What is a plankton?
A plankton is a body of vegetable and animal beings which live in the sea.
They cannot usually move on their own, and even when they can, they do not have the strength to go against the currents, the winds or the tides which carry them along. Most of them are tiny creatures.
A plankton from the first link of the chain of marine life, being the food for many sea creatures.
The live near the coast, where they can find the mineral salts and the light which they need to survive.
And because plankton is eaten by many fish, this explains why the cost is the best place for fishing, whereas the high sea is the worst.
Numerous microscopic algae and animals, who live by gazing on the pastures are also forms part of plankton. And as well as fish, there are many other eaters of plankton, such as sponges, mussels, corals and whales.
What about the insects which can go underwater?
There are fewer insects that live in water than on the earth. Among them is the Pond-skater, which swims underwater, floating in the air. The Lesser Water Boatman swims with his stomach upside down, dives down when he sees something I can eat. Both the Water Scorpion, which is flat and oval in shape, and the thin Water Stick Insect, have tubes through which they breathe.
The Jellyfish and Sharks who are known as dangerous.
Are jellyfish dangerous? Jellyfish are sea creatures, usually with mushroom shaped bodies and tentacles which can sometimes sting and cause injury.
In Australia, there is one type of jellyfish which can cause the death of a human within minutes!
The common jellyfish is relatively harmless, despite its transparent body being up to half a meter wide! But underwater Swimmers can get painful stings from the “Portuguese Man of War” jellyfish which looks like an upturned boat.
And what about the sharks? Are all sharks dangerous? Usually, when we talk about sharks, we are thinking of the man eaters, such as White Shark.
But really, these ferocious creatures are only one type of shark, which in turn belong to a very large family of animals. The man-eating shark is the best-known representative of this family, and justly deserves its reputation.
The White Shark is more common in Australian seas in underwater than anywhere else – whereas in Europe, it is the Blue Shark which is more common. And although this is a smaller type of shark, it is still best avoided!
In the North Atlantic, we meet the Sand Shark, always ready to attack, and very dangerous.
But the most dangerous of all sharks is the Tiger Shark – only four meters long, but fierce and always on the look-out for something to eat.
Then there is the Hammerhead Shark, with the courage to attack other sharks as well as humans.
The Whale Shark is the biggest living fish, up to twenty meters long. But it is harmless and peace-loving feeding on plankton and living in tropical seas. The Elephant Shark lives in the Northern Atlantic. Only a little smaller is the Elephant shark – so called because when it is young, it has a long muzzle rather like and elephant’s trunk.
How do deep sea fish live?
Deep sea fish live completely in the dark, where green plants cannot grow. They have to withstand a strong water pressure and intense cold. For this reason, many have luminous parts to their bodies. Others have eyes trained to pick up the tiniest glow or speck of light. Others are blind, relying on their powers of touch and many have very thick skins. All feed on remains floating down from the surface and on other marine life.