CHOICE
BIO-MONITORING PARAMETERS?
STRUCTURAL COMPONENTS
The aquatic ecosystem consist several components
as shown in Fig.2. Almost all these components are affected directly or indirectly
by pollution. For evaluation of water quality only some of these components can
be used fruitfully as bio-monitoring parameters. The planktonic organisms in a
river system cannot be used as indicator of water quality. They are generally
not native of the place of their collection due to their passive movement I flowing
waters. CPCB during development and testing of bio-monitoring methodology along
with Duch experts has established the fact after a three-year exercise on Yamuna
River. The bethic macro-invertebrates were found to be best suitable among all
other living systems present in aquatic ecosystem due to the following facts:
- Visible
to the unaided eye;
- Stretches
having different quality support diverse macro-invetebrate communities;
- Taxonomy
is well developed;
- Sampling
and observations comparatively easy;
- Provide
good experimental possibilities;
-
Useful in assessing the impact of municipal, industrial, oily and agricultural
wastes; and
- Community
response is sensitive to organic loading, substrate alteration and toxic pollution
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On the contrary,
the only disadvantage is that quantitative sampling is sometimes difficult. Under
the Indo-Duch Project, on development of bio-monitoring methodology, several methods
for evaluation of bethic macro-invertebrates were tried and the following two
methods finally adopted:
Sequential
comparison:
The method involves a pair wise comparison of sequentially encountered individuals,
and the differences of two specimen which can easily be observed up to the species
level whereon taxonomic skill is required. When the next observed animal is different
from the last one, a new run starts. The diversity is the ratio of the total number
of organisms encountered. The ratio thus obtained (diversity) has a value between
about 0 and 1. High diversity of benthic animals always supports a good quality
of water.
BMWP (Bio-Monitoring Working Party) Site Score:
This method involves a qualitative inventory of the presence of local macro-invertebrate
benthic fauna up to the family level of taxonomic precision. All possible families
having saprobic indicator value are classified on a score-scale of 1 to 10 according
to their preference for saprobic (oxygen availability)) water quality. The score-class
1 families are mainly occurring in water bodies with a high oxygen demand, whereas
the score-class 10 families are restricted to water bodies with low oxygen demand.
There are 7 intermediate score classes. The saprobity scores of all families registered
are averaged to produce site score.
FUNCTIONAL COMPONENTS
During water quality monitoring of the Yamuna, it was observed that there is a
significant change in diurnal concentration of dissolved oxygen is a function
of photosynthesis, respiration and diffusion. Odum, the noted ecologist, has developed
a method for measurement of photosynthesis and respiration based on diurnal change
in dissolved oxygen. He also proposed a system of classification pf waters according
to level of saprobity or eutrophication. When evaluated, this system worked very
well in the Yamuna river and subsequently in the in the Tungbhadra, the Chaliyar
and the Damodar rivers. The findings of all the three approaches were used in
the yardstick as explained in the following paragraphs.
