Benthic zone

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amphipods, a polychaete worm, a snail, and a chironomous
midge larva
Coastal habitats
Ocean surface
Open ocean
Sea floor

The benthic zone is the ecological region at the lowest level of a

invertebrates, such as crustaceans and polychaetes.[4] Organisms here generally live in close relationship with the substrate and many are permanently attached to the bottom. The benthic boundary layer, which includes the bottom layer of water and the uppermost layer of sediment directly influenced by the overlying water, is an integral part of the benthic zone, as it greatly influences the biological activity that takes place there. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, and bay mud
.

Description

Part of a series related to
Benthic life
Benthopelagic (coupling)        Seabed
By size
By type
By location
    • endobenthos
    • epibenthos
    • hyperbenthos
By habitat
    Shallow:
bivalve reef
                   mangrove forest • coral reef
                   seagrass meadow
        Deep: seamount • cold seep
                   hydrothermal vent
Communities
Related

Oceans

The benthic region of the ocean begins at the shore line (intertidal or littoral zone) and extends downward along the surface of the continental shelf out to sea. Thus, the region incorporates a great variety of physical conditions differing in: depth, light penetration and pressure.[5] Depending on the water-body, the benthic zone may include areas that are only a few inches below the surface.

The continental shelf is a gently sloping benthic region that extends away from the land mass. At the continental shelf edge, usually about 200 metres (660 ft) deep, the gradient greatly increases and is known as the continental slope. The continental slope drops down to the deep sea floor. The deep-sea floor is called the

ocean trenches known as the hadal zone.[6] For comparison, the pelagic zone is the descriptive term for the ecological region above the benthos, including the water column up to the surface. At the other end of the spectrum, benthos of the deep ocean includes the bottom levels of the oceanic abyssal zone.[7]

For information on animals that live in the deeper areas of the oceans see aphotic zone. Generally, these include life forms that tolerate cool temperatures and low oxygen levels, but this depends on the depth of the water.[8]

Lakes

As with oceans, the benthic zone is the floor of the lake, composed of accumulated sunken organic matter. The littoral zone is the zone bordering the shore; light penetrates easily and aquatic plants thrive. The pelagic zone represents the broad mass of water, down as far as the depth to which no light penetrates.[9]

Organisms

Main article: Benthos

Benthos are the organisms that live in the benthic zone, and are different from those elsewhere in the

Carcharhinidae such as the lemon shark.[11]

Because light does not penetrate very deep into ocean-water, the energy source for the benthic ecosystem is often marine snow. Marine snow is organic matter from higher up in the water column that drifts down to the depths.[12] This dead and decaying matter sustains the benthic food chain; most organisms in the benthic zone are scavengers or detritivores. Some microorganisms use chemosynthesis to produce biomass.

Benthic organisms can be divided into two categories based on whether they make their home on the ocean floor or a few centimeters into the ocean floor. Those living on the surface of the ocean floor are known as

infauna.[10] Extremophiles, including piezophiles, which thrive in high pressures, may also live there. An example of benthos organism is Chorismus antarcticus
.

Nutrient flux

Sources of food for benthic communities can derive from the water column above these habitats in the form of aggregations of

dinoflagellates and foraminifera, colonize quite rapidly on detritus matter while forming a symbiotic relationship with each other.[17][18] In the deep sea, which covers 90-95% of the ocean floor, 90% of the total biomass is made up of prokaryotes. To release all the nutrients locked inside these microbes to the environment, viruses are important in making it available to other organisms.[19][20]

Habitats

Modern

hadal (below 6,000 meters).[23]

The lower zones are in deep, pressurized areas of the ocean. Human impacts have occurred at all ocean depths, but are most significant on shallow continental shelf and slope habitats.[24] Many benthic organisms have retained their historic evolutionary characteristics. Some organisms are significantly larger than their relatives living in shallower zones, largely because of higher oxygen concentration in deep water.[25]

It is not easy to map or observe these organisms and their habitats, and most modern observations are made using remotely operated underwater vehicles (ROVs), and rarely submarines.[26][27]

Ecological research

Benthic

trophic pathways.[28] The presence of macroinvertebrates such as Amphipoda also affect the dominance of certain types of algae in Benthic ecosystems as well.[29] In addition, because benthic zones are influenced by the flow of dead organic material, there have been studies conducted on the relationship between stream and river water flows and the resulting effects on the benthic zone. Low flow events show a restriction in nutrient transport from benthic substrates to food webs, and caused a decrease in benthic macroinvertebrate biomass, which lead to the disappearance of food sources into the substrate.[30]

