PROCESSES AFFECTING NEWLY-SETTLED JUVENILES AND THE CONSEQUENCES TO SUBSEQUENT COMMUNITY-DEVELOPMENT

Processes affecting the growth and mortality of the juvenile benthic l ife-stages that immediately follow larval metamorphosis and settlement are as important as those processes controlling the supply of settlin g larvae or later interactions among established adults. In addition, the ecology of juveniles is often distinctly different from that of ot her life-stages, including differences in interactions with predators and competitors and responses to the physical environment. In particul ar, newly-settled stages often experience quantitatively or qualitativ ely different predation than older life-stages. We have documented thi s in a New England hard substrate community where the wrasse, Tautogol abrus adspersus, and two species of tiny gastropods, Mitrella lunata a nd Anachis lafresnayi, prey on newly-settled and juvenile ascidians bu t not on adults. An extensive series of field experiments was conducte d using artificial pilings placed subtidally. Results demonstrated tha t (1) the predators were extremely active and fairly specific in their prey, (2) predators could eliminate prey species regardless of settle ment densities, (3) predation varied drastically with life-stage, and (4) predators control community structure and composition by altering the number of settling larvae that survived their first several weeks to become identifiable recruits. Because of differences in predator ab undances the development and species dominance within the community va ried drastically between sites.