Does primary colonization or community structure determine the succession of fouling communities?

Abstract

Predicting the relevance of initial colonization and subsequent species interactions for succession in marine sessile communities is difficult because the effects of both factors depend on highly variable environmental processes (e.g. currents, topography, upwelling and others). Depending on the successional stage at which a new species arrives, it can either rapidly colonize in large numbers or its colonization success might be suppressed by resident species. In order to assess the roles of (i) initial colonization and (ii) subsequent species interactions on community development, we examined the succession of fouling assemblages that established on artificial substrata during two different seasonal periods, i.e. austral winter/spring and spring/summer. At 16. weeks of age communities that were initiated in different seasons varied significantly in composition and diversity. During each period (winter/spring and spring/summer), multispecies fouling consortia of different ages (hereafter termed "old" and "young") were reciprocally transplanted between two neighbouring study sites and their succession was documented. After 8. weeks of transplantation communities of different ages maintained their differences in diversity even in the face of environmental change. However, during winter/spring the spreading of the dominant species P. chilensis caused more rapid convergence between all communities at both sites. During the spring/summer period, the high initial abundances of the weak competitor Bugula neritina led to the maintenance of differences between resident and transplanted assemblages within each site. Later colonizers, including the dominant competitor P. chilensis, however, could recruit onto B. neritina and started to spread in the communities. These results suggest that the early and intermediate succession of fouling communities in highly productive marine environments such as the Humboldt Current System is driven by the temporal and spatial variability of propagule supply, while the long-term stability of these communities depends on the identity of colonizers and their competitiveness. © 2010 Elsevier B.V.