The concept “lagoon” is well accepted in vernacular Latin languages

1. Biodiversity and ecosystem functioning in coastal lagoons; special reference to microbial communitiesRutger de WitUMR 5119 CNRS & Université Montpellier II "Ecosystèmes lagunaires". Case 093, Place Eugène Bataillon, F-34095 Montpellier Cedex 05, France e-mail: rde-wit@univ-montp2.fr

2. Lagoons are shallow water bodies separated from the ocean by a barrier, connected at least intermittently to the ocean by one or more restricted inlets, and usually oriented shore-parallel Kjervé 1994, adapted from Pritchard - Phleger The concept “lagoon” is well accepted in vernacular Latin languages Lagoon = Laguna (Sp, I), Lagoa (P), Lagune (F), - Etang, Bassin (F), Albufera (E), Sabkah (evaporative env) Barrier =Cordon littoral (F, E), Lido (I) Inlets =Grau (F, I), les passes (F), Gola (Sp, Mar Menor) Nonetheless, most North American scientific literature uses term “estuary” when coastal lagoon is more appropriate; e.g., Laguna Madre, Lake Pontchartrain, Waquoit Bay

3. Bassin d’Arcachon Mesotidal lagoon (2-4 m tidal range) on average 3 m (1,9 – 4,9 m) (180 km2) 155 km2 of which 40 km2 subtidal Tidal prism = 200-400 106 m3 Annual Fresh water input = 1200 106 m3 Brenta bernicla (40 000 in winter) photo P.J. Labourg Oysterculture Prairies of Zostera noltii (70 km2)

4. 1960 1977 1990 The shore of the Bassin d’Arcachon Has been heavily urbanised during the last decades (data Conservatoire du Littoral)

5. Classical approach – biodiversity: Biodiversity Environmental conditions

6. How to explain biodiversity? -> How to manage coastal lagoons to conserve biodiversity? αandβ biodiversity β biodiversity: different habitats - importance of habitat conservation (maintenance of gradients, mosaics and ecotones) αbiodiversity: coexistence - ecological theory Niche assembly rules (most often microbiological tradition) Neutral theory (current version Hubbell, 2001)

7. Most microbiologists adhered to the paradigm: Everything is everywhere, but, the environment selects (Baas-Becking, 1934) This statement implicitly rejects the neutral theory, which is based on assuming biogeographical patterns and stochasticity Lourens G.M. Baas-Becking Currently this statement is questioned in the microbiological community and the study of biogeography of micro-organisms is a developing field of research

8. Resource competition and coexistence (I): Competitive exclusion – and “the paradox of the plankton” (G.E. Hutchinson, 1961) In microbiology: use of continuous cultures Since the 80’s (Taylor and Williams 1975, Gottschal & Thingstad, 1982, Tilman, 1982)stable coexistence of two competing specieswhen competing for two limiting resources has been observed and predicted. -> idea: number of limiting substrates = number of potentially coexisting species at equilibrium

9. Resource competition and coexistence (II): Patchiness of resources and fluctuating resource supply allow to increase the number of coexisting species (Van Gemerden, 1974; Turpin et al., 1979) Intermediate Disturbance Hypothesis (Connell, 1978) Long stable conditions allow competitive exclusion and favour K-strategists Disturbance create new conditions for r-strategists Disturbance creates patchiness and fluctuations

10. Resource competition and coexistence (III): number of limiting substrates = number of potentially coexisting species at equilibrium Huisman & Weissing (2001) found that when 3 or more substrates are limiting then in many cases equilibrium is not achieved Deterministic chaos.

11. Theory of multiple stable states (Scheffer & Carpenter) - Lakes Van de Koppel et al. (2001). Do multiple stable states occur in natural ecosystems? Evidence from tidal flats. Ecology 82: 3449 - 3461. Mussel beds Multiple stable states can generate mosaic structures in a spatial setting -> thus contribute to creating -biodiversity

12. Comparing biodiversity of bacteriaplancton in two lagoons (Benlloch et al., 1995) Bassin d’Arcachon Etang de Prévost Arcachon Prévost The 16S rRNA gene clone libraries (50 sequences for each) show higher taxonomic diversity for Prévost (8 lineages) than for Arcachon (5 lineages)

13. The 16S rRNA gene clone libraries (50 sequences for each) show higher redundancy for Arcachon than for Prévost The 100 sequences had been retrieved and amplified directly from the environment – not 1 corresponded to cultured strains isolated from these lagoons

14. Zostera noltiimeadows in theBassin d ’Arcachon

15. Macro-algal proliferation Etang de Prévost - Sacca di Goro

16. bacteria Macro-organisms Arcachon Prévost Biodiversity Eutrophication Do bacteria behave differently along the eutrophication gradient?

17. Spending some efforts: New Bacteria and Archaea can be isolated from many environments Table 1: Novel bacterial and archaeal species isolated from sediments in the Bassin d’Arcachon. ______________________________________________________________________ Desulfospira joergensenii(Finster et al, 1997a)*)- sulfate-reducing bacterium Desulfocapsa sulfoexigens(Finster et al, 1998)*)- sulfur-reducing bacterium Sulfospirillum arcachonense(Finster et al, 1997b)*)- S disproportionating bacterium Desulfubacula IO2801 and IO2802(Bourguès, 1996)!),- sulfate-reducing bacteria Desulfovibrio strains A1 and A28(Cifuentes, 2003) !)- sulfate-reducing bacteria Cytophaga strain A25(Cifuentes, 2003) £)- fermenting bacterium Mesophilic Crenarchaeota(Cifuentes, 2003) ______________________________________________________________________

18. 16 S rRNA sequences of Bacteria retrieved from sediments (Cifuentes et al., 2000) Sediment communities dominated by δ – proteobacteria (most sulfate reducers)

19. 16 S rRNA gene Phylogenetic tree Sulfate-reducing bacteria ISOLATE 1 ISOLATE 2 Acetate (+ - N) Lactate (- N) Fructose (+ -N) "Desulfovibrio caledoniensis" 85 100 Desulfovibrio dechloracetivorans 100 Desulfovibrio aespoeensis 100 Desulfovibrio profundus 62 Desulfovibrionaceae Desulfovibrio bastinii 99 95 Desulfovibrio zosterae 88 Desulfovibrio salexigens 87 100 Desulfovibrio gigas Desulfovibrio gabonensis 99 Desulfomicrobium apsheronum Desulfomicrobium baculatum 100 90 Desulfuromonas thiophila 100 Desulfuromonas acetoxidans Desulfonema limicola 86 99 Desulfonema ishimotoei 85 Desulfosarcina variabilis Desulfobacula phenolica 100 Desulfobacteriaceae 97 Desulfobacula toluolica Desulfospira joergensenii 100 Desulfobacter postgatei 73 Desulfobacter latus 99 Desulfobacter halotolerans 100 Acinetobacter baumannii Thiobacillus hydrothermalis 100 Halobacterium salinarum 0.05

20. Novel approach – biodiversity and ecosystem functioning Classical approach – biodiversity: Ecosystem - functioning Biodiversity Environmental conditions Manipulated Biodiversity Promoted by D. Tilman (grass prairies), first work using bacteria Naeem et al., 2000

21. Theoretical predictions of relation between biodiversity and a selected ecosystem function (competition models) Sampling effect Niche differentiation These models neglect possible positive interactions (amensalism, mutalism, facilitation)