MICROFAUNA
Michael J. Kennish
Department of Marine and Coastal Sciences,
School of Environmental and Biological Sciences,
Rutgers University, New Brunswick, NJ, USA
Definition
Microfauna are minute organisms typically found in high
abundances in estuarine and coastal marine bottom sediments (Fenchel, 1969, 1978; Alongi, 1990; Day et al.,
2012). They are not only important members of the benthos but also play a significant ecological role in pelagic
environments (Fenchel, 1988, 2001). The term is largely
reserved for protozoans (ciliates and foraminifera) which
pass through a sieve mesh size of 100 mm (Fenchel,
1978), although other organisms are included as well
(Kennish, 2001). The zooflagellates, the smallest protozoans weighing $10
À11 g, are important microfauna in
estuaries (Kennish, 1986).
Description
The ciliates, which range in weight from $10
À10 to
10
À6 g, are among the best studied protozoan groups
(Kennish, 1986). They generally reach greatest numbers
and biomasses in fine sediments and in bacterial mats of
estuaries, typically attached to grain surfaces or in interstitial spaces where they often form complex communities.
Many species of microfauna are known from studies of
benthic ecosystems, and many others are vital to pelagic
food chains and thus system function (Fenchel, 2001).
Bibliography
Alongi, D. M., 1990. Abundance of benthic microfauna in
relation to outwelling of mangrove detritus in a tropical coastal
region. Marine Ecology Progress Series, 63, 53–63.
Day, J. W., Crump, B. C., Kemp, W. M., and Yanez-Arancibia, A. (eds.),
2012. Estuarine Ecology, 2nd edn. New York: Wiley-Blackwell.
Fenchel, T., 1969. The ecology of marine microbenthos.
IV. Structure and function of the benthic ecosystem, its chemical
and physical factors and the microfauna communities with
special references to the ciliated protozoa. Ophelia, 6, 1–182.
Fenchel, T., 1978. The ecology of micro- and meiobenthos. Annual
Review of Ecological Systematics, 9, 99–121.
Fenchel, T., 1988. Microfauna in pelagic food chains. In Blackburn,
T. H., and Sorensen, J. (eds.), Nitrogen Cycling in Coastal Marine
Environments. New York: John Wiley and Sons, pp. 57–65.
Fenchel, T., 2001. The role of microorganisms. In Levin, S. (ed.),
Encyclopedia of Biodiversity. Waltham, Massachusetts:
Academic Press, pp. 207–219.
Kennish, M. J., 1986. Ecology of Estuaries: Biological Aspects.
Boca Raton, Florida: CRC Press.
Kennish, M. J. (ed.), 2001. Practical Handbook of Marine Science,
3rd edn. Boca Raton, Florida: CRC Press.
Cross-references
Benthic Ecology
Meiofauna
Macrofauna
MICRONUTRIENTS
Manuel Flores Montes
Department of Oceanography, Federal University of
Pernambuco, Recife, Pernambuco, Brazil
Synonyms
Microminerals; Minor elements; Nutrients; Trace
elements
Definition
Micronutrients are essential elements with biological
functions at small concentrations (<0.01 %). They include
minerals required in low quantities for the growth of
organisms. In analytical chemistry, a trace element is
a chemical element with a concentration of less than
100 parts per million (ppm).
Description
Importance: Minor and trace elements are required by
autotrophs, although their availability in estuaries is usually not limiting to growth. In estuaries, these elements
are typically available, free, or combined to meet the
demand of phytoplankton. This availability can yield high
levels of biomass (Day et al., 2012).
Sources: Most biologically important compounds
entering an estuary are from riverine sources, in particulate or dissolved forms. When river water mixes with seawater, these compounds are retained in an estuary
(Bianchi, 2007).
Species: Trace elements include iron, cobalt, chromium, copper [2], iodine, manganese, selenium, zinc,
and molybdenum. Micronutrients also include vitamins,
which are organic compounds that organisms require
in low concentrations (Falkowski and Raven, 2007).
The most commonly occurring forms of iron are the
insoluble form (Fe 3
+ ) and the soluble form (Fe 2
+ ). Speciation studies have shown that dissolved copper in
most natural waters is mainly organically complexed
(Stumm and Morgan, 1996). By dominating copper speciation, organic complexation may control copper’s
bioavailability.
Demand: Microelements and trace elements are essential for autotrophic organisms; they are required as nutrients in very small concentrations. They are essential to
the photosynthetic process, being key constituents of chlorophyllous pigments and enzymes. Many investigators
have shown that iron (Fe) is the most important bioactive
trace element. N 2 -fixing cyanobacteria require larger
amounts of iron than other micronutrients.
Bibliography
Bianchi, T. S., 2007. Biogeochemistry of Estuaries. Oxford: Oxford
University Press.
