Bioturbation
Encyclopedia
In oceanography
, limnology
, pedology
, geology
(especially geomorphology
and sedimentology
), and archaeology
, bioturbation is the displacement and mixing of sediment
particles (i.e. sediment reworking) and solutes (i.e. bio-irrigation) by fauna (animals) or flora (plants). The mediators of bioturbation are typically annelid
worms (e.g. polychaete
s, oligochaetes
), bivalves (e.g. mussel
s, clam
s), gastropods, holothurians, or any other infaunal or epifaunal organism
s. Faunal activities, such as burrowing, ingestion and defecation of sediment grains, construction and maintenance of galleries, and infilling of abandoned dwellings, displace sediment grains and mix the sediment matrix. In aqueous environments, the sediment-water interface
increases in area as a result of bioturbation, affecting chemical fluxes and thus exchange between the sediment and water column. Some organisms may further enhance chemical exchange by flushing their burrows with the overlying waters, a process termed bioirrigation
. Benthic flora can affect sediments in a manner analogous to burrow construction and flushing by establishing root structures. Bioturbation is a diagenetic
process and acts to alter the physical structure, as well as the chemical nature of the sediment.
, pedology
, geomorphology
, and archaeology
, bioturbation is the physical rearrangement of the soil profile by soil life
. Plants and animals exploit the solum
for food, and shelter and, in the process, disturb the fabric of the soil and the underlying parent material
. Burrowing animals and insects, and plant root systems create passageways for air and water movement, changing soil morphology
. A passageway created by an animal that becomes backfilled with soil is known as a krotovina. Invertebrates that burrow and mound soil tend to produce a biomantle topsoil (soil biomantle
), and as such are primary agents of horizonation http://www.uky.edu/AS/Geography/People/Faculty/Wilkinson/2005-WilkinsonHumphreysPedogenesisAJSR.pdf. Uprooted trees break up bedrock, transport soil downslope, increase the heterogeneity of soil respiration
rates, and disrupt soil horizonation. Bioturbation was initially unrecognized as a pedogenic
force. The term didn't exist before 1952, when bioturbation was coined to aid in ichnological
assessments. Bioturbation appeared in the soil and geomorphic literature in the early 1980s, and remains a key element of the pedogenic lexicon. Bioturbation is central to the soil biomantle
concept formulated in 1990. The biomantle is the upper part of soil produced largely by biota, dominantly by bioturbation. Biomantles tend to be one-layered when formed in homogeneous materials, and two-layered when formed in mixed fine-and-coarse materials. Bioturbation by burrowing animals results in soil landscapes that are both polygenetic and polytemporal.
s are often used to describe sediment biogeochemistry
. Commonly, these models take the form of ordinary differential equations or partial differential equations in which bioturbation appears as a diffusive
term completed or not with advective terms. A diffusive description is often adopted to avoid quantifying the plethora of mixing modes resulting from faunal activities. The diffusion coefficient describing the intensity of bioturbation is usually determined by fitting mathematical models to vertical distributions of natural radioactive tracer
s, radioisotopes resulting from nuclear weapon
testing, or introduced particles, such as glass
bead
s tagged with radionuclide
s or inert fluorescent particles.
was first realised by Charles Darwin
, who devoted his last scientific book to the subject (The Formation of Vegetable Mould through the Action of Worms, 1881). Modern research has provided further insight into the evolutionary and ecological role of bioturbation. In modern ecological theory, bioturbation is recognised as an archetypal example of ‘ecosystem engineering’, modifying geochemical gradients, redistributing food resources, viruses, bacteria
, resting stages and eggs. From an evolutionary perspective, recent investigations provide evidence that bioturbation had a key role in the evolution of metazoan life at the end of the Precambrian
Era.http://www.nioo.knaw.nl/ppages/jmiddelburg/downloads/1/Meysman_tree.pdf
, or the study of "trace fossils". In some cases bioturbation is so pervasive that it completely obliterates sedimentary structures
, such as cross-bedding
. It thus has an impact on the disciplines of sedimentology
and stratigraphy
within geology.
Oceanography
Oceanography , also called oceanology or marine science, is the branch of Earth science that studies the ocean...
, limnology
Limnology
Limnology , also called freshwater science, is the study of inland waters. It is often regarded as a division of ecology or environmental science. It covers the biological, chemical, physical, geological, and other attributes of all inland waters...
, pedology
Pedology
Pedology may refer to:*Pedology *Pedology *Pediatrics...
, geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
(especially geomorphology
Geomorphology
Geomorphology is the scientific study of landforms and the processes that shape them...
and sedimentology
Sedimentology
Sedimentology encompasses the study of modern sediments such as sand, mud , and clay, and the processes that result in their deposition. Sedimentologists apply their understanding of modern processes to interpret geologic history through observations of sedimentary rocks and sedimentary...
), and archaeology
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...
, bioturbation is the displacement and mixing of sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
particles (i.e. sediment reworking) and solutes (i.e. bio-irrigation) by fauna (animals) or flora (plants). The mediators of bioturbation are typically annelid
Annelid
The annelids , formally called Annelida , are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches...
worms (e.g. polychaete
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
s, oligochaetes
Oligochaeta
Oligochaeta is a subclass of animals in the biological phylum Annelida, which is made up of many types of aquatic and terrestrial worms, and this includes all of the various earthworms...
), bivalves (e.g. mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
s, clam
Clam
The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...
s), gastropods, holothurians, or any other infaunal or epifaunal organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
s. Faunal activities, such as burrowing, ingestion and defecation of sediment grains, construction and maintenance of galleries, and infilling of abandoned dwellings, displace sediment grains and mix the sediment matrix. In aqueous environments, the sediment-water interface
Sediment-water interface
In oceanography and limnology, the sediment-water interface is the boundary between bed sediment and the overlying water column. The topography of this interface is often dynamic, as it is affected by physical processes and biological processes ....
increases in area as a result of bioturbation, affecting chemical fluxes and thus exchange between the sediment and water column. Some organisms may further enhance chemical exchange by flushing their burrows with the overlying waters, a process termed bioirrigation
Bioirrigation
Bioirrigation, or simply irrigation, refers to the process of benthic organisms flushing their burrows with overlying water. The exchange of dissolved substances between the porewater and overlying seawater that results is an important process in the context of the biogeochemistry of the oceans....
. Benthic flora can affect sediments in a manner analogous to burrow construction and flushing by establishing root structures. Bioturbation is a diagenetic
Diagenesis
In geology and oceanography, diagenesis is any chemical, physical, or biological change undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surface alteration and metamorphism. These changes happen at relatively low temperatures and pressures...
process and acts to alter the physical structure, as well as the chemical nature of the sediment.
Soil bioturbation
In soil scienceSoil science
Soil science is the study of soil as a natural resource on the surface of the earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils.Sometimes terms which...
, pedology
Pedology
Pedology may refer to:*Pedology *Pedology *Pediatrics...
, geomorphology
Geomorphology
Geomorphology is the scientific study of landforms and the processes that shape them...
, and archaeology
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...
, bioturbation is the physical rearrangement of the soil profile by soil life
Soil life
Soil life or soil biota is a collective term for all the organisms living within the soil.-Overview:In balanced soil, plants grow in an active and steady environment. The mineral content of the soil and its heartiful structure are important for their well-being, but it is the life in the earth that...
. Plants and animals exploit the solum
Solum
The solum in soil science consists of the surface and subsoil layers that have undergone the same soil forming conditions. The base of the solum is the relatively unweathered parent material, termed substratum....
for food, and shelter and, in the process, disturb the fabric of the soil and the underlying parent material
Parent material
In soil science, parent material is the underlying geological material in which soil horizons form...
. Burrowing animals and insects, and plant root systems create passageways for air and water movement, changing soil morphology
Soil morphology
Soil morphology is the field observable attributes of the soil within the various soil horizons and the description of the kind and arrangement of the horizons. C.F...
. A passageway created by an animal that becomes backfilled with soil is known as a krotovina. Invertebrates that burrow and mound soil tend to produce a biomantle topsoil (soil biomantle
Soil Biomantle
The soil biomantle can be described and defined in several ways. In broad and simplest terms, the soil biomantle is the organic-rich bioturbated upper part of soil, including the topsoil where most biota live, reproduce, die, and become assimilated...
