ABSTRACT: Priapulids are potentially important in structuring soft-bottom communities in temperate and arctic regions, and this study is a first attempt to evaluate their importance in zoobenthic communities. Halicryptus spinulosus is an important component of the zoobenthos of the northern Baltic Sea. It is competitive in harsh environmental conditions as it can withstand hypoxia and hydrogen sulphide. The natural food selection of H. spinulosus consists mainly of detritus (62 to 68% of the stomach contents) and 10 infaunal categories (the amphipod Monoporeia affinis and other crustaceans being most frequent). The effects of H. spinulosus on both meio- and macrofauna were studied experimentally. Significant negative effects were found for both meiofauna (nematodes and total abundance) and macrofauna (Manayunkia aestuarina, oligochaetes and total abundance). The effects on recruitment (mainly larval Macoma balthica) were also significant. In the field, total abundance and the number of nematodes were also significantly reduced by the presence of H. spinulosus. The effects of H. spinulosus on other fauna is suggested to be a consequence of predation in combination with disturbance.

KEY WORDS: Halicryptus spinulosus · Priapulida · Meiofauna · Macrofauna · Macoma balthica · Recruitment · Predation · Disturbance

Published in MEPS Vol. 163 (1998) on March 12
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1998