information
on the distribution of diversity and the bio-physical processes structuring regional ecosystems.
This is particularly true in temperate reef systems beyond depths easily accessible to divers. Yet these
systems harbor a diversity of sessile life that provide essential ecosystem services, sustain fisheries and,
as with shallower ecosystems, are also increasingly vulnerable to anthropogenic impacts and environmental
change. Here we use cutting-edge tools (Autonomous Underwater Vehicles and ship-borne
acoustics) and analytical approaches (predictive modelling) to quantify and map these highly productive
ecosystems. We find the occurrence of key temperate-reef biota can be explained and predicted
using standard (depth) and novel (texture) surrogates derived from multibeam acoustic data, and
geographic surrogates. This suggests that combinations of fine-scale processes, such as light limitation
and habitat complexity, and broad-scale processes, such as regional currents and exposure regimes, are
important in structuring these diverse deep-reef communities. While some dominant habitat forming
biota, including canopy algae, were widely distributed, others, including gorgonians and sea whips,
exhibited patchy and restricted distributions across the reef system. In addition to providing the first
quantitative and full coverage maps of reef diversity for this area, our modelling revealed that offshore
reefs represented a regional diversity hotspot that is of high ecological and conservation value. Regional
reef systems should not, therefore, be considered homogenous units in conservation planning and
management. Full-coverage maps of the predicted distribution of biota (and associated uncertainty) are
likely to be increasingly valuable, not only for conservation planning, but in the ongoing management
and monitoring of these less-accessible ecosystems.