areas. However, several data and knowledge gaps were identified that should be addressed before further ORE development. The resulting spatial layers provide a baseline for impact assessment by industry and regulators, and support decision-making for sustainable ORE development in Australian waters.

This submission creates a static snapshot of data from the Autonomous Underwater Vehicle (AUV) and stereo-BRUV annotation data from the National Environmental Science Program (NESP) Elizabeth and Middleton Reef survey. More details on the survey can be found at https://www.nespmarine.edu.au/document/elizabeth-and-middleton-reefs-lord-howe-marine-park-post-survey-report.

Diel partitioning of animals within ecological communities is widely acknowledged, yet rarely quantified. Investigation of most ecological patterns and processes involves convenient daylight sampling, with little consideration of the contributions of nocturnal taxa, particularly in marine environments. Here we assess diel partitioning of reef faunal assemblages at a continental scale utilizing paired day and night visual census across 54 shallow tropical and temperate reefs around Australia. Day/night differences were most pronounced in the tropics, with fishes and invertebrates displaying distinct and opposing diel occupancy on coral reefs. Tropical reefs in daytime were occupied primarily by fishes not observed at night (64% of all species sighted across day and night, and 71% of all individuals). By night, substantial emergence of invertebrates not otherwise detected during sunlit hours occurred (56% of all species, and 45% of individuals). Nocturnal emergence of tropical invertebrates corresponded with significant declines in the richness and biomass of predatory and herbivorous diurnal fishes. In contrast, relatively small diel changes in fishes active on temperate reefs corresponded to limited nocturnal emergence of temperate invertebrates. This reduced partitioning may, at least in part, be a result of strong top-down pressures from fishes on invertebrate communities, either by predation or competitive interference. For shallow reefs, the diel cycle triggers distinct emergence and retreat of faunal assemblages and associated trophic patterns and processes, which otherwise go unnoticed during hours of regular scientific monitoring. Improved understanding of reef ecology, and management of reef ecosystems, requires greater consideration of nocturnal interactions. Without explicit sampling of nocturnal patterns and processes, we may be missing up to half of the story when assessing ecological interactions.