Jellyfish Lake

Field trip to Jellyfish Lake on Eil Malk island, Rock Islands Palau. Water sampling from above and below the thermocline. Students used Vernier LabQuests and sensors to measure temperature, salinity, and pH. Water on top was colder and less salty while water below was warmer and saltier. Students concluded that recent rain events contributed to this marked stratification of the lake. Recent population declines of the golden mantle jellyfish observed first hand.

At the site with other K-12 Palau students visiting Jellyfish Lake.

Ongeim’l Tketau - Jellyfish Lake

Image Attribution: By Lukas from Munich, Germany - originally posted to Flickr as Palau_2008030818_4734, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=9492961

Jellyfish Lake Location from Google Maps

A UNESCO World Heritage Site

Golden Jellyfish, Mastigias papua etpisoni

This subspecies of golden jellyfish is found only in Jellyfish Lake in Palau. The lake is a brackish marine lake which is no longer connected to the sea. The jellyfish migrate across the lake each day from west to east and then back again as they follow the sun and avoid the shady edges of the lake. This migration allows the jellyfish to avoid their anemone predators near shore.

Recent Population Declines

Image Citations: w:en:Aquaimages (talk | contribs) - Own work CC BY-SA 2.5

Golden jellyfish numbers dropped dramatically in response to the 2015/16 El Nino drought in Palau. The Koror State Government closed the lake to visitors for two years. By 2019 golden jellyfish numbers were back in the millions and tourism at the lake was reopened.

In September of 2022 another marked population decline was observed, likely due to increased temperatures in the lake. The Koror State Government did not officially close the lake however some tour operators suspended tours. On this field trip in November 2022 only 5-6 golden jellyfish were observed in the middle of the lake.

Jellyfish Lake Permit

Palauan can get special permission to visit Jellyfish Lake. International tourists must pay for a $100 permit to visit the lake. The money funds conservation efforts by the State of Koror in the Rock Islands.

Moon Jellyfish

In contrast to the low numbers of golden jellyfish, PCC students observed large numbers of Moon Jellies at Jellyfish lake on November 11, 2022. Do these more common type of jellyfish have a competitive advantage in warmer waters?