Macrobenthos consists of the organisms that live at the bottom of a water columnJ.S. Link, C.A. Griswold, E.T. Methratta, J. Gunnard, Editors. 2006
Documentation for the Energy Modeling and Analysis eXercise (EMAX)
.

United States Department of Commerce The United States Department of Commerce is an executive department of the U.S. federal government concerned with creating the conditions for economic growth and opportunity. Among its tasks are gathering economic and demographic data for bus ...

, Northeast Fisheries Science Center. Reference Document 06-15 Chapter 8. and are visible to the naked eye. In some classification schemes, these organisms are larger than 1 mm; in another, the smallest dimension must be at least 0.5 mm. They include polychaete worms,

pelecypod Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biva ...

s, anthozoans,

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the s ...

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throug ...

ascidian Ascidiacea, commonly known as the ascidians, tunicates (in part), and sea squirts (in part), is a polyphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" m ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...

s. The marine macrobenthos community is a critical component and reliable indicator of the biotic integrity of marine ecosystems, especially the

intertidal The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species ...

ecosystems. On the one hand, macrobenthos plays a vital role in maintaining ecosystem functions, such as

material cycling Material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical and chemical properties, or on their geologi ...

sediments Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity In physics, gravity () is a fundame ...

and energy flow in food webs. On the other hand, macrobenthos is relatively sedentary and therefore reflects the ambient conditions of sediments, in which many pollutants (e.g., heavy metals and

organic enrichment Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product o ...

) are ultimately partitioned. CC-BY icon

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Heavy metal pollution is one of the most common anthropogenic pressures that impact marine ecosystems (e.g., intertidal zones, coastal waters, and estuaries), which has been documented by many studies throughout the world. Heavy metal contaminants can result in adverse toxic effects on benthic organisms, leading to the changes in composition, structure, and ecosystem function of macrobenthic communities. For example, in

Aveiro Lagoon The Aveiro lagoon (''Ria de Aveiro'') is a lagoon in Portugal. It is located on the Atlantic coast of Portugal, south of the municipality of Espinho and north of Mira (to the north of the Cape Mondego). Its average area covers approximately . It ...

(Portugal), with the increase of

mercury contamination Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver and was formerly named hydrargyrum ( ) from the Greek words, ''hydor'' (water) and ''argyros'' (silver). A heavy, silvery d-block element, m ...

, the total

abundance Abundance may refer to: In science and technology * Abundance (economics), the opposite of scarcities * Abundance (ecology), the relative representation of a species in a community * Abundance (programming language), a Forth-like computer prog ...

and

species richness Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative ab ...

decreased, and tolerant taxa increased; in Incheon Harbour (Korea) and the coastal zone south of

Sfax Sfax (; ar, صفاقس, Ṣafāqis ) is a city in Tunisia, located southeast of Tunis. The city, founded in AD849 on the ruins of Berber Taparura, is the capital of the Sfax Governorate (about 955,421 inhabitants in 2014), and a Mediterrane ...

(Tunisia), macrobenthic community gradually changed with the pollution levels, and

species diversity Species diversity is the number of different species that are represented in a given community (a dataset). The effective number of species refers to the number of equally abundant species needed to obtain the same mean proportional species abundan ...

decreased with decreased distance from the pollution source. However, most of the studies were conducted in the subtidal zones other than intertidal zones, which are more vulnerable to human activities. Macrobenthos consists of numerous taxa, and different species have a different tolerance to environmental pressures. For example,

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made ...

s ''

Capitella capitata Capitella capitata is a polychaete worm that grows up to 10 cm in length. It is often blood-red in colour. The species is sedentary and fragile, with a flexible body. ''Capitella capitata'' occurs on muddy sand, gritty sand, fine sand or r ...

'' and '' Heteromastus filiformis'' are naturally tolerant to environmental disturbance, which could live well in a highly organic enrichment and/or heavy metal polluted area, while some taxa (e.g., polychaete '' Magelona dakini'' and amphipods ''Perioculodes longimanus'') are inherently sensitive to environmental disturbance, and could not survive in such highly polluted zones. File:Capitella capitata (Fabricius 1780) (30726945752).jpg, The polychaete ''

'' File:Heteromastus filiformis (I781) (14471214033).jpg, The polychaete '' Heteromastus filiformis'' File:Perioculodes longimanus.jpg, The amphipod ''Perioculodes longimanus'' This indicates that each species has evolved a unique survival strategy to adapt to different environmental conditions, even though it may be similar in some ways with other species. When facing loads of contaminants, such as metal(loid)s and organic enrichment or other contaminants gradients, macrobenthos have to make some reactions to resist such adverse environmental conditions. Therefore, macrobenthic responses may reflect different types and levels of pollutant impacts. A visual examination of macroorganisms at the bottom of an aquatic ecosystem can be a good indicator of water quality.Mulligan CN, Fukue M and Sato Y (2010
''Sediments Contamination and Sustainable Remediation''
page 30, CRC Press. . File:Posidonia oceanica Portofino 02.jpg,

Seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the or ...

. File:Nerr0878.jpg,

Echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the s ...

s File:Scheibenanemonen (Actinodiscus spec).jpg, Stony

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and ...

s File:Seasquirt.jpg, A

sea squirt Ascidiacea, commonly known as the ascidians, tunicates (in part), and sea squirts (in part), is a polyphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" m ...

being used as a substrate for a

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, ...

's egg spiral.

References

{{aquatic organisms Hydrology