Temporal Variation in Cyprid Quality and Juvenile Growth Capacity for an Intertidal Barnacle

Implicit in past studies of recruitment is the assumption that all new recruits possess the same capacity for juvenile growth, and that observed variation in juvenile growth and survival is due entirely to spatial and temporal variation in food availability, magnitude of physical stresses, and intensity of competition and predation. We set out to determine if daily larval cohorts of the barnacle Semibalanus balanoides differ in mean physiological quality and, therefore, in their potential for recruiting to adult populations. To assess larval physiological quality, we measured the organic content of nonfeeding cyprid larvae attaching on five dates (10–15 d intervals) during the 1995 recruitment season. Juvenile physiological quality was determined by monitoring the growth, under controlled laboratory conditions, of individuals attaching on seven dates (3–15 d intervals) during the same season. Both cyprid organic content and juvenile growth capacity differed significantly among daily cohorts. We suggest that variation in cyprid organic content may explain previous observations of temporal variation in cyprid metamorphic success and early juvenile mortality and further suggest that variation in juvenile growth capacity contributes to differences in recruitment success of daily cohorts.