Life in the Open Ocean Biome

Of the eight biomes in the world the open ocean is by far the largest. This environment is well suited to marine life of both animals and plants as it contains the elements that are essential for the growth of both plant and animal tissue. In the upper layers of the ocean, sunlight filters through the water and there is not as much variation of temperature in the water of the ocean as there is on the land. The buoyancy characteristics of water make it possible for huge marine mammals, such as whales, move about with ease. On land an animal of equal size would find it very difficult to manoeuvre.

These factors combine to make it possible for the ocean biome to support a wide diversity of life. All of the major groups of animals are represented. Plant life exists where there is sunlight and most of this is in primitive form.

There are three main groups of life in the ocean biome – nekton, benthos and plankton. The nekton are strong swimming animals, such as the fish of the ocean. The benthos are the animals and plants that live on or are attached to the bottom and the plankton are the microscopic animals and animals that drift through the water.


The nekton group of marine life in the ocean biome consist of vertebrates – animals with backbones – the largest of which are fish of various kinds. Some have very unique features, such as enormous mouths or luminescent characteristics that allow them to shine in the darkest depths of the ocean. They are able to live in deep regions where the water pressure is extremely high because the pressure inside their body is the same as it is outside the body.

Some nektons are mammals, such as whales, seals, dolphins, walruses and porpoises. They are warm-blooded and breathe air, which is why they must come to the surface on a regular basis. There are also reptiles, such as turtles and snakes that make their home in the open ocean.


Examples of benthos include sponges, barnacles and corals that attach themselves to solid objects in the open ocean. There are also shell fish in this category, such as crab, lobster, and crayfish that move along the ocean floor. Some fish are included in this category because of their bottom feeding habits, such as sole and flounder. Seaweed and sea grass are also considered examples of benthos life in the ocean biome.

There are two main categories of benthos, depending on the part of the ocean floor on which they are found. These are the shallow category and the deep category. The dividing line is at a depth of about 185 meters. It usually represents the edge of the Continental shelf where sunlight cannot penetrate to the deeper levels. The highest amount of life is found in the shallow zone.


Plankton are the smallest plants and animals in the world. They are one-celled organisms that live in the sunlit areas of the open ocean. Some of them are very weak swimmers and others look like miniature shrimp. There are still others that have perfect symmetry and look like elaborate crystals.

Marine biologists are always studying life in the open ocean biome. Every day brings new discoveries and there is still much that remains to be learned about this biome.