The Hawai'i Voices of Science episodes tell natural resource stories on Hawai'i Island.
Coral bleaching is a global crisis. Warmer water temperatures cause corals to react by expelling algae, called zooxanthellae, leaving stark white corals in their wake. If corals stay bleached for too long, the whole reef could die. Our reefs are home to a wide variety of sea life, and to lose this biodiversity would be devastating. But reef biologists in Kaloko-Honokohau say there’s still time to help control the warming that’s underway.
Voices of Science: Coral Bleaching in the Pacific
Coral bleaching is a global crisis. Our reefs are home to a wide variety of sea life, and to lose this biodiversity would be devastating.
Narrator: For the National Park Service, I’m Brittni Connell. And you’re listening to Voices of Science.
Narrator: In the Hawaiian Creation Chant, the Kumulipo, the coral polyp is described as the first animal to form on Earth. Coral polyps are tiny translucent organisms, distantly related to jellyfish. They attach themselves to rocks or the seafloor and replicate building massive colonies made up of millions. These form what we know as the coral reef.
The creation chant says that out of darkness, coral was born. It's the first organism created and in a way, it's the first stone in the foundation of the earth.
And today, that stone is shifting.
Boat crew: Do you want to feed me the line? Narrator: Sallie Beavers, ecologist and chief of resources management at Kaloko-Honokohau National Historical Park, eases the research boat over one of the park’s coral reefs. Hawaii’s coral reefs, like many around the world, are succumbing to dramatic bleaching events.
The National Park Service’s Pacific coral reef team, is diving below the surface to measure and take pictures of the corals.
Boat crew: Okay, I’m in neutral.
Driver: Okay, going in!
Narrator: The team dives below us. But up on deck? Sallie shows us what they’re seeing down there. She has a binder of pictures from previous dives.
Sallie: So, these are photos, this is all live coral... This is our harbor... You can see all this is nice and green. That's good, you want that. That's all the houses for the fish and the other invertebrates other than coral.
Narrator: She points to a photo of stark white corals,
Sallie: ...but this is all dead. That’s just rubble now. So, from one hundred percent alive coral cover to seventy seven percent dead.
Narrator: Sallie is talking about the impact from the 2015 global coral bleaching event. A global bleaching event is declared when multiple bleaching episodes have been recorded in multiple reefs spanning more than 100 km across the Indian, Pacific, and Atlantic oceans. This event was a record breaker for the Pacific.
Basically, in one season, the corals in this section of reef went from one hundred percent alive ...
Sallie:...To seventy seven percent dead.
Narrator: As Sallie talks, she points to photos of the reef in various stages of health. The green coral looks good– green means healthy. Green means that there are tiny plant cells living inside the coral. Tiny plant cells that make food and provide oxygen for the corals.
Sallie: Coral is...Coral polyps are living animals. They have a dependent relationship with a unicellular algae that's called zooxanthellae. The coral really depends on that algae for a lot of its nutrients to live... when the coral gets stressed, it will eject that algae.
Narrator: And once the algae is out…
Sallie: The tissue is white, like ice cream white. Just really startling white.
Narrator: Like little coral ghosts.
Narrator: Judging from Sallie’s photos and the stories her team told us, the reef below is beautiful. When reefs are healthy, they are a vibrant world of life under the sea. But reefs are also fragile and sensitive to change. Changes in temperature are one of the things that stress corals out. Corals like relatively warm water, they thrive in it, but when water temperatures get too high for too long the algae is forced to leave, leaving bleached, white corals in their wake. If temperatures stabilize, the algae could come back. But if corals stay bleached for too long, they basically starve and the whole reef could die. Corals are the cornerstone, or foundation, of this ecosystem. They are home to the widest variety of fishes, invertebrates, and marine algae found on the planet. To lose this type of biodiversity would be devastating.
Sallie: You know the kid game Jenga where you have all those little stacks of rectangular shapes, and you take out one or two, and everything's fine. And you take out that one, and it all comes crashing down. That's how I think of the coral ecosystem. It really matters.
Narrator: Coral reef scientists have been monitoring reef health in the park for over a decade. Sallie says there were global bleaching events in 1998 and 2002. But from 2014 to 2017, the Pacific was having bleaching events like never before; and the water temperatures were staying warmer longer. In 2015 it was the worst on record for Hawaii’s reefs. This escalation in Hawaii’s bleaching events has been surprising...
Sallie: I mean, we in Hawaii have been spoiled...until now, the conventional thinking was, well, we’ll get bleaching, but we're somewhat protected because we're in the center of the Pacific, we have cool groundwater coming in in many places, well not in the older islands, but we were seeing year after year, Fiji, the South Pacific, and Australia bleaching... And we were being spared. But nobody is thinking that anymore. And I feel like I took our reef for granted.
Really sad ...It's just really depressing. Because there's so much of it, it's hard to see ... If there were no more bleaching events, if everything was pretty good for ten years or so, it would come back, but ... The concern is if we keep having more frequent events, the coral is never able to get a leg up. A polyp up. Narrator: The National Park Service is studying and monitoring coral reefs across the park system, from the Caribbean to the Pacific, to understand patterns in reef health. In order to help give the heat-stressed corals a better chance at survival, some parks have put guidelines in place to prevent reef damage from boats and anchors, and some, like Kaloko-Honokohau National Historical Site, work with their surrounding communities to protect corals from land-based pollution. Coral reef ecologists around the world are even looking at genetics to try to find species resilient to disturbances and establish coral nurseries. Sallie: We're hoping for bright spots… we're hoping to find little areas where the coral looks like it's doing okay and it made it through there. We're looking for little recruits of baby coral. So we're hoping to find, I think what every reef biologist around the world is looking for, what's surviving and what can be encouraged. What are the resilient spots?
Narrator: But Sallie says just growing resilient species in a nursery is not enough to address the causes of coral bleaching.
Sallie: When you do things like coral nurseries or finding the super coral, and growing more of those, you're just treating the symptoms, right? If you want to address the problem, then we have to address climate change.
Narrator: Sallie pulls the boat back to shore and we head back to her office. She says we can all do our part to address coral bleaching by making small moves in our everyday lives. Choices like eating sustainable foods, or walking or biking instead of driving a car, could help control the warming that’s underway in our oceans.
Sallie: There's still just a little bit of time, and we've got to do everything that we can to do that, and that takes all the governments and the political will around the world to do it. And we are seeing that.
Sallie : Addressing the problem in our own way, each individually ... it's trotted out all the time that think globally, act locally, but it actually works. Makes a difference.
Narrator: Voices of Science is produced by the National Park Service in cooperation with the Acoustic Atlas at Montana State University.Our staff includes Jennifer Jerrett, David Restivo, and me, Brittni Connell.
Special thanks to Jon Jokiel, Sally Beavers, Sheila McKenna,Kailea Carlson, and Eric Brown at Kaloko Honokohau National Historical Park. To learn more about the park, visit their website at nps.gov/kaho. Find more episodes of Voices of Science at go.nps.gov/vos. Thanks for listening.