Life Under Water


Life Under Water

The earth’s surface consists of about 75% of water and the oceans are known to hold about 96.5% of all earth’s water. Aquatic ecosystems are of two types:

  • fresh water
  • salt water

Part of the deep sea includes the mid-water and the ocean floor. The rivers and coastal vegetation supply nutrients to the sea or ocean. The sea holds a lot of mysteries, some still yet undiscovered.

The many mysteries of the sea may not include those sea monsters envisioned in children’s fairytale stories, but it holds a lot of unanswered questions for the world seeing that Spongebob doesn’t actually exist, and the only sponges in the Sea don’t live in pineapples and can’t sing that theme song.

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The sea is a very large aquatic body housing millions of life ranging from the smallest (phytoplanktons), algae, to major sea animals. Researchers have been able to explore no more than 1 per cent of the life forms in the sea, due to its depth.

Marine animals as studied by scientist are said to possess greater body diversities than that of land animals. Their body structures require a broad description that is, into the various phyla-groups.

The total of different species in the sea is still unknown, only 250 000 species of aquatic life forms have been identified, out of the 400 000 estimated range. This estimated value may soon change once scientists get a better view of life on the ocean floor.

From the observation of mariners, marine organisms can seem odd. Some of these creatures glow in the dark, some are cartilaginous or bony. Some plants inhabiting saltwater have been observed to grow faster and die young. These distinctions occur as a result of the physical and chemical characteristics of the water body.

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Some sea animals live in a particular place they mark out as their territory and protect it from intruders, while others migrate seasonally from mid-ocean to the high seas. Below are some of the various life forms in the sea and their characteristics:

  • Planktons: These are one of the most abundant of organisms in the sea, ranging from the largest to the smallest that are hardly seen, and are mostly situated on the ocean floor. Plankton is a general name used to describe other sea organisms like; algae, bacteria, protozoans, crustaceans, molluscs and coelenterates.

It is different from nekton, which is composed of strong swimming animals and also from the benthos, which includes creeping and burrowing organisms, sessile and others situated on the seafloor too. Some large floating seaweed (e.g. Sargasso…) are not considered as planktons but pleuston.

Pleustons are life forms that live in the interface of air and water. Phytoplankton’s are seasonal and vary in the region. The larger species are mostly found in the coastal region and certain equatorial areas where there is an abundance of nutrient enabling them to grow well. The smaller species called ‘’prochlorophytes’’ is found in the tropical and mid-ocean waters.

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Aside from the phytoplankton, large algae (keep, seed surf grasses) are also an inhabitant of the sea but dwell in the shallow-zone contributing little or nothing to the productivity of the ocean due to their location.

  • Freshwater fish: They seek out a particular territory and mark it as their own only allowing legible females in to mate with them, but after the mating ceremony the female fish swims off with her eggs, depositing the eggs on a different location and leaving it to develop and grow on its own.
  • The adult eel: They are found in the freshwater streams and rivers in Europe and Northern America when they reach maturity and are ready for spawning, the females all in groups move downstream to join the males that live in the brackish water. Altogether they travel across the Atlantic to their spawning ground which is the Sargasso Sea, this journey may take up to a month or two. They deposit their eggs at a depth of about 110 km. But unlike some other aquatic beings, eels die leaving the young to fend for itself. Most sea animals do not exhibit parental care as terrestrial animals do, and the eel is that example.
  • Starfish: as the name implies is a star-shaped Echinodermata (phylum) belonging to the class Asteroidea. They are also known as asteroids- being in the class of Asteroidea. About 1500 species of the starfish are found in Sea beds in all oceans. They have a central disc and usually five arms, though the number of arms vary in different species. They are marine invertebrates, they have no brain or blood, they have a tough, leathery skin, and they have eyes and can eat outside their bodies. However, not all starfish are star-shaped.
  • Whales: one of largest inhabitants of the sea. They are mammals, and they share the defining traits of that group; warm-blooded, give birth to their young ones alive unlike other fishes that lay eggs, they breathe air, suckle their young ones on milk and they have hair. They are entirely aquatic mammals with specialized adaptative features as flippers and tail flukes for living in water. But even with their fascinating nature, they are almost extinct due to man’s continual actions to hunt them down gor of their productive worth (e.g. whale oil…)
  • Dolphins: Dolphins are also another example of fascinating aquatic creatures. They have smooth, rubbery skin and are usually coloured in some mixture of black, white and grey. They have two flippers or fins on their sides and a triangular fin on the back. Like whales, they have an insulating layer of blubber (fat) underneath their skin. They have a very playful nature and are mostly seen on the surface.

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So many more life forms exist in the seas with equally fascinating characteristics aside from the ones listed above. Life under the sea has a special hue to it, water absorbs light ray different from air. In the sea, the shorter wavelength of light ray (blue and green in colour) penetrate deeper than longer wavelengths (red and yellow in colour).

This makes it possible to see the water light blue hue 10 meters into the ocean, but ongoing deeper it appears darker than night. Planktons deep in the sea that do not receive sunlight and therefore do not experience photosynthesis depend highly on the photosynthetic activities that occur on the water surface.

The ocean does not contain so much plant life due to the lack of nutrients in the ocean to that compared on land. Aquatic life in the sea all exist in the food chain, ranging from the planktons to the larger animals at the top of the food chain.

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Life in the sea is uncountable; the algae, planktons, small fishes, large sea monster( whales, sharks, dolphins..), those that dwell on the seashore (e.g. snail, slams, sand polar, etc.), the hidden ones living in the deepest and darkest part of the seas, all of which are of different species with fascinating characteristics.

The many mysteries and wonders of life that exist deep in the ocean are still left uncovered till date. But with the help of science, researchers and I to tell their story, all these mysteries will be uncovered.

Igbaji Ugabi Chinwendu, from Cross River State, Nigeria. As a Business Educator, he is profoundly interested in teaching and managing business. Started blogging 2010 and officially 2013. He holds the esteemed positions of Chief Executive Officer (CEO) and Director at Freemanbiz Communication and Writers King LTD, demonstrating his leadership and expertise in the field.


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