California Academy of Sciences team finds ocean warming reaching deeper than expected

SAN FRANCISCO (KGO) — Some researchers will go to almost any length to advance science. But for Luiz Rocha, it’s more like any depth. Rocha and a team from the California Academy of Sciences in San Francisco recently returned from an expedition to deep coral reefs, located off Guam. At more than 330 feet, it’s a layer known as the Twilight Zone.

“So those depths are very hard to get to. We can do it by technical diving, which is the way we do it. But you can also do it with ROVs and with submarines. They’re much more expensive than the way we do it. But because it requires a lot of logistics, a lot of time, a lot of funding. The end result is that those that are really hard to study, very few people do it, and we don’t know much about it,” Rocha explains.

What they’re learning is both exciting and concerning. As we reported previously, the Academy team identified roughly 20 new deep-reef species, ranging from sea slugs to hermit crabs to a variety of unique ocean creatures never seen before. Terry Gosliner is senior curator of invertebrate zoology.

“So this is really filling in a gap in an area of the ocean. This depth range between about 300 ft to 500 ft, that we really know so little about. And we are finding that a lot of the species that inhabit this area are completely different than those that are found in shallow water. And we’re also finding that, they’re different than the organisms that have been found in deeper water,” says Gosliner.

To lure in specimens, the team deployed a multi-leveled scaffolding in the coral, known as an autonomous reef monitoring structure. Over time, Sea creatures enter and make themselves at home. But senior curatorial assistant Johanna Loacker says there’s more to the process than what the eye can see.

“We can get the DNA of fish that may have left some waste as they swam past, and now they’re long gone. But we have this reference of when where they were there. Things that may have settled on arms plates and then died and were only there for a short time, but we still have remnants of their DNA,” she says.

But another emerging data set is more troubling. Luiz Rocha and his team have uncovered evidence suggesting that ocean warming, a trend blamed for bleaching and sometimes killing coral worldwide, is reaching deeper than expected, possibly into the Twilight Zone.

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“We don’t have all of the data analyzed yet, but it’s strongly suggesting that there is a warming trend even at those depths. So for a long time, people thought that the, that those depths, Twilight Zone between 300 and 500 ft or so, it was a refuge for shallow, shallow water organisms that were really suffering with warming. But what we’re seeing is that those deeper water, masses, they are warming as almost as quickly as the shallow ones, and the impact can be as great at those depths as it is in the shallows, so that the impact of that isn’t just for the species that are native to those depths. That was a little escape hatch for other animals,” Rocha explains.

Rocha also uncovered evidence of corral damage at lower depths during a survey in the Indian Ocean. The data is helping to drive an initiative at the Academy known as Hope for Reefs – with the goal of reversing the damage in oceans around the world.

“There’s a lot of fish. And all of those are suffering with the impacts at those depths. And, one of the saddest things, I think, is that we might be losing species even before we get to know them,” he adds.

The academy team placed than a dozen ARMS collection pods in the water in 2018, they’re believed to be some of deepest reef monitoring devices of their kind in the world.