Each day, more than 10 million golden jellyfish perform a habitual migration within Jellyfish Lake, a remote marine lake on the island of Palau. While jellyfish are often know for drifting aimlessly at sea, these golden jellies propel themselves forward by pumping water through their golden bells. This daily dance draws numerous visitors to the Pacific Island’s Jellyfish Lake each year.
Each morning, the jellyfish congregate on the lake’s western shore, waiting for the sun’s arrival. As the day continues, the jellyfish mirror the sun’s movement, propelling themselves from the western shore to the middle of the lake, and, as the sun sets, back to the western bank.
By following the sun’s familiar movements, the jellyfish avoid a major predator, anemones, which reside in the lake’s shaded places. In the centuries since the 12,000-year-old saltwater lake was formed, these jellyfish have evolved to cope with the lack of natural predators and have therefore lost their sting. For this reason, Jellyfish Lake is a popular diving hot spot. Recently, diver Nadia Aly visited the lake, taking thousands of incredible pictures of the phenomenon, including a selfie.
The unique migration that takes place in Jellyfish Lake is all caused by a need for direct sunlight. Golden jellyfish need sunlight to survive, as the sun’s rays provide important nutrients to the algae-like organisms that inhabit the jellyfish’s tissues. Formally called zooxanthellae, these endosymbiotic dinoflagellates create energy through photosynthesis, and provide that to the jellyfish in exchange for inorganic molecules. Without the sun, these organisms would die, robbing their hosts of important, life-giving energy.