Bleaching in sponges on temperate mesophotic reefs observed following marine heatwave events

Climate change driven extreme events such as marine heatwaves (MHWs) can have dramatic impacts on ecosystems, with thermal stress often resulting in localised die-offs and visible signs of bleaching organisms. Such are reported widely shallower ecosystems but less studied deeper mesophotic (MEs) where collecting data is more expensive. However, these biodiverse play important ecological roles, so understanding climate at depths important. Here we use benthic imagery collected part a large-scale monitoring program to explore cup sponge ‘morphospecies’ (i.e. morphologically distinct organisms readily identified imagery) MEs across eastern Tasmania, region experiencing rapid ocean warming. We find an increased incidence surveys following MHWs, currently no evidence for mass mortality bleaching. Our results suggest that this morphospecies may be useful tracking the region. Future efforts should directed towards better physiological limits its range timing closely follow MHW events. Sponges form dominant component temperate sponges therefore ongoing priority.