Hidden Islands within Islands

Jellyfish Lakes


Golden jellyfish

Jellyfish lakes are very special marine lakes. They can be filled with millions of Masitigias papua jellyfish. M. papua are also called 'Golden jellyfish' because they are filled with golden-coloured zooxanthellae: tiny algae that can photosynthesize. There are less than 15 jellyfish lakes in the world, which ephasises their uniqueness and fragility. The region of Raja Ampat in Indonesia has at least 3 jellyfish lakes known to science.


We still do not know how it is possible that certain marine lakes harbour millions of jellyfish, while others have none. Furthermore, we do not know how and why jellyfish populations fluctuate over time. For example, one lake was recorded to have millions of jellyfish, but when researchers returned a few months later the lake was empty. It is important we understand how jellyfish lakes function in order to adequately protect them.





Jellyfish lakes face multiple threats:

  • Aquaculture
    Some marine lakes are used as fish ponds, which has high impacts on all biota.
  • Climate change
    Global warming may influence jellyfish abundance and health.
  • Unregulated tourism
    High numbers of tourists are known to have dire effects on jellyfish populations.


In order to protect jellyfish lakes, the team is working together with the government of Indonesia to form a conservation and management plan specifically for jellyfish lakes. Furthermore, we work on educating local homestays, live-aboards and dive resorts to educate tourists on the do's and don'ts when visiting a jellyfish lake.

English versions of two flyers we have made can be found here and here.
Versions in Bahasa Indonesia can be found here and here.




Monitoring project

We have set up a long-term monitoring program with the University of Papua. We monitor jellyfish populations in marine lakes over time. Two to four times a year, a team of students, people from NGOs, and scientists visit jellyfish lakes to study the following characteristics:

  • Jellyfish abundance. This is done via video transects.
  • Jellyfish morphology. We are interested whether size distributions fluctuate. Furthermore, morphology also gives information on jellyfish health.
  • Benthic biodiversity. Benthic populations may affect jellyfish populations.
  • Water quality. These include water temperature, pH, dissolved oxygen content and salinity.