Ocean heat waves are threatening marine life, biodiversity
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What are ocean heat waves? They are defined as periods of extreme temperatures lasting five days or more. They have become increasingly common in recent decades.
The Earth’s number of annual ocean heat wave days spiked by around 54 percent. That was between 1987 and 2016. That's according to a study published in Nature Climate Change. Abnormally high temperatures are occurring more frequently. They also lasting for longer periods of time.
Underwater heat waves pose a massive threat to marine ecosystems. That's according Damian Carrington explaining for the Guardian. The ecosystems are already at risk due to several issues. These include overfishing and rampant plastic pollution.
Extreme temperatures exact damage on foundational organisms. These include kelp forests and seagrass meadows. It also includes coral reefs. These framework species provide shelter and food. This is for many other ocean creatures. The temperatures sweep through oceans much like wildfires blaze through forests on land. Such destruction will likely have cascading consequences for marine biodiversity. The study’s authors make this warning.
Researchers were led by Daniel Smale. He is an ecologist. He belongs to Great Britain’s Marine Biological Association. He turned to 116 previously published academic studies to assess the effects of ocean heat waves. The papers yielded data from more than 1,000 ecological records. This enabled the team to hone in on multiple recorded instances of unusually high temperatures.
The scientists identified regions and species deemed most vulnerable to temperature surges. They reflected on eight specific heat waves.
Which areas topped the list? The Pacific and Atlantic Oceans. And also the Indian Ocean. More places emerged as particular concerns. These included the Caribbean’s coral reefs and Australia’s seagrass. It also included California’s kelp forests. That's according to Mary Papenfuss writing for the Huffington Post.
In terms of species, the team notes that stationary plants and animals were the hardest hit. That's according to the Pacific Standard’s Kate Wheeling. Tropical fish and mobile invertebrates were able to cope with the heat. They did so by moving to different habitats.
The researchers actually observed heightened levels of fish diversity during periods of above-average temperatures. This is likely due to the animals’ mass migration toward friendlier waters. The same trend did not prove true for sea-dwelling birds. Shifting habitats limited the avian creatures’ access to prey. That's according to John Timmer reporting for Ars Technica.
Marine heat waves are triggered by heat from the sun and shifting warm currents. That's according to Reuters’ Alister Doyle. Wheeling explained it further. Because the phenomenon is measured relative to average ocean temperature, it can occur in any region at any point during the year. El Nin?o is a regularly occurring climate pattern. It makes the waters of the central and eastern Pacific warmer than normal. It appears to exacerbate incidents of extreme heat. But heat waves can (and do) occur without the presence of El Nin?o. That's according to The New York Times’ Kendra Pierre-Louis and Nadja Popovich.
Pierre-Louis and Popovich explain that damage to ocean habitats will also affect humans who rely on fishing and fish farming. But the researchers’ findings are most consequential for marine ecosystems.
“Certainly there’s going to be changes with climate change to marine communities. But still the sun is going to shine. Plankton is going to grow. Things are going to eat that plankton. So it's not like the oceans are going to become the dead sea." That's according to Nick Bond talking to the Pacific Standard. He is a climatologist at the University of Washington. He was not involved in the study.
“It's just that, as a consequence of what we're doing to the oceans, there's going to be different marine communities in different places than what we're used to,” Bond concludes. “Obviously that is a problem because we're sort of set up for what the climate is now rather than what it is going to be in the future."