), and as such are primary agents of horizonation http://www.uky.edu/AS/Geography/People/Faculty/Wilkinson/2005-WilkinsonHumphreysPedogenesisAJSR.pdf. Uprooted trees break up bedrock, transport soil downslope, increase the heterogeneity of soil respiration
Soil respiration
Soil respiration refers to the production of carbon dioxide when soil organisms respire. This includes respiration of plant roots, the rhizosphere, microbes and fauna....
rates, and disrupt soil horizonation. Bioturbation was initially unrecognized as a pedogenic
Pedogenesis
Pedogenesis is the science and study of the processes that lead to the formation of soil ' and first explored by the Russian geologist Vasily Dokuchaev , the so called grandfather of soil science, who determined that soil formed over time as a consequence of...
force. The term didn't exist before 1952, when bioturbation was coined to aid in ichnological
Ichnology
Ichnology is the branch of geology that deals with traces of organismal behavior, such as burrows and footprints. It is generally considered as a branch of paleontology; however, only one division of ichnology, paleoichnology, deals with trace fossils, while neoichnology is the study of modern traces...
assessments. Bioturbation appeared in the soil and geomorphic literature in the early 1980s, and remains a key element of the pedogenic lexicon. Bioturbation is central to the soil biomantle
Soil Biomantle
The soil biomantle can be described and defined in several ways. In broad and simplest terms, the soil biomantle is the organic-rich bioturbated upper part of soil, including the topsoil where most biota live, reproduce, die, and become assimilated...
concept formulated in 1990. The biomantle is the upper part of soil produced largely by biota, dominantly by bioturbation. Biomantles tend to be one-layered when formed in homogeneous materials, and two-layered when formed in mixed fine-and-coarse materials. Bioturbation by burrowing animals results in soil landscapes that are both polygenetic and polytemporal.
Modelling bioturbation
Mathematical modelMathematical model
A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used not only in the natural sciences and engineering disciplines A mathematical model is a...
s are often used to describe sediment biogeochemistry
Biogeochemistry
Biogeochemistry is the scientific discipline that involves the study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment...
. Commonly, these models take the form of ordinary differential equations or partial differential equations in which bioturbation appears as a diffusive
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
term completed or not with advective terms. A diffusive description is often adopted to avoid quantifying the plethora of mixing modes resulting from faunal activities. The diffusion coefficient describing the intensity of bioturbation is usually determined by fitting mathematical models to vertical distributions of natural radioactive tracer
Radioactive tracer
A radioactive tracer, also called a radioactive label, is a substance containing a radioisotope that is used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or tissue...
s, radioisotopes resulting from nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...
testing, or introduced particles, such as glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
bead
Bead
A bead is a small, decorative object that is usually pierced for threading or stringing. Beads range in size from under to over in diameter. A pair of beads made from Nassarius sea snail shells, approximately 100,000 years old, are thought to be the earliest known examples of jewellery. Beadwork...
s tagged with radionuclide
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
s or inert fluorescent particles.
Evolutionary significance
Bioturbation's importance for soil processes and geomorphologyGeomorphology
Geomorphology is the scientific study of landforms and the processes that shape them...
was first realised by Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
, who devoted his last scientific book to the subject (The Formation of Vegetable Mould through the Action of Worms, 1881). Modern research has provided further insight into the evolutionary and ecological role of bioturbation. In modern ecological theory, bioturbation is recognised as an archetypal example of ‘ecosystem engineering’, modifying geochemical gradients, redistributing food resources, viruses, bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, resting stages and eggs. From an evolutionary perspective, recent investigations provide evidence that bioturbation had a key role in the evolution of metazoan life at the end of the Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
Era.http://www.nioo.knaw.nl/ppages/jmiddelburg/downloads/1/Meysman_tree.pdf
Geology
Patterns of bioturbation may be preserved in lithified rock, and the study of such patterns is called ichnologyIchnology
Ichnology is the branch of geology that deals with traces of organismal behavior, such as burrows and footprints. It is generally considered as a branch of paleontology; however, only one division of ichnology, paleoichnology, deals with trace fossils, while neoichnology is the study of modern traces...
, or the study of "trace fossils". In some cases bioturbation is so pervasive that it completely obliterates sedimentary structures
Sedimentary structures
Sedimentary structures are those structures formed during sediment deposition.Sedimentary structures such as cross bedding, graded bedding and ripple marks are utilized in stratigraphic studies to indicate original position of strata in geologically complex terrains and understand the depositional...
, such as cross-bedding
Cross-bedding
In geology, the sedimentary structures known as cross-bedding refer to horizontal units that are internally composed of inclined layers. This is a case in geology in which the original depositional layering is tilted, and the tilting is not a result of post-depositional deformation...
. It thus has an impact on the disciplines of sedimentology
Sedimentology
Sedimentology encompasses the study of modern sediments such as sand, mud , and clay, and the processes that result in their deposition. Sedimentologists apply their understanding of modern processes to interpret geologic history through observations of sedimentary rocks and sedimentary...
and stratigraphy
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
within geology.