Ocean heat wave known as 'The Blob' blamed for killing half the population of bird species
Common murre colony on South Island of Semidi Islands, in the Alaska Maritime National Wildlife Refuge south of the Alaska Peninsula, in 2014. (Brie Drummond/U.S. Fish and Wildlife Service)
A new study has revealed that an extensive marine heat wave killed nearly half of a seabird’s population in Alaska, leaving long-lasting impacts on the species.
The University of Washington study recently published in the journal Science suggested that 4 million common murres died following unusually warm conditions in the northeastern Pacific Ocean between 2014 and 2016.
Researchers said they analyzed data from more than a dozen colonies across the Gulf of Alaska and the Bering Sea before the extensive heat wave, whose extensive warm patch of water was colloquially nicknamed "The Blob", and after to develop their estimates.
Researchers analyzed over a dozen colonies across the Gulf of Alaska and the Bering Sea, both before and after the extensive heatwave - nicknamed "The Blob" due to its unusual and extensive warmth.
"This study shows clear and surprisingly long-lasting impacts of a marine heat wave on a top marine predator species," Julia Parrish, a UW professor of aquatic and fishery sciences and of biology and co-author, said in a statement. "Importantly, the effect of the heat wave wasn’t via thermal stress on the birds, but rather shifts in the food web leaving murres suddenly and fatally without enough food."
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Common murre colony on South Island of Semidi Islands, in the Alaska Maritime National Wildlife Refuge south of the Alaska Peninsula, in 2021. (Brie Drummond/U.S. Fish and Wildlife Service)
Before the marine heat wave, around 8 million of the stout, tuxedo-styled birds were estimated to have lived off the ocean and rocky coastline of Alaska.
The birds, known for diving to great depths for food, likely suffered from starvation due to the heat wave’s impact on their supply.
"Recent population abundance estimates since then have found no evidence of recovery, suggesting that the heatwave may have led to an ecosystem shift," researchers stated.
Biologists also noted changes in crab and fish populations, which also suffered extensive die-offs during one of the greatest heat waves in recorded history.
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Water temperature anomalies from September 2014 (NOAA)
According to climatologists, stout ridges of high pressure off the coast of North America are responsible for the development of the warm weather blobs.
The weather pattern results in gentle winds and less cloud cover than normal, which helps to heat surface water temperatures.
Researchers previously determined that a 1-degree Celsius increase in sea surface temperatures for an extended period often triggers mass casualty events.
"Whether the warming comes from a heat wave, El Niño, Arctic sea ice loss or other forces, the message is clear: Warmer water means massive ecosystem change and widespread impacts on seabirds," Parrish stated. "The frequency and intensity of marine bird mortality events is ticking up in lockstep with ocean warming."
Researchers said it is unknown when or if the population of common murres will ever recover, which is worrisome and could be a sign of more widespread ecological changes to come.