Whale population in Glacier Bay is bouncing back after heat wave that killed North Pacific sea life, researchers say

Authored by ktoo.org and submitted by GreasyGallimimus

Humpback whales were hit hard by “the blob”—a warm water event that killed off all kinds of sea life in the North Pacific. Researchers at Glacier Bay National Park and Preserve say the humpback population is rebounding.

The reflection of Mt.Wright ripples on the glassy water of Glacier Bay National Park and Preserve until a humpback breaks the surface for a huge mouthful of fish.

Chris Gabriel is a biologist with the park service. She has been observing whales here for over 30 years, but the sight of one of the mammals up so close still wows her. She snaps a few photos and checks them.

“So, that’s identifiable enough for us to tell what individual that is,” she said, looking at the image.

Whales are recognizable by their unique dorsal fins and flukes.

The photos and a log of the whale’s coordinates are the two newest entries in a data set that stretches back to 1973 — it may be the longest-running humpback study in the world. Some whales have returned here for more than 40 years. Some are older than Gabriel.

It’s long-term observational data like this that makes it possible to correlate changes in the ocean with their effects on the species that live there. Researchers could track the severity of a recent marine heat wave because the whale population sank by more than 70%, then stayed low. Lately, there’s a glimmer of hope in the data. The humpback whale population is growing.

“It’s been really encouraging last year, and this year to start to see the number of calves we’ve been seeing after the marine heat wave. And so, it really gives me hope that when the conditions are good, they’re really very resilient,” Gabriel said.

Remember “the blob?” From 2014 to 2016, consistent, record-high ocean temperatures in the northern Pacific decimated the humpback population that visits the preserve. The year before the blob, Gabriel counted an all-time high of more than 160 whales. The next year, only a quarter of them came back.

That two-year heat wave had a three-year hangover: the humpback population stayed low until 2020. This study reveals how deeply the marine ecosystem was affected.

“The whales were kind of a sentinel, that showed us what happened. Otherwise, we would not really have known. And I think it’s important to keep doing this work because we can come back in five years, 10 years, 20 years, and look at what the whales are telling us,” Gabriel said.

The numbers aren’t quite up to where they used to be, but Gabriel expects the population to stay healthy — as long as ocean conditions stay stable.

“It wouldn’t be surprising if there’s another blob event in the next 10 or 20 years,” said John Walsh, the Chief Scientist at the International Arctic Research Center at the University of Alaska Fairbanks.

He’s anticipating another oceanic heat wave because his lab has attributed events like “the blob” to human-caused climate change. He studies the blob through the lens of Arctic sea ice. And he found that, like whales, ice recovered somewhat a few years after the warming.

“We’ll have these modest recoveries after the big events. And then there’ll be another big extreme, somewhere down the road,” he said.

In other words, each time the ecosystem takes a hit, it bounces back. But each time a little less. He says we can count on that for the next few decades.

“The system has inertia in it. It’s like a freight train. You can put on the brakes, but it’s not going to stop on a dime, it might stop at half a mile,” Walsh said. “So I think we basically have to be ready for more of the consequences of what we’ve already done.”

Back on the preserve, a cow-calf pair comes up to breathe together. Their backs are slick, dark arches on the water.

There are eleven calves this year. During the heat wave, there were years without any calves at all.

The pair is a sign of the ecosystem righting itself, for now. Gabriel puts the boat in gear as she jots down the time of their breath; she knows she has 3-5 minutes until the whales surface again.

123456American on August 23rd, 2021 at 01:04 UTC »

The earth is healing!?

Spleefy1 on August 22nd, 2021 at 23:03 UTC »

Wholes 🐋

NorthernSparrow on August 22nd, 2021 at 21:41 UTC »

I study this population of humpbacks a bit (the biologist in the article, Chris Gabriele, is a co-author on 3 recent papers with me - one out last year, one in press, one in review). The article’s talking about the whales bouncing back earlier this year from the 2014-2016 marine heat wave, not the more recent heatwave. We just published an in-depth study of an adult male who died during that earlier heatwave & we’re learning more about its impacts. But the impact of this summer’s more severe heat wave has yet to be felt. For example, humpback whale females lay down fat for about a year before becoming pregnant, and then the pregnancy lasts another year before the calf shows up, so there’s often a 2 year lag between a drop in prey and a subsequent drop in calving. When prey is affected the females tend to simply not get pregnant, but you don’t realize that till a year later when calves don’t show up. In other words we may not see the effect of this year’s heat wave on the whales until the calving seasons of late 2022 and late 2023.

Anyway, whales, and other species, do start to bounce back after each of these events once their prey base has a few years to recover. They are indeed amazingly resilient - IF they are given a a chance to recover body condition. What marine biologists are increasingly worried about though is that the heat events are becoming both more severe & more frequent. There’ll be less and less time in between to bounce back. It could become a death of a thousand cuts. Whales are astonishingly tough & resourceful (they can fast for a year if they have to, & they can cross an ocean basin at the drop of a hat in search of prey) but there are limits to what they can do if the prey base goes through repeated hits. What we’re really all hoping is that entire populations of whales, and their entire prey base, all manage to shift northward together. Range shifts like that are underway in other whale species already (for example the North Atlantic right whale started shifting north in approx 2011) but it remains to be seen if they will find good new prey patches.