Oceanic heat wave caused by climate change could endanger marine life, Bay Area scientists say

SAN FRANCISCO (KGO) -- Although you won't see it in most weather reports, we're being affected by a heat wave, and it could have a profound effect on creatures -- from whales to sharks to threatened sea stars.

We may not notice it, but marine creatures off the Bay Area coast are already feeling the heat.

Ocean temperatures in the North Pacific have been recording historic highs due to what's commonly known as a "blob," or marine heat wave. The current mass of warm water is one of the largest on record.

Jaime Jahncke is a marine ecologist with Pt. Blue Conservation Science.

He routinely monitors long stretches of the ocean shelf off Northern California. That's the deep-water area, where whales and other creatures normally find an abundant supply of krill and other food sources.

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But on a recent cruise within the last several months...

"We only saw two blue whales. Blue whales feed exclusively on krill, compared to more than 40 that we saw last year," Jahncke said. "We only counted within the last two weeks or so, but between 50 and 60 humpback whales, compared to 170 some."

Jahncke is concerned that warming waters could be forcing the whales closer to shore in search of food that's migrating away from the deep-water shelf.

"And one thing that was pretty clear from the distribution of the humpbacks is that the few ones that we counted, they all of them were closer to shore and not at the shelf break," Jahncke said. "Again, there was no krill, a shelf break. So, where they were closer to shore, most likely feeding or looking for the fish."

Marine scientists have observed similar migrations during earlier marine heat waves and say they can put the whales on a collision course, leaving them vulnerable to being struck by passing ships or tangled in fishing nets.

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Kathi George is with the Marine Mammal Center in Sausalito, which treats injured marine animals.

"So, it's definitely important to pay attention to the ocean conditions and temperatures to understand where the whales may be. And that could help us in being more proactive about our management efforts and finding ways to reduce the co-occurrence or the risk of co-occurrence between large whales and human activity. And that could be ship strikes or entanglement," she said.

Previous marine heat waves have also triggered deadly chain events.

In 2016, a wasting disease wiped out a species of sea stars that help keep hungry sea urchins in check. Freed from their main predator, the urchins began gobbling up miles of critical kelp forests.

Juvenile great white sharks have begun appearing in shoreline nurseries along the Monterey Bay, miles north of their normal habitats.

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And George says other species face the same challenges.

"Absolutely. We're seeing bottlenose dolphins come further north. They used to be down in Southern California in the 80s," she said. "And as the ocean temperature has gradually increased, they are following the prey following the warming temperatures, and they are off of our shores. We've been having a lot of dolphin sightings off of Pacifica and Ocean Beach in San Francisco over the last couple weeks."

The marine heat wave may also be influencing wetter weather and higher humidity on shore. But some observers believe there's a chance this blob could dissipate sooner than some earlier heat waves, because of its large size and shallower depth.

For the time being, researchers are tracking an ocean phenomenon invisible to the rest of us, but with a critical impact on the marine life off our coast.