September 14, 2026
As our climate warms, marine heatwaves (MHWs) are becoming more frequent and longer lasting (e.g. Oliver et al. 2018a). Detrimental consequences for marine ecosystems, fishing, aquaculture and the tourism industry include:
- Large-scale dieoffs of habitat forming species, as seen in the diebacks or collapses of kelp forests in Tasmania (e.g. Kajtar et al. 2021), Western Australia (e.g. Wernberg et al. 2021) and California (e.g. McPherson et al. 2021), or extensive bleaching seen on many coral reefs (e.g. Leggat et al. 2019).
- Range shifts bringing new species into a region, potentially driving increased competition or displacement of endemic species, for example, the establishment of tropical fish species in waters off southern Western Australia during the 2010-11 marine heatwave (Lenanton et al. 2017).
- Increased occurrence of harmful algal blooms which can cause large-scale die-off of fish and shellfish, as seen in South Australia in 2013 (Roberts et al. 2017)
- Precautionary interventions such as moving insurance populations into captivity such as the intervention to protect Red Handfish during the 2023–24 Tasman Sea MHW (e.g. Hobday et al. 2024), or closures of fisheries such as the Californian Dungeness crab fishery during the 2014–16 ’the Blob’ marine heatwave (Jardine et al. 2020).
- Increased bacterial or viral disease outbreaks, such as the Pacific Oyster Mortality Syndrome outbreak in Tasmania during the 2015–16 MHW (Ugalde et al. 2018; Shi et al. 2024) or the case of humans suffering Vibrio infection during a 2018–19 MHW in the Baltic Sea (Brehm et al. 2021).
- Increased stress on organisms resulting in reduced condition, as seen in a laboratory study simulating MHW impacts on Green Lipped Mussels (Venter et al. 2023), or decreased reproductive success as seen in multiple invertebrate species off Oregon during the 2014–16 ‘the Blob’ marine heatwave (Shanks et al. 2019).
While the science around marine heatwaves is relatively mature for open ocean regions where large-scale climate drivers can play an important role, our understanding of marine heatwaves in the nearshore and estuaries is still developing. These coastal and estuarine systems are typically bathymetrically, hydrodynamically and ecologically complex, with socio-ecological co-dependencies.
