Species interactions in soft sediments: Factors in the distribution ofNereis (Hediste) diversicolorin the Tamar estuary

Abstract

The second in a series of field experiments to determine the factors controlling the distribution of Nereis (Hediste) diversicolor (Polychaeta) in the Tamar estuary (Plymouth) was carried out over a five month period from March to July, 1985. N. diversicolor in their natural sediments were transplanted to enclosures at two tidal levels on a mudflat at the seaward end of the estuary. Treatments were arranged to detect larval N. diversicolor settlement and growth in the presence or absence of either Nephtys hombergi or epibenthic predators (crustaceans and fish), in their own or the transplant site sediments. Significant caging effects masked the role of N. hombergi as a predator of N. diversicolor, but there was evidence that epibenthic predators had an effect at lower shore levels. The organic resources of the sediments emerged as the factor most likely to account for the success of larval N. diversicolor settlement, being generally too poor at the transplant site to support this species.