Effects of adult infauna on new recruits: implications for the role of biogenic refuges

Abstract

Abundances of many macrofaunal species are enhanced around biogenic structures, yet some species show a reduced survival around such structures. High densities of macrofauna occur around the tubes of Diopatra cuprea (Bosc), but successful recruitment of the bivalve Mulinia lateralis (Say) is inhibited by high post-settlement mortality. Laboratory experiments were conducted to test the effects of two polychaetes, Nereis succinea (Frey and Leuckart) and Streblospio benedicti (Webster), on the survival of newly-recruited Mulinia lateralis. In the field these polychaetes are abundant around Diopatra cuprea tubes and rare in the same habitat when tubes are absent. Recently metamorphosed Mulinia lateralis were added to azoic sediment cores in the laboratory which contained 0, 1×, 2× or 4× field densities of either Nereis succinea or Streblospio benedicti. Survival of Mulinia lateralis in treatment cores ranged from 29 to 70% in control cores and both Nereis succinea and Streblospio benedicti were found to reduce survival of the bivalve. These results suggest that, in the field, Diopatra cuprea indirectly modify the environment by altering local fauna which then inhibit the recruitment of some taxa.