Aquatic mesocosms for data validation : interest, limitations and recommandations

1. Workshop ‘In situ trialing for ecological and chemical studiesin support of WFD implementation’Pau, France – 14-15 May 2008 Aquatic mesocosms for data validation : interest, limitations and recommandations Laurent Lagadic & Thierry Caquet Équipe Écotoxicologie et Qualité des Milieux Aquatiques INRA, Rennes Laurent.Lagadic@rennes.inra.fr

2. Mesocosms Definitions • Odum (1984) : "bounded and partially enclosed outdoor experimental setups ... falling between laboratory microcosms and the large, complex, real world macrocosms". • Lalli (1990) : "physically confined multitrophic and self-maintaining systems ... whose size is sufficient to enable pertinent sampling and measurements to be made without seriously influencing the structure and dynamics of the system". • Touart (1991) : "an intermediate-sized system ... that can be replicated and manipulated to test both structural and functional parameters".

3. Complexity - Realism Replicability Natural ecosystems Artificial streams Experimental ponds Enclosures Mesocosms Studies onmechanisms of toxicity(lethal and sublethal effects) Long-term global scale changesLandscape impactsBiomonitoring Studies on populations (including recovery) and between-species interactions Studies on ecological processes Identification of effect criteriaExperimental validation of tools In situ validation and definition ofbiomonitoring strategies in the field Identification of specific responses Mesocosms Definitions LABORATORY CONDITIONS OUTDOOR CONDITIONS Isolated species Simplified food-web Microcosm From Caquet et al. (1989, 2000)

4. Conditions for use of mesocosmsfor data validation • Exposure conditions • Variability - Replicability • Recovery • Effect propagation

5. Single species tests Indoor microcosms With adjuvant Application Without adjuvant No effect of the adjuvant on herbicide water concentration Exposure conditions Influence of a tank-mix adjuvant on herbicide (fomesafen) concentration in water From Jumel et al. (2002), Lagadic et al. (2007) and Coutellec et al. (2008)

6. Single species tests Indoor microcosms Outdoor mesocosms Without adjuvant With adjuvant Application With adjuvant Without adjuvant No effect of the adjuvant on herbicide water concentration Obvious effect of the adjuvant Exposure conditions Influence of a tank-mix adjuvant on herbicide (fomesafen) concentration in water From Jumel et al. (2002), Lagadic et al. (2007) and Coutellec et al. (2008)

7. Variability - Replicability From Caquet et al. (2001)

8. Variability in control mesocosms : CV = (s/x)*100 0 CV 10% -50 20% -100 40% Variation between means (%) -150 60% -200 80% -250 100% -300 1 2 3 4 5 6 7 8 9 10 11 12 Number of replicates Variability - Replicability Number of replicates needed to detect a significant reduction of one given effect criterion according to its variability in control mesocosms(t test;  = 0,05, 1 -  = 0,80) Effect of treatment -175

9. Recovery Definitions HARAP – 1999 Recovery is defined as return of a measured parameter (e.g., the abundance of a population) to the normal range of the controls. CLASSIC – 2002 “Recovery” means the return of a disturbed system to a status comparable to an undisturbed system.Recovery is possible inherently from within the system (autochthonous) or via recolonization (allochthonous). Recovery has to be used by experts to determine the "Ecologically Acceptable Concentration" (EAC) for a particular compound.

10. High Low Density Low High Stability of age structure Low High Geneticdiversity Low High Voltinism Uni- Multi- Dispersal capacity High Low Natural mortality High Low Natural stochasticity Low High Recovery Theoretical relationship between biological traits and recovery DipteransColeopteransHeteropterans Recolonisation potential EphemeropteransOdonates MolluscsCrustaceans Adapted from Kedwards (2000)

11. Open mesocosmstreated (n = 4) & untreated (n = 4) Covered mesocosmstreated (n = 4) & untreated (n = 4) Recovery Role of connectivity between static experimental ecosystems • Study design • April 22, 2003 : treatment with deltamethrin, and covering • Monitoring of effects for more than one year (April ’03 - June ’04) • Principal Response Curve (PRC) analysis of abundance data From Hanson et al. (2007)

12. In both open and covered ponds, recovery occurredafter 40 days Recovery Role of connectivity between static experimental ecosystems • Zooplankton •  Open control • Open treated  Covered treated From Hanson et al. (2007)

13. Recovery occurred after 60 days in the open mesocosms Recovery Role of connectivity between static experimental ecosystems • Benthic macroinvertebrates Recovery did not occurin the isolated ponds •  Open control • Open treated  Covered treated From Caquet et al. (2007)

14. 20 Control 0.5 µg/l 15 1.25 µg/l 5 µg/l 10 Mean cumulated number of egg-masses per snail 5 * * * * * 0 0 2 4 6 8 10 12 Weeks after treatment Effect propagation Linking levels of biological organisation Freshwater snails (Lymnaea) exposed to 3 concentrations of hexachlorobenzene (HCB)in outdoor pondmesocosms • In HCB-exposed snails : • Reduced individual growth • Increased production of eggs From Baturo et al. (1995)

15. Control 0.5 µg/l 1.25 µg/l Gastropods Cdt Weeks after treatment Effect propagation Principal Response Curve (PRC) analysisof the abundance of invertebrate taxa From Caquet (2000) (unpublished)

16. Glycogen Visceral mass Corn starch Polysaccharide hydrolysis enzyme activity(µg glucose equivalent/min/mg protein) Glycogen concentration (µg/g fresh weight) Mantle Rice starch Hours after treatment Hours after treatment Effect propagation Enhanced glycogen enzymatic breakdownin exposed snails From Baturo et al. (1995)

17. HCB Change in the structure of gastropod community Enhanced glycogenbreakdown Increase in fecundity Increase in population density Effect propagation : Linking levels of biological organisation Explanatory hypothesis Effect on CNS(dorsal bodies ?) Change in neurohormonal control of reproduction

18. Effect propagation : Linking levels of biological organisation Freshwater snails (Lymnaea) exposed to repeated applicationsof fomesafen (one concentration) in outdoor pondmesocosms From Jumel et al. (2002)

19. * * * Ovipository activity (mean cumulated number of clutches per individual) Treatments Treatments Treatments Concentration in testosterone-like (ng/ovotestis) Glycogen concentration (µg/g fresh weight) ** * * * Time (days) Time (days) Concentration in estradiol-like (ng/ovotestis) Time (days) Effect propagation Responses of energetic and hormonal biomarkers Effect on reproduction Fomesafeninhibits reproduction (decreased number of clutches, i.e. fecundity, by individual) Fomesafen induces : • enhanced glycogen breakdown • decrease of sexual steroid levels From Jumel et al. (2002)

20. Conclusions Guidance for summarizing and evaluating aquatic micro- and mesocosm studies de Jong et al., 2008 http://www.rivm.nl./bibliotheek/rapporten/601506009.pdf

21. Many thanks to the people who contributed to the acquisition of the data used in this presentation

22. Thank you for your attention