Assessing the state of environments is not an easy task, and today it is one of the greatest challenges we have to conserve the nature. In many cases, the studies that are in charge of this use different environmental and ecological factors that help them to know about the state of he alth and the quality of that environment, as well as the changes that it undergoes.
An example of this is the use of animal or plant species (or groups of these), which serve as excellent biological tools to assess an entire ecological system. In this article on our site, we will tell you about the bioindicator organisms, what they are, what types there are, their importance and we will see some examples.
What are bioindicators?
Bioindicators are organisms that contain part of the environmental information that surrounds them, and as we mentioned, it can be an animal species or plant (or a group of species) that reflects the abiotic or biotic state of the environment, represents the impact of environmental changes on a habitat, community or ecosystems, or indicates the diversity of other species.
Characteristics of bioindicator species
It is generally considered that bioindicator species should be:
- Sensitive to their environment.
- Abundant (like some dominant species).
- Conspicuous.
- Easy to identify.
To select and analyze a bioindicator species, its ecology, way of life and wide geographical distribution must be thoroughly known, as well as being able to differentiate between natural cycles and those produced by anthropogenic stress.
What are bioindicator species used for?
The importance of using these organisms as tools for the conservation of natural areas has several reasons:
- Evaluate the impact of human activity: on the one hand, through them it is possible to evaluate the impact of human activities in an area instead of scanning the entire site.
- Warn of environmental changes: on the other hand, they are important because in many cases some of the bioindicator species provide early information and thus an alert, about environmental change.
- Evaluate the effects of toxics: Bioindicators are also a good way to monitor the effects of toxic substances, often difficult to evaluate directly in nature.
- Evaluate species richness: They are also useful for evaluating the richness of species present in a site, through extrapolation, since many sometimes this is impossible due to the high number that can exist, as in the case of the tropics, for example.
Although this can be difficult because a species is not always representative of all the biota (all the species present) of the place.
Types of bioindicators
Currently there are various classifications of bioindicator organisms. Some authors speak of these three types of bioindicators:
Air bioindicators
As their name indicates, they are species through which we can assess the state and quality of the air. Some examples are:
- Lichens: These organisms, which are often mistaken for plants, are actually the result of a symbiosis between a fungus and an algae photosynthesizer, are used as bioindicators for the detection of hydrocarbons, acids and other toxic substances found in the air through the accumulation of these substances in their tissues. These organisms are used as air bioindicators in many parts of the world.
- Bees: Another example is bees. These animals (and the honey they produce) are bioindicators of urban air pollution, thanks to the structure of their legs that can retain air particles and thus detect the existence of toxic agents such as pesticides, heavy metals or even carbon dioxide. presence of radioactive agents that may exist in cities in Spain.
- Gekos or salamanquesas: species of the Diplodactylus family are sensitive to air pollution by sulfur dioxide and other gas emissions by industries. Air pollution negatively affects the abundance and fertility of species such as Diplodactylus conspicillatus and Rhynchoedura ornata, present in Australia.
Water bioindicators
Within the water bioindicators, we find:
- Insects: Plecopteran invertebrates such as stoneflies, are sensitive to low oxygen concentrations in water, especially their states. immature serve as bioindicators of water quality. Hemiptera species, such as coryxids, are also good indicators of the salinity of hot springs, as well as of surface-active substances such as detergents and soaps. The caddisflies, which live in very clean waters, as well as the mayflies that are also used to determine the quality of the water.
- Amphibians: species of frogs and salamanders are excellent indicators of environmental quality, as they are very sensitive to environmental conditions such as drought or pollution. Because their skins are permeable, they can accumulate toxic substances such as fungicides, soil fertilizers and insecticides, they could be detected.
- Peces: the presence of 5% of carnivorous fish species such as piranhas (family Serrasalmidae), indicate a he althy aquatic environment. Other species such as salmon and trout (Salmonidae) and corvinas (Sciaenidae) inhabit waters with high levels of oxygen, so they are also bioindicators of their quality.
Soil bioindicators
Some of the best soil bioindicators are:
- Collembola: these invertebrate inhabitants of the soil help to assess the quality of the soil by detecting the presence of polluting hydrocarbons. Its abundance in areas contaminated with components such as pyrenes, naphthalene, chrysene, among others, is negatively affected. The same was seen with other invertebrates such as dipterans, spiders, ants and others.
- Mites: these are invertebrates that are very sensitive to the conditions in their environment, so they are excellent bioindicators of soil he alth where they live, since they can give information about the presence of insecticides. These animals are very abundant in soils highly rich in organic matter, decreasing in poor and polluted lands.
- Fungi: These organisms that form a natural part of soils store radioactive substances in their tissues (just like lichens) that affect their environment. Being a food source for humans, detecting these toxic compounds in time is of vital importance, which is why many quality studies are based on them to detect this type of contaminant.
Examples of bioindicators
In addition to the aforementioned classification, many authors consider that the most correct is to classify the different types of bioindicators in this way:
- Environmental bioindicators.
- Ecological bioindicators.
- Bioindicators of biodiversity.
The basic division is that environmental and ecological indicators are used to detect changes in the environment, while biodiversity indicators reflect the diversity of the global biota. However, these categories are not mutually exclusive, as some species that respond to environmental changes may also reflect the diversity or response of other species. Next, we will see some examples of them.
Beetles
Carabid beetles have been widely and successfully used in different types of indicator studies. Most of them focused on the species' response to changing environmental conditions, for example, such as forest fragmentation. In addition to this, ground beetles have been used in urban ecology studies, habitat type classification, and site quality assessment.
Other beetles of the tenebrionid family are soil bioindicators and give warning about desertification, since they are species that they are adapted to arid environments, so they are used to determine areas that could suffer a higher degradation of the environment.
Birds
Waterfowl species have been used as bioindicators of contamination by heavy metals such as lead, cadmium and arsenic, in wetland environments. Because these birds live and feed at these sites, they consume these substances along with their food.
Other bird species, such as the gentoo, chinstrap and Adélie penguins (order Sphenisciformes) have useful characteristics for pollutant monitoring, being long-lived species located at the top of food chains, are used to determine the concentrations of toxic substances and plastics through the analysis of their stomach contents.
Otters
These animals of the Mustelidae family are good indicators of the state and quality of rivers and lakes where they live, since when these bodies of water lose their nutrient quality and in the same way the richness of species on which otters feed, they abandon them looking for other similar ones. Currently, its presence is a clear indication of the good he alth of the waters.
