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Abioindicator is anyspecies (anindicator 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.[2] For example,copepods and other small watercrustaceans that are present in manywater bodies can be monitored for changes (biochemical,physiological, orbehavioural) that may indicate a problem within their ecosystem. Bioindicators can tell us about the cumulative effects of differentpollutants in the ecosystem and about how long a problem may have been present, whichphysical and chemical testing cannot.[3]
Abiological monitor orbiomonitor is anorganism that providesquantitative information on the quality ofthe environment around it.[4] 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.
Abiological 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 orGeobacillus).[5] Biological indicators can be described as the introduction of a highly resistant microorganisms to a given environment beforesterilization, tests are conducted to measure the effectiveness of the sterilization processes. As biological indicators use highly resistantmicroorganisms, any sterilization process that renders them inactive will have also killed off more common, weakerpathogens.
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, morequalitative.These organisms (or communities of organisms) can be used to deliver information on alterations in the environment or the quantity of environmentalpollutants by changing in one of the following ways:physiologically,chemically orbehaviourally. The information can be deduced through the study of:
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.[6] 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.[7] Small sets of indicator species can also be used to predict species richness for multiple taxonomic groups.[8]
The use of a biomonitor is described asbiological monitoring 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 andgenotype into the study area.[citation needed]
The use of a biomonitor is described asbiological monitoring. This refers to the measurement of specific properties of an organism to obtain information on the surrounding physical and chemical environment.[9]
Bioaccumulative indicators are frequently regarded as biomonitors. Depending on the organism selected and their use, there are several types of bioindicators.[10][11]
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.[12]
An important limitation of bioindicators in general is that they have been reported as inaccurate when applied to geographically and environmentally diverse regions.[13] 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.[14]
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, includingmosses,lichens,tree bark,bark pockets,tree rings, andleaves. As an example, environmental pollutants can be absorbed and incorporated into tree bark, which can then be analyzed to pollutant presence and concentration in the surrounding environment.[15] The leaves of certain vascular plants experience harmful effects in the presence of ozone, particularly tissue damage, making them useful in detecting the pollutant.[16][17] These plants are observed abundantly in Atlantic islands in the Northern Hemisphere, the Mediterranean Basin, equatorial Africa, Ethiopia, the Indian coastline, the Himalayan region, southern Asia, and Japan.[18] These regions with high endemic richness are particularly vulnerable to ozone pollution, emphasizing the importance of certain vascular plant species as valuable indicators of environmental health in terrestrial ecosystems. Conservationists use such plant bioindicators as tools, allowing them to ascertain potential changes and damages to the environment.
Lichen are well known bio-indicators used to monitor and measure pollution levels. Recognised scales exist allowing the level of pollution to be assessed depending on the species composition present.[19] Most well known is the Hawskworth Rose scale. The utility of lichen in this respects comes from the different tolerance different species have to various pollutants, meaning presence and absence of certain key species can be used to gauge overall pollution levels. As an example,Lobaria pulmonaria has been identified as an indicator species for assessing stand age and macrolichen diversity in Interior Cedar–Hemlock forests of east-central British Columbia, highlighting its ecological significance as a bioindicator.[20] The abundance ofLobaria pulmonaria was strongly correlated with this increase in diversity, suggesting its potential as an indicator of stand age in the ICH.[20] Another Lichen species,Xanthoria parietina, serves as a reliable indicator of air quality, effectively accumulating pollutants like heavy metals and organic compounds. Studies have shown thatX. parietina samples collected from industrial areas exhibit significantly higher concentrations of these pollutants compared to those from greener, less urbanized environments.[21] This highlights the lichen's valuable role in assessing environmental health and identifying areas with elevated pollution levels, aiding in targeted mitigation efforts and environmental management strategies.
