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)

250

300

350

400

450

500

550

15/6 15/7 15/8 15/9 15/10 15/11 15/12 15/1 15/2 15/3

Relative Variations of Water Level (cm)

4.2 Mm3

1.2 Mm3 ≈ 30%

Usable?? By whom=> Conflicts?

? Hydro. => Filing up?

Andes • Ganges • Limpopo • Mekong • Nile • Volta

1. Lakes monitoring (temperatures)

0

5

10

15

20

25

15/6 15/7 15/8 15/9 15/10 15/11 15/12 15/1 15/2 15/3

Daily Variations of Temperatures (°C)

dT (Bottom of the Lake)

dT (air)

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 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

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?

40%

50%

60%

70%

80%

90%

100%

REF PICK1 PICK2 PICK3 PICK4 PICK5

Y (%)A

D

C

BC

AB

AF= 41.643; P< 0.001

Preliminar experiments have confirmed the allelopathic potential ofCeratophyllum submersum.

Andes • Ganges • Limpopo • Mekong • Nile • Volta

4. Pesticides?

0%

10%

20%

30%

40%

50%

60%

70%

Agri Ref

Dytiscidae

Hydrophylidae

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 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’…