Māris kļaviņŠ, azamat azizov, JĀnis zaļoksnis environment, pollution, development: the case of uzbekistan

a – oligotrophic 
waters; b – the gradual 
accumulation of 
organic sediments and 
biological productivity 
growth; c – coastal 
overgrowth formation 
and the conversion 
of water body into 
eutrophic; d – most 
of the water body is 
overrun by sediments, 
the foreshore is 
completely overgrown; 
e – lake turns into a 
swamp.

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8. WATER POLLUTION
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Productivity
Biological diversity
Dissolved substances
Desired fish species
Low value fish species
Oligotrophic 
 
Mesotrophic 
 
Eutropic
These three main causes lead to the disintegration of the lake 
ecosystems and the loss of biodiversity in lakes as living environ-
ments, as well as the decline of the biodiversity and productivity. 
The  interrelation  of  various  organism  groups  or  organisms  – 
indicators are used for biological determination of the trophic level 
in lakes. 
To  remedy  the  consequences  of  eutrophication,  different 
methods  are  used,  but  first  of  all  the  inflow  of  biogenic  elements 
must be curbed, i.e., the change of land use as the determinant of 
eutrophication is necessary. Often the biogenic elements must be 
removed from the lake ecosystem. Deepening of the lake, sludge 
removal  is  one  of  the  effective,  albeit  extensive  and  expensive 
methods, as is the use of biological methods – mowing and removal 
of  vegetation,  change  of  species  composition  (especially  fish)  and 
intensive fishing.
The most significant signs and criteria of eutrophication are as 
follows:
 
Š
increased algae production, often more than 10 times;
 
Š
the  color  spectrum  and  turbidity  of  the  water  intensifies, 
transparency is reduced to 0.5 m and less, a depth of blue-
green algae mass silt and leach reaches more than 2 kg of 
green mass per cubic meter of water;
 
Š
loss of oxygen saturation in the deeper layers, and 
disappearance of benthic fauna and cold-water spawning fish 
species;