Lightning Lecture AMOS Annual Meeting and International Conference on Tropical Meteorology and Oceanography

Ecosystems around the world negatively impacted by marine heatwaves (#1004)

Dan Smale 1 , Thomas Wernberg 2 , Eric Oliver 3 , Mads Thomsen 4 , Ben Harvey 5 , Sandra Straub 2 , Michael Burrows 6 , Lisa Alexander 7 , Jessica Benthuysen 8 , Markus Donat 7 , Ming Feng 9 , Alistair Hobday 10 , Neil Holbrook 11 , Sarah Perkins-Kirkpatrick 7 , Hilliary Scannell 12 , Alex Sen Gupta 7 , Ben Payne 6 , Pippa Moore 5
  1. Marine Biological Association of the United Kingdom, UK
  2. UWA Oceans Institute and School of Biological Sciences, Perth
  3. Department of Oceanography, Dalhousie University, , Halifax, Nova Scotia
  4. School of Biological Sciences, University of Canterbury, Christchurch
  5. Aberystwyth University, Aberystwyth
  6. Department of Ecology, Scottish Association for Marine Science, Scottish Marine Institute, Oban
  7. University Of New South Wales, Kensington, NSW, Australia
  8. Australian Institute of Marine Science, Crawley
  9. CSIRO Oceans and Atmosphere, Perth
  10. CSIRO Oceans and Atmosphere, Hobart
  11. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart
  12. School of Oceanography, University of Washington, Seattle

Recent work has demonstrated that marine heatwaves (MHWs) have become longer and more frequent over recent decades and these trends are likely to accelerate in the future. Here we examined historical trends in MHW characteristics and identified regions where MHW changes are collocated with areas of high diversity value, species living at the upper level of their thermal tolerances, and regions concurrently impacted by non-climatic anthropogenic stressors.

In a global meta-analysis of 116 research papers, we examined responses of organisms, populations and communities to eight distinct MHW events. All events were associated with negative ecological impacts. Sessile species like corals were most heavily impacted while some mobile species experienced no deleterious impacts. Some fish responses to MHWs were positive, largely related to the invasion of tropical species into temperate regions.

A species-level analysis demonstrated that populations living closer to the warm limit of their species distributions are more negatively impacted by MHWs, as they are more likely to experience conditions that exceed their thermal tolerances.

Finally, an examination of three globally important habitat-formers found that increases in the frequency of MHW days was significantly associated with increases in coral bleaching, decreases in seagrass density and deceases kelp biomass, explaining between 30 to 40% of the ecological performance of these taxa.

Our study shows that MHWs cause widespread ecological impacts (i.e. across multiple taxa, regions and processes) and can drive step-wise shifts in ecosystem structure and functioning. Given that they are predicted to intensify with anthropogenic climate change, MHWs are likely to be prominent agents of ecological change in the coming decades.