The SEA is a real reserve of life. Not only its surface takes up more than 70% of the earth's surface, but its enormous depth averaging over 20 miles makes it a three-dimensional world of enormous capacity that has many levels throughout its area.
Life is found in all parts of the sea, in all depths. There is an intense active life on its banks. On a lower level of the continental shelf life is also very active. Further from the coast there is more life at higher levels near the surface. But life also exists in the depths of the deepest channels and plays its role in the ecological system of the sea.
The food chain
Of course, the countless billions of marine animals need a lot of food. Although there is a large amount of algae like in Lake Sargasso, it is not the main food source. In fact, algae play a very minor role.Over 90% of the basic organic materials that make up and burn off all marine life are synthesized in illuminated layers of water that are free from the many species of "phytoplankton".
Phytoplankton are microscopic plants that float close to the surface and can use sunlight. They need light to do their jobs and to live, just like most land plants need sunlight. Phytoplankton produce food through photosynthesis, a process that uses solar energy to convert minerals in the ocean into food. This is important as they cannot synthesize their own food.
Just as land vegetation is the staple food of all land animals, so plant life is the fodder of seafarers.
Large layers of phytoplankton slide through the ocean, usually the densest, where "waves" pick up minerals from the ocean floor or where currents carry those nutrients. The main consumers of phytoplankton are the small animals called "zooplankton". These sink to depths of 1,000 to 4,000 feet below the surface during the day and rise every night to participate in a feeding frenzy. Other small fish that feed on phytoplankton and some that eat zooplankton follow this migration value and together form what is known as the "deep expansion layer". It is so thick that the first time sonar depths were used, this layer was often mistaken for the seabed, which resulted in inaccuracies in seabed maps.
Eating zooplankton is "nekton".These predators include thousands of species of fish. At the "pyramid" meal, approximately 1,000 pounds of seaweed (at the base of the pyramid) supports 100 pounds of herbivores (the next step in the pyramid). This in turn will produce ten kilograms of carnivorous marine life. Ultimately, ten pounds of fish will make one pound of human flesh. Therefore, to supply the market with ten pounds of fish, the ocean must provide 1,000 pounds of microscopic plankton "food".
The "red tide"
Sometimes a certain type of microscopic marine life called "dinoflagellates" experiences a "population boom" centered on astronomical numbers. They reproduce at such a high density that large bodies of water turn red, brown, or amber due to their pigments, a phenomenon known as the "red tide". The concentration may be too high to survive and they produce a very toxic substance in the water that kills fish and seabirds in the area. The toxins released from the water into the atmosphere by breaking waves irritate human respiratory tracts and sometimes cause beach resorts to be temporarily closed. A high yield of hydrogen sulfide can darken black houses painted with white lead in a nearby coastal town.
Marine methods of protecting and survival
One wonders how a certain form of marine life, given all its predators, can prevent extinction. But different types of marine life as a species have many different opportunities to survive. One way is hyperproductive reproduction. Small diatoms, the most numerous microscopic plants, can produce one billion offspring in a month. Haddock lays up to nine million eggs at a time. Oysters lay up to 500 million eggs a year. One billion mackerel on the south coast of Cape Cod produce about 64 billion eggs during the mating season. Eggs, small fish and other forms of marine life are quickly eaten by a large number of predators of all kinds. In mackerel, it is estimated that only one to ten fish per million eggs survive to maturity. Mortality is between 99.98% and 99.99%. Still, there are many mackerel, haddock and oysters. The same goes for many other animals, such as mussels, shrimp, etc. It is only the predator that tends to throw things off balance and destroy entire species.
Other fish protect their eggs or chickens, rather than relying solely on numbers. In some sharks the eggs hatch and the newly hatched fish live long on the mother's back. Some fish catch their eggs on rocks, plants, etc. Some protect them with foam and membranes. In other species, the male carries the eggs in his mouth or in a bag (such as the hippocampus) until they hatch. However, the young are usually left alone after hatching. But the dolphin, a mammal, continues to protect its young from predators.
Since almost all marine animals have predators looking for them, camouflage is often used. The butterflyfish, for example, have an eye patch on their body to distract the attacker from the head. The back of the fish in the open sea is green or black, because that is what the sea looks like from above. But seen from below, the sea surface seems silver or whitish. As a result, the bottom of most fish has this color.
Sea cucumber can have the strangest method of protection. When he is in danger, he simply expels the intestines. Obviously, the hungry predator prefers to cook a meal with the intestines rather than the tasteless leather bag that remains. Then a new gut grows from the "empty bag." Spicy cells help more static or stable animals, such as warriors, to fight their enemies. Others rely on speed, alertness, size or strength. Some of the deep-sea fish have a unique protection device. They emit a bright cloud to hide their flight. Other fish emit strong flashes of light to scare off predators or to temporarily "blind" them.
In the three-dimensional world of the sea, where visibility is limited to a distance of 30 meters and the environment is much heavier than air, the creator provided equipment that land animals do not have. One is the "sixth sense" that most fast-swimming fish have. It is a longitudinal system of channels that runs from the head to the tail and is called the "lateral line". This means that the fish also feel small changes in external pressure. In this way, thousands of fish can stay together in a "school" and move together and quickly change direction as a single body. You are also warned from a distance not to approach enemies. It also helps you avoid obstacles like the glass wall of an aquarium.
Life at the bottom of the ocean
At the bottom of the sea, 20 km or more below sea level, the pressure is enormous in almost freezing weather and darkness penetrates. However, life is still there. But it seems quieter and the population is much smaller. Sea cucumbers walk slowly on the muddy bottom for up to a year and a half and “eat” clay, that is, they absorb diffuse clay in order to get rid of the small organisms present or search for “debris”. organic waste falling from above. Few creatures are as big as a mouse. Most are smaller than bees. Networks larger than a hundredth of an inch produce small clams, worms, and crustaceans.
Some fish and other animals in the abyss are blind. Walking majestically, they are creatures with spider legs, like rods, with hairy feet to hold them above the mud. The "fragile stars" associated with the starfish sometimes spread over the ocean floor. Even at depths of 3,600 feet or more, a single-jet fish swims in search of food on the bottom. The seabed is covered with paths and trails. Photos taken at Challenger Deep, southwest of Guam, 35,800 feet deep, show strange animals an inch or two in length.