Photo: Deepansh Mishra/entry-the sanctuary wildlife photography awards 2016.
On a jagged mossy rock, a Pacific Reef Egret leans forward, motionless. As though admiring its own reflection. A wave breaks against the rock, sending salt spray and fish towards the patient hunter. Snap! Fish make their way into the hungry predator’s mouth.
Binoculars down. Pan out. Two plainclothes researchers (GK and Chutney) jump out from behind a fallen bulletwood tree onto a south Andaman Island beach.
GK: Whoa! Did that egret just catch a fish out of the sea? I thought they stick around forests and fields in the company of deer and cows.
Chutney: True… but here we are where forest and sea meet. So, when I’m not diving, I go birding.
GK: I don’t know, I like birding here, but shore birds are confusing. And frankly I know nothing about the sea.
Chutney: Learn to dive. It’s a different world underwater. Corals are ‘rainforests of the sea’.
GK: Are you serious?
Chutney: I am. Plants and animals exhibit similar adaptations even in the marine world. Safety in numbers, colour means poison, symbiosis!
LIFE IN SEAWAER
By now, you must be familiar with living in and breathing the nitrogen-oxygen mixture that we call air. Life in the sea is different. To start with, it is salty and continually in motion. If the currents don’t take you from one ocean basin to another, the tides will see-saw you, roughly every six hours, to land and back.
Life is governed by physical factors we scarcely notice on land. Take density. A cubic metre of seawater weighs 1,025 kg. on average, while the same volume of air at sea level weighs just 1.275 kg. That’s more than 800 times the weight on each square inch of your skin in seawater than in air. Then, there’s depth. As you go deeper, a whole range of conditions – temperature, pressure, light, nutrients… change around you.
While conditions are practically the same at 10 m. above sea level, at a depth of 10 m. the increase in pressure from one atm. to two atm. significantly affects buoyancy (atm. represents the standard atmosphere, a unit of...