Science

New NOAA reports on Alaska’s oceans highlight disruptive warming trends

The annual Ecosystem Status Reports from the National Oceanic and Atmospheric Administration collect a wide range of data to better assess maritime trends and help steer fisheries management.

Elizabeth Siddon, who edited a report on the eastern Bering Sea, called the annual documents “anthologies of the ecosystems as we know them” — collaborative efforts pulling information from scientists, community members and industry groups, among others. The reports released this week also cover the Gulf of Alaska and Aleutian Islands.

If there’s any theme in this year’s detailed surveys of Alaska’s marine systems, it’s heat. The three areas assessed all involve “sustained warm conditions” that are affecting environment dynamics like sea ice and water columns, as well as the composition of animal stocks thriving and failing in recent years. The assessments factor into harvest policies set by the North Pacific Fisheries Management Council and touch any Alaskans who depend on sea animals, whether for work or food.

Many of the most startling trends in the reports are happening in the Bering Sea, which this year saw alarming declines in crab populations, abysmal salmon returns across Western Alaska and seabird die-offs.

“Although the collapses are coincident in 2021, they reflect cumulative dynamics over the last few years. The mechanisms are not fully understood, but a common thread in these collapses is the marine environment in the northern Bering Sea, which underwent an abrupt and dramatic change starting in late 2017,” according to a brief on the full report.

The northward creep of groundfish stocks along with changing predation patterns in the ocean have been raising concerns about “food web dynamics and carrying capacity” in the northern Bering Sea for several years now, particularly around the shrinking pool of cold water on the seafloor south of St. Lawrence Island.

Farther south, data from community monitors on St. Paul Island has shown increasing salinity in the water from a loss of sea ice. That, in turn, is having an effect on the presence of algal coccolithophore blooms, dense blobs of rapidly expanding microscopic plants that can be toxic to animals or clog up ocean waters.

This year, lower temperatures across the region tied to a moderate La Nina event have helped curb the yearslong warming trends and led to conditions projected to stay closer to “near-normal temperatures for the Bering Sea through spring of 2022.”

But most of the dynamics at play are part of the “new normal” for the Bering Sea, which has been in an “extended warm phase since approximately 2014,” according to the document.

In the Gulf of Alaska, the “biological community is still in transition from the 2014-2016 and 2019 marine heatwave periods, even though ocean temperatures have returned to pre-heatwave conditions,” according to NOAA.

Researchers observed reductions in animal stocks for everything from capelin smelts to humpback whales in Prince William Sound. While salmon returns overall were larger than in recent years, this is attributed to more pink salmon in the Gulf of Alaska.

Likewise, in the Aleutian Islands a bump upward in salmon returns is likely because of abundant Eastern Kamchatka pink salmon, which were recorded at their second-highest levels on record. Rockfish are also replacing Atka mackerel and pollock as dominant foragers in much of the region.

“Record high sea surface temperature in the western and central Aleutians drove a moderate marine heat wave in those areas; temperatures are now close to the long term average,” the 2021 report notes.

Paralytic shellfish toxins remain a threat to humans, and were measured at “75x above the regulatory limit in Unalaska.”

Overall, researchers believe the waters of the Aleutians are becoming less productive and harder for fish stocks to thrive in at previous levels.

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