New ecosystem reports by NOAA Fisheries offer details of the impact of climate change on Alaska’s marine ecosystems in the Gulf of Alaska, Bering Sea and Aleutian Islands, including heatwave periods and sustained warm conditions.
NOAA scientists note that the Gulf of Alaska has been in transition since marine heatwave periods from 2014 through 2016 and again in 2019, with some marine populations decreasing and others increasing.
This year was the second consecutive year without marine heatwave conditions. Mixed trends were noted in the prey base in the Gulf, with the abundance of zooplankton that provide food for fish, whales and other marine life below average-to-average overall, and the abundance of forage fish, including herring and age-one Pollock higher than in previous years.
Groundfish predators such as Pacific cod, arrowtooth flounder and Pacific halibut were in reduced quantity, while sablefish biomass increased. Salmon harvests also rose from the lows in 2020, mostly driven by increased numbers of pink salmon.
The Bering Sea has seen cumulative impacts of sustained warm conditions since 2014. The Aleutians Islands meanwhile have experienced sustained warm conditions since 2013, resulting in the combined biomass of Pacific Ocean perch and northern rockfish now being higher than that of Atka mackerel and Pollock, which used to be the dominant pelagic foragers. Fall 2020 sea ice formation was delayed by warm ocean temperatures and there was variable sea ice thickness due to winds across the northern and southern regions.
The study said cumulative years of sustained warm conditions likely have played a role in declines in snow crab and Bristol Bay red king crab abundance and declines in Yukon-Kuskokwim salmon runs, as well as seabird colony failures. Still the Bristol Bay sockeye run proved the largest since 1963.
In the Aleutians, sea surface temperature were near average over much of the year. Still the western and central Aleutians saw record high temperatures in August through September within the satellite time series starting 2003. At Unalaska toxins in blue mussels were above the regulatory level; in 2021 they were 75 times the regulatory level, according to the report.
Relatively high total mercury concentration was observed in 25% of Steller sea lion pups sampled to date in the western and central Aleutians. Research also showed that phthalates, a type of plastics derived contaminant, was found in seabirds throughout the Aleutians.