Species pool structure explains patterns of Antarctic rock-encrusting organism recruitment

Abstract

Understanding the population dynamics of benthic communities is impossible without understanding the processes related to their initial development, including recruitment. In polar areas, encrusting organisms, such as bryozoans, polychaetes, sponges and ascidians, are amongst some of the most species-rich and abundant groups of macrofaunal organisms, yet knowledge about their ecology is far from being complete. In this study, by investigating established encrusting assemblages and recruitment onto experimental substrate, we examine the level of similarity between adult populations and newly recruited assemblages in the polar realm. This study was conducted during the austral summer of 2010–2011 in Maritime Antarctica at King George Island (62°S, 58°W) at two locations contrasting in their biological and physical conditions. Despite the small distance (~3 km) between the two study sites, the local species pools (species composition, numerical abundance) differed significantly and had a great influence on the observed recruitment pattern. The species composition of new recruits overlapped with that of nearby assemblages at all examined locations. The dominance structure was also identical, with bryozoans being the major component of these assemblages. The numbers of species and individuals in the newly recruited communities and local resident assemblages were also strongly correlated. The obtained results suggest that the recruitment of encrusting fauna in the Antarctic can be very localized and occurs in close vicinity to adult populations.