Data from multibeam echosounder surveys taken as part of the Ningaloo Outlook project were classified into various seafloor cover types according to their hardness, rugosity and depth. The classifications were validated with towed video ground truth where it was available. This dataset describes two AOIs which are explicitly part of the Ningaloo Outlook Deep Reefs project. Substratum classifications were applied using multibeam backscatter angular response curves along with rugosity as input to a maximum likelihood classifier. See original metadata record(s) and associated attached documents for accuracy estimates, alternate classification techniques, and additional surveyed areas. https://doi.org/10.25919/kssa-5b46 https://doi.org/10.25919/kttc-x397 https://doi.org/10.25919/8m65-7k26

Kelps are in global decline due to climate change, including ocean warming. To identify vulnerable species, we need to identify their tolerances to increasing temperatures and whether tolerances are altered by co-occurring drivers such as inorganic nutrient levels. This is particularly important for those with restricted distributions, which may already be experiencing thermal stress. To identify thermal tolerance of the range restricted kelp Lessonia corrugata, we conducted a laboratory experiment on juvenile sporophytes to measure performance (growth, photosynthesis) across its thermal range (4 – 22 °C). We found the upper thermal limit for growth and photosynthesis to be ~ 22 – 23 °C, with an optimum of ~ 16 °C. To determine if elevated inorganic nitrogen availability could enhance thermal tolerance, we compared performance of juveniles under low (4.5 µmol/day) and high (90 µmol/day) nitrate conditions at and above the thermal optimum (16 – 23.5 °C). Nitrate enrichment did not enhance thermal performance at temperatures above the optimum but did lead to elevated growth rates at the thermal optimum 16 °C. Our findings indicate L. corrugata is likely to be extremely susceptible to moderate ocean warming and marine heatwaves. Peak sea surface temperatures during summer in eastern and northeastern Tasmania can reach up to 20 – 21 °C and climate projections suggest that L. corrugata’s thermal limit will be regularly exceeded by 2050 as south-eastern Australia is a global ocean-warming hotspot. By identifying the upper thermal limit of L. corrugata we have taken a critical step in predicting the future of the species in a warming climate.