The above video might call to mind the “jellyfish forest” in a certain Pixar movie, but divers have nothing to fear from the eponymous inhabitants of Jellyfish Lake. (I’m pretty sure oceanographers can only mention Finding Nemo once every few months or they start to lose credibility, so you bet I waited for an optimal time to use that reference.) Located in Palau, an island country located north of Papua New Guinea, Jellyfish Lake was connected to the ocean about 12,000 years ago. Falling sea levels stranded the lake on land, and although it is still connected to a nearby lagoon through fissures in the surrounding limestone, the lake is effectively isolated. This temporal and spatial separation has been a boon for the millions of golden jellyfish that call Jellyfish Lake home. The jellyfish have a symbiotic relationship with algae, known as zooxanthellae, that live inside their tissues. The zooxanthellae provide the jellyfish with sugars for energy, and the jellyfish offer protection. This arrangement may remind you of the one between coral polyps and algae. Since the zooxanthellae photosynthesize, they need adequate sunlight, and that’s where the jellyfish become critical.  Each morning, the jellyfish start off in the sunny eastern part of the lake, and swim westward around midday to follow the sun.  As you can see in the above video, this makes for a visual delight for snorkelers.  (Scuba diving is not permitted.)  Even better, the jellyfish’s nematocytes (stinging cells) are not felt by humans.  Vacation to Palau, anyone?

Cover Image from http://www.grindtv.com/outdoor/nature/post/jellyfish-lake-diver-surrounded-by-millions-of-jellyfish/