Colonisation of newly-opened habitat by a pioneer species, Alvinella pompejana (Polychaeta: Alvinellidae), at East Pacific Rise vent sites

Abstract

Animal communities on the walls of deep-sea hydrothermal chimneys are distributed in mosaics of patches that may evolve as local environmental conditions change and biological interactions develop. Alvinella pompejana Desbruyères et Laubier, 1980 is one of the first metazoan colonisers of new surfaces created by mineral precipitation, and therefore may be particularly important in community establishment in active parts of smokers. Here our goal was to investigate the colonisation mechanisms of A. pompejana in new patches and determine whether these mechanisms may influence population structure and reproductive patterns in this species. We deployed a series of TRAC (Titanium Ring for Alvinellid Colonisation) devices at East Pacific Rise (EPR) vent sites to compare the size and stage (i.e. reproductive maturity) distribution of A. pompejana individuals between recently colonised patches (TRACs) and established patches (grabbed by submersible). TRACs deployed for short time periods (11 d to 1 mo) were generally colonised by smaller individuals than those found in background populations or in TRACs deployed for longer time periods (>1 mo). Colonists into new patches were a mix of juveniles and individuals that were sexually mature but non-reproductive (i.e. not producing gametes), whereas background population and older patches harboured a mixture of individuals at different stages including reproductive females. Although some individuals may have recruited on TRACs as larvae, the major colonisation process involved was probably immigration of post-larval stages. In long-term TRAC, reproductive females were not reproductively synchronised. In this dynamic environment, reproduction would be triggered by the disturbance/migration processes, explaining the heterogeneity observed in reproductive patterns.