Research from the University of Victoria has gone to new lengths to highlight how marine heatwaves can not only dramatically impact marine ecosystems but reshape ocean life as we know it, by offering a stark preview into the future of ocean warming.

From 2014 to 2016, the pacific coast of North America experienced the longest marine heatwave ever recorded, with temperatures reaching two to six degrees above historical averages over a prolonged period of time.

It’s according to researchers from the University of Victoria’s Baum Lab that this marine heatwave alone resulted in the ‘unprecedented ecological disturbance’ of some thousands of kilometres of North American west coast. 

By reviewing the findings from 331 primary studies and governmental reports, the researchers believe they are now gaining a better understanding of the ecological impacts of marine heatwaves, including its effect on marine life.

According to the study, around 240 different species were found outside of their typical geographic range during the heatwave, with many of them found further north than ever before. Several species, such as the northern right whale dolphin and the sea slug Placida cremoniana were found over 1,000 kilometres north of their typical habitat.

The heatwave caused widespread kelp and seagrass decline and many kelp forests collapsed. Species from sea stars to seabirds died on unprecedented scales and unusual mortality events were observed in several species of marine mammal. Meanwhile, a key rocky shore predator, Pycnopodia helianthoides, came close to extinction.

Researchers found that many of the impacts of the heatwave were cascading, with direct impacts on some species driving complex dynamics that affected everything from plankton to whales. Temperature-linked diseases – such as sea star wasting disease – also contributed to ecosystem collapse, while the reduced abundance and nutritional quality of forage fish cased issues for predators. Meanwhile, plankton communities reorganised and offshore oceanographic productivity was found to be altered.

The heatwave also came with a weighty economic cost that saw the closure of multiple fisheries – driven by changes in species interactions, disease proliferations, and habitat loss – deliver financial losses in its hundreds of millions of dollars.

“As heatwaves become more frequent and intense under climate change, the 2014-16 Northeast Pacific marine heatwave provides a critical example of how climate change is impacting ocean life, and how our future ocean may look,” said Julia Baum, University of Victoria marine ecologist and special advisor, climate.

“This study underscores the urgent need for proactive, ecosystem-based marine conservation strategies and climate change mitigation measures.”

According to the paper – now published in the scientific journal, Oceanography and Marine Biology: An Annual Review – the 2014 to 2016 marine heatwave in the Northeast Pacific, despite its exceptional duration and geographic scope, shares “many ecological impacts with other marine heatwaves observed around the world.” 

These recurrent patterns, including changes in primary productivity, shifts in species distribution, disease outbreaks, and fisheries disruptions, emphasise the need, say the study’s authors, for enhanced monitoring and adaptive strategies. 

“By understanding the similarities and differences between marine heatwaves, we can better predict and mitigate the future consequences of these extreme events on marine ecosystems and the human communities that rely on them,” states the paper.

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