Croissance de juvéniles de Nereis diversicolor nourris avec des détritus d’halophytes

The comparative effect of the uptake of fresh and degraded detritus of halophytic plants, harvested from salt marches of the Mont Saint-Michel Bay (France), on the growth of a juvenile population of the annelid polychaete N. diversicolor (L.) was studied under experimental conditions in summer 1993. Fresh and degraded detritus of Spartina anglica, Halimione portulacoides and Salicornia europeae, as well as the green algae Enteromorpha sp. were distributed separately to homogenous set of juveniles for a 75 d period. The highest growth rate was obtained for worms fed with Enteromorpha sp. Administration of fresh detritus of a given halophyte species to N. diversicolor juveniles always leads to a significantly higher growth rate than did degraded detritus. This is probably due to a great microbial biomass occurring on the fresh detritus, which is moreover, much better assimilated than the detritus they colonize.