WIBBLE WOBBLE, JELLY IN A LAKE

Photo courtesy of aSIMULAtor

The thought of swimming in a lake packed full of millions of jellyfish isn’t one that most people would jump at, but what if you were guaranteed not to be stung?

Tourists have been flocking to a lake on the island of Palau, once connected to the Pacific Ocean; the lake has since been isolated by the sea level dropping and now offers a unique diving and snorkeling experience. Despite still being connected to the ocean through fissures and tunnels in the limestone, the 12,000 year old lake has been sufficiently isolated, allowing the golden jellyfish (Mastigias sp.) and the moon jellyfish (Aurelia sp.) to thrive in algae-rich waters with no threat from predators.

The sequestered lake has facilitated the evolution of these jellyfish to be substantially different from their close relatives living in the nearby lagoons. Their cnidocytes or stinging cells have weakened over time and now pose no threat to people swimming through a swarm (or to use the collective noun, a smack) of them. There are now up to eight million of these pacified jellyfish populating the meromictic lake, providing quite an exclusive and popular tourist attraction. Kevin Davidson has spent the last 15 years charting the trips in Jellyfish Lake, ‘people who have a fear of jellyfish freak out – some just turn around and leave but there are no dangers’, he said. ‘The jellyfish have slowly lost their stinging cells,’ he added. ‘It’s unusually quiet and you can just feel hundreds of soft blobs touching your skin as you move through the water.’
 
Scuba diving by tourists in the lake is not allowed for a couple of reasons; the bubbles from scuba tanks can harm the jellyfish if they collect beneath their bell and the anoxic layer that begins at about 15 meters contains high concentrations of hydrogen sulfide which can be absorbed through the skin of a diver which can lead to death.

Jellyfish Lake is currently the only one of Palau's marine lakes open to tourists and will set you back $35 for a 10 day pass.

By Lucas Lowe