Some organisms are very sensitive to pollution in their environment, so if contaminants are present, the morphology, physiology or behavior of the organisms may change or even die. Therefore, various living species can often be used to measure chemical levels in their environment. Bioindicators are living organisms such as plants, algae, lichens, fungi, plankton, animals and microorganisms that give an idea about the health of the natural ecosystem in the environment. These organisms are also an important tool for detecting positive or negative changes in the environment and their subsequent impact on human populations.
There are certain factors that govern the presence of bioindicators in the environment, such as light, water, temperature, and the transmission of suspended (not precipitated) solids. Thanks to the application of bioindicators, the natural state, contamination or pollution level / degree of a particular area can be predicted. The state of the environment can be effectively monitored with the use of bioindicator species due to their resistance to ecological variability. Bioindicators can tell the cumulative (cumulative or total) effects of different pollutants in the ecosystem and how long a problem may have been present, what physical and chemical tests cannot.
Bioindicators are currently used and promoted by various organizations (World Conservation Union, International Union for Conservation of Nature) as a tool for biological monitoring and assessment of human effects. Plants, animals or microorganisms can be bioindicators.
Herbal Indicators
Plants are used as very precise tools for predicting and recognizing environmental stresses. Recently, the problem of water pollution has intensified due to industrialization and urbanization. The presence or absence of certain plants or other vegetation provides ample information about environmental health.
Lichens and Bryophytes (liverweeds along with black algae are found in this phylum) are powerful bioindicators of air quality. Lichens, which can often be found on tree trunks, rocks or surfaces such as soil, are organisms that include both fungi and algae. Lichens are a good indicator of the surrounding air quality, as they need fresh air to thrive. It can be said that forests have clean air depending on the amount and type of lichen on the trees. The extinction of lichens in a forest can indicate the presence of environmental stresses such as high levels of sulfur dioxide, sulfur-based pollutants, and nitrogen oxides. Different types of lichen have different levels of sensitivity to air pollution, so an idea of the pollution level can be gained by observing which species are present.
Scientists have used an algae species called Hylocomium splendens as a natural indicator of heavy metals in the remote tundra environment of northwestern Alaska. Wolffia globosa (an aquatic herbaceous plant species also called duckweed) is an important species in demonstrating cadmium sensitivity and is also used to indicate cadmium contamination.
Marine plants also provide valuable information for predicting the state of the ocean environment, as they are immobile and quickly balance with their natural environment. The composition and total biomass of algae species in water systems serve as an important measure of nutrient loading, such as organic water pollution, nitrogen and phosphorus. Algae (algae) blooms are often used in lakes and rivers to show large nitrate and phosphate spikes.
Animal Indicators
Changes in animal populations can indicate harmful changes caused by pollution in the ecosystem. Changes in population density can indicate a negative impact on the ecosystem. Population changes may be the result of the relationship between populations and food sources; If food resources become scarce and cannot meet the population demand, this will be followed by the reduction of the population in question. For example, if pollution causes a plant to go extinct, there will be a decline in the population of animal species whose life depends on feeding that plant. Conversely, overpopulation may have occurred due to opportunistic growth of a species in response to the loss of other species in an ecosystem. On the other hand, stress-related non-lethal effects can occur in the physiology, morphology of animals, and behavior of individuals long before the responses are expressed and observed at the population level. These kinds of responses are not lethal, they can be very useful as “early warning signals” for predicting how populations will respond more.
Animal indicators also help detect the amount of toxin found in animals’ tissues. For example, levels of some liver enzymes in fish increase when exposed to contaminants in the water. Frogs are also bioindicators of environmental quality and environmental changes. Frogs are mainly affected by changes in freshwater and terrestrial habitats. This makes them important bioindicators of ecological quality and change. The increase in the number of mutated frogs in the USA is used as an indicator of the toxins in their environment.
Benthic Indicators for Water Quality Testing
Invertebrates can also be bioindicators; Aquatic invertebrates tend to be bottom-feeding (also known as benthic or macroinvertebrates) that live near the bottom of bodies of water. Benthic (feeding on the bottom) macro invertebrates are found in the benthic zone of a stream or river (the waters from the coast to the deepest parts of the sea or oceans). Macro invertebrate species (aquatic insects, crustaceans, worms, and mollusks) can be found in almost every stream and river except some of the world’s harshest environments. Benthic indicators are often used to measure the biological components of freshwater streams and rivers. In general, if the biological functioning of a stream is considered to be in good condition, it is assumed that the chemical and physical components of the stream are also in good condition.
Benthic indicators are widely used in water quality tests in the United States.
