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  • I started initially studying terrestrial ecology, but I stumbled into a scuba diving

  • class where I learned to dive right here along the Monterey breakwater wall.

  • It was a really rough day.

  • The surf was big.

  • We barely made it into the water.

  • And I mean, we couldn't even hardly see our hands in front of our faces because it was so

  • murky. It's freezing cold.

  • And I just thought it was the coolest thing.

  • I was like, it can't get better than this.

  • And from that moment, I just became fascinated by kelp forest ecosystems.

  • My name is Josh Smith, and I am a postdoctoral researcher at the National

  • Center for Ecological Analysis and Synthesis.

  • I've been studying kelp forest ecology for about 11 years.

  • Most of my research has been specifically in Monterey Bay.

  • Being in a kelp forest is much like being in a redwood forest.

  • Kelp grow really tall.

  • They grow all the way from the sea floor up to the surface.

  • They can grow up to 80 feet tall.

  • The reef is covered in life of all kinds of different colors, invertebrates and fishes

  • that are on the bottom underwater.

  • There's life everywhere, all the way up to the surface.

  • We set up surveys years and years ago.

  • They started in 1992 and it was in response to the Exxon Valdez oil spill, which was up

  • in Alaska. But there was this recognition that we knew very little about these

  • habitats. And if we are going to be able to assess damages, you kind of needed to know

  • what was there. And one of the things that affords, of course, is that you have the

  • opportunity to see change.

  • And you can see that there are these coastal ecosystems, kelp forests and rocky intertidal

  • areas, and things come and go and they change.

  • My name is Pete Raimondi.

  • I'm a professor at UC Santa Cruz in the Department of Ecology and Evolutionary

  • Biology. My primary interest is in kelp forests along the coast of California and

  • rocky intertidal areas, which we think of as tidepools.

  • Back when we were driving this area, 2012, 2013, the kelp was so thick that we'd have to

  • anchor the boat way out here and then swim under the canopy to get to the location where

  • we were going to do our surveys.

  • Now we can pretty much just pull up right to our dive site, you know, drop anchor and go.

  • But in 2013, things began to seriously change.

  • It was shocking. I'd never seen anything like it.

  • We saw starfish starting to disintegrate, basically in front of us.

  • We would see these things on the bottom that we call Ghost Stars, which were the outline

  • of the sea star. The white and the white was bacteria.

  • All these sea stars were basically just dissolving under water.

  • They lose their arms, they twist and get torsion.

  • And it's really it's it's really pretty nasty.

  • It was like the underwater world was like in its last stages.

  • That sea star wasting syndrome decimated several species of sea stars up and down the

  • coast. One species that was hit particularly hard was this sunflower sea star that we call

  • Pycnopodia. And this is a very large sea star that grows to be the size of an extra

  • large pizza. They have 24 arms and they cruise along the reef for sea urchins.

  • And sea urchins are these spiny baseball sized animals that like to eat kelp.

  • Now, normally in a kelp forest, these native sea urchin grazers are living down, tucked

  • away in the cracks and crevices and they're eating drift kelp.

  • In 2014, we had a major marine heat wave.

  • These marine heatwaves are a product of climate change, and all of these anomalies

  • are like nothing we've seen, you know, in the last 100 years, one was the blob, which

  • was this really warm seawater that showed up in the northeastern Pacific Ocean.

  • And the other was this warm equatorial water that came up that was from a major El Nino

  • event. And so this major marine heat wave just completely bathed all of central and

  • northern California. And this really warm water and kelp needs really cold, nutrient

  • rich water to thrive.

  • And so the combination of lots and lots of sea urchins and very bad environmental

  • conditions for kelp caused the kelp forests to collapse.

  • We're really hoping to learn more about sea urchin behavior.

  • We want to know how much kelp sea urchins actually eat and what's that critical point

  • when sea urchins shift from passively grazing on drift where they're tucked away in

  • the crevices to now storming out of the crevices, eating live kelp.

