104
the true effect) of the complex impact various pollutants have on living beings at the
place where they live.
In contrast, bioindication methods perceive the time dimension of the negative
effects of pollutants in the ecosystem and are based on the response of living beings
to the simultaneous sum (synergism) of all the influences of different environmental
factors (Das et al. 2013). Bioindication methods lead to results and conclusions
which speak of the cumulative effect of long-term influence of different (small, but
rising) concentrations of pollutants in the air, which cannot be detected by methods
of physical and chemical measurement of air pollution (Wolterbeek 2002). The bioindication method most often uses the indicator organism as a pollution-detecting
instrument. In this regard, there are two types of monitoring the response of the
organism indicator to the changed environmental conditions: passive biomonitoring
and active biomonitoring. Passive biomonitoring means monitoring organisms in
places where they are naturally present (natural habitats), while active biomonitoring involves the use of indicator organisms as transplants. Moss, lichen, or some
vascular plants can be used as indicator organisms (Balabanova et al. 2017; Aničić
Urosević et al. 2020). The best bioindicators of air quality are lichens (Loppi 2014;
Will-Wolf et al. 2015).
Lichens are symbiotic organisms made up of fungi, most commonly from the
Ascomycotina subphylum, and algae from the divisions Cyanobacteriophyta or
Chlorophyta (Nash 2008). In this structure, algae and fungi have changed so much
and lost their independence that they can no longer be found as such freely in nature.
Both members benefit from this symbiosis as they complement each other and
enable the others’ survival. The algae perform photosynthesis and supply the fungus
with organic matter, while the fungus absorbs the mineral salt-rich water from the
substrate with the help of hyphae. The exchange of matter between the algae and the
fungus is done through their cell walls. The fungi are regarded as lichen builders as
they predominate in quotative terms (Gadd 2011).
Lichens are very sensitive to the changes in air quality. They do not possess the
protective surface layer on their thallus, so the pollutants can breach the inside of the
lichen thallus uninterrupted. Lichens feed by absorbing the nutrients from the air
(water vapor) and, to a lesser extent, from the substrate. The level of lichen metabolism increases when they are in a hydrated state, so in such a state, they are more
sensitive to the quality of the air than when they are dry. The hydrated state occurs
just in time when precipitations “wash away” harmful substances from the air and
bring them to the thallus of the lichens. Lichens do not have the ability of shedding
individual body parts in the manner of which vascular plants shed their leaves, thus
getting rid of accumulated harmful substances. The accumulation of harmful substances in the thallus of the lichens is favored by the fact that lichens do not have the
ability of excretion, so whatever they adopt, it remains permanently in their bodies.
Lichens are characterized by very slow growth due to them metabolizing throughout
the year. The negative influences of harmful substances cannot be quickly remedied,
so it is possible to monitor them for an extended period of time.
S. Ristić et al.
the true effect) of the complex impact various pollutants have on living beings at the
place where they live.
In contrast, bioindication methods perceive the time dimension of the negative
effects of pollutants in the ecosystem and are based on the response of living beings
to the simultaneous sum (synergism) of all the influences of different environmental
factors (Das et al. 2013). Bioindication methods lead to results and conclusions
which speak of the cumulative effect of long-term influence of different (small, but
rising) concentrations of pollutants in the air, which cannot be detected by methods
of physical and chemical measurement of air pollution (Wolterbeek 2002). The bioindication method most often uses the indicator organism as a pollution-detecting
instrument. In this regard, there are two types of monitoring the response of the
organism indicator to the changed environmental conditions: passive biomonitoring
and active biomonitoring. Passive biomonitoring means monitoring organisms in
places where they are naturally present (natural habitats), while active biomonitoring involves the use of indicator organisms as transplants. Moss, lichen, or some
vascular plants can be used as indicator organisms (Balabanova et al. 2017; Aničić
Urosević et al. 2020). The best bioindicators of air quality are lichens (Loppi 2014;
Will-Wolf et al. 2015).
Lichens are symbiotic organisms made up of fungi, most commonly from the
Ascomycotina subphylum, and algae from the divisions Cyanobacteriophyta or
Chlorophyta (Nash 2008). In this structure, algae and fungi have changed so much
and lost their independence that they can no longer be found as such freely in nature.
Both members benefit from this symbiosis as they complement each other and
enable the others’ survival. The algae perform photosynthesis and supply the fungus
with organic matter, while the fungus absorbs the mineral salt-rich water from the
substrate with the help of hyphae. The exchange of matter between the algae and the
fungus is done through their cell walls. The fungi are regarded as lichen builders as
they predominate in quotative terms (Gadd 2011).
Lichens are very sensitive to the changes in air quality. They do not possess the
protective surface layer on their thallus, so the pollutants can breach the inside of the
lichen thallus uninterrupted. Lichens feed by absorbing the nutrients from the air
(water vapor) and, to a lesser extent, from the substrate. The level of lichen metabolism increases when they are in a hydrated state, so in such a state, they are more
sensitive to the quality of the air than when they are dry. The hydrated state occurs
just in time when precipitations “wash away” harmful substances from the air and
bring them to the thallus of the lichens. Lichens do not have the ability of shedding
individual body parts in the manner of which vascular plants shed their leaves, thus
getting rid of accumulated harmful substances. The accumulation of harmful substances in the thallus of the lichens is favored by the fact that lichens do not have the
ability of excretion, so whatever they adopt, it remains permanently in their bodies.
Lichens are characterized by very slow growth due to them metabolizing throughout
the year. The negative influences of harmful substances cannot be quickly remedied,
so it is possible to monitor them for an extended period of time.
S. Ristić et al.