Ocean odysseys

Polar explorers

The pale sun shines down from a cold, clear sky, spilling light across a frozen landscape. Ice glitters blue and white, rising from the sea in cliffs and jagged peaks. Suddenly, the still air is split by a piercing crack. A mountainous glacier fractures, a shard shearing away, crashing into the sea. The waves jostle the smaller fragments drifting on the surface, startling a flock of birds that rests upon one.

They take to the air with a chorus of angry calls. Their feathers gleam, soft grey and snowy white, a smart black cap crowning their head. Elegant wings carry them away, long tail streamers trailing in a fork behind them. They’re restless. Something inside of them, instinct and an internal clock, is stirring, telling them it’s time to move. It’s time to head north.

The Arctic tern is one of the world’s most spectacular migrants. Every year, these intrepid explorers fly the length of the planet and back again. They spend our summer nesting at the very top of the Northern Hemisphere, from the UK right up into the Arctic circle. As the season starts to change, they head south, reaching the ice of Antarctica just in time for the southern summer. Some might see both polar bears and penguins in the space of a few months! This nomadic lifestyle means Arctic terns live in a state of perpetual summer, experiencing more daylight than any other animal.

Ocean drifters

For two long years, the tiny creature drifted with ocean currents like a leaf on the wind. At first, it was flattened and transparent, a see-through sliver of life, a miniature ghost in the vast Atlantic. But eventually, it transformed. Its body rounded out, becoming more cylindrical, a glass noodle just a few inches long.

Finding itself free of the open ocean, close to shore, the creature rode the tides into a river mouth. Its transformation continued, its skin darkening, no longer transparent. Against the odds, it battled its way upriver until it found a suitable freshwater home. There it spent years feeding and growing. Now, the time has come to travel once again. It must leave its tranquil river, swim thousands of miles out to sea and, with its final act, lay eggs and start the cycle all over again.

European eels have an extraordinary life. It begins as an egg in the Sargasso Sea, hatching into a strange larval stage known as a leptocephalus. This drifts back to coastal waters, where it becomes a glass eel and enters a river mouth. The next stage, called an elver, swims upstream and grows into what’s known as a yellow eel. Finally, as an adult ‘silver eel’, it swims back to the Sargasso Sea to spawn.

Rock roamers

Waves crash against the rocky shore. The foaming water slams against stone, sand and shell, the unbridled power of the ocean unleashed on the fringes of the land. The sea scours away anything that isn’t secured. But some small creatures stand strong against the briny onslaught. Tiny grey cones dot the rocks, unmoved by the raging sea.

For hours they’ve clung there, exposed to the air and the scorching sun, their soft bodies protected by a hard shell of calcium carbonate. But this is the moment they’ve been waiting for. As the tide flows in, slowly submerging them beneath the water, they finally come to life. The limpets begin to move.

Not all incredible journeys cover vast distances. Limpets may only wander half a metre from their home site over the course of the high tide. They roam the rock, feeding on algae scraped up with their rasping radula – the limpet equivalent of a tongue with teeth. The remarkable thing about their journey is that they always return to the same spot. They follow a trail of their own mucus back to their ‘home scar’. This is a depression in the rock, formed by that single limpet grinding its shell down into that exact spot, over and over again, clinging on until the next foraging foray.