  • That's a really fundamentally important behavioral shift that we're really interested

  • in learning more about.

  • These sea urchins in many places, completely clear cut the kelp all the way to the reef

  • surface and formed what we call sea urchin barrens.

  • And these are places where the urchins have overgrazed the kelp.

  • There's no macroalgae left.

  • It's just a carpet of purple.

  • We've discussed the sea urchins that eat kelp, and we discussed the Sunflower Sea

  • Star, which is a known predator of sea urchins.

  • There's another predator of sea urchins that we have here in Monterey Bay, and that's the

  • Southern Sea Otter.

  • Part of the reason why we still have patches of kelp forests along the Monterey Peninsula

  • is because the otters are helping to maintain those remnant patches of kelp

  • forests. They are targeting the healthy urchins in those patches of kelp.

  • However, because the otters are not foraging on sea urchins in the barrens, they're not

  • actively contributing to recovery.

  • These are the the major grazers that are eating all of the kelp.

  • So these urchins, again, they emerged from crevices and they were no longer eating drift

  • and they started eating live kelp.

  • So in the lab, we're looking to see what actually causes that behavioral shift.

  • How do predators play a part in that?

  • So it's been really remarkable to see how fast the ecosystem can change, how quickly

  • kelp can become deforested, and how quickly these sea urchin barrens can happen.

  • And I wish I could just look back into time and see how often does this happen before?

  • How long did the Barrens persist?

  • Were there barrens?

  • Because to us, it seems like this happened really quickly.

  • We lost all the kelp.

  • I have to remind myself that my perception and my window into these changing forest

  • ecosystems is just a fraction of time on the geologic time scale.

  • The kelp forests seem to be recovering right now, and we're in a period of really cold

  • water and at least recently and things seem to be coming back in.

  • We're in a pretty fortunate situation, to be completely honest, because I think that

  • unlike a lot of environments, people actually are very interested in this.

  • This interest has led to.

  • An immense amount of information that we would not have had.

  • So like in the sea star wasting, probably 90% of the information that was from people,

  • citizens, and that's because they're interested and they care.

  • And so I think that that's a huge plus, and I would just hope that that stays.

  • It's hard to speculate about what might happen.

  • These are really dynamic ecosystems.

  • There are all kinds of invertebrates and birds and things that depend on kelp as a

  • subsidy. The kelp also ends up in offshore and in the canyon, and so the kelp that's

  • ripped out eventually makes its way offshore.

  • Some of it sinks down.

  • It's not just important for the animals that live there, but kelp forests are also

  • fundamentally important in buffering climate change.

  • In one way that they do that is like plants on land kelp actually take in CO2.

  • And when that kelp is ripped out and transported offshore, that carbon that the

  • kelp has has captured is ultimately sequestered into deep sea sediments.

  • And what's so great about kelp?

  • You're not convinced already?

  • Well, kelp is kelp is what we call a foundation species.

  • So it supports the entire forest ecosystem by providing habitat and food for all of the

  • animals that live here.

  • With all of these changes that are happening, what we're seeing is the

  • foundation being unraveled.

  • It's being deforested, and it's not being deforested because of harvest.

  • It's being deforested because of these other processes that are happening, these marine

  • heatwaves and the sea urchin outbreaks that can occur over several hundred kilometers

  • with ocean warming globally and climate change, you know, like a blob that really

  • initiated all of this back in 2014, that that blob was this area of warm water that

  • showed up in the northeastern Pacific Ocean.

  • And my understanding still that, you know, we don't really know why it showed up.

  • It just did. And it's unclear how kelp forests are going to respond to these

  • recurring marine heatwaves.

I started initially studying terrestrial ecology, but I stumbled into a scuba diving

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Dive into a vanishing, invisible forest to see what climate has changed(Dive into a vanishing, invisible forest to see what climate has changed)

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    happynostalgia2 に公開 2023 年 07 月 18 日
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