Golden jellyfish, Mastigias sp., occur perennially in
high numbers in several tropical marine lakes in Palau.
Medusae in Jellyfish Lake were estimated to number
1.8 million in 1996 (Dawson et al., 2001). The strong
1997–1998 El Niño Southern Oscillation (ENSO) event
may have caused the disappearance of Mastigias sp