Day, J. W., Kemp, M. W., Yánez-Arancibia, A., and Crump, B. C.,
2012. Estuarine Ecology, 2nd edn. Hoboken: Wiley-Blackwell.
MICRONUTRIENTS
437
Michael J. Kennish
Department of Marine and Coastal Sciences,
School of Environmental and Biological Sciences,
Rutgers University, New Brunswick, NJ, USA
Definition
Microfauna are minute organisms typically found in high
abundances in estuarine and coastal marine bottom sediments (Fenchel, 1969, 1978; Alongi, 1990; Day et al.,
2012). They are not only important members of the benthos but also play a significant ecological role in pelagic
environments (Fenchel, 1988, 2001). The term is largely
reserved for protozoans (ciliates and foraminifera) which
pass through a sieve mesh size of 100 mm (Fenchel,
1978), although other organisms are included as well
(Kennish, 2001). The zooflagellates, the smallest protozoans weighing $10
À11 g, are important microfauna in
estuaries (Kennish, 1986).
Description
The ciliates, which range in weight from $10
À10 to
10
À6 g, are among the best studied protozoan groups
(Kennish, 1986). They generally reach greatest numbers
and biomasses in fine sediments and in bacterial mats of
estuaries, typically attached to grain surfaces or in interstitial spaces where they often form complex communities.
Many species of microfauna are known from studies of
benthic ecosystems, and many others are vital to pelagic
food chains and thus system function (Fenchel, 2001).
Bibliography
Alongi, D. M., 1990. Abundance of benthic microfauna in
relation to outwelling of mangrove detritus in a tropical coastal
region. Marine Ecology Progress Series, 63, 53–63.
Day, J. W., Crump, B. C., Kemp, W. M., and Yanez-Arancibia, A. (eds.),
2012. Estuarine Ecology, 2nd edn. New York: Wiley-Blackwell.
Fenchel, T., 1969. The ecology of marine microbenthos.
IV. Structure and function of the benthic ecosystem, its chemical
and physical factors and the microfauna communities with
special references to the ciliated protozoa. Ophelia, 6, 1–182.
Fenchel, T., 1978. The ecology of micro- and meiobenthos. Annual
Review of Ecological Systematics, 9, 99–121.
Fenchel, T., 1988. Microfauna in pelagic food chains. In Blackburn,
T. H., and Sorensen, J. (eds.), Nitrogen Cycling in Coastal Marine
Environments. New York: John Wiley and Sons, pp. 57–65.
Fenchel, T., 2001. The role of microorganisms. In Levin, S. (ed.),
Encyclopedia of Biodiversity. Waltham, Massachusetts:
Academic Press, pp. 207–219.
Kennish, M. J., 1986. Ecology of Estuaries: Biological Aspects.
Boca Raton, Florida: CRC Press.
Kennish, M. J. (ed.), 2001. Practical Handbook of Marine Science,
3rd edn. Boca Raton, Florida: CRC Press.
Cross-references
Benthic Ecology
Meiofauna
Macrofauna
MICRONUTRIENTS
Manuel Flores Montes
Department of Oceanography, Federal University of
Pernambuco, Recife, Pernambuco, Brazil
Synonyms
Microminerals; Minor elements; Nutrients; Trace
elements
Definition
Micronutrients are essential elements with biological
functions at small concentrations (<0.01 %). They include
minerals required in low quantities for the growth of
organisms. In analytical chemistry, a trace element is
a chemical element with a concentration of less than
100 parts per million (ppm).
Description
Importance: Minor and trace elements are required by
autotrophs, although their availability in estuaries is usually not limiting to growth. In estuaries, these elements
are typically available, free, or combined to meet the
demand of phytoplankton. This availability can yield high
levels of biomass (Day et al., 2012).
Sources: Most biologically important compounds
entering an estuary are from riverine sources, in particulate or dissolved forms. When river water mixes with seawater, these compounds are retained in an estuary
(Bianchi, 2007).
Species: Trace elements include iron, cobalt, chromium, copper [2], iodine, manganese, selenium, zinc,
and molybdenum. Micronutrients also include vitamins,
which are organic compounds that organisms require
in low concentrations (Falkowski and Raven, 2007).
The most commonly occurring forms of iron are the
insoluble form (Fe 3
+ ) and the soluble form (Fe 2
+ ). Speciation studies have shown that dissolved copper in
most natural waters is mainly organically complexed
(Stumm and Morgan, 1996). By dominating copper speciation, organic complexation may control copper’s
bioavailability.
Demand: Microelements and trace elements are essential for autotrophic organisms; they are required as nutrients in very small concentrations. They are essential to
the photosynthetic process, being key constituents of chlorophyllous pigments and enzymes. Many investigators
have shown that iron (Fe) is the most important bioactive
trace element. N 2 -fixing cyanobacteria require larger
amounts of iron than other micronutrients.
Bibliography
Bianchi, T. S., 2007. Biogeochemistry of Estuaries. Oxford: Oxford
University Press.
Day, J. W., Kemp, M. W., Yánez-Arancibia, A., and Crump, B. C.,
2012. Estuarine Ecology, 2nd edn. Hoboken: Wiley-Blackwell.
MICRONUTRIENTS
437