MEPS 189:181-193 (1999)  -  doi:10.3354/meps189181

ABSTRACT: Benthic mesocosm experiments have highlighted the importance of bioturbation in maintaining levels of diversity and setting community structure in subtidal macrobenthic assemblages. In the mesocosm facility of the Norwegian Institute for Water Research (NIVA) at Solbergstrand, Norway, partitioned boxes of sediment were subjected to continuous disturbance through bioturbation for a period of 20 wk. The effect of type and intensity of bioturbation on the macro-infauna was examined by exposing different partitioned areas to different bioturbating species at different densities. The 3 test macrofauna species used were the bivalves Nuculoma tenuis (subsurface deposit feeder) and Abra alba (surface deposit/suspension feeder) at 3 different densities, and the heart urchin Brissopsis lyrifera (subsurface burrowing deposit feeder) at a single density. The presence of N. tenuis at low densities resulted in significantly higher levels of α and β diversity than were observed in the undisturbed or highly disturbed treatments. Previous experiments have shown that B. lyrifera also elicits a response in the associated fauna consistent with the 'intermediate disturbance hypothesis'. Such a response was not observed in the A. alba treatments. Multivariate data analysis demonstrated that the response of the associated fauna was influenced by the identity of the organism causing the disturbance. It was also evident that different elements of the community responded differently to bioturbation. This paper makes comparisons between the responses of macrofauna and meiofauna to bioturbation. Our experimental results suggest that the identity, density and distribution of large bioturbating organisms are important factors in the structuring of infaunal communities and in setting and maintaining levels of diversity in apparently homogeneous areas.

KEY WORDS: Diversity · Disturbance · Bioturbation · Macrofauna · Meiofauna · Nuculoma tenuis · Abra alba · Brissopsis lyrifera