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Scientists Use Manta Probes to Monitor Water Quality at world-famous Jellyfish Lake, Palau

Scientists Use Manta Probes to Monitor Water Quality at world-famous Jellyfish Lake, Palau


* Note: This article written by the team at Coral Reef Research Foundation.
The Coral Reef Research Foundation undertakes a wide variety of marine research activities in the Palau Islands, located in the western Pacific, just north of the equator. Palau is a remarkable tropical archipelago and is a renowned diving destination, also made famous by Jellyfish Lake, a unique marine ecosystem that is home to millions of Golden jellyfish. Jellyfish Lake (known locally as Ongeim’l Tketau) is singular with its daily migration of millions of jellyfish medusae following the sun across this salt water lake, and is the most-loved tourism site in Palau.

Coral Reef Research Foundation, 2023.


Coral Reef Research Foundation



The population of medusae in Jellyfish Lake varies from year to year due to the physical conditions of the lake related to weather patterns and impacted by El Niño/La Niña climate variation. The changes in physical conditions, such as temperature, salinity, and oxygen, are important to measure accurately on a regular basis, concurrent with jellyfish population numbers and sizes. Over the last twenty years, one challenge has been to find and use water quality measuring instruments that can withstand the daunting tasks of rough boat trips and backpack hiking into these remote salt water environments, in an area with no support services. Accurate, repeatable data, month to month, are essential to understand the past dynamics and immediate future of the lake and its iconic jellyfish inhabitants.  




A Eureka manta+ 35 is used regularly to measure water quality parameters (temperature, salinity, oxygen, pH chlorophyll a and depth) to understand the physical relationships of the lake to atmospheric conditions and thus how this influences the numbers of Golden jellyfish. We have found our Eureka instrument to be superior to others in reliability, durability, and ruggedness.   




The use of Eureka probes has helped us to understand the dynamic relationships between the physical and the biological in Jellyfish Lake. Although variation in climate, such as El Niño and La Niña, is beyond our control, accurate data on change and resultant trends have allowed us to make predictions on the future status of jellyfish populations, important in the management of human use of the lake.


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