Sometime around 12,000 years ago, jellyfish got trapped in a lake on Eil Malk in the Rock Islands of what’s now Palau. They’ve since flourished into a population in the millions, far outnumbering the population of just around 30,000 people that live in the country.
Over time, the cnidarians’ sting got weak, and they began subsisting on the algae-like organisms in the lake. Each day they make a transit en masse across the lake to follow the sun’s path to encourage the photosynthesis of the organisms that are embedded symbiotically in their tissues. They evade the dark shadows near the shore where their enemies the anemones live, a predator likely introduced by humans, and before sunrise reset to their original position to await the dawn.
Tourists to Palau often snorkel in the jellyfish lake, although the disruption of the jellyfish is somewhat controversial. The Jellyfish Lake as it is known is actually not the only jellyfish lake in Palau, but it is the only one open to human-jellyfish interaction. While the jellyfish do have something of a sting, it is too weak to be felt by the people who drift with the jellyfish just under the water’s surface.
See the jellyfish in action in this video courtesy of National Geographic:
JELLYFISH LAKE, Rock Islands, Palau
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