Macro invertebrates are almost always present and are easy to sample and identify. This is largely due to the fact that most macrovertebrates are visible to the naked eye, typically have a short life cycle (usually a single season long), and are generally sedentary. Pre-existing river conditions such as river type and flow will affect macroinvertebrate communities, so various methods and indexes will be appropriate for certain stream types and within specific eco-regions. Some benthic macroinvertebrates are highly tolerant of various water pollution while others are not. The changes in population size and species types in specific study areas indicate the physical and chemical status of streams and rivers. Tolerance values are widely used to assess water pollution and environmental degradation such as human activities (eg selective logging and forest fires) in tropical forests.
Microbial Indicators
Microorganisms are generally used as health indicators of aquatic and terrestrial ecosystems. Being plentiful, they are easy to test and readily available. Microorganisms are an important part of ocean biomass and are responsible for most of the productivity and nutrient cycle in a marine ecosystem. Microorganisms have a rapid growth rate and react even to low levels of contaminants and other physicochemical and biological changes. In terms of research, they give important signs of environmental change. Some microorganisms produce new proteins known as stress proteins that can be used as early warning signs when exposed to certain contaminants such as benzene and cadmium. By measuring the levels of stress proteins, an idea can be obtained about the level of pollution in the environment.
Microbial indicators can be used in a variety of ways to detect environmental contaminants in water, including the use of bioluminescent bacteria. The presence of toxins in water can be easily monitored by changes in the digestive system of microbes that are blocked or impaired by the presence of toxins that can cause changes in the amount of light emitted by bacteria. Compared to other conventional tests available, these tests are very fast to monitor, but the limitation is that they can only show changes due to the presence of toxins in the organisms. One such example is the bacterium Vogesella indigofera, which quantitatively reacts to heavy metals. Under the influence of metal contamination, these bacteria produce blue pigmentation, an important marker of morphological changes that can be effectively observed visually. Alternatively, pigment production is inhibited when they are in the vicinity of hexavalent chromium. Pigment production can be attributed to the relationship between chromium concentration and blue pigmentation formation by bacteria.
Microalgae have gained attention in recent years for a variety of reasons, including being more susceptible to pollutants than many other organisms. These organisms are abundant in nature, they are an important ingredient in many food webs, are easy to culture and use in assays, and there are few ethical issues in their use. Euglena gracilis is a mobile, freshwater unicellular photosynthetic flagellate. Although Euglena is highly tolerant of acidity, it responds quickly and precisely to environmental stresses such as heavy metals or inorganic and organic compounds. Typical responses are motion inhibition and change of orientation parameters. Moreover, this organism is very easy to use and grow, making it a very useful tool for eco-toxicological assessments. A very useful feature of this organism is the gravitational orientation, which is very sensitive to pollutants. Gravireceptors are broken down by contaminants such as heavy metals and organic or inorganic compounds. Therefore, the presence of such substances is associated with the random movement of cells in the water column. For short-term tests, the gravitactic orientation of E. gracilis is very sensitive.
Biomonitors, Biological monitoring
Bio organisms are mainly used to describe the properties of a biosphere. These organisms are known as bioindicators or biomoniators, both of which can vary significantly. The use of a biomonitor is defined as biological monitoring and is the use of the characteristics of an organism to obtain information about certain aspects of the biosphere. When examining the environment, the quality of changes that occur can be determined by bioindicators, while biomonitors (biomonitoring) are used to obtain quantitative information about environmental quality. Biomonitoring also includes data on past exacerbations and the effects of various variables. Good biomonitoring can also be used to show the presence of the contaminant and to provide additional information on the amount and intensity of exposure.
Monitoring can be used for various biological processes or systems to observe temporal and spatial changes in health status, to evaluate the effects of specific environment or anthropogenic (human-generated) stressors, and to evaluate the applicability of anthropogenic measures. In most cases, baseline data are collected for predetermined biotic conditions. Reference sites should be characterized by very little external interference (eg anthropogenic disturbances, land use change, invasive species). The biotic conditions of a particular indicator type are measured over time in both the reference zone and the study zone. Data collected from the study site is compared with similar data collected from the reference site to understand the relative environmental health or integrity of the study area. An important limitation of bioindicators in general is that they are incorrectly reported when applied to geographically and environmentally different regions. Consequently, researchers using bioindicators must consistently ensure that each set of indexes is relevant to the environmental conditions they plan to monitor.
Species diversity is used as the main element in biological monitoring, which is considered a valuable parameter in determining the health of the environment. Biomonitoring is an essential component of water quality assessment and has become an integral part of conducting studies on water pollution. Biomonitors are freely available all over the world. Basically, they reflect the natural effect on living things and can be understood and used with minimal preparation and training.
