Jellyfish Lake, Eil Malk Island, Palau, Pacific Ocean

• Golden jellyfish
Beginning in about the fall of 1998, a precipitous decline in the golden jellyfish medusa population was detected in Jellyfish Lake. By December 1998, the medusa population had declined to zero.
Based on their extensive investigation of the disappearance of the golden jellyfish medusae, Dawson et al. determined that the most likely cause was an El Niño weather event that raised the water temperature so that the symbiotic algae (Zooxanthellae) that live within the golden jellyfish medusae and the syphistomae (scyphozoan polyps) could not survive.
In January 2000, the golden jellyfish medusae were observed in Jellyfish Lake for the first time since April 1999. By May, 2012, the medusae population had returned to pre-decline levels.