In the fall of 2015, two years into a heatwave in the Pacific Ocean colloquially known as "the Blob," an unusually large influx of common murres, a small northern seabird, began to wash ashore.
They overwhelmed rehabilitation centers.
They stopped laying as many eggs.
Their starved carcasses littered the coasts from California to the Gulf of Alaska.
Scientists believe they now know what went wrong. The answer involves the Blob and how it rippled across multiple levels of the marine food web, and it comes amid more reports of rapidly warming oceans.
In the winter of 2013, a mysterious blanket of abnormally warm water appeared in the Gulf of Alaska and wreaked havoc on marine ecosystems from the Bering Strait to Mexico for three long years. Species lower in the food web that prefer colder waters, which tend to be fattier, more nutritious phytoplankton and zooplankton that feed the forage fish eaten by sea lions and sea birds -- were replaced by warmer water species of lower nutritional value.
A whole new ecosystem was establishing itself all the way up the food chain, said Julia Parrish, professor of marine sciences at the University of Washington and a co-author on a new study published in PLOS One that characterizes murre mortality and breeding failures during the heatwave. Parrish also directs the Coastal Observation and Seabird Survey Team (COASST), the largest citizen monitoring program of beached birds in the world.
Fish populations shifted to colder or deeper waters, making it harder for top predators, including two types of auklets similar to murres, to find food.
But that still doesn't explain the murres.
Common murres are the masters of their universe. One of the best adapted seabirds in the northern hemisphere, they can outfly other seabirds and speed from shelf to coast in a few hours. Underwater, they're agile enough to catch fast-moving prey and strong enough to dive to the depth of two football fields.