Distribution models of temperate rocky reef habitat-forming species on the continental shelf in Eastern Australia: setting the baseline to monitor and predict future changes

Habitat-formers (e.g. kelp beds, corals, sessile invertebrate assemblages) are key to the structure and functioning of reef ecosystems worldwide. In southeast Australia, a region identified as a global hotspot for climate-driven ocean warming, the structure and distribution of deep (> 30 m) benthic sessile communities are poorly known given these habitats are hard to quantitatively survey. Using high-resolution imagery of the seafloor from a recent national-scale AUV-based survey program, we establish a critical baseline about the latitudinal gradient in benthic community composition from 27°S to 43°S on the eastern seaboard of Australia. Large-scale latitudinal variability between three major community types (sub-tropical, warm temperate and cool temperate) mostly correlates with primary productivity and temperature climatology, while local scale variability relates well with depth. Using environmental variables that capture past climatology both in terms of mean and extreme conditions, we develop alternative distribution models for several habitat-forming species. We compare model performance, discriminate between different types of latitudinal distribution (e.g. truncated or continuous), and discuss these results in the context of ongoing and future ocean changes. Our study provides an important benchmark to detect and predict future climate-driven changes in SE Australia, and our methodology has general applicability for monitoring of deep reef environments.