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Easter Island’s Reefs: A Harbinger of What’s to Come?

Divers from the California Academy of Sciences decompress after visiting a deep reef near Easter Island. Luiz Rocha/California Academy of Sciences

The tiny island's reefs have barely been studied, but they may give us a glimpse of the ocean's future.

Written by: Nathaniel Scharping

Easter Island is a tiny dot of land nearly lost among the waves in the Pacific Ocean. But the seclusion is a boon to biologists, as the island hosts a number of species found nowhere else. It's a place where time and isolation drove species along entirely unique evolutionary paths.

By virtue of remoteness, Easter Island's reefs have existed almost completely free of scientific scrutiny. But that changed this year when a team of biologists from the California Academy of Sciences made the lengthy journey in the hopes of expanding our sphere of knowledge around the island. There, in the virtually unexplored reefs, they discovered an ecosystem that may serve as a preview of what coral reefs the world over may someday look like.

One of the iconic Moai stares into the distance on Easter Island. Luiz Rocha/California Academy of Sciences


Hope Through Knowledge

The excursion was part of the academy's Hope for Reefs initiative, a five-year project encompassing nearly 20 separate expeditions to reefs around the world. Their goal is to catalogue reef health and discover strategies to protect these fragile environments threatened by climate change. The environs around Easter Island could contain species and ecologies uniquely suited to surviving dramatic ecological shifts—a clear mandate for more research.

"The mere fact that it takes two days to get there by … normal airline traffic is indicative of the fact that it's not an easy place to get to, it’s sort of stuck out there. That is a clue to anyone who studies the distribution of organisms on Earth that there might be something different going on there," says Rich Mooi, the Curator of Invertebrate Zoology and Geology at the Academy and a specialist in sea urchins who took part in the expedition.

There were only scant clues about life on Rapa Nui. Speaking before he left, Mooi said that he knew of only one published study describing the sea urchins of Easter Island, a paper from the 1970s containing descriptions of seven species which he believed to be partly inaccurate. His mission on the island was simply to find out what was there, he said, and potentially discover how they fit into the larger ecosystem.

The twilight zone team aboard a dive boat. California Academy of Sciences

Arrival

Once Mooi's team arrived at the island they, along with Chilean colleagues, embarked on a series of dives over roughly two weeks. Mooi explored the crystalline waters with a snorkel and flippers, while other members of the team dove to depths approaching 400 feet to explore the deep-water reefs further offshore.

The team made the most of their narrow time frame. Mooi not only turned up all seven species of sea urchin he was looking for, he added two more previously unknown to exist on the island. Luiz Rocha, who heads the ichthyology department at the Academy, and his deep-water team collected four new species of fish along with a sea biscuit, a kind of sand dollar, tinted a brilliant orange, which Mooi labelled as "definitely new."

A new species of sea biscuit discovered on one of the team's deep dives. Rich Mooi/California Academy of Sciences

There's likely far more to discover in deeper reefs that rarely see human visitors. At depths of several hundred, feet, divers have to ascend slowly in order to avoid decompression sickness (the "bends"), which makes every minute at the bottom a precious commodity. Nevertheless, the team achieved success on the bottom, picking up three of the four new fish species in one dive — Rocha says he discovered new species by picking specimens at random.

"We spent the first 10 minutes of the dive collecting fish and then the last two or three minutes kind of grabbing every invertebrate we thought looked interesting," he said. "And because the deep reefs there are so unknown, even grabbing random invertebrates like we do, we find new species all the time."

Easter Island's remarkably clear water also aided the team's efforts. Even hundreds of feet beneath the surface the reefs were illuminated by cerulean-hued sunlight, bright enough to gather specimens without lights. At similar depths on other reefs, Rocha says, they would have been plunged into darkness. Far from any significant landmass, Easter Island doesn't harbor the plankton and other lifeforms, in addition to the pollution, that serve to darken the waters elsewhere.

An eel twines through the corals. Bart Shepherd/California Academy of Sciences

About Those Corals

The corals themselves hint at an intriguing story playing out today. In a time when reefs around the world are dying due, in part, to warming oceans, Easter Island's corals are actually undergoing a renaissance. The corals appear to be thriving, and there is little of the bleaching that plagues other reefs, according to Rebecca Albright, a coral specialist and Assistant Curator of Invertebrate Zoology with the Academy.

In a time where coral coverage on most reefs averages 30 to 40 percent, she says that Easter Island's reefs spread across some 80 percent of the available surface area. But what makes the Easter Island habitat even more unique is the fact that the reefs are dominated by just two species of corals—a far cry from the riotous diversity that most reefs are known for. While Albright says that she knows of about 13 species that have been recorded there, Pocillopora verrucosa and Porites lobataa, two especially tough species, dominate the reefs around Easter Island.

