Study: Rising sea temperatures to blame for Common Murre deaths

Common Murre carcasses
Common Murre carcasses found washed ashore near Whitter, Alaska, in 2016. Photo by David B. Irons

New research published in the open-access journal PLOS ONE suggests that a severely reduced food supply caused by unusually elevated sea temperatures is to blame for an estimated 1 million Common Murre deaths between 2015 and 2016. 

Dr. John Piatt of the U.S. Geological Survey and colleagues examined the connection between an unusual amount of dead or dying Common Murres that appeared starved with a severe marine heatwave caused by a large mass of unusually warm seawater nicknamed the “Blob,” joined later by a strong El Niño, a press release said. 

The researchers analyzed data on dead and dying birds and investigated the reproduction rates of murres at breeding colonies. The team found that an unprecedented proportion of breeding colonies failed to produce any young between 2015 and 2017, just after the marine heatwave began. 

Previous studies show that the warmer water temperatures led to a reduced quantity and quality of phytoplankton, which leads to a lower quantity and quality of the fish Common Murres eat, as well as increased competition for those fish. These forces resulted in the murres’ starvation and lack of reproductive success.

“The unprecedented loss of about a million Common Murre seabirds in the Northeast Pacific during the severe and prolonged marine heatwave of 2014-16 raised a red-flag warning about the state of marine ecosystems on the continental shelf of western North America,” the authors said.

“As this study demonstrates, the murre die-off revealed the onset of a major disruption in the flow of energy through marine food-webs, which led ultimately to alarming declines in reproductive output and population size of murres, other seabirds, commercial fish, and great whales during 2016-19. 

“Researchers are only beginning to understand the mechanisms and full magnitude of effects of the 2014-16 heatwave, and what it portends if such heatwaves become stronger and more frequent, as predicted.”

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