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A bioindicator is any species (an indicator species) or group of species whose function, population, or status can reveal the qualitative status of the environment. The most common indicator species are animals. For example,
copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...
s and other small water crustaceans that are present in many
water bodies A body of water or waterbody (often spelled water body) is any significant accumulation of water on the surface of Earth or another planet. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as p ...
can be monitored for changes (biochemical,
physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
, or behavioural) that may indicate a problem within their ecosystem. Bioindicators can tell us about the cumulative effects of different pollutants in the ecosystem and about how long a problem may have been present, which physical and chemical testing cannot. A biological monitor or biomonitor is an organism that provides
quantitative Quantitative may refer to: * Quantitative research, scientific investigation of quantitative properties * Quantitative analysis (disambiguation) * Quantitative verse, a metrical system in poetry * Statistics, also known as quantitative analysis ...
information on the quality of
the environment The natural environment or natural world encompasses all living and non-living things occurring naturally, meaning in this case not artificial. The term is most often applied to the Earth or some parts of Earth. This environment encompasses t ...
around it. Therefore, a good biomonitor will indicate the presence of the pollutant and can also be used in an attempt to provide additional information about the amount and intensity of the exposure. A biological indicator is also the name given to a process for assessing the sterility of an environment through the use of resistant microorganism strains (e.g. '' Bacillus'' or ''
Geobacillus ''Geobacillus'' is a bacterial genus from the family of Bacillaceae The Bacillaceae are a family of gram-positive, heterotrophic, rod-shaped bacteria that may produce endospores. Motile members of this family are characterized by peritrichou ...
''). Biological indicators can be described as the introduction of a highly resistant microorganisms to a given environment before sterilization, tests are conducted to measure the effectiveness of the sterilization processes. As biological indicators use highly resistant
microorganisms A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
, any sterilization process that renders them inactive will have also killed off more common, weaker pathogens.


Overview

A bioindicator is an organism or biological response that reveals the presence of pollutants by the occurrence of typical symptoms or measurable responses and is, therefore, more
qualitative Qualitative descriptions or distinctions are based on some quality or characteristic rather than on some quantity or measured value. Qualitative may also refer to: *Qualitative property, a property that can be observed but not measured numericall ...
. These organisms (or communities of organisms) can be used to deliver information on alterations in the environment or the quantity of environmental pollutants by changing in one of the following ways:
physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
ly, chemically or behaviourally. The information can be deduced through the study of: # their content of certain elements or compounds # their morphological or cellular structure #
metabolic Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
biochemical Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology an ...
processes # behaviour # population structure(s). The importance and relevance of biomonitors, rather than man-made equipment, are justified by the observation that the best indicator of the status of a species or system is itself. Bioindicators can reveal indirect biotic effects of pollutants when many physical or chemical measurements cannot. Through bioindicators, scientists need to observe only the single indicating species to check on the environment rather than monitor the whole community. Small sets of indicator species can also be used to predict species richness for multiple taxonomic groups. The use of a biomonitor is described as
biological monitoring In analytical chemistry, biomonitoring is the measurement of the body burden of toxic chemical compounds, elements, or their metabolites, in biological substances. Often, these measurements are done in blood and urine. Biomonitoring is performed ...
and is the use of the properties of an organism to obtain information on certain aspects of the biosphere. Biomonitoring of air pollutants can be passive or active. Experts use passive methods to observe plants growing naturally within the area of interest. Active methods are used to detect the presence of air pollutants by placing test plants of known response and
genotype The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...
into the study area. The use of a biomonitor is described as
biological monitoring In analytical chemistry, biomonitoring is the measurement of the body burden of toxic chemical compounds, elements, or their metabolites, in biological substances. Often, these measurements are done in blood and urine. Biomonitoring is performed ...
. This refers to the measurement of specific properties of an organism to obtain information on the surrounding physical and chemical environment. Bioaccumulative indicators are frequently regarded as biomonitors. Depending on the organism selected and their use, there are several types of bioindicators.


