A devastating marine heat wave known as the “warm blob” has led to the deaths of nearly 4 million common murres in Alaska, a staggering loss that has left the population at half its former size. The event, which occurred from 2014 to 2016, was particularly brutal, with beachings over 1,000 times normal rates.
A new study published in Science has shed light on the impact of warming waters on Alaska’s common murres. Researchers analyzed data from 13 colonies surveyed between 2008 and 2022 and found that colony size dropped by half after the marine heat wave. The decline was even steeper in colonies along the eastern Bering Sea, with a 75% loss.
The study estimates that about half of Alaska’s common murre population died as a result of the event, and no recovery has been seen yet. According to co-author Julia Parrish, a wildlife biologist at the University of Washington, the effect of the heat wave was not due to thermal stress on the birds but rather shifts in the food web leaving murres suddenly and fatally without enough food.
The “warm blob” had a devastating impact on ocean productivity, affecting the food supply for top predators like seabirds, marine mammals, and commercially important fish. The study concludes that starvation was likely the cause of the mass mortality event.
Climate change is exacerbating this issue, with persistent warming conditions becoming more common. Another recent study found that a 1 degree Celsius increase in sea surface temperature results in multiple seabird mass mortality events.
The researchers warn that warmer waters mean massive ecosystem changes and widespread impacts on seabirds. Parrish states, “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.”
As seabird populations fail to recover, scientists are sounding the alarm about the tipping point of ecosystem rearrangement where recovery back to pre-die-off abundance may not be possible.
Source: https://scitechdaily.com/4-million-dead-warm-blob-disaster-causes-catastrophic-loss