Jellyfish Lake is an isolated saltwater lake in the Pacific island of Palau. In the geologic past it was tied to the ocean acquring jellyfish. These jellyfish have become an isolated population lossing thier nematocysts (stinging cells). They thrive in the lake at high number due to the lack of predators. [from Rick Macpherson] The jellies have acquired algal endosymbionts in their tissue (same genus as the zooxanthellae in coral)… during the day, the jellies rise to the surface in masses and track along the surface of the lake as the earth rotates… at night, the jellies sink to the deeper, anoxic but hyper-nitrogen waters of the lake to “fertilize” their algal tentants.