Depth moderates loss of marine foundation species after an extreme marine heatwave: could deep temperate reefs act as a refuge?

Marine heatwaves have been documented around the world,
causing widespread mortality of numerous benthic species on shallow
reefs (< 15 m depth). Deeper habitats are hypothesized to be a
potential refuge from environmental extremes, though we have little
understanding of the response of deeper benthic communities to marine
heatwaves. Here, we show how increasing depth moderates the response
of seaweed- and coral-dominated benthic communities to an extreme
marine heatwave across a subtropical-temperate biogeographical
transition zone. Benthic community composition and key
habitat-building species were characterised across three depths (15,
25 and 40 m) before and several times after the 2011 Western
Australian marine heatwave to assess resistance during and recovery
after the heatwave. We found high natural variability in benthic
community composition along the biogeographic transition zone and
across depths with a clear shift in the composition after the marine
heatwave in shallow (...