Benthos

The benthos is composed of all organisms living at the bottom of a body of flowing or standing water. The layer occupied by the benthos is called the benthic zonewhich is the lowest layer of a lake, sea, stream or river. This zone, of course, ranges from the shallow depths where water meets land, to the extreme depths that humans have not yet been able to explore. Benthos, therefore, vary greatly and can be observed crawling, burrowing, swimming close to the bottom or remaining attached to the substrate. Many tend to rely on food sources that sink to the bottom, such as inorganic matter and dead organisms, but benthos also feed on each other. The area above the benthic zone where the organisms that swim or float: the pelagics – are found is called the pelagic zone.

Note that the phytobenthos, zoobenthos y benthic microflora in the benthic zone are the equivalents of primary producers, consumers y decomposersrespectively.

Types of benthos

Benthos use all areas at the bottom of a water body and can be classified into three groups according to their habitat.

Hyperbenthos

These are organisms that have the ability to swim and live close to the bottom, but are not attached to it. Rock cod are hyperbenthic fish.

Epibenthos

Epibenthos spend their lives attached to the ground, on rocks or shells and include sponges.

Endobenthos

Instead of living on the seabed, these organisms have adapted to live within sediments, often creating underground tunnels. An example of endobenthos is the sand dollar.

Roles played by benthos

The benthos has the purpose of maintaining balance in the environment. Filter feeders, for example, such as mussels living in the benthic zone, play an essential role in maintaining the health of water bodies by cleaning them of pollutants and debris as part of their feeding process. Many benthos in shallow waters also rely on dead organic matter as a source of nutrition, decomposing and recycling it. This makes them very important for nutrient cycling and the return of nutrients to the environment in usable forms. Certain benthos are also useful to scientists because they can indicate the health and quality of the water. For example, a decrease in the number of caddis flies, which are very sensitive to pollutants, may indicate an increase in pollution and waste in the water.

Examples of benthos

Deep-sea anglerfish

As their name suggests, these anglerfish live in the depths of the sea where it is cold and dark. Some of them emit light from the spine attached to their heads to attract prey on dark bottoms. As we can see in the picture below, the tip, where the bioluminescenceis perfectly positioned to allow fish to capture their prey. Once a organism gets close enough to the light source, the anglerfish closes its large mouth, creating a cage with its teeth. In addition, because these organisms live in hostile environments, when a male monkfish matures, it spends the rest of its life as a parasite attached to a female anglerfish, ensuring that the reproduction of the female anglerfish species is still occurring. It is these adaptations that allow monkfish to survive in very shallow water.

Witchfish

These are deep-sea organisms that look like eels and rely on the carcasses of organisms that sink to the bottom for food. When a large animal, such as a whale, dies and its body sinks to the bottom, hagfish enter the body and consume the flesh. This is how these organisms recycle organic matter that reaches the seafloor. The hagfish has also adapted to breathe through its skin when it is buried in the mud, and although it has eyes very simple and almost blind, hagfish have an exceptionally strong sense of smell and touch, which allows them to find food in the dark. Finally, to protect themselves, hagfish can produce a slimy substance that helps them fight off predators.

Seagrasses

These are flowering plants that perform the photosynthesisThey are therefore only found in the photic zone, where sunlight can reach the bottom. Seagrasses benefit the environment by stabilising the seabed with their roots. They also provide shelter and food for some organisms, they can slow down waves and reduce the erosion and, like terrestrial plants, help to reduce the amount of carbon dioxide in the soil and, like terrestrial plants, help to reduce the amount of carbon dioxide in the soil. carbon dioxide present in the environment.

• Nekton aquatic organisms that swim freely in water, such as whales, jellyfish and turtles.
• Neuston small surface-dwelling organisms in aquatic habitats, such as fish spiders and floating plants.
• Plankton small aquatic organisms that float or drift with the current of the water, such as algae and some worms.
• Zone deep: the deep water layer of a standing body of water, such as a lake or pond, where the temperature is significantly cooler than the surface layer.