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Coastal Fisheries Show Surprising Resilience To Marine Heat Waves

Rutgers-led research found that marine heat waves -- prolonged periods of unusually warm ocean temperatures -- haven't had a lasting effect on the fish communities that feed most of the world.

The finding is in stark contrast to the devastating effects seen on other marine ecosystems cataloged by scientists after similar periods of warming, including widespread coral bleaching and harmful algal blooms.

“There is an emerging sense that the oceans do have some resilience, and while they are changing in response to climate change, we don’t see evidence that marine heat waves are wiping out fisheries,” said Alexa Fredston, the lead author of the study who conducted the research as a postdoctoral associate in the Global Change Research Group, part of the Department of Ecology, Evolution and Natural Resources in the Rutgers School of Environmental and Biological Sciences (SEBS.)

The study, published in Nature, assessed effects on commercially important fish such as flounder, pollock and rockfish based on data extracted from long-running scientific trawl surveys — conducted by towing a net along the seafloor — of continental shelf ecosystems in North America and Europe between 1993 and 2019. The analysis included 248 marine heat waves with extreme sea bottom temperatures during this period. The researchers were surprised to find that marine heat waves in general don’t show major adverse effects on regional fish communities.

Although declines in biomass did occur after some marine heat waves, the researchers said these cases were the exception, not the rule. Overall, they found that the effects of marine heat waves aren’t distinguishable from the natural variability in these ecosystems.

“The oceans are highly variable, and fish populations vary quite a lot,” said Fredston, now an assistant professor of ocean sciences at University of California, Santa Cruz. “Marine heat waves can drive local change, but there have been hundreds of marine heat waves with no lasting impacts.”

In addition to assessing the impact on the total quantity of organisms in a given area, known as biomass, the researchers examined whether marine heat waves were causing changes in the variety of fish species composing fish communities. For example, evidence might show the loss of species associated with cold water and an increase in species associated with warm water, a phenomenon known as tropicalization.

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