Because the benthic system regulates energy in aquatic ecosystems, studies have been made of the mechanisms of the benthic zone in order to better understand the ecosystem. Benthic diatoms have been used by the European Union's Water Framework Directive (WFD) to establish ecological quality ratios that determined the ecological status of lakes in the UK.[31] Beginning research is being made on benthic assemblages to see if they can be used as indicators of healthy aquatic ecosystems. Benthic assemblages in urbanized coastal regions are not functionally equivalent to benthic assemblages in untouched regions.[32]

Ecologists are attempting to understand the relationship between

gross primary production (GPP) may be important in maintaining biodiversity hotspots in littoral zones in large lake ecosystems. However, the relative contributions of benthic habitats within specific ecosystems are poorly explored and more research is planned.[35]

See also

References

  1. ^ "Benthos". 22 April 2022.
  2. ^ Wetzel, Robert G. (2001). Limnology: Lake and River Ecosystems, 3rd edn. Academic Press, San Diego. pp. 635–637.
  3. ^ Fenchel, T.; King, G.; Blackburn, T. H. (2012). Bacterial Biogeochemistry: The Ecophysiology of Mineral Cycling, 3rd edn. Academic Press, London. pp. 121–122.
  4. ^ "What Are Benthos?". Baybenthos.versar.com. 2006-01-23. Retrieved 2013-11-24.
  5. ISBN 9780128211618
    .
  6. ISBN 9781438118819
    .
  7. ^ Nichols, Williams (2009): "abyssal zone"
  8. ^ Nichols, Williams (2009): "aphotic zone"
  9. ISBN 9781597260435
    .
  10. ^ a b Walag (2022) p.2
  11. ISBN 0-8117-2875-7
    .
  12. ISBN 978-3-319-60154-0
    .
  13. ^ "Epifaunal - Definition and More from the Free Merriam-Webster Dictionary". Merriam-webster.com. 2012-08-31. Retrieved 2013-11-24.
  14. ^ Godson (2022) p.90
  15. doi:10.1016/0079-6611(88)90053-5
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  16. doi:10.1016/0198-0149(80)90092-8
    .
  17. ^ "Foraminifera". Retrieved 7 December 2014.
  18. ^ "foraminifera". Retrieved 7 December 2014.
  19. ^ Organisms Amplify Diversity: An Autocatalytic Hypothesis
  20. ^ Macroecological drivers of archaea and bacteria in benthic deep-sea ecosystems - NCBI
  21. ^ Harris, P. T.; Baker, E. K. 2012. "GEOHAB Atlas of seafloor geomorphic features and benthic habitats – synthesis and lessons learned", in: Harris, P. T.; Baker, E. K. (eds.), Seafloor Geomorphology as Benthic Habitat: GeoHab Atlas of seafloor geomorphic features and benthic habitats. Elsevier, Amsterdam, pp. 871-890.
  22. ^ Harris, P. T.; Baker, E. K.; 2012. Seafloor Geomorphology as Benthic Habitat: GeoHab Atlas of seafloor geomorphic features and benthic habitats. Elsevier, Amsterdam, p. 947.
  23. ^ "Coastal and Marine Ecological Classification Standard (CMECS)". 2012. {{cite journal}}: Cite journal requires |journal= (help)
  24. ^ Harris, P. T., 2012. "Anthropogenic threats to benthic habitats", in: Harris, P. T.; Baker, E. K. (eds.), Seafloor Geomorphology as Benthic Habitat: GeoHab Atlas of seafloor geomorphic features and benthic habitats. Elsevier, Amsterdam, pp. 39-60.
  25. ^ Royal Belgian Institute of Natural Sciences, news item March 2005 Archived September 28, 2011, at the Wayback Machine
  26. ISBN 9781118332559
    .
  27. ^ Tillin, H. M.; et al. "Marine Monitoring Platform Guidelines: Remotely Operated Vehicles for use in marine benthic monitoring" (PDF). Peterborough, UK: Joint Nature Conservation Committee. p. 1. Retrieved 15 June 2022.
  28. S2CID 84495019
    .
  29. S2CID 54598097
    .
  30. S2CID 55593045
    .
  31. S2CID 33631675
    .
  32. hdl:1912/6981
    .
  33. S2CID 85061936
    .
  34. OCLC 671782244
    .
  35. S2CID 84535584
    .

External links

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