Use

In most instances, baseline data for biotic conditions within a pre-determined reference site are collected. Reference sites must be characterized by little to no outside disturbance (e.g. anthropogenic disturbances, land use change, invasive species). The biotic conditions of a specific indicator species are measured within both the reference site and the study region over time. Data collected from the study region are compared against similar data collected from the reference site in order to infer the relative environmental health or integrity of the study region. An important limitation of bioindicators in general is that they have been reported as inaccurate when applied to geographically and environmentally diverse regions. As a result, researchers who use bioindicators need to consistently ensure that each set of indices is relevant within the environmental conditions they plan to monitor.


Plant and fungal indicators

The presence or absence of certain plant or other vegetative life in an ecosystem can provide important clues about the health of the environment: environmental preservation. There are several types of plant biomonitors, including
moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...
es,
lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.tree bark Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines, and shrubs. Bark refers to all the tissues outside the vascular cambium and is a nontechnical term. It overlays the wood and consist ...
,
bark pocket Bark pockets are patches or inclusions of bark partially or fully embedded in the wood of a tree. They can also be used as biomonitors. Bark pockets are considered a nuisance in the lumber industry because they are considered a defect, and lower t ...
s,
tree ring Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...
s, and
leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
. Fungi too may be useful as indicators. Lichens are organisms comprising both fungi and
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
. They are found on rocks and tree trunks, and they respond to environmental changes in forests, including changes in forest structure –
conservation biology Conservation biology is the study of the conservation of nature and of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. It is an int ...
, air quality, and climate. The disappearance of lichens in a forest may indicate environmental stresses, such as high levels of
sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
, sulfur-based pollutants, and
nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral *Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide *Nitrogen dioxide (), nitrogen(IV) oxide * Nitrogen trioxide (), or n ...
s. The composition and total biomass of algal species in aquatic systems serve as an important metric for organic water pollution and nutrient loading such as nitrogen and phosphorus. There are genetically engineered organisms that can respond to toxicity levels in the
environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...
; ''e.g.'', a type of genetically engineered grass that grows a different colour if there are toxins in the soil.


Animal indicators and toxins

Changes in animal populations, whether increases or decreases, can indicate pollution. For example, if pollution causes depletion of a plant, animal species that depend on that plant will experience
population decline A population decline (also sometimes called underpopulation, depopulation, or population collapse) in humans is a reduction in a human population size. Over the long term, stretching from prehistory to the present, Earth's total human population ...
. Conversely, overpopulation may be opportunistic growth of a species in response to loss of other species in an ecosystem. On the other hand, stress-induced sub-lethal effects can be manifested in animal physiology, morphology, and
behaviour Behavior (American English) or behaviour (British English) is the range of actions and mannerisms made by individuals, organisms, systems or artificial entities in some environment. These systems can include other systems or organisms as wel ...
of individuals long before responses are expressed and observed at the population level. Such sub-lethal responses can be very useful as "early warning signals" to predict how populations will further respond. Pollution and other stress agents can be monitored by measuring any of several variables in animals: the concentration of toxins in animal tissues; the rate at which deformities arise in animal populations; behaviour in the field or in the laboratory;Université Bordeaux et al
MolluSCAN ''eye'' project
and by assessing changes in individual physiology.