Four new species of fish discovered on Easter Island.: Luiz Rocha/California Academy of Sciences

These two species have caught the interest of researchers because they seem much better prepared than other corals to deal with climate change. If the oceans continue to grow more inhospitable, reefs around the world may start to look more like Easter Island's two-species population. By studying these species now, Albright hopes to predict the future of coral reefs around the world, where hardiness may win out over biodiversity.

There are differences between Easter Island and the rest of the world, of course, such as its extreme southern latitude and cooler water temperatures, but the island is proof that reefs can survive even in uncommon and relatively harsh conditions.

It's not just the corals either; the diversity of species is much reduced across all divisions of the tree of life. The island hosts around 140 species of fish, according to Rocha, compared to the nearly 1,000 that populate French Polynesia, the nearest major reef system. But at Easter Island, many of the fish look like nothing else in the world. About a quarter of them are endemic to island, meaning that they've been there long enough to evolve into completely different species.

A member of the twilight team with equipment used on the dive. Luiz Rocha/California Academy of Sciences

Unique Advantages

Although the ocean ecosystem appears to be doing well, there are still signs of human intervention. In fact, in an ironic about-face, the corals may be thriving precisely because of the islanders' presence. A reliance on fish from the reefs for their diet has depleted the closer reefs of large predatory fish, the kind that typically prey on sea urchins. In their absence, the urchin population has bloomed, and with it, their appetite for algae. This isn't the helpful zooxanthellae algae that sustains the coral, but a different species that actually contests with the corals for real estate on the reefs. Absent their nemesis, the corals have thrived.

"They’re talking now about this marine phase shift from an algal-dominated community to a coral dominated community … mediated by the sea urchins," Mooi says. "By eating the algae, the sea urchins are making it possible for the corals to make a comeback."

Sea urchins nest in a rock formation. Rich Mooi/California Academy of Sciences

Although there's no scientific data recounting the transition, local fisherman and dive shop owners hold that it happened sometime during the 1980s, over the course of a few years. Where algae once bloomed, corals and sea urchins took over. Though the end result is beneficial for the corals, the human fingerprints are nevertheless a worrying sign.

Tangles of fishing line caught in the corals are a testament to the fishermen's persistence, and the bodies of predatory fish hanging in the market leave little doubt as to where some of the fish are going. On an island with few natural resources, fishing is a prerequisite of survival, and has been a dominant feature of Rapa Nui culture for centuries.

The ecological transition that's occurring in the ocean bears startling parallels to the one that occurred on the island itself sometime in the last few hundred years. An ecosystem built around large palm trees shifted to a landscape dominated by grasses, disrupting the natives ability to farm and significantly hobbling their ability to survive on the island.

Team member Bart Shepherd, the Director of the Steinhart Aquarium, gathers samples on a dive. Luiz Rocha/California Academy of Sciences

What's playing out at sea will not be as destructive as its counterpart on land. The islanders have felt the pull of modernization, and now rely in large part on tourism for sustenance, meaning that they don't depend as heavily on the reefs. Still, there is a growing awareness that the underwater ecosystems are worthy of conservation as well.

In 2014, 20 organizations, from the island and elsewhere, banded together to conserve the oceans surrounding Rapa Nui. Called "Mesa del Mar," and organized largely by the islanders, one of the group's most ambitious proposals is the establishment of a formal conservation area around the island in conjunction with the Chilean government.

The goal, according to founder Sebastián Yancovic Pakarati, is to establish protected marine environments while also preserving the rich tradition of artisanal fishing on the island. Key to this is educating the public, creating a local body to manage the reefs and preventing illegal commercial fishing activities around the island. There have been problems in the past with the overexploitation of some sharks and lobsters, as well as the illegal sale of corals from the reefs, Pakarati says, and the goal is to reduce this kind of harmful activity while allowing sustainable practices to flourish.

A team member observes a fake concrete Moai placed underwater on the reef. Luiz Rocha/California Academy of Sciences

The group recently organized a conference on the island, featuring presentations from researchers, journalists and citizens, surrounding the issue of marine conservation. It's part of a larger push to increase awareness of the reefs, and has involved educational events with local schoolchildren, coastal cleanups and outreach efforts. Ultimately, Pakarati wants the inhabitants of Easter Island to be the driving force behind conservation efforts there.

The wealth of findings brought back by the Academy team underscores the need for greater conservation and management of Easter Island's reefs, he says. Not only that, but the researchers' findings promise to resonate outside of the island's sphere of influence as well, as tropical reefs around the world begin to experience similar conditions.

Like it or not, the combination of natural and artificial influences that birthed Easter Island's unique aquatic terroir have given it the dubious honor of serving as a bellwether for the future.

Nathaniel Scharping is the staff writer at Discover Magazine