Far out in the Bay of Bengal, to the east of Sri Lanka, the ocean rearranges itself every year.
The surface seems ordinary. But beneath it, cold, nutrient-rich waters rise, pushing upwards like a swelling dome. For a brief window between May and September, this patch of sea turns into one of the most active feeding zones in the Indian Ocean.
Scientists call it the Sri Lanka Dome.
And for Olive Ridley turtles, it has become a destination.
Recent satellite tracking has revealed that turtles nesting along India’s eastern coastline are not dispersing randomly into the ocean, as once believed. They are travelling with purpose, crossing hundreds of kilometres to gather in this single, food-rich zone.
The question is no longer where they go. It is why they all go here.
An ocean engine
To understand the pull of the Sri Lanka Dome, scientists point to a powerful process: upwelling.
Think of it as an underwater fountain.
Winds and ocean currents interact in a way that lifts deep, cold water towards the surface. As it rises, it carries nutrients that have remained locked in the depths. When these nutrients meet sunlight, they trigger a surge in plankton — tiny organisms that form the base of the marine food chain.
This bloom sets off a cascade. Small fish arrive to feed, and what was once open water becomes a concentrated feeding ground.
The Sri Lanka Dome forms annually, usually beginning in May, strengthening through July and August, and fading by September.
As it intensifies, it draws in a wide range of marine life — fish, whales, seabirds, and turtles.
The journey begins in India
Along India’s eastern coast, the story begins on sandy beaches in Odisha and Tamil Nadu.
At sites like Gahirmatha and Rushikulya, thousands of Olive Ridley turtles come ashore each year to nest in mass events known as arribadas.
After laying eggs, they return to the sea. For decades, what followed remained unclear.
Where did they go after nesting? Did they scatter across the ocean, or follow a pattern?
Recent satellite tracking has revealed that turtles nesting along India’s eastern coastline are not dispersing randomly into the ocean, as once believed. Photograph: (Facebook)
Satellite transmitters have begun to answer these questions.
Researchers from the Wildlife Institute of India tagged turtles along the coast, tracking their movements in real time. The data revealed that turtles from different nesting beaches, separated by large distances, were converging in the same region of the ocean near Sri Lanka.
That region was the Sri Lanka Dome.
Early tracking data shows that some turtles have already travelled to the Sri Lanka Dome, an oceanic region known for high marine productivity, said Supriya Sahu, Additional Chief Secretary, Environment, Climate Change and Forest Department.
Long message, but trust me, it will be worth your time. Here is a remarkable update from Tamil Nadu’s tagged turtles. Early tracking data shows that some have already travelled to the Sri Lanka Dome, a little known ocean region where marine life gathers in extraordinary numbers.… pic.twitter.com/h2yUzvOLiW
— Supriya Sahu IAS (@supriyasahuias) April 25, 2026
Why the dome matters
For a species like the Olive Ridley, survival depends on timing and energy.
Nesting is physically demanding. After laying eggs, turtles need to rebuild their energy reserves. The Sri Lanka Dome offers exactly that — a dense, reliable food source in an otherwise vast and unpredictable ocean.
Olive Ridleys are known to be highly migratory, but this specific route — linking Indian nesting beaches to a seasonal feeding ground near Sri Lanka — was not clearly documented before. Photograph: (Wikipedia)
This explains why turtles are willing to travel long distances to reach it.
The discovery also reshapes how scientists understand marine migration. Olive Ridleys are known to be highly migratory, but this specific route — linking Indian nesting beaches to a seasonal feeding ground near Sri Lanka — was not clearly documented before.
It also suggests that the dome is not just a feeding zone, but a convergence point — a rare instance where animals from distant coastlines gather in one place, drawn by the same ecological trigger.
More than just turtles
While current tracking data focuses on Olive Ridleys, the implications extend further.
Such nutrient-rich zones typically attract a wide range of marine species. Plankton blooms support fish populations, which in turn draw larger predators.
Scientists believe the Sri Lanka Dome likely supports a broader marine network, even if current data is centred on turtles.
Highlighting the significance of the findings, Supriya Sahu said the movement patterns show that turtles depend on a connected ocean system, where feeding grounds, migration corridors, and nesting beaches are all interlinked.
A conservation wake-up call
Conservation efforts for sea turtles have traditionally focused on protecting nesting beaches. But the Sri Lanka Dome shows that safeguarding coastlines alone is not enough. These turtles depend on a network that spans countries and open waters.
Calling for conservation measures, Supriya Sahu said efforts must go beyond coastal boundaries and involve cross-border cooperation, as wildlife movements are not restricted by geography.
The dome itself is vulnerable.
Changes in ocean temperature, shifting wind patterns, and human activity could disrupt the delicate conditions that create this upwelling. If the dome weakens or shifts, the consequences could ripple across species that depend on it.
It is a reminder that some of the most critical ecosystems are not forests or reefs that we can see, but shifting, seasonal phenomena in the open sea.
And for India’s Olive Ridley turtles, this dome near Sri Lanka is what makes their long migration possible.