Frogs and toads

Amphibians, particularly anurans (frogs and toads), are increasingly used as bioindicators of contaminant accumulation in pollution studies.Simon, E., Braun, M. & Tóthmérész, B. Water Air Soil Pollut (2010) 209: 467. doi:10.1007/s11270-009-0214-6 Anurans absorb toxic chemicals through their skin and their larval gill membranes and are sensitive to alterations in their environment. They have a poor ability to detoxify pesticides that are absorbed, inhaled, or ingested by eating contaminated food. This allows residues, especially of organochlorine pesticides, to accumulate in their systems. They also have permeable skin that can easily absorb toxic chemicals, making them a model organism for assessing the effects of environmental factors that may cause the declines of the amphibian population. These factors allow them to be used as bioindicator organisms to follow changes in their habitats and in ecotoxicological studies due to humans increasing demands on the environment. Knowledge and control of environmental agents is essential for sustaining the health of ecosystems. Anurans are increasingly utilized as bioindicator organisms in pollution studies, such as studying the effects of agricultural pesticides on the environment. Environmental assessment to study the environment in which they live is performed by analyzing their abundance in the area as well as assessing their locomotive ability and any abnormal morphological changes, which are deformities and abnormalities in development. Decline of anurans and malformations could also suggest increased exposure to ultra-violet light and parasites.Center for Global Environmental Education. What are the frogs trying to tell us? OR Malformed Amphibians. Retrieved from http://cgee.hamline.edu/frogs/archives/corner3.html Expansive application of agrochemicals such as glyphosate have been shown to have harmful effects on frog populations throughout their lifecycle due to run off of these agrochemicals into the water systems these species live and their proximity to human development. Pond-breeding anurans are especially sensitive to pollution because of their complex life cycles, which could consist of terrestrial and aquatic living. During their embryonic development, morphological and behavioral alterations are the effects most frequently cited in connection with chemical exposures. Effects of exposure may result in shorter body length, lower body mass and malformations of limbs or other organs. The slow development, late morphological change, and small metamorph size result in increased risk of mortality and exposure to predation.


Crustaceans

Crayfish Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...
have also been hypothesized as being suitable bioindicators, under the appropriate conditions.


Microbial indicators


Chemical pollutants

Microorganisms can be used as indicators of aquatic or terrestrial ecosystem health. Found in large quantities, microorganisms are easier to sample than other organisms. Some microorganisms will produce new
proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
, called stress proteins, when exposed to contaminants such as cadmium and benzene. These stress proteins can be used as an early warning system to detect changes in levels of pollution.


In oil and gas exploration

Microbial Prospecting for oil and gas (MPOG) is often used to identify prospective areas for oil and gas occurrences. In many cases, oil and gas is known to seep toward the surface as a hydrocarbon reservoir will usually leak or have leaked towards the surface through buoyancy forces overcoming sealing pressures. These hydrocarbons can alter the chemical and microbial occurrences found in the near-surface soils or can be picked up directly. Techniques used for MPOG include
DNA analysis Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...
, simple bug counts after culturing a soil sample in a hydrocarbon-based medium or by looking at the consumption of hydrocarbon gases in a culture cell.


Microalgae in water quality

Microalgae Microalgae or microphytes are microscopic algae invisible to the naked eye. They are phytoplankton typically found in freshwater and marine systems, living in both the water column and sediment. They are unicellular species which exist indiv ...
have gained attention in recent years due to several reasons including their greater sensitivity to pollutants than many other organisms. In addition, they occur abundantly in nature, they are an essential component in very many food webs, they are easy to culture and to use in assays and there are few if any ethical issues involved in their use. ''
Euglena gracilis ''Euglena gracilis'' is a freshwater species of single-celled alga in the genus ''Euglena''. It has secondary chloroplasts, and is a mixotroph able to feed by photosynthesis or phagocytosis. It has a highly flexible cell surface, allowing it to ...
'' is a motile, freshwater, photosynthetic flagellate. Although ''Euglena'' is rather tolerant to acidity, it responds rapidly and sensitively to environmental stresses such as heavy metals or inorganic and organic compounds. Typical responses are the inhibition of movement and a change of orientation parameters. Moreover, this organism is very easy to handle and grow, making it a very useful tool for eco-toxicological assessments. One very useful particularity of this organism is gravitactic orientation, which is very sensitive to pollutants. The gravireceptors are impaired by pollutants such as heavy metals and organic or inorganic compounds. Therefore, the presence of such substances is associated with random movement of the cells in the water column. For short-term tests, gravitactic orientation of ''E. gracilis'' is very sensitive. Other species such as ''
Paramecium biaurelia ''Paramecium biaurelia'' is a species of unicellular ciliates under the genus ''Paramecium'', and one of the cryptic species of ''Paramecium aurelia''. It is a free-living protist in water bodies and harbours several different bacteria as endos ...
'' (see '' Paramecium aurelia'') also use gravitactic orientation. Automatic bioassay is possible, using the flagellate ''
Euglena gracilis ''Euglena gracilis'' is a freshwater species of single-celled alga in the genus ''Euglena''. It has secondary chloroplasts, and is a mixotroph able to feed by photosynthesis or phagocytosis. It has a highly flexible cell surface, allowing it to ...
'' in a device which measures their motility at different dilutions of the possibly polluted water sample, to determine the EC50 (the concentration of sample which affects 50 percent of organisms) and the G-value (lowest dilution factor at which no-significant toxic effect can be measured).


