Flow modifies the effect of biodiversity on ecosystem functioning: an in situ study of estuarine sediments

The effect of flow and biodiversity on ecosystem functioning was investigated in an estuarine system using in situ benthic chambers. Macrofaunal communities were artificially assembled to manipulate both species richness and functional trait richness. In addition, naturally occurring communities were sampled in order to determine the effect of macrofaunal and sediment disruption. Ecosystem functioning was assessed by measurement of nutrient release (NH4-N) from the sediment, a process essential for primary production. Natural and assembled communities were found to differ significantly, demonstrating the effect of experimental manipulation on the system. Flow was found to have a highly significant effect on ecosystem functioning in both natural and assembled communities in treatments containing macrofauna. No significant difference between static and flow treatments was found in macrofaunal-free controls, indicating that flow generates an effect through promoting changes in bioturbatory activity of the infauna causing greater disruption to the sediment. In assembled communities, functional richness significantly increased ecosystem functioning. Species richness had no influence in assembled communities. (C) 2002 Elsevier Science B.V. All rights reserved.