An estimated 4 million common murres in Alaska were killed by a marine heat wave. That number represents about half of the murres' total population. The catastrophe is thought to be the largest die-off of a single animal species in recorded history. About a decade ago Pacific surface temperatures shot up eleven degrees as a high pressure system stalled over the ocean and circulating currents died down. They called it the "blob", and it convulsed marine ecosystems. The blob lasted for three years, and humans began to see evidence of the damage done as carcasses washed up on beaches. The effect on murres, a black and white seabird that spends most of its life at sea except for breeding, was discussed in a journal article recently published in Science. What scientists learned about the die-off is that it was a lot worse than estimated, and that the birds have not yet begun to rebound [photo courtesy of US Fish & Wildlife] Previous estimates of the death toll ranged from a half to one million murres.
The warming ocean temperatures led to a die-off of the birds' main fish prey. Ocean surface temperatures breached records last year and into this year. Scientist are worried that the high temperatures and its disastrous impacts on marine wildlife may be a harbinger of the future, Murres are normally resilient to changes in their environment, but impact of prolonged ocean heat seems to have overwhelmed the birds. A similar type of disastrous population decline occurred when Atlantic cod off of Newfoundland were overfished. Once thought to be an inexhaustible source of protein, Atlantic cod have failed to recover despite a ban on cod fishing in Newfoundland waters.