Jellyfish Lake
Interesting facts
- Millions of golden jellyfish cross the lake every day, and each one spins counterclockwise as it swims, apparently to give its algae even exposure to the sun.
- In Palauan the lake is called Ongeim'l Tketau, which translates as 'Fifth Lake'.
- Jellyfish-eating sea anemones live at the lake's eastern end, and scientists think the golden jellies evolved to head west early in the afternoon to escape them.
- A dense band of purple sulphur bacteria floats just below the oxygen line, absorbing all the sunlight so the deep water beneath is dark yet remarkably clear.
- Seawater enters through three tunnels near the surface, so tides inside the lake are only about a third as high and peak some 100 minutes later than outside.
- Only about 2.5 percent of the lake's volume is exchanged with each tide, leaving its life largely cut off from the lagoon nearby.
- Over time the golden jellyfish have lost almost all the spots and club-shaped appendages that their lagoon relatives, the spotted jellyfish, still carry.
- At night the golden jellies spend around 14 hours swimming up and down to the edge of the toxic layer, probably to collect nitrogen for their algae.
- It is one of only about 200 known saline lakes whose layers never mix, and unlike most of them it was never a freshwater lake.
- The lake is one of roughly 70 marine lakes scattered across Palau's Rock Islands.
Why it is worth it
Jellyfish Lake is a small marine lake on the island of Eil Malk in Palau's Rock Islands, and it is home to vast numbers of golden jellyfish that drift across it every day in pursuit of the sun. The lake is about 460 metres long and 160 metres wide, ringed by forested limestone, and it was formed around 12,000 years ago, when the sea rose after the last ice age and flooded a hollow in an ancient Miocene reef. It is still linked to the ocean through fissures and tunnels in the rock, but the exchange is slight, so the lake has evolved as a world of its own.
Two kinds of jellyfish live here: moon jellyfish and a subspecies of golden jellyfish, Mastigias papua etpisoni. The golden jellies carry symbiotic algae in their tissues and get part of their food from them, which is why they follow the light. In the early morning they swim from the centre of the western basin toward the east, then turn back in the early afternoon and gather on the western side as sunset approaches. Their population collapsed in 1998, most likely because an El Niño event warmed the water, and then gradually rebuilt, returning to earlier levels by 2012.
Below the surface the lake is permanently layered. Oxygenated water extends down to roughly 15 metres; beneath it lies a dark, oxygen-free layer rich in hydrogen sulphide, which reaches more than 80 milligrams per litre near the bottom at about 30 metres. Because bubbles harm the jellyfish and the deep water is toxic, the lake is explored only by snorkelling; scuba diving is not permitted.
Getting there
The lake is reached by boat from Koror, Palau's largest town, a trip of about 45 minutes through the Rock Islands. Roman Tmetuchl International Airport (ROR) is about 29 km away; the capital, Ngerulmud, lies about 46 km away in a straight line.
Plan your visit
We have no confirmed visit data yet. Once it is confirmed, this block also carries the date it was checked.
Nearby places
- Rock Islands Southern Lagoon 9.8 km · lagoon
On these lists
From the encyclopaedia
Jellyfish Lake is a marine lake located on Eil Malk island in Palau. Eil Malk is a part of the Rock Islands, a group of small, rocky, mostly uninhabited islands in Palau's Southern Lagoon, between Koror and Peleliu. There are about 70 other marine lakes located throughout the Rock Islands. Millions of golden jellyfish migrate horizontally across the lake daily.
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