IMIS

In laboratory, one sediment core was subsampled by means of 3 cut-off plastic syringes (2.7 cm I.D., surface area of 5.72 cm2, 0-10 cm top sediment) in order to obtain three pseudoreplicates. The nematodes (38–1000 mm) were extracted from sediment subsamples by sieving each pseudoreplicate and by centrifuging the material retained by a 38 μm mesh net with Ludox HS-40 (density of 1.15–1.18 g cm−3). For each pseudoreplicate, 100-120 nematodes were randomly picked out using a fine pin under a stereomicroscope (Zeiss Discovery V20, magnification 40×), transferred from formalin to glycerol through a series of ethanol-glycerol solutions and finally mounted on permanent glass slides in anhydrous glycerin. Nematodes were identified under a microscope (100x magnification) at the genus level using dedicated pictorial and identification keys.