Comparative studies on salt marsh processes: Mont Saint Michel Bay, a multi-disciplinary study

International audienceThe macrotidal salt marshes of Mont Saint Michel Bay have been intensively studied since 1990. The pioneer zone, with Salicornia sp. and Spartina anglica, corresponding to the Spartina alterniflora salt marshes of the east American coast, is restricted to a small area and has a low primary productivity. The largest part of the marsh is covered by Halimione portulacoïdes with a net annual primary productivity - aerial part - (NAPP) of up to 3600 g DW m-2 y-1.This NAPP varies considerably in space and time, on an annual basis. Preliminary results show that these salt marshes export dissolved material and import particulate matter. Stable isotopes techniques showed that if diatoms play an important role in invertebrate diet, a part of salt marsh organic matter produced by plants is used by some invertebrates such as Nereis diversicolor. Experimental studies show that this species is capable of growing and reproducing with a diet composed of H. potulacïdes and Salicornia sp. particulate detritus. Pesticides are used as markers to determine the marine area influenced by freshwater and organic matter produced in reclaimed salt marshes that were intensively farmed