The vertical distribution of the meiofauna has already been related to many structural aspects of the environment. The most important factor, that is mentioned before, is oxygen, as all other environmental factors are influenced by the oxygen supply to the sediment. This is a case study, from a station along the Belgian coast (790) and a station in the Westerschelde (W022), in which the vertical distribution of meiobenthos is related to the biogeochemistry. Emphasis has been made on the specific distribution of the nematodes genera. Samples were taken in a period with high organic input and a period with low organic input. As station 790 is characterised by a well oxidised, coarse sandy sediment, all parameters showed less steeper gradients in comparison with those in station W022. Station W022 consists of a fine, silty sediment with a much thinner oxidised layer. As a responce to the higher microbial activities in summer, the highest densities of specific nematodes genera were found in the surface layers of the sediment, for both stations. This shift towards the upper layers in June, was extremely accentuated in station W022 and tended to be species specific: only Sabatieria species could survive, and had even their highest abundance in the anoxic 'subsurface' (3- 4 cm). Out of Spearman rank correlations and Canonical Correspondence Analysis, it can be concluded that feeding sources (algae), besides redox potential are "important structuring forces in the coarse sandy station (790), while the oxic/anoxic state of the sediment is the most important determining factor in the fine silty sediment (W022). |
