So is it the 20 million or so Golden Jellyfish serenely pulsating through an emerald tranquility that draws so many people? Yes, probably it is. Phenomenal stuff I think you’d agree. What many people don’t realize is the knife edge of existence that these Jellyfish live on.
Try this experiment. Take one 3/4 full bucket of dirty water. Leave it to sit somewhere sheltered out of reach for 1 week. If it’s left undisturbed the sediment settles. What you get is your own miniature version of a Meromictic Lake. Big whoop you might say but I am going somewhere with this.
So instead of having one three quarters of a bucket, you now have a volume of approximately 94 million buckets and leave it to settle within an island of the equatorial Western Pacific for 12,000 years or so.
A Meromictic Lake such as Palau’s Jellyfish Lake is one that does not get mixed as a typical lake does. Turbulence very rarely exists that disturbs the sediment, and wind is causing minimal ripples on it’s surface. Given enough time these lakes develop layers within that suspension of dirt.
Denser particles fall faster than less dense ones. Chemicals even separate and react with each other within their layers. Distinct biological and chemical boundaries develop. Meromictic Lakes are extremely rare, Meromictic Lakes that have 20 million jellyfish living in them are rarer still. So how would you survive in a big bucket of dirty water as a jellyfish? These jellyfish have done it and done it in an incredible way.
They have living within their bodies algae, that like other plants, photosynthesize in sunlight. The algae produce what is essentially a form of sugar which the jellyfish, as an animal metabolizes, this gives energy to move itself through the water, grow and reproduce. Waste products from the metabolic process in turn provide in combination with sunlight what the algae needs to produce more sugars. So what you have is an animal that carries within it, it’s own farm, producing it’s own food.
As long as the jellyfish stays in the sunlit water it’s algae will provide it with food. How idyllic you might say, oh to be a jellyfish? However it’s not all Paradise in Palau for them.
Firstly, they sink, so they have to keep swimming to stay in the sunlight. Imagine 20 million Dories all singing “Must keep swimming, must keep swimming” all day. Secondly the sun moves across the sky and the jellyfish need to optimize the amount of sunlight their algae get, the more sunlight the more energy. So as the sun moves so do they.
The jellyfish migrate over a daily cycle. The sun rises in the east, they swim to the east end of the lake, the sun passes overhead and sets in the west, the jellyfish swim towards the west. When the sun sets they sink down about 15m into the depths where there are layers of hydrogen sulphide devoid of oxygen. Here they absorb vital trace chemicals before swimming back up towards the lightening sky before dawn.
It’s at this point that my interest went through the roof. It doesn’t matter where you live on this planet, the sun rises at a different point on the horizon every day of the year. Think about Stonehenge for instance. Even on the equator it varies by 40 degrees or so from midsummer to midwinter.
So what in effect happens is that the jellyfish swim to the east end of the lake but that “end” varies by 40 degrees over the course of a year. This migration in itself is a spectacular biological phenomenon, but additionally the trees and jungle that surround and shelter the lake from the wind also cast their shadows upon it, creating a sudden barrier, a “no-go” zone of no-light if you will, the jellies actively avoid this darkness once they get there. It’s not as simple as that though because in certain areas there lurks waiting, death.
This is prime time real estate here because this is where the jellies pass each day on their way from east to west. They become concentrated at the bottleneck and if a jelly becomes entangled in the sticky tentacles of the anemone it will be slowly consumed.
In some areas of the lake, trees have fallen that lie exactly where the jellies are drawn by the sunlight, and during certain times of the year, during certain parts of it’s own 40 degree migration across the horizon, the sun rises and shines its light over a section of the lake where a tree and its anemones wait.
In recent years, something far more devastating than anemones has arrived in Jellyfish Lake. Tourism.
Ten’s of thousands of tourists go there every year. They cover themselves in sun cream which is poisonous to the jellies and bring with them invasive species that are taking over and wreaking havoc in this finely balanced, sensitive system.
In 2016 Palau suffered from an El Nino event. Very little rain fell for months and gradually the salinity and temperature of the lake increased. The jellies started to die.
A study by the Coral Reef Research Foundation in Palau counted the numbers of Jellyfish in the lake in 2016. Remember the healthy lake originally had an estimated 20+million jellies. In Mar 2016, there were 600,000 jellies; Apr 2016, 300,000 jellies; May 2016, 45,000 less than 1 cm, and; Jun 2016, 0.
It could be argued that El Nino is to blame for this die off. Back in 1998 there was another such event which wiped out the jellies. It took 2 years for them to recover. The difference now is that there are 100,000 people going in there covered in sunscreen and invasive species larvae. What is also interesting is that the other jellyfish lakes in Palau under the same weather conditions did not experience this total die off. So what is the real reason?
Certainly an environment as unique and sensitive as this needs to be managed by people who understand what they are dealing with. It is after all a UNESCO World Heritage Site.
Ironically it was also the cauldron full of gold for Koror State, the legislative owners of the lake, who were charging visitors $50 each to visit. However no showers were available to wash off any potential invasive species or sun cream, no toilets were available on site and there was minimal supervision of visitors in the lake.
Now the cauldron is empty.
(Richard Brooks is a media producer based in Palau. His company Lightning Strike Productions covers everything from underwater to aerials. You can see more of his work here: www.lightningstrikeproductions.co.uk)