Marine heatwaves as drivers of biological and ecological change: implications of current research patterns and future opportunities

As humans accelerate global environmental change, extreme climatic events are increasing in frequency, duration, and intensity. In marine environments, extreme events of particular concern are marine heatwaves (MHWs). Previous reviews synthesising subsets of field-based research examining the ecological effects of these short-term warming events have found they could drive important changes to ecosystems. Here, we reviewed the traits of published literature that has used field, laboratory, and modelling approaches to examine the biotic effects of MHWs, and highlight some of the key findings. Since its first use in this context in 2013, the term “marine heatwave” has generally been used in field-based literature primarily documenting changes in abundance, biodiversity, species distributions, and mortality, primarily in fish and molluscs. Research is increasingly also conducted in laboratory settings, with these investigations focussing on changes in mechanistic processes such as growth and biochemical responses, often in smaller or less motile organisms including seagrasses, algae, molluscs, and crustaceans. Given their different applications, these complementary approaches will provide a more complete understanding when used to consider the same taxonomic groups. Moreover, those manipulating MHWs in laboratory experiments could benefit from the consideration of a range of MHW traits (intensity, duration, and their combination), for species in both isolation and combination, and in the presence of additional abiotic stressors. As such, where future research into MHWs use varied approaches and treatment settings, they will contribute to a more holistic understanding of the biological and ecological effects of future short-term warming events in our ocean.