Jellyfish Lake in Palau, an island nation in the Pacific Ocean would be the perfect setting for an episode of fear Factor – a lake teeming with millions of golden jellyfish. But never fear…the jellyfish here don’t sting!
Snorkelling enthusiasts at Jellyfish Lake witness one of nature’s wonders at work. Believed to be around 12,000 years old, the small lake (420m long and 30m deep) was once connected to the sea. With time, it got isolated by a natural barrier and developed an ecosystem of its own as a landlocked saltwater lake. There are about 70 such marine lakes that dot the island. But Jellyfish Lake is unique due to the presence of the fragile bulbous beings.
Jellyfish are known for drifting to and fro at the whim of ocean currents – but not all species are so passive. The millions of golden jellyfish that pack Palau’s Jellyfish Lake spend much of their lives on the move. Here’s how they go about their journey.
At sunrise
Before sunrise, the jellies cluster along the saltwater lake’s western shore. Each morning around 6, when the sun is up, they begin to swim toward the light. Pumping water through their bells, these jellyfish use a type of jet propulsion to follow the sunlight until they nearly reach the eastern shore – stopping just short of the shadows caused by lakeside trees.
Dependence on sunlight
Sunlight is plentiful on this remote Pacific island, which is a good thing because golden jellyfish don’t just enjoy basking in the sun; they need its light to survive. Solar rays nourish essential, algae-like organisms called zooxanthellae, which live symbiotically in the jellies’ tissues and provide their hosts with energy as a byproduct of their photosynthesis.
Migration at sunset
Golden jellyfish rest relatively contentedly in place at midday when the tropical sun remains high overhead. But each afternoon, as the sun continues its slow crawl toward the western horizon, the jellies change course and return to the western shore to wait the dawn of a new day.
This remarkable migration pattern has a crucial consequence: The jellyfish avoid the shaded lakeshore areas where their primary predators, anemones, live.
How does it benefit the ecosystem?
The daily migration also benefits the lake, which once had an outlet to the sea but has been long since become isolated. As the gelatinous hordes swim back and forth across the lake they mix it waters – and churn the nutrients and small organisms that form the base of the food chain.
With no major predators to attack them, the jellyfish trapped in the lake gradually evolved and lost their sting. Moreover they thrived in millions! Every day, they move horizontally across the lake seeking the warmth of the sun and reverse their direction as the sun sets.
Picture Credit : Google
