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What are Benthos?

Michael Anissimov
Updated May 21, 2024
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The benthos are animals that live on or underneath the sea bed, in what is called the benthic zone. They can be contrasted with plankton, which are free-floating. Some common benthos animals are various sea worms (especially polychaete annelids), seagrass (a type of flowering plant), clams, oysters, sea cucumbers (a type of echinoderm), brittle stars, sea anemones, sea stars, sea squirts (tunicates), nudibranchs (mollusks), and various shrimp and shrimp-like crustaceans, to name a few.

Along with the macroscopic benthos listed above are extremely abundant microscopic benthos, including water bears (tardigrades), nematodes (the most abundant multicellular animal on Earth), gastrotrichs, small crustaceans like copepods, foraminifera (common protists), diatoms, and assorted amoeboids, ciliates, and flagellates. Because light tends to be poorer on the sea bed than at the surface, and almost absent at depths below 200 m (656 ft), the foundation of the benthos food chain focuses more on dead animals and plants that fall from above than active photosynthesis.

Benthic organisms cover the entire surface of the oceans, though they are much rarer in locations off continental shelves. Some benthos are adapted to living close to the shore, even in the intertidal region, where they can sustain being out of water for hours on end thanks to special adaptations. Others, such as sea cucumbers, are adapted to living in the darkest depths of the oceans. The deep sea benthos is among the most unusual, and includes unicellular organisms over an inch across that are capable of leaving tracks, giant sea anemones up to 2 m (6 ft) across, and giant isopods (related to pill bugs) the size of house cats. Some of these benthic organisms are very poorly understood, and research into them is ongoing.

All the organisms in the world are completely dependent on benthic organisms to survive. These organisms stir up and consume the carcasses of animals that sink to the bottom, excreting them as feces, which dissolves into nutrients that gets carried back to the surface again in upwelling. In this fashion, carbon does not build up at the bottom of the ocean without getting carried back again. Otherwise, over millions of years all the world's carbon would be sequestered in the deep sea, leaving none for any form of life.

Frequently Asked Questions

What exactly are benthos?

Benthos are organisms that live on, in, or near the seabed, also known as the benthic zone. This diverse group includes both plants and animals, ranging from microscopic bacteria to large species like crabs and starfish. They play a crucial role in aquatic ecosystems, contributing to the breakdown of organic matter and serving as a food source for other marine life.

How do benthic organisms adapt to their environment?

Benthic organisms have evolved various adaptations to survive in their unique habitats. Many have developed strong anchoring mechanisms to withstand currents, while others possess specialized feeding apparatuses to sift or dig for food in the sediment. Some benthos, like tube worms, can even tolerate extreme conditions such as those found near hydrothermal vents.

What is the importance of benthos in the marine ecosystem?

Benthos are integral to marine ecosystems, playing key roles in nutrient cycling and sediment turnover. They act as primary producers, decomposers, and prey for higher trophic levels. According to a study published in the journal 'Marine Ecology Progress Series,' benthic communities can influence water clarity and nutrient availability, impacting the overall health of marine environments.

Can benthos be found in all aquatic environments?

Yes, benthos can be found in nearly all aquatic environments, from the deepest parts of the ocean to the smallest freshwater streams. Their presence and diversity vary depending on factors such as water depth, temperature, salinity, and substrate type. Each environment hosts a unique assemblage of benthic species adapted to local conditions.

What are some examples of benthic animals?

Examples of benthic animals include sessile organisms like corals and sponges, burrowing creatures such as clams and worms, and mobile species like lobsters and sea cucumbers. These animals are often categorized by their size, with macrobenthos being visible to the naked eye and meiobenthos being smaller, requiring magnification to be seen clearly.

How do human activities impact benthic communities?

Human activities such as pollution, dredging, and bottom trawling fishing practices can severely impact benthic communities. These actions can lead to habitat destruction, reduced biodiversity, and altered ecosystem functions. Studies have shown that areas protected from such disturbances often have more resilient and diverse benthic populations, highlighting the need for conservation efforts.

AllThingsNature is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Michael Anissimov
By Michael Anissimov

Michael is a longtime AllThingsNature contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

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Michael Anissimov

Michael Anissimov

Michael is a longtime AllThingsNature contributor who specializes in topics relating to paleontology, physics,...

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