A lake with stingless jellyfish and hints of hotter seas

Bracing for death, a swimmer takes a breath, slips into the lake and is soon surrounded by hundreds of pulsing, orange jellyfish. He must be very careful: His next move could prove fatal.

>>Richard C PaddockThe New York Times
Published : 4 Nov 2019, 07:36 AM
Updated : 4 Nov 2019, 07:36 AM

But it’s not the swimmer whose life is at risk. It’s the jellyfish. A bump from the swimmer could mean a death sentence.

In a rare marine lake on a hatchet-shaped atoll in Indonesia, four species of jellyfish have evolved in isolation and lost their ability to sting humans. There are believed to be millions of these benign jellyfish in Kakaban Lake, which has become a popular spot for tourists intrepid enough to reach the remote archipelago known as the Derawan Islands.

But it’s a fragile ecosystem, and these animals are vulnerable both to climate change and the growing numbers of visitors who casually invade their space.

Colliding with one of these delicate, easily injured jellyfish can spell its doom, as a wounded one is far more susceptible to being nibbled to death by small fish also inhabiting the lake. For that reason, swimmers here are not allowed to use flippers and are urged to swim as slowly and gently as they can. But the jellyfish are so numerous, it can be hard to avoid harming them.

And as more tourists arrive, the dangers to the jellyfish are escalating.

At times, the wooden dock at Kakaban Lake gets so crowded with divers in their black wetsuits that they resemble the sea lions basking in the sun at San Francisco’s Pier 39.

Not all of the divers arrive with an environmentally sensitive mindset, either.

A group of more than 80 employees of the Indonesian tax collector’s office recently came to the lake on a team-building exercise, traveling from the city of Tarakan in North Kalimantan province, about three hours away by boat.

The tax workers, many of them wearing life jackets, formed a giant circle in the lake, kicking and treading water, oblivious to the creatures around them.

Their leader shouted instructions over a bullhorn, and someone unfurled a banner that floated on the water. A drone snapped their picture.

A dive guide who watched the scene unfold figured the photo cost the lives of hundreds of jellyfish.

There are about 200 marine lakes in the world, part saltwater and part freshwater, and stingless jellyfish have evolved in several of them. Without any ocean predators, jellyfish no longer needed their natural defence system, and their sting evolved into one so weak that people don’t feel it.

For scientists, these lakes serve as proxies to explore what may come as ocean waters heat up because of climate change.

“The lakes have environmental conditions that are warmer, more acidic and less oxygenated — in a way, a projection of our future climate,” said Intan Suci Nurhati, a climate and ocean researcher at the Indonesian Institute of Sciences.

Many thousands of years ago, Kakaban Lake was a lagoon connected to the sea. But the island was elevated during a period of geologic uplift, creating a 92-acre lake that today is surrounded by a ridge over 130 feet high.

The lake, a mix of saltwater and rainwater and noticeably warmer than the surrounding sea, is still connected to the ocean through underground fissures, but the openings are too small for an exchange of any but the smallest life-forms.

Kakaban Lake is the main attraction of Kakaban Island, one of about 30 islands, nearly all uninhabited, in the Derawan archipelago, which lies some 35 miles off Borneo. The archipelago, located in the Sulawesi Sea, is known as one of the world’s best diving spots, offering crystal-clear waters, manta rays, sea turtles and whale sharks.

The world’s best-known jellyfish lake, in the nation of Palau, suffered a dramatic population crash in 2016, most likely because of drought and increased salinity caused by an El Niño weather condition. The deaths underscored how vulnerable the animals are to fluctuations in their environment.

While the jellyfish continue to thrive on Kakaban, the island has just two human inhabitants: Suari, 28, and his uncle, Jumadi, 48. Their extended family owns the strip of land where visitors can dock and hike over a wooden walkway to the lake.

On some days, hundreds of tourists arrive. But after they leave, life on Kakaban is lonely.

“It is really quiet here,” Suari said.

About 4,000 people, mostly Muslim, live on nearby Maratua, the largest of the Derawan islands. Most are Bajau people, renowned as deep-sea divers, whose ancestors arrived here from the Philippines eight generations ago.

Darmansyah, a former chief of the Bohesilian village on Maratua, said residents of the atoll were still mainly fishermen.

“Bajau people are not interested in farming,” he said. “We always run to the sea.”

But he is no longer fishing for a living, he said. Instead, like most other residents, he is happy to see a growing investment in tourism, including the recent construction of an airport and several new dive resorts.

Residents are building dozens of homestay units — holiday lodging in a family’s home — in anticipation of a tourist boom. Darmansyah, 60, has built two such units.

Maratua has at least two marine lakes. One, Haji Buang, once had jellyfish to rival Kakaban Lake. But about five years ago, its owner, Hartono, thought he could make some quick cash by raising more than 30 hawksbill sea turtles in the lake.

Only after he put the turtles in the water did he discover that it would be illegal to sell their shells because the species is critically endangered.

The hawksbills, which feed on jellyfish, have nearly exterminated the lake’s population.

“Now I regret it,” said Hartono, 62. “There used to be more jellyfish than in Kakaban Lake, but we didn’t realise this could be a tourist area.”

Hartono said he wanted to catch the turtles so he could return them to the sea — with the hope that the jellyfish population would recover.

The local tourism agency at Haji Buang is spending over $40,000 to build facilities there, including a wooden bridge, dock and covered seating area.

Hartono said he had no interest in preserving nature for nature’s sake but appreciated the government’s investment in his property.

He said he would abide by the wishes of tourism officials and not cut down trees or build houses on the lake’s edge.

“I would rather build and develop this,” he said as he tossed his cigarette butt into the lake. “If you leave it like this, it will only stay like this.”

© 2019 New York Times News Service