Golden Jellyfish

Photo of a Golden Jellyfish taken by Dr. Alexander Mustard. More of his photos can be found at

Domain: Eurkaryota
Kingdom: Animalia
Phylum: Cnidaria
Class: Scyphozoa
Order: Rhizostomeae
Family: Mastigiidae
Genius: Mastigias
Species: papua etpisoni

Last time, we talked about Jellyfish Lake in the Palau region of the Caroline Islands archipelago. We learned that the meromictic lake, which has distinct layers of water that do not intermix, is the only place you can find Golden Jellyfish.

I highly recommend putting this place on your bucket list, not only would you get killer pictures but you’ll experience something unlike anywhere else in the world! Now, let’s move on to the special guest of the day.

Golden Jellyfish (Mastigias papua etpisoni) are a species of jellyfish that are closely related to the spotted jellyfish that can be found in the lagoons near Jellyfish Lake. Like coral, they benefit from a close relationship with zooxanthellae. What, did you think coral were the only ones to be best friends with the greatest algae of the ocean?

Like coral, the jellyfish house the zooxanthellae in their tissue which gives the jellyfish their golden color. They also have a mutualistic relationship with the algae; the golden jellies provide housing, waste that the algae uses for nutrients, and sunlight in exchange for the sugar that the zooxanthellae don’t use from photosynthesis.

In fact, it’s the sugar that gives the jellies all the energy they need to grow and reproduce, because they don’t gather food on their own since they lost their ability to sting prey through untold years of evolution. It also allows them to propel and migrate through the water, giving the zooxanthellae access to sunlight throughout the day as the sun moves across the sky, casting shadows on the lake.

This migration has a positive effect on the lake’s ecosystem, by stirring up the nutrients and microorganisms found in the water, providing one of the only sources of circulation in the layers they inhabit. So in this scenario everyone wins: the zooxanthellae get everything they need to make food, the jellies get all the leftovers, and the surface of the lake gets stirred up for the other organisms that call it home.

But the jellies aren’t without predators. They’re preyed upon by anemones that concentrate in areas that the jellies frequently migrate through, creating a bottleneck effect. Thankfully, the sheer number of Golden Jellyfish provide their predators a healthy diet without affecting the population too much.

I find these guys to be really cool creatures to study just because of their relationship with the zooxanthellae and their ecosystem. In general, the whole lake is fascinating and worth the time to read about. It’s a wonderful example of how crazy nature can become when isolated from what used to be similar environments and/or species.

Sources and cool links to check out:


Jellyfish Lake

Photo of golden jellyfish in Jellyfish Lake, Palau. Photo taken by Dr. Alex Mustard, and more can be found on his website

I’m going to take a brief interlude to talk about something different. Don’t worry though I have a reason for this!

Several archipelagos dot the Pacific Ocean, but today I’m going to talk about one in particular. The Republic of Palau is made up of several hundred islands that are populated by a people who have been shaped by the sea and nature. There are so many cool islands to choose from, I bet you could easily spend a few years there and still not see everything. Today, though, we’re going to focus on a unique lake found in the Rock Islands of Palau, Jellyfish Lake.

Jellyfish Lake is a brackish marine lake that is located near the sea. The lake is fed by rainwater, but it isn’t considered a fresh water lake because it’s a bit saltier than freshwater, although it doesn’t match the salinity of the nearby ocean. Jellyfish Lake is also largely isolated from the ocean, so where does the salt water come from?

One of the unique things about this lake is that they’ve found tunnels and fissures in the surrounding limestone that actually connect the lake to the ocean, and that’s where the salt comes from. However, another unique thing about this lake is that unlike other tropical lakes there’s no circulation movement of water.
In other words, the lake has no current and the wind only affects the surface water, so the lake has developed distinct layers making this a meromictic lake. As cool as that sounds, the coolest thing about the lake is how it got its name.

Jellyfish Lake is home to the nonstinging Golden Jellyfish, which can’t be found anywhere else in the world! The main attraction to this place is the sheer number of jellyfish that you can find in the lake–at least over a million of little animals to safely swim with!

The biggest reason I wanted to talk about this lake is because I want to visit it myself. For a while, Palau officials closed the lake to tourism due to a drastic drop in the Golden Jellyfish numbers, so they wanted to run studies and try to help the jellyfish population.

Now, the numbers are back at healthy levels and they have reopened the lake to visitors. So grab your fins, snorkel, and mask and go have a relaxing swim with these harmless jellyfish and experience a world unlike any other—I know I’m going to!

Read more about jellyfish and Jellyfish Lake here: