INDIRECT MEASUREMENT OF THE BIOMASS OF NE MATODES FROM THE SUBTIDAL MEIOBENTHOS OF THE ENGLISH-CHANNEL

Three subtidal stations in the English Channel were used to compare bi ovolume techniques versus direct weighting for calculating nematode bi omass : two fine-sand stations, station 1, Pierre Noire, and station 2 , Bale de Seine, and a coarse-sand station, station 3, Trezen Vraz. Co nformity was found between biomass values computed from Wieser's formu la and direct weighting only at station 2. Mean individual dry weigth by direct weigthing was 0,45 mu g for station 1, 0,76 mu g for station 2 and 0,43 mu g for station 3. Two morphotypes appeared at the two fi ne-sand stations and only one at the coarse-sand station. Size spectra at station 1 showed species assemblage with density and biomass peaki ng at 0,5 - 1 mm. These peaks moved towards high size class at station 2. Station 3 displayed density and biomass curves cumulating at the 0 ,5 - 1 mm and 1 - 2 mm size classes, respectively. Nematode size and m orphology being different for the three stations, mean individual biom ass has thus to be determined for each individual community.