Importance of top-down and bottom-up processes as divers of meiobenthic assemblage structure
A large part of the world’s species diversity is to be found in soils and sediments. This high biological diversity already becomes manifest at small spatial (= local) scales, and raises two fundamental ecological questions. The first deals with the functional implications of diversity. It is now well-established that changes in species composition, distribution and abundance can strongly influence various aspects of ecosystem functioning. The second question inquires after the mechanisms which structure such diverse communities. This involves ‘historical’ aspects like speciation and evolution, but also – and especially – those mechanisms responsible for the assembly of communities where multiple species with seemingly similar ecological roles coexist. Indeed, local diversity is strongly affected by biological interactions including predation, competition and facilitation, and by interactions between organisms and their environment.
In spite of several claims that meiofauna play an important role in benthic carbon fluxes, their trophic position and functioning remain poorly understood. This at least partly results from a limited understanding of the feeding ecology of most species. Mouth morphology, for instance, points at a predatory feeding behavior of a variety of nematode species, but only recently it has been demonstrated and quantified the predatory role of few marine nematode species using a combination of natural stable isotope ratios of N and C and dedicated laboratory experiments what enables a better understanding of population dynamics in the field. Here we investigate how trophic and ‘indirect’ interactions influence the diversity and functioning of the meiobenthic assemblage.