Finding a refuge for corals amid decimated reefs in the Galápagos

Photo by Greg Asner / DivePhoto.org

Adapted from Bing Maps.

The Galápagos Islands are not widely known for their coral reefs.  Most visitors to the islands’ waters seek big charismatic residents like  sharks, manta rays, sea lions and whales, or unique creatures like  marine iguanas. Dive shops in the Galápagos almost exclusively advertise  the opportunity to see these large creatures, while few mention corals.  Yet the archipelago is home to vibrant reefs, and we commenced the  global Reefscape project there.

Perhaps  so little is mentioned about reefs in the Galápagos today because of a  history of coral bleaching across the archipelago. The scientific  literature reports ocean temperature spikes of up to 4 degrees Celsius  (7.2 degrees Fahrenheit) during the 1982-83 and 1997-98 El Niño events,  and again to a much lesser degree in 2015. El Niño’s hot waters pushed  many corals beyond their thermal tolerances, resulting in widespread  reef-scale bleaching.


Reef off Darwin and Wolf Islands, northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

Coral, which is an animal, has a symbiotic relationship with algae.  Known as zooxanthellae, these algae live within the coral’s exposed  polyp tissues and are a crucially important photosynthetic source of  carbon for the host. Bleaching refers to when coral, which has a  naturally white underlying structure comprised of calcium carbonate,  loses its more colorful symbiotic algae. Bleaching does not necessarily  spell death for coral: If the hot-water event passes quickly, the coral  will reunite with its algal partner, regain its color and avoid  starvation. If, however, ocean warming events are extreme, persist for a  long time or occur frequently, then corals die, sometimes resulting in  the devastation of vast expanses of reef. While El Niño has brought  coral-killing hot water to the Galápagos on a periodic basis for  millennia, new research suggests that the frequency and intensity of  warm ocean conditions may be increasing (Hughes et al. 2018).


The 2015 ocean warming event (NOAA).

The 1982-83 El Niño reportedly wiped out more than 90 percent of all shallow-water corals in the Galápagos — that is, corals living within about 20 meters (66 feet) of the ocean  surface. That event was followed by another in 1997-98, and yet another  in 2015. The ecological impacts of repeated ocean warming remain poorly  understood in the Galápagos, as they do for many of the world’s coral  reefs. The geography of bleaching, recovery and resistance to warming  water is virtually unknown because monitoring is very limited.

In  December 2017, we visited the Galápagos to survey coral reefs and to  gather ecological information on their extent and condition. We also  interviewed dive-industry professionals and scientists who witnessed the  effects of El Niño and coastal development on the reefs. We focused on  the current health of coral species and we surveyed total coral cover,  an overall indicator of reef condition.


Reefscape off Darwin and Wolf Islands, northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

Starting on Santa Cruz, the most inhabited island in the Galápagos,  we joined a dive operation to observe shallow reefs along the shoreline.  We found very little coral cover, around 1 to 3 percent, which our  hosts described as deeply diminished compared to “the old days”. Yet  they didn’t just blame El Niño, but also increasing coastal pollution  and fishing.

Like most oceanic islands, the Galápagos have a  history of increasing fishing pressure dating back to European whalers,  and culminating in recent news of the Ecuadorian government seizing a Chinese fishing vessel with more than 6,000 sharks taken from protected waters around the  islands. In addition to large-scale commercial fishing, local  communities have also impacted the reefs of the Galápagos. One  dive-industry professional told his story of decades of coastal fishing,  including years of highly damaging activities like using marine mammals  such as sea lions for bait. His story is not unique, and although he  gave up such fishing practices more than 20 years ago to become an  underwater guide, he thinks illegal fishing is commonplace. The islands  have a growing population and too few jobs.


Fish in the northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

Scientific research from around the world has repeatedly highlighted negative impacts of reef-fish removal on coral cover and condition. On Santa Cruz Island, we interviewed a prominent marine biologist whose work demonstrates that the removal of herbivorous reef fish allows for the spread of algae that inhibits coral growth. Low coral cover near Santa Cruz may be related to fishing as much as it is to El Niño.

Next,  we traveled to San Cristóbal, joining dive professionals to survey a  reef off a remote part of the island, and again we found just 1 to 3  percent coral cover, despite no signs of coastal development. One  scientist told us that our observations off San Cristóbal are what he  expected, given the severity of El Niño events over the past three  decades. The coral we did see was arrayed in a seemingly helter-skelter  pattern, and we never saw a coral colony greater than a few feet in  diameter. The experience reaffirmed the idea that tracking changes in  corals at a reefscape scale requires huge and spatially detailed  monitoring areas. Today, however, scientists cannot easily monitor coral  health at regional to global scales.

Santa Cruz and San  Cristóbal are on the eastern side of the Galápagos archipelago, bathed  in the cool Humboldt current. To compare these with eastern conditions,  we visited the very remote reefs of Darwin and Wolf islands to the  extreme northwest. They are far enough north to lie in the path of the  much warmer Panama current flowing into the region from the northeast.  As with the other islands, the Darwin and Wolf reefs reportedly  underwent widespread bleaching in the 1982-83 El Niño. Yet scientists recently reported coral recovery in this northwestern region,  and we too found massive coral colonies, some reaching 4.5 meters (15  feet) in diameter and covering well over 50 percent of the seafloor.  Some areas we surveyed had more than 80 percent live coral cover.


Hammerhead shark, northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

There were more positive impressions from the Darwin and Wolf reefs:  We observed enormous schools of reef fish, including critically  important herbivores that help maintain coral cover by consuming  fast-growing algae. From herbivores to apex predators, such as the big  schools of charismatic hammerheads and scores of moray eels, the entire  ecosystem stood out as a refuge from the pervasive negative news about  coral reef bleaching in the Galápagos. The abundance of life on these  outer islands supports the emerging idea that there will be refugia of coral survival and recovery dotting the planet as we face an increasingly difficult ocean climate for reef ecosystems.

Our work in the Galápagos yielded three salient findings that we hope to explore in subsequent stops along the global Reefscape  survey. First, although warm ocean events such as El Niño can wipe out  vast areas of reef, coral survival and regrowth is evident, and recovery  time truly matters. Scientifically, however, we know little about these  processes and their geographic distributions. Second, our direct  actions, be they destructive overfishing or constructive fisheries  management, have a huge impact on the future of coral reef ecosystems.  Third, one size does not fit all when it comes to coral reefs — even an  archipelago hammered by coral-killing warm waters can harbor amazing  refugia. We need to find them, champion their protection and include  them in our global effort to conserve coral reefs into the future.


School of barracuda, northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

School of hammerhead sharks, northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

Reefscape in the northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

School of fish, northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

Reef shark, northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

Marinescape in the northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

Moray eel, northwest Galápagos. 

Photo by Greg Asner / DivePhoto.org.

This article originally appeared on Mongabay.org.

Last updated July 25, 2018

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