Benthic zone
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers.
[1] Organisms living in this zone are called benthos and include microorganisms (e.g., bacteria and fungi)[2][3] as well as larger invertebrates, such as crustaceans and polychaetes.
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.
Generally, these include life forms that tolerate cool temperatures and low oxygen levels, but this depends on the depth of the water.
Sources of food for benthic communities can derive from the water column above these habitats in the form of aggregations of detritus, inorganic matter, and living organisms.
The microbes found in the benthic zone, specifically dinoflagellates and foraminifera, colonize quite rapidly on detritus matter while forming a symbiotic relationship with each other.
Some organisms are significantly larger than their relatives living in shallower zones, largely because of higher oxygen concentration in deep water.
[26][27] Benthic macroinvertebrates have many important ecological functions, such as regulating the flow of materials and energy in river ecosystems through their food web linkages.
Because of this correlation between flow of energy and nutrients, benthic macroinvertebrates have the ability to influence food resources on fish and other organisms in aquatic ecosystems.
For example, the addition of a moderate amount of nutrients to a river over the course of several years resulted in increases in invertebrate richness, abundance, and biomass.
These in turn resulted in increased food resources for native species of fish with insignificant alteration of the macroinvertebrate community structure and trophic pathways.
Benthic algae has been used as an inherently good subject for studying short term changes and community responses to heterogeneous conditions in streams.
[33] Periphyton populations suffer from high natural spatial variability while difficult accessibility simultaneously limits the practicable number of samples that can be taken.
[34]: 60 Benthic gross primary production (GPP) may be important in maintaining biodiversity hotspots in littoral zones in large lake ecosystems.