Macroinvertebrates

Macroinvertebrates are useful and convenient indicators of the ecological health of water bodies and terrestrial ecosystems. They are almost always present, and are easy to sample and identify. This is largely due to the fact that most macro-invertebrates are visible to the naked eye, they typically have a short life-cycle (often the length of a single season) and are generally sedentary. Pre-existing river conditions such as river type and flow will affect macro invertebrate assemblages and so various methods and indices will be appropriate for specific stream types and within specific eco-regions. While some benthic macroinvertebrates are highly tolerant to various types of water pollution, others are not. Changes in population size and species type in specific study regions indicate the physical and chemical state of streams and rivers. Tolerance values are commonly used to assess water pollution and
environmental degradation Environmental degradation is the deterioration of the environment (biophysical), environment through depletion of resources such as quality of air, water and soil; the destruction of ecosystems; habitat destruction; the extinction of wildlife; an ...
, such as human activities (e.g. selective logging and wildfires) in tropical forests.


Benthic indicators for water quality testing

Benthic macroinvertebrates are found within the
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. The name comes from ancient Greek, βένθος (bénthos), meaning " ...
of a stream or river. They consist of
aquatic insect Aquatic insects or water insects live some portion of their life cycle in the water. They feed in the same ways as other insects. Some ''diving'' insects, such as predatory diving beetles, can hunt for food underwater where land-living insects c ...
s, crustaceans, worms and
mollusks Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000  extant species of molluscs are recognized. The number of fossil species is esti ...
that live in the vegetation and stream beds of rivers. Macroinvertebrate species can be found in nearly every stream and river, except in some of the world's harshest environments. They also can be found in mostly any size of stream or river, prohibiting only those that dry up within a short timeframe. This makes the beneficial for many studies because they can be found in regions where stream beds are too shallow to support larger species such as fish. Benthic indicators are often used to measure the biological components of
fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
streams and rivers. In general, if the biological functioning of a stream is considered to be in good standing, then it is assumed that the chemical and physical components of the stream are also in good condition. Benthic indicators are the most frequently used water quality test within the United States. While benthic indicators should not be used to track the origins of stressors in rivers and streams, they can provide background on the types of sources that are often associated with the observed stressors.


