cpwf‐v3 ecological externalities
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CPWF Volta Science Workshop: Management of Small Reservoirs for Multiple PurposesTRANSCRIPT
CPWF‐V3Ecological externalities
Ph. Cecchi (IRD G-eau)S. Sanogo (Univ. Bobo)
(logos to be added)
Andes • Ganges • Limpopo • Mekong • Nile • Volta
1. Lakes monitoring (water level)
Level and temperature loggers installation (June 2011)
4.2 Mm3
1.2 Mm3 ≈ 30%
Usable?? By whom=> Conflicts?
? Hydro. => Filing up?
Andes • Ganges • Limpopo • Mekong • Nile • Volta
1. Lakes monitoring (temperatures)
Mean depth = 2.1 mVertical Mixing sensitivity
Mechanical Buffer?
Andes • Ganges • Limpopo • Mekong • Nile • Volta
2. Ceratophyllum submersumProliferation since a couple of years
1/ Strong LOCAL preoccupation:‐ Infrastructures‐ Fishery
2/ METABOLISM consequences‐ Quality & productivity
3/ SCIENTIFIC priority‐ causes & impacts
From an ecosystem perspective, the simultaneous dominance of cyanobacteriain the phytoplankton pool (> 60%) and the invasion of water massesby huge amounts of macrophyte do point out without ambiguity
the advanced eutrophication status of the Boura reservoir.
Andes • Ganges • Limpopo • Mekong • Nile • Volta
MACROPHYTES(clear)
PHYTOPLANKTON(turbid)
BEFORENOW
WHEN?
WHY?
Both states are RESILIENT
Andes • Ganges • Limpopo • Mekong • Nile • Volta
Algae Turbidity
SedimentResuspension
Nutrients
Cerato
? Allelopathy
? Pesticides
? Hydrodynamics
? Agri. practices
? Origins
Fish? Structure
Diagnose: realized by V3 projectRemediation: support to local communities
Andes • Ganges • Limpopo • Mekong • Nile • Volta
3. Allelopathy?
Preliminar experiments have confirmed the allelopathic potential ofCeratophyllum submersum.
Andes • Ganges • Limpopo • Mekong • Nile • Volta
4. Pesticides?
Macro‐invertebrates communities exhibited contrasted patterns in agriculture‐impacted versus reference stations
Andes • Ganges • Limpopo • Mekong • Nile • Volta
4. Pesticides?
Tee shirt distributed by an agrochemical company in Ghana(Binaba, April 2011).
Commercial formulation(paraquat‐based)found in fields(Boura, March 2012).
Andes • Ganges • Limpopo • Mekong • Nile • Volta
5. Perspectives: towards chemical ecology
1/ What could be the cumulative effects (antagonism / synergy / others) of both allelopathic metabolites and phytosanitary by‐products on the aquatic productivity and diversity?
2/ What could be the effects on the growth performancesof irrigated cultures?
3/ Implementation of dedicated experiments using pesticides collectedby passive samplers (in situ), pure molecules (paraquat) and allelopathic metabolites
4/ Impacts on aquatic food web structure and on selected irrigated crops.
Output: better understanding of the nexus linking‘Agricultural Intensification’ & ‘Ecosystem Resilience’…