MEPS 486:79-91 (2013)  -  DOI: https://doi.org/10.3354/meps10351

ABSTRACT: For marine organisms with complex life cycles, recruitment of dispersive propagules is highly variable in time and space, and can have important consequences for population and community dynamics. Recruitment often occurs in patches already occupied by adults that could alter its effects on communities. Using an experimental approach, we examined the effects of initial recruitment of a common bryozoan (Conopeum seurati) and barnacles in the presence/ absence of a large and abundant solitary ascidian (Pyura dalbyi) on the composition of a marine fouling community occurring on artificial substrate. The presence of P. dalbyi and different initial recruitment patterns both influenced overall community composition, but did not interact. The main effect of P. dalbyi on communities was to reduce the amount of available primary space and alter the abundance and cover of other taxa. Different initial recruitment patterns also altered the abundance of a small number of taxa, but the direction of differences was variable. There were interactive effects of P. dalbyi and initial recruitment on 2 species. When there were no initial bryozoan or barnacle recruits, the colonial ascidian Diplosoma listerianum had a higher cover without P. dalbyi than when P. dalbyi was present, but when we inoculated plates with other recruits, D. listeranium was unaffected by the presence of P. dalbyi. In the first month of community development, C. seurati colonies had an overall higher cover on C. seurati recruitment treatments than on other recruitment treatments. C. seurati also had higher colony cover on the primary space of C. seurati recruitment treatments where P. dalbyi was present than on C. seurati treatments without P. dalbyi, but there was no interaction between other recruitment/P. dalbyi treatment pairs. Differences did not persist beyond one month, or lead to overall changes in community composition. The results of this experiment suggest that any combined effects of recruitment and the presence of established adults on individual taxa are likely to be complex and may not always alter overall community composition.

KEY WORDS: Recruitment · Sessile invertebrate · Community · Ascidian · Bryozoan · Barnacle