ADVERTISEMENTS:
After reading this article you will learn about the bio-monitoring of aquatic ecosystem and terrestrial ecosystem.
Bio-Monitoring of Aquatic Ecosystem:
Among the different ecosystems, the water bodies constitute the major types of living environment, as over seventy per cent of the planetary ecosystem is located in different types of water bodes viz. inland water ecosystems, oceanic system and estuarine ecosystems.
Each kind of aquatic system contains a large number of inorganic and organic compounds in suspended or dissolved state and with a variety of plant and animal life. All these components (chemical or abiotic and biological or biotic) exist in a dynamic equilibrium in a fixed space and time.
ADVERTISEMENTS:
Thus the pollution of water bodies invariably affects both aquatic flora and fauna. Thus the studies on this aquatic ecology involving analysis of physicochemical and biological parameters and also the complementary relationship among themselves are quietly significant.
Looking at the relationships between free living aquatic organisms, it is clear that there is a variety of organisms which are potentially present in each category of aquatic ecosystem, and that these groups differ very much by their increasing levels of organisation and morphological complexity.
Since the middle of the 19th century, freshwater biologists have been concerned with the changes where pollution conditions bring about the change in natural communities of aquatic organisms. They noticed that certain organisms shows a specific relation to the purity of water, organisms present in polluted water differ from those found in clear water.
However, Kolkwitz and Marsson (1908) made the definite breakthrough in the concept of “biological indicators of pollution” in their so-called “saprobic system”. The saprobic system is based on different zones of organism enrichment, each of which is characterised by specific plant and animal species.
ADVERTISEMENTS:
On the whole, three saprobic levels were recognised, viz. polysaprobic (a zone of reduction processes), and oligosaprobic zone (a zone of oxidation processes). Subsequently after years of research, a number species were identified as a marker of different saprobic zones (Table 12.1).
During the past couple of decades, many limnologists suggested a couple of methods for application of saprobic systems. A few selective algal indices assessments were also employed for water quality monitoring. For instance, Nygaard (1949) proposed five indices to evaluate the organic pollution of various water bodies on the basis of algal indices.
These indices have been developed on the basis of the fact that various algal groups have differential tolerance to organic pollution and nutrient enrichment. The Nygaard’s algal indices computation system is shown in Table 12.2.
Similarly, Palmar (1969) also attempted to use algae in pollution index preparation on the basis of studies of about 60 algal genera with 60 species. But in recent years, several other types of diversity and similarity indices were attempted for assessment of water quality.
Some commonly used similarity and diversity indices are shown in Table 12.2. Some commonly used diversity and similarity indices are presented in Table 12.3. The advantages of these indices in bio-monitoring purpose are many-fold, though there are a number of limitations too (Table 12.4).
On the whole, among the aquatic organisms—algae (planktonic and benthic), micro-invertebrates, molluscs and to some extent fishes are good water quality indicators. For a considerable period these indicators were being used for water quality assessment in rivers, reservoirs and lakes.
However, for selection of each indicator species category the following criteria should be considered:
1. The species must be highly susceptible to pollution stress:
2. The species must be easily recognisable and must have wide distribution pattern:
ADVERTISEMENTS:
3. The species should be easily sampled:
4. The species should have low genetic and biological variability; and
5. The species should preferably be known from previous ecological or physiological studies.
Bio-Monitoring of Terrestrial Ecosystem:
In terrestrial system, air and soil quality can also be monitored by using indicator organisms. Since the mid-nineteenth century, botanists have been aware of the sensitivity of lichens to urban environment. The degeneration of epiphytic industrial areas was first noticed by Nylander (1866). Thereafter a number of scientific studies were carried out with respect to the sensitivity of lichens to air pollutants.
ADVERTISEMENTS:
In recent years, biologists have given much attention to the use of sensitive plants like lichens, moss, and angiosperms in air pollution bio-monitoring due to their known sensitivity to gaseous pollutants and particulate matter. From lichen frequency analysis the index of atmospheric purity (IAP) was measured in urban environment.
With such IAP data or frequency of species occurring at various sites, air pollution map can be prepared. Such types of study were carried out in several countries over the years. Pollution zonation in Haldia industrial town or in Calcutta city was attempted by Santra and Mitra, (1992).
It is interesting to note the fact that urban traffic flow has significant correlation with the frequency of occurrence of lichen (Table 12.5). Thus the indicator values of several species are very reliable and also useful for air quality mapping.
Soil biota shows a wide diversity, and the occurrence of soil biota in terms of diversity and density is very important for soil quality monitoring. Soil mites, microarthopods and earthworm etc., have special utility value in terms of fertility and toxicity.
