Several years ago, Digital Journal reported on the tens of thousands of common murres, an abundant North Pacific seabird, starved and washed ashore onto beaches from California to Alaska.
John Piatt, a research wildlife biologist for the U.S. Geological Survey said at the time that two major marine wildlife ecosystems off the west coast of the U.S. and Canada have been affected by the Pacific’s warming waters.
But it wasn’t just seabirds that were dying. There were other marine animal deaths and disappearances during that same time period, including other seabird species, Pacific cod, sea lions, Guadalupe fur seals, and humpback whales, just to name a few. But the big question researchers asked was – “What was causing the seabirds to starve to death?”
In a study published Wednesday in the journal PLOS ONE, a group of scientists from various state and federal agencies, universities and bird rescue organizations documented the die-off and concluded that record-breaking heat caused systemic changes in the Pacific Ocean from 2014 through 2016, resulting in the extreme mortality rate in the seabirds.
Remember “the blob?”
Many readers might remember “the blob,” an expanse of very warm water 1,000 miles long, 1,000 miles wide, and 300 feet deep that hugged the coast of North America from Mexico to Alaska, a stretch of 2,000 miles or longer.
The blob was first detected in 2013 and lasted through 2015, and during those years, the West Coast of North America began to see a lot of marine animal deaths, presumed to be from a massive algae bloom caused by the overly warm waters of the Pacific Ocean.
Dr. Andrew Trites, director of the UBC Marine Mammal Research Unit, said at the time that with the number of fin whales, humpbacks and other whales washing ashore dead or dying, he suspected “the blog” was also responsible for a toxic algae bloom that had poisoned the krill the whales dined on. A the time, Dr. Tritrs’ explanation was considered to be just speculation.
Extreme mortality of common murre population
It was thought that 62,000 or more common murres, a seabird that looks sort of like a penguin, washed ashore dead or dying during the summer of 2015 and spring of 2016, but according to the research paper, carcass recovery suggests this was only a fraction of the birds that died.
Lead researcher and study co-author Julia Parrish said the number of birds that are estimated to have died is alarming. Using data from nearly 5,800 beach surveys, public reports, and data from dozens of seabird rehab centers from Alaska to California, the researchers concluded the die-off was much higher.
The study says: “We estimate that between 470,000 to 1,030,000 birds died in the Gulf of Alaska during the heatwave. This total probably included birds overwintering from Bering Sea colonies, and it suggests that as much as one-quarter of all murres breeding in the Gulf of Alaska and the southeast Bering Sea might have been killed.”
The four-year study concluded the common murres were dying from starvation due to warmer ocean temperatures affecting plankton, the tiny aquatic organisms that are a big part of the ocean’s food chain. Many fish species, including salmon, eat plankton, and whatever a salmon eats, so too will a murre.
“The death of all of these murres suggests to us that those large fish were also having a hard time and the reason why we know about the murres is, a dead bird floats but a fish sinks,” Parrish said.
“No other factor was found that could explain the magnitude or spatial extent of these events,” Piatt said. “With heatwave impacts on their food supplies from below and above in the food chain, murres were caught in an ‘ecothermic vise’ and populations were severely impacted for years.”