When a heat wave swept through the northeast Pacific Ocean between 2014 and 2016, it changed the marine makeup of the Gulf of Alaska: The warm water decimated some commercial fish populations.
Some species bounced back right away. But a recent study from the National Oceanic and Atmospheric Administration shows others are rebounding more slowly.
NOAA’s study charted the impacts of the heat wave — also known as “the blob” — on the Gulf’s marine species through 2019.
Some of the blob’s impacts on local marine life were immediate. Rob Suryan is a program manager for NOAA in Juneau, and the lead author on the study. He said in 2015 and 2016, thousands of common murres were found dead.
“Especially noticeable in the Prince William Sound, near Whittier, actually,” he said. “A beach was just littered with thousands of carcasses.”
In this study, NOAA focused on longer-term trends using data from Gulf Watch Alaska, a group ufnded by the Exxon-Valdez Oil Spill Trustee Council that monitors species recovery in Alaska waters.
Suryan said there were three different long-term impacts on the abundance of observed species.
Some species did well, such as sablefish and some varieties of zooplankton that do better in warmer water. Other species saw no change, or change that lasted only a year.
“And then a negative response, of course, is something that declines and is persistently in a lower state than what it was before the heat wave,” Suryan said.
Several of those fish are key to Alaska businesses and dinner plates, including sockeye salmon and Pacific cod.
Suryan said it’s important information to know and continue to study, since scientists anticipate more heat waves in the future.
“Part of it has to do with feedback loops as the conditions that are causing these warming events begin to magnify and build and are additive over time,” he said.
The data isn’t uniform across species or geography. Some fish, including certain populations of herring, are rebounding more rapidly. But taken altogether, the data paints a picture of an ecosystem still reeling from a warming ocean.
Suryan said the study will be included in an assessment sent from NOAA Fisheries to the North Pacific Fisheries Management Council, the agency that sets policy in Alaska’s federal waters.
Declines in cod population already prompted the council to close Alaska’s cod fishery in 2020.