CHANGES IN EPIFAUNAL ASSEMBLAGES IN RESPONSE TO MARINA OPERATIONS ANDBOATING ACTIVITIES

A number of features of epifaunal assemblages suggest that they have t he potential to provide an excellent integrated field-based measure of marine environmental quality. In this study we have used epifaunal as semblages to investigate the ecological effects of potential gradients of environmental stress arising from marina operations and boating ac tivities. Replicate slate panels, initially colonized by solitary asci dian-dominated assemblages at a site remote from marina operations, we re placed at five sites in or near each of two boat mooring areas, Oka hu Bay boat harbour and Pine Harbour marina, in the Waitemata Harbour, New Zealand. In addition, panels were immersed at Station Bay, a site remote from marina operations and boating activities. Sites were posi tioned along putative gradients of contaminant levels (e.g. copper and zinc), as well as hydrodynamic and sedimentation regimes. The changes in assemblage structure on panels immersed at sites along these gradi ents were compared. After 3-6 months, significant differences were evi dent among the epifaunal assemblages along the gradients of environmen tal stress. the most conspicuous effect was the loss of cover. bq, the abundant and spatially dominant solitary ascidians at sites inside th e marinas. Concomitant with this loss, was a marked increase in space availability, and a small increase in the cover of sponges, hydroids, erect and encrusting bryozoans, and colonial ascidians. There were als o significant differences in assemblage structure between Pine Harbour and Okahu Bay, as well as between the marinas and Station Bay. Copyri ght (C) 1996 Elsevier Science Ltd