The influence of bioturbatory macrofaunal species diversity on nematode communities

Infauna in sediments provide important physical and biogeochemical services, but are under increasing pressure from anthropogenic activities, such as benthic trawling. It is known that trawling disturbance has substantial effects on the larger benthic fauna, reducing density and diversity and altering community structure, biomass, production, bioturbation and biogeochemical processes. To investigate the mechanisms by which trawling impacts on the density of large benthic macrofauna may influence the smaller meiofauna, a mesocosm experiment was conducted in which benthic nematode communities from a non-trawled area were exposed to different densities of 7 large (>10 mm) naturally co-occurring, bioturbating species which are potentially vulnerable to trawling disturbance. The results showed that total abundances of nematodes were lower if any one of these large macrofauna species were present, but that no clear nematode community effects could be assigned to macrofauna density differences. It may be, however, that it is not the density of bioturbators that affects the nematodes, but the range of bioturbatory activity. It is interesting to consider, then, whether the diversity of bioturbators, rather than their density, may influence the associated meiofaunal communities. Here we describe results from additional treatments in which the diversity of bioturbators was manipulated.