The Palau archipelago, located in the Western Pacific east of the Philippines, consists of more than 250 islands. Most are uninhabited, covered in primary tropical rainforest and mangroves. While this description already promises adventure, the existence of a lake populated by millions of jellyfish on one of these islands makes the region truly extraordinary.
Location of the Jellyfish Lake
Boat approaching Eil Malk Island
The island of Eil Malk (or Mecherchar) measures 6 km by 4.5 km with an area of about 19 km². Like the majority of the islands in the archipelago, it is not inhabited by humans due to its small size.
This island has several lakes. One of them, nestled in the green setting of the tropical forest and bordered by mangroves, looks like any other lake in the region when observed from the shore…
…but when you dive, you discover the fantastic treasure it holds: welcome to Jellyfish Lake!
12,000 years ago, falling sea levels trapped a large volume of water and its inhabitants in a natural basin in the heart of the island. This is how “Ongeim’l Tketau” lake was formed. In the absence of predators, the jellyfish flourished until they completely took over the waters, which today are fed mainly by rain.
Golden jellyfish (Mastigias sp.)
The lake mainly contains two species: the golden jellyfish (Mastigias sp.) and the moon jellyfish (Aurelia sp.). The lake covers 57 hectares (460 m long by 160 m wide). With a population once estimated at about 8 million individuals, an encounter is inevitable with every movement of a fin.
A swimmer among the jellyfish
Although they still have stinging cells, these jellyfish are harmless to humans: their “stings” are too small to be felt through human skin.
Throughout the day, the jellyfish follow the sun. They host a symbiotic algae, zooxanthellae, which produces nutrients through photosynthesis. In exchange for protection, the jellyfish benefits from this food generated by light. They also descend deeper to seek nitrogen, but never exceed 15 meters: beyond that, the water becomes anoxic (deprived of oxygen) and toxic to most organisms.
Under a jellyfish sky
Since 2016, the population has dropped from 8 million to about 600,000 specimens. Scientists suspect the El Niño phenomenon: drought reduces the influx of fresh water, increasing the salinity of the lake beyond the threshold for jellyfish development.
Jellyfish in the Jellyfish Lake of Palau
A similar situation occurred in the late 90s after another El Niño episode. The population rebuilt itself then; we hope history will repeat itself.
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