An investigation of the impacts on biodiversity and ecosystem functioning of soft sediments by the non-native polychaete Sternaspis scutata (Polychaeta: Sternaspidae)

Abstract

In recent years the non-native polychaete Sternaspis scutata has rapidly expanded its range in inshore muddy sediments along the coast of SW England (UK). To determine the impact the arrival of this moderately large infaunal deposit feeding polychaete could have on benthic biodiversity and ecosystem function, a mesocosm experiment has been conducted. Sternapsis scutata were added to undisturbed sediment cores containing natural fauna. Individuals of S. scutata were added at densities 2x and 10x the current abundance of this species at the collection site in Plymouth Sound. Nutrient fluxes and macrobenthic diversity were assessed after a period of fifty days. Despite the very large increase in biomass caused by the addition of S. scutata to the sediment cores there was no significant difference in the diversity of the resident benthic biota in treated cores. It is concluded that despite its size, the relative immobility of S. scutata dictates that its presence has little impact on the species around it. The addition of this species did significantly reduce the release of nitrite (NO 2 -) and increase the release of ammonium (NH 4 +) from the sediment. These findings support the assertion that the relationship between biodiversity and ecosystem functioning is idiosyncratic.