Laboratory experiments on the infaunal activity of intertidal nematodes

The impact of oxygen on the vertical distribution of an intertidal nematode community was investigated in a manipulation experiment with sediments collected from the Oosterschelde (The Netherlands). The vertical distribution of nematodes was examined in response to sediment inversion in perspex cores with or without the presence of an air-flushed silicone tube introducing oxygen to the bottom sediment layer. Following an incubation of 1 week, peak densities of nematodes were recorded in the deep layers of the sediment in cores with subsurface oxygenation. In contrast, this concentration of nematodes was absent in the cores that lacked bottom oxygenation and the majority of the total assemblage was still located in anoxic sediment layers. This suggests that oxidised sediments with traces of oxygen represent favourable conditions for nematodes and indicates that these nematodes are tolerant to short-term anoxia and burial. Observations on the species level suggest that oxygenation, primarily through its direct impact on geochemical properties of the sediment, may be an important factor governing the subsurface activity of nematodes. [KEYWORDS: nematodes ; vertical distribution ; estuarine sediments ; experiment - oxygen