Biodiversity in salt marshes: from patrimonial value to ecosystem functioning. The case study of the Mont-Saint-Michel bay

Abstract

Until 1979, European salt marshes were known only through the inventories of fauna and especially of flora. On such criteria, the salt marshes of the Mont-Saint-Michel bay (France) were regarded as most significant of the French coasts. However, it took 20 years of research on the role of these wetlands of the estuaries-salt marsh systems to highlight the ecological, social and economic interest of this ecotone, between continental and marine systems, a long time considered as territory "without value", except for stock breeders or hunters.

Does the invasive plant Elymus athericus modify fish diet in tidal salt marshes?

“…The intertidal area covers 220 km 2 and contains 180 km 2 of mud and sand flats and 40 km 2 of salt marshes. Salt marshes are drained by a dense creek system (Lefeuvre et al, 2000) and are flooded during 43% of tides when the tidal range is greater than 11.25 m. Flooding lasts on average 2 h per tide. The rest of the time the salt marsh, including tidal creeks and vegetated tidal flats, is emerged.…”

“…Salt marshes are complex ecotones between terrestrial and marine systems and are among the most productive systems of the biosphere (Lefeuvre et al, 2000). Since the introduction of the outwelling concept (Odum, 1968), which states that tidal events export detrital organic matter produced in salt marshes to marine waters, strong evidence has also indicated that the export of organic matter from terrestrial to aquatic systems supports secondary production (Loneragan et al, 1997;Kurata et al, 2001).…”

“…Since the introduction of the outwelling concept (Odum, 1968), which states that tidal events export detrital organic matter produced in salt marshes to marine waters, strong evidence has also indicated that the export of organic matter from terrestrial to aquatic systems supports secondary production (Loneragan et al, 1997;Kurata et al, 2001). Consequently, salt marshes generally have a very high conservation value, directly as a result of their species complement and because of their role as a feeding ground for migrant birds (Norris et al, 1997;Lefeuvre et al, 2000), and fish, especially juveniles (Boesch and Turner, 1984;Laffaille et al, 2001Laffaille et al, , 2002.…”

“…Because natural salt marshes dominated by Atriplex portulacoides are highly productive and provide large quantities of organic matter (from 1080 to 1990 g dry weight of net aerial primary production m ÿ2 yr ÿ1 ), they provide habitat refuges and food resources to sustain high densities of Orchestia gammarella (Lefeuvre et al, 2000). It is therefore hypothesized that the new habitat created by E. athericus is likely to reduce food resources for young fish during high tides and to disturb salt marsh trophic and consequently nursery functions.…”

Âge et taux moyen d’accrétion verticale des schorres du Saint-Laurent estuarien, en particulier ceux de Montmagny et de Sainte-Anne-de-Beaupré, Québec

“…4). En anglais, cette zone est appelée pioneer zone ou pioneer marsh (Erchinger, 1985 ;Bouchard et al, 1998 ;Dijkema, 1998 ;van Rijn, 1998 ;Lefeuvre et al, 2000). Lefeuvre (2000) a utilisé l'expression « zone pionnière » à la place de haute slikke et a reconnu l'existence de trois niveaux dans le schorre : infé-rieur, moyen et supérieur, ce qui correspond à la réalité chez nous pour les schorres naturels les plus étendus.…”