5.2 Biodiversity protection
Only by taking account of information received from the
riverside residents, it is can think indeed that impoverishment in biological
resources of the basin would be accelerated considerably with the population
increase. Also, although specifically inventories do not prove the hypothesis,
it estimates with the rhythm of current deforestation that several hundreds of
floristic and fauna species are threatened of extinction or disappear.
Face to this situation, it is pressing to protect the basin
zones being of ecological interest not only ethical but also economic. Aside,
Wouto forest classified, the complex forest of Eto-Lili in rehabilitation, some
forest gallery maintained and Bayémé Zoo restoration project in
sight by Ministry of Environment and Forest Resources, it can create in the
strongly degraded zones other forest reserves and integral surfaces protected
with participative management like Togodo and Amakpapé forests
classified respectively in the Mono and Haho basins and this by taking account
soil vocation and bordering populations daily considerations.
5.3 Fight against eutrophication
According to Ryding and Rast, fighting key is the
bio-filtration process which is efficient and consists in enhancing large
filtrating zooplankton. Amount of zooplankton filtrating needs to balance
respective phytoplankton production, which can be achieved by appropriate fish
stock management. Daphnia sp. is organism recommended for phytoplankton removal
by filtration.
Also, denitrification process through this
balance equation: NO3- -* NO2, is chemical reaction
only takes place under anoxic conditions. Thus, the bacteria employ the
NO3- as source of oxygen. Many saprophytes carry
out the process such as Micrococcus, Spirillum, Bacillus, Escherichia, and
Pseudomonas ...
Two others strategies with their methods can be using to
control and restrict eutrophication in Zio river and lake (Lac-Togo); they are:
Ecological control variable and Technological measures outline (Table 8)
below:
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Eutrophication control
|
|
Ecological control variable
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Technological/Ecotechnological measures
|
|
External nutrient-load from the
drainage basin
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* Control of point sources : sewage
treatment,
algal ponds, sewage diversion from the catchments
area,
water-saving technologies in industrial
establishments, reduction of liquid
manure losses in
animal husbandry, low P-content in detergents ;
* Control of diffuse sources : protective
zones,
proper application of fertilizers, soil stabilizing-
technical in
agriculture, afforestation, seepage
trenches, pre-dams, P-elimination plant,
reed belts,
retention basins for storm water
|
|
Internal load
from the
sediment
|
Phosphorus
|
* Hypolimnion aeration
* Injection of nitrate into the lake sediment
|
|
Nutrient
|
* lake bottom sealing *
sediment dredging
|
|
Export of nutrients by discharge
|
Deep water release (reservoirs)
|
|
Export of phosphorus into the
sediment
|
Precipitation by means of Al- or Fe-minerals
|
|
Water residence time
|
Flushing with water low in nutrients
|
|
Phytoplankton sedimentation
|
* Subdivision of the water body by baffles
* Introducing mineral substances
|
|
Zooplankton growth
|
Produce artificial feeding of zooplankton during
the lack
seasons
|
|
Zooplankton mortality
|
Reduction of zooplankton eating fish by high stocks of predacious
fish (biomanipulation)
|
Source: Ryding and Rast in «The Control of
Eutrophication of Lakes and Reservoirs»
(vol.1, 1989, USA)
| 