Global context

In Europe, the Water Framework Directive (WFD) went into effect on October 23, 2000. It requires all EU member states to show that all surface and groundwater bodies are in good status. The WFD requires member states to implement monitoring systems to estimate the integrity of biological stream components for specific sub-surface water categories. This requirement increased the incidence of biometrics applied to ascertain stream health in Europe A remote online biomonitoring system was designed in 2006. It is based on bivalve
mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000  extant species of molluscs are recognized. The number of fossil species is esti ...
s and the exchange of real-time data between a remote intelligent device in the field (able to work for more than 1 year without '' in-situ'' human intervention) and a data centre designed to capture, process and distribute the web information derived from the data. The technique relates bivalve behaviour, specifically shell gaping activity, to water quality changes. This technology has been successfully used for the assessment of coastal water quality in various countries (France, Spain, Norway, Russia, Svalbard (
Ny-Ålesund Ny-Ålesund ("New Ålesund") is a small town in Oscar II Land on the island of Spitsbergen in Svalbard, Norway. It is situated on the Brøgger peninsula ( Brøggerhalvøya) and on the shore of the bay of Kongsfjorden. The company town is owned and ...
) and New Caledonia). In the United States, the
Environmental Protection Agency A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
(EPA) published ''Rapid Bioassessment Protocols,'' in 1999, based on measuring macroinvertebrates, as well as periphyton and fish for assessment of water quality. In South Africa, the Southern African Scoring System (SASS) method is based on benthic macroinvertebrates, and is used for the assessment of water quality in South African rivers. The SASS aquatic biomonitoring tool has been refined over the past 30 years and is now on the fifth version (SASS5) in accordance with the
ISO/IEC 17025 ISO/IEC 17025 General requirements for the competence of testing and calibration laboratories is the main ISO/IEC standard used by testing and calibration laboratories. In most countries, ISO/IEC 17025 is the standard for which most labs must ho ...
protocol. The SASS5 method is used by the South African
Department of Water Affairs The Department of Water and Sanitation is one of the departments of the South African government. It is responsible for the state of water and sanitation in South Africa. In May 2009, following the election of Jacob Zuma, the Department of W ...
as a standard method for River Health Assessment, which feeds the national River Health Programme and the national Rivers Database. The imposex phenomenon in the
dog conch ''Laevistrombus canarium'' ( commonly known as the dog conch or by its better-known synonym, ''Strombus canarium'') is a species of edible sea snail, a marine gastropod mollusc in the family Strombidae (true conches). Known from illustrations i ...
species of
sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...
leads to the abnormal development of a penis in females, but does not cause sterility. Because of this, the species has been suggested as a good indicator of pollution with organic man-made tin compounds in Malaysian ports.


See also

* Biological integrity *
Biological monitoring working party The biological monitoring working party (BMWP) is a procedure for measuring water quality using families of macroinvertebrates as biological indicators. The method is based on the principle that different aquatic invertebrates have different to ...
(a measurement procedure) *
Biosignature A biosignature (sometimes called chemical fossil or molecular fossil) is any substance – such as an element, isotope, or molecule – or phenomenon that provides scientific evidence of past or present life. Measurable attribute ...
* Ecological indicator * Environmental indicator * Indicator value *
MERMOZ MERMOZ (also, MERMOZ project and Monitoring planEtary suRfaces with Modern pOlarimetric characteriZation) is an astrobiology project designed to remotely detect biosignatures of life. Detection is based on molecular homochirality, a characteri ...
(remote detection of lifeforms) * Sentinel species


References

Herek, J. S., Vargas, L., Trindade, S. A. R., Rutkoski, C. F., Macagnan, N., Hartmann, P. A., & Hartmann, M. T. (2020). Can environmental concentrations of glyphosate affect survival and cause malformation in amphibians? Effects from a glyphosate-based herbicide on Physalaemus cuvieri and P. gracilis (Anura: Leptodactylidae). Environmental Science and Pollution Research, 27(18), 22619–22630. https://doi.org/10.1007/s11356-020-08869-z


Further reading

*


External links


Environmental Biomarkers Initiative at Pacific Northwest National Laboratory
– U.S. Department of Energy, Richland, WA
Volunteer Monitoring Program
– U.S. EPA

– South Africa

by Isidro A. T. Savillo * ttps://www.protakscientific.com/biological-indicators ''Biological Indicators for Sterilization''– Protak Scientific {{Authority control Ecology Ecotoxicology Measurement of biodiversity Water quality indicators Water pollution Indicators