Fungi is also useful as bioindicators, as they are found throughout the globe and undergo noticeable changes in different environments.[22]
Lichens are organisms comprising both fungi andalgae. They are found on rocks and tree trunks, and they respond to environmental changes in forests, including changes in forest structure –conservation biology,air quality, and climate. The disappearance of lichens in a forest may indicate environmental stresses, such as high levels ofsulfur dioxide, sulfur-based pollutants, andnitrogen oxides.The composition and total biomass of algal species in aquatic systems serve as an important metric for organicwater pollution and nutrient loading such as nitrogen and phosphorus.There aregenetically engineered organisms that can respond totoxicity levels in theenvironment;e.g., a type of genetically engineered grass that grows a different colour if there are toxins in the soil.[23]
Changes in animalpopulations, whether increases or decreases, can indicatepollution.[24] For example, if pollution causes depletion of a plant, animal species that depend on that plant will experiencepopulation decline. Conversely,overpopulation may be opportunistic growth of a species in response to loss of other species in an ecosystem. On the other hand,stress-inducedsub-lethal effects can be manifested in animalphysiology,morphology, andbehaviour of individuals long before responses are expressed and observed at the population level.[25] 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 oftoxins in animal tissues; the rate at which deformities arise in animal populations; behaviour in the field or in the laboratory;[26] and by assessing changes in individual physiology.[27]
Amphibians, particularly anurans (frogs and toads), are increasingly used as bioindicators of contaminant accumulation in pollution studies.[28] Anurans absorb toxic chemicals through their skin and their larval gill membranes and are sensitive to alterations in their environment.[29] They have a poor ability to detoxify pesticides that are absorbed, inhaled, or ingested by eating contaminated food.[29] This allows residues, especially of organochlorine pesticides, to accumulate in their systems.[29] 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.[29] 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.[30]
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.[citation needed] 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.[citation needed] Decline of anurans and malformations could also suggest increased exposure to ultra-violet light and parasites.[30] 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.[31]
Pond-breeding anurans are especially sensitive to pollution because of their complex life cycles, which could consist of terrestrial and aquatic living.[28] During their embryonic development, morphological and behavioral alterations are the effects most frequently cited in connection with chemical exposures.[32] Effects of exposure may result in shorter body length, lower body mass and malformations of limbs or other organs.[28] The slow development, late morphological change, and small metamorph size result in increased risk of mortality and exposure to predation.[28]
Crayfish have also been hypothesized as being suitable bioindicators, under the appropriate conditions.[33] One example of use is an examination of accumulation ofmicroplastics in the digestive tract ofred swamp crayfish (Procambarus clarkii) being used as a bioindicator of wider microplastics pollution.[34]
Bats respond noticeably to environmental changes and have therefore been suggested as potentially valuable bioindicators.[35] Although the number of studies is still relatively small, existing evidence suggests that bats are likely to be excellent indicators in environments like rivers, forests, and urban areas.[36] Nevertheless, further research across large geographic regions is necessary, and building research networks is essential to achieve this. There are also some challenges in using bats as bioindicators, including the difficulty of distinguishing cryptic species and identifying flying bats through their calls. Additionally, it is often challenging to determine which environmental factors shape bat distribution and behaviour.[36]
Microorganisms can be used as indicators ofaquatic orterrestrialecosystem health. Found in large quantities, microorganisms are easier to sample than other organisms. Some microorganisms will produce newproteins, calledstress proteins, when exposed to contaminants such ascadmium andbenzene. These stress proteins can be used as an early warning system to detect changes in levels of pollution.[citation needed]
Microbial Prospecting for oil and gas (MPOG) can be used to identify prospective areas for oil and gas occurrences.[citation needed] In many cases, oil and gas is known to seep toward the surface as ahydrocarbon reservoir will usually leak or have leaked towards the surface throughbuoyancy 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 includeDNA analysis, 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.[37]
Microalgae 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 is a motile, freshwater, photosynthetic flagellate. AlthoughEuglena 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 ofE. gracilis is very sensitive.[38][39]Other species such asParamecium biaurelia (seeParamecium aurelia) also use gravitactic orientation.[40]
Automaticbioassay is possible, using the flagellateEuglena gracilis in a device which measures their motility at different dilutions of the possibly polluted water sample, to determine theEC50 (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).[41][42]
Macroinvertebrates are useful and convenient indicators of theecological health of water bodies[43] and terrestrial ecosystems.[44][45] 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.[46] 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.[46] 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.[9] Tolerance values are commonly used to assess ecological effects of water pollution[47] such as pesticide contamination with theSPEAR system[48] andenvironmental degradation, such as human activities (e.g.selective logging andwildfires) in tropical forests.[49][50]
Benthic macroinvertebrates are found within thebenthic zone of a stream or river. They consist ofaquatic insects,crustaceans, worms andmollusks that live in the vegetation and stream beds of rivers.[9] 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.[51] 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.[9] Benthic indicators are often used to measure the biological components offresh water 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.[9] Benthic indicators are the most frequently used water quality test within the United States.[9] 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.[52]
InEurope, theWater Framework Directive (WFD) went into effect on October 23, 2000.[53] 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[13] A remote online biomonitoring system was designed in 2006. It is based on bivalvemolluscs and the exchange of real-time data between a remote intelligent device in the field (able to work for more than 1 year withoutin-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) and New Caledonia).[26]
In the United States, theEnvironmental Protection Agency (EPA) publishedRapid Bioassessment Protocols, in 1999, based on measuring macroinvertebrates, as well asperiphyton andfish for assessment ofwater quality.[1][54][55]
InSouth 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 SASSaquatic biomonitoring tool has been refined over the past 30 years and is now on the fifth version (SASS5) in accordance with theISO/IEC 17025 protocol.[46] The SASS5 method is used by the South AfricanDepartment of Water Affairs as a standard method for River Health Assessment, which feeds the national River Health Programme and the national Rivers Database.[citation needed]
Theimposex phenomenon in thedog conch species ofsea snail 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 inMalaysian ports.[56]
{{cite book}}:|journal= ignored (help)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
