Miss Shinae Montie1, Dr Mads Thomsen1, Mr François Thoral1,2, Dist. Prof. David Schiel1
1University Of Canterbury, Christchurch, New Zealand, 2NIWA, Wellington, New Zealand
Marine heatwaves (MHWs) have become more prevalent and can damage coastal ecosystems characterised by unique biogeographical communities with cultural and economic importance. Analyses of changes to MHWs typically focus on broad oceanic scales, with less emphases on seasonality or nearshore ecosystems. Here we analyse >40 years of seasonal changes to MHW metrics, like intensity, frequency, and duration, on global scales for 12 coastal realms and regional scales for 10 coastal bioregions in New Zealand. We demonstrate the ecological importance of analysing seasonal coastal MHWs using a case study from the east coast of New Zealand’s South Island that experienced the hottest summer on record in 2017/18. This MHW resulted in widespread declines in Southern Bull kelp (Durvillaea spp.), with local extinction in a harbour where wave action was low, and air and sea temperatures were high but also severe impacts on Durvillaea antarctica in wave-exposed areas that prior to the heatwave had experienced a seismic uplift. Today, four years after the MHW, much of the space left vacant following loss of bull kelp has been replaced by smaller turf and foliose seaweeds, and in the protected harbour, also the kelp Undaria pinnatifida in winter months. Our results highlight coastal MHWs, particularly over summer months, and their ecological impacts are becoming stronger and more severe, in southern New Zealand.
Presentation Slides – Shinae Montie
Biography:
Shinae Montie is a Ph.D. student based at the University of Canterbury in New Zealand. Her research focuses on the impact and ecological legacies of extreme marine heatwaves on coastal algal and seagrass communities in New Zealand and Australia.
