The lake is connected to the ocean water of the lagoon by fissures and tunnels in the limestone of ancient Miocene reef. This reef is so ancient, that it dates back to when the Himalayas first began to rise. A marine lake is defined as "a unique ecosystem which forms when a depression in a porous, calcareous landscape is flooded by rising sea-levels. Connected in various ways to the sea, they form a continuum from complete isolation to lagoon-like. Marine lakes can contain a variety of habitats which foster adaptive radiation and rapid evolution of the biological assemblages."
The jellyfish that inhabit the reef are of the scyphozoan class. The predominant species of jellyfish are the golden jellyfish, species Mastigias. They are quite similar the the spotted jellyfish that inhabit the nearby lagoon however, they are morphologically, physiologically, and behaviorally distinct from them. The golden jellyfish migrate horizontally across the lake throughout the course of the day in order to increase and perpetuate the growth of the symbiotic algae that they rely on for nutrients.
Above is a graph representing the stratification of the lake. It is divided into two layers, an oxygenated upper layer (mixolimnion) and a lower anoxic layer (monimolimnion).The stratification of the lake is caused by conditions which prevent or restrict the mixing of water vertically. Causes of this condition are:
1. The lake is surrounded by rock walls and trees which substantially block the wind flow across the lake that would cause mixing.
2. The primary water sources for the lake (rain, runoff and tidal flows through tunnels) are all close to the surface.
3. The lake is in the tropics where seasonal temperature variation is small so that the temperature inversion that can cause vertical mixing of lakes in temperate zones does not occur.
