Science

New Year on the reef

Feather stars remain hidden during the day time, coming out at night to feed. Photo: Shreya Yadav  

It is twilight by the time we get off the boat and into the water. I empty the air from my dive jacket, put theregulator into my mouth, and begin to descend into the darkness head first, feet up.

The reef appears before me in shadows. Faint outlines of spurs and grooves mark the bottom — ravinesformed by the erosion of waves over thousands of years. Five beams from our five torches zigzag across the dark water, and we follow them along the reef.

Have you ever been out on a walk at night? Have you noticed how the leaves of the Rain Tree close anddroop during sunset, or that the branches of fig trees seem suddenly alive with the shuffling of bats? It’s even better if you take a torch. The grass on the lawn will begin to glitter in greenish pinpricks– reflected light from the eyes of funnel web spiders, which live close to the ground – or perhaps of a gecko out on a night-time hunt.

The reef at night

Underwater too, animals are waking up or falling asleep. Tonight, 15 metres under the surface of the Arabian Sea, the water is calm and clear. A flash of two butterflyfish hovering close to a crevice in the rock suddenly catches the light of my torch. They are like mirror images of each other, positioned tail-to-tail, and I notice that they have changed colour for the night. The bits of their body that were white in the daytime are now a greyish black. This is a special skill butterflyfish have. Camouflaged this way, predators will find it harder to see them. I try to go closer but they disappear between two coral boulders.

We swim along, our lights illuminating other circles of activity. A feather star on top of a coral boulder is waking up, stretching out its 12 long arms into the gentle current. During the day, feather stars hide away from the sight of predators. But at night, when their biggest enemies are asleep, they wake up and begin their slow walk around the reef, picking up bits of food they find in the water. We follow this feather star for a while until we notice a pair of hermit crabs tottering across the seafloor, shells perched on their back. Hermit crabs live inside the old and discarded shells of other animals. I wonder where they are off to tonight – they seem to be in a big rush.

Who else wakes up when it’s dark?

I wish I could tell you all the things we saw. Creeping sea cucumbers feeling for prey with their finger-like suction pads, transparent polychaete worms , reef sharks on a hunt – so many creatures wake up when we’re falling asleep. Just like the grass that twinkles with the eyes of spiders and lizards, the water too constantly glows and fades with bright green dots of bioluminescent plankton – tiny plants and animals that produce light when they move.

When we come up to the surface, all the stars are out, and the Earth has completed another orbit around the sun. It is the 1st of January, 2016.


Our code of editorial values

Related Topics
This article is closed for comments.
Please Email the Editor

Printable version | Jun 18, 2021 6:34:57 PM | https://www.thehindu.com/in-school/sh-science/New-Year-on-the-reef/article14169421.ece

Next Story