DISTURBANCE OF BENTHIC INFAUNA BY SEDIMENT-REWORKING ACTIVITIES OF THE LUGWORM ARENICOLA-MARINA

The influence of the lugworm Are nicola marina on the abundance of other benthic species was studied in the westernmost part of the Wadden Sea. Small squares (1 m2) within depopulated 144-m2 plots were recolonized with various (naturally-occurring) lugworm densities (0-10-20-40-80 and 0-25-50-75-100 per m2). These plots were sampled during the summer. Lugworms were found to have a strongly negative effect on the densities of C. volutator. At 0-density lugworms, the numbers of C. volutator were high. These were halved at 17 lugworms per m2 (i.e. the mean density on the tidal flats of the Dutch Wadden Sea), and were further reduced at higher lugworm densities (e.g. 20% remained at 40 lugworms per m2). Laboratory observations of Corophium behaviour in the presence of Arenicola suggest that sediment-reworking lugworms stimulate Corophium to emigrate. Effects of lugworms on other benthic species were also studied in the same way. Lugworms were found to have strongly negative effects on the juvenile densities of various worm and bivalve species (Nereis diversicolor, Nephtys hombergii, Heteromastus filiformis, Scoloplos armiger, Pygospio elegans, Capitella capitata and Mya arenaria, Cerastoderma edule, Macoma balthica, Angulus tenuis, respectively).