Impact of predation and sediment disturbance by Carcinus maenas (L.) on free-living nematode community structure

A microcosm experiment was conducted to investigate the effects of continuous and episodic biological disturbance by Carcinus maenas on estuarine nematode assemblages from sand and mud for a period of 57 days. Univariate methods of data evaluation failed to reveal major changes in community structure. Distributional techniques (dominance curves) were more sensitive in detecting changes in diversity patterns in the sand assemblage. Results of multivariate analyses indicated that nematode assemblages had changed characteristically due to biological disturbance. The observed changes in nematode community structure were the result of confounded effects of predation and modification of the sediment due to crab activity. Nematode assemblages from the organic-poor sand were mainly affected by crab predation, those from the organic-rich mud were mainly affected by changes to the sediment due to crab feeding activity. Effects of biological disturbance on both nematode assemblages were dependent on the frequency of disturbance events.