Earth’s seas and oceans provide habitats for an incredible variety of life,. From the warm, sunlight shallows to the inky, icy depths, they are home to everything from microscopic single-celled algae to plankton, invertebrates, coral, fish and huge marine mammals such as whales.
World Beneath the Waves
Peer beneath the surface of any ocean and you may be surprised to learn that the ocean has ‘gardens’ – of coral and maerl, whose reefs provide important homes for many other species. Coral attracts fish species, while urchins and sea cucumbers call maerl home. By protecting these areas, we help conserve the whole ecosystem (a community of plants, animals and microbes in an area) by keeping marine food chains intact.
Corals are tiny organisms – called polyps – that create the world’s great reefs. Colourful coral beds make you think of warm climates, but cold-water coral lives in deeper, colder waters, including off the coast of Scotland. In deep, cold water they feed by capturing food particles from the surrounding water so don’t need sunlight to survive.
Maerl is a hard seaweed that forms spiky underwater ‘carpets’ on the seabed, known as maerl beds. It is found throughout the Mediterranean, along most of the Atlantic coast from Portugal to Norway, and in the English Channel, Irish Sea and North Sea. The white beaches in the West of Scotland are made of maerl that has been crushed and then bleached white.
Our oceans are divided into five layers or zones – each with their own unique characteristics and inhabitants – that stretch from the surface to the depths. As you go deeper, beyond the sunlight zone, light stops penetrating the water. In the twilight zone some light penetrates, but not enough for plant growth. Then comes the midnight zone, where no light reaches. Diving deeper still, into the largely unexplored abyssal zone, temperature drops, pressure increases and the creatures get weirder. Finally, nearly three times deeper than the average sea floor, come the trenches, complete with total darkness and unimaginable pressures. The Marina Trench is the deepest part of the ocean, 11,034 metres (almost 7 miles) deep. By comparison, Mount Everest is 8,848 m tall.
Researching the depths of our oceans can be tricky but technology makes the job easier. Remotely Operated Vehicles (ROVs) are underwater robots that allow researchers to explore our oceans while staying above the surface. They often have cameras to record underwater and ‘claws’ to allow the controller to take samples for study.
Gallery of the Curious
Over 60% of the ocean is more than a mile deep and it forms the planet’s most mysterious habitat.
We are a long way from knowing all there is to know about our oceans’ unexplored depths. But manned submersibles and remote-operated vehicles (ROVs) continue to search ever deeper, bringing new knowledge, and new species to the surface. So just what weird and wonderful creatures live beneath the waves?
Anglerfish live throughout the layers of our oceans, from the shallows to the depths. The females of some anglerfish have a lure on the end of their spines which have migrated to their nose.
Some squid use bioluminescence to hide from predators. By matching the look of sunlight from above they can hide their shape from predators.
In jellyfish, bioluminescence is mostly used as a defence mechanism. The glowing and flashing nature is a distraction to predators and can surprise them giving time for an escape.