Huge ‘hot blob’ in Pacific Ocean killed almost a million seabirds

Katie Ramirez
January 19, 2020

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The unprecedented death of almost one million birds between 2015 and 2016, whose remains washed ashore in Alaska, US, was brought on by a severe and long-lasting marine heat wave, a new study says. They appeared to have starved, but the underlying cause and its potential connection to the "Blob" and heatwave has been unclear.

Common murres have wonderful tools for finding forage fish, but have an Achilles heel: Murres must eat 56% of their body mass every day, the equivalent of 60 to 120 finger-fed feed fish. Herring, sardines, anchovies, and even juvenile salmon are no match for a hungry murre.

"Many of the species that we're talking about - both the birds and the fish - are pretty resilient", Parrish said.

The study-which its authors expect to inform research on other mortality events related to marine heatwaves-was published just weeks after University of Washington scientists found what some have called "the blob 2.0" forming in the Pacific.

"Think of it as a run on the grocery stores at the same time that the delivery trucks to the stores stopped coming so often", explains second author Julia Parrish, professor in the University of Washington School of Aquatic and Fishery Sciences. It happened between 2015 and 2016 in the northeast Pacific Ocean. Black with white bellies, adult murres can dive more than 200 yards beneath the surface in search of food, the release says.

The team reviewed studies of fish and plankton collected by fisheries during the time the blob was at its peak, as well as other field studies and reports, and concluded that the warmer temperatures in the water had increased the metabolism of these cold-blooded ocean dwellers. Warming increased with the arrival of a powerful El Niño in 2015-2016. Other animals also died off, including sea lions, tufted puffins and baleen whales. Although seabirds are known to have periodic die-offs, this one was far larger than the typical event. In Alaska, observations of murre carcasses were up to 1,000 times higher than normal.

More than three-quarters of the dead murres were found in the Gulf of Alaska, but the actual number is likely to be around one million as only a small number of birds that die at sea are normally washed ashore.

For some reason, many had failed to make the annual migration from Alaska.

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As numerous birds that died were breeding-age adults, colonies across the region failed to produce chicks in the numbers that would normally be expected in the years during and after the heatwave.

"Food demands of large commercial ground fish like cod, pollock, halibut and hake were predicted to increase dramatically with the level of warming observed with the blob", says biologist John Piatt, from the US Geological Survey's Alaska Science Center.

"It was astonishing and alarming, and a red-flag warning about the tremendous impact sustained ocean warming can have on the marine ecosystem", Piatt said.

It was a 1,600 kilometer stretch of ocean that warmed by 3 to 6 degrees Celsius.

"As the bottom of the ecosystem was shifting in not good ways, the top of the ecosystem was demanding a lot more food", Parish said.

"Food demands of large commercial groundfish like cod, pollock, halibut and hake were predicted to increase dramatically with the level of warming observed with the blob, and since they eat numerous same prey as murres, this competition likely compounded the food supply problem for murres, leading to mass mortality events from starvation", Piatt said.

It's been revealed that about a million seabirds died at sea in less than a year in something that's called one of the largest mass die-offs in recorded history.

While the Blob persisted off the coast of the United States, production of phytoplankton or microscopic algae dropped and "the largest harmful algal bloom in recorded history" stretched from California to the Gulf of Alaska in 2015.

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