CPWF‐V3 Ecological externalities

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CPWF Volta Science Workshop: Management of Small Reservoirs for Multiple Purposes

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CPWF‐V3 Ecological externalities

  1. 1. CPWF‐V3Ecological externalities Ph. Cecchi (IRD G-eau) S. Sanogo (Univ. Bobo) (logos to be added)
  2. 2. 1. Lakes monitoring (water level)Level and temperature loggers installation (June 2011) Usable? ? By whom 4.2 Mm3 => Conflicts? ? Hydro.  => Filing up? 1.2 Mm3 ≈ 30% Andes • Ganges • Limpopo • Mekong • Nile • Volta
  3. 3. 1. Lakes monitoring (temperatures) Mean depth = 2.1 m Vertical Mixing sensitivity Mechanical Buffer? Andes • Ganges • Limpopo • Mekong • Nile • Volta
  4. 4. 2. Ceratophyllum submersum Proliferation 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 cyanobacteria in the phytoplankton pool (> 60%) and the invasion of water masses by huge amounts of macrophyte do point out without ambiguity  the advanced eutrophication status of the Boura reservoir. Andes • Ganges • Limpopo • Mekong • Nile • Volta
  5. 5. Both states are  RESILIENT NOW BEFORE WHEN?MACROPHYTES PHYTOPLANKTON (clear) (turbid) WHY?Andes • Ganges • Limpopo • Mekong • Nile • Volta
  6. 6. ? Pesticides Algae Turbidity ? Agri. practices ? Allelopathy Cerato ? Origins Nutrients ? Hydrodynamics Sediment Fish Resuspension ? Structure Diagnose: realized by V3 project Remediation: support to local communities Andes • Ganges • Limpopo • Mekong • Nile • Volta
  7. 7. 3. Allelopathy? Preliminar experiments have confirmed the allelopathic potential of Ceratophyllum submersum. Andes • Ganges • Limpopo • Mekong • Nile • Volta
  8. 8. 4. Pesticides? Macro‐invertebrates communities exhibited contrasted patterns in  agriculture‐impacted versus reference stations Andes • Ganges • Limpopo • Mekong • Nile • Volta
  9. 9. 4. Pesticides? Tee shirt distributed  Commercial formulation by an agrochemical  (paraquat‐based) company in Ghana found in fields (Binaba, April 2011). (Boura, March 2012). Andes • Ganges • Limpopo • Mekong • Nile • Volta
  10. 10. 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 performances of irrigated cultures? 3/ Implementation of dedicated experiments using pesticides collected by 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’… Andes • Ganges • Limpopo • Mekong • Nile • Volta

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