Marine Soft-Bottom Community Establishment Following Annual Defamation: Larval or Adult Recruitment?

Abstract

Recolonization, following annual summer defaunation of a large-area1 soft-bottom community in Hillsborough Bay, Tampa, Florida, USA was investigated to determine whether adult or larval recruitment was primarily responsible for reestablishing the community. Two quantitative sampling designs were employed: (1) Samples of the natural bottom were collected one month after each defaunation during 1975. 1976 and 1977, and washed through a 500 pm sieve; (2) containers of azoic sediment were placed and collected weekly during a 10-week period immediately following the 1978 defaunation, and washed through a 250 pm sieve. The weekly samples contained almost all newly settled larvae, (99.7 VD), while the monthly samples contained only 41 O/O newly settled larvae. Whether the community was established by adult or larval settlement appeared to be taxon specific. Polychaetes and molluscs were mostly present as newly metamorphosed larvae. Amphipods, cumaceans and flatworms were initially present as adults. The discrepancies in the results stem from differences in methodologies of the two designs. The conclusion follows that methodologies must be tailored to the specific question posed, and that in this study, the majority of the initial comnlunity was established by larval rather than adult settlement.