Growth strategies of an abundant reef-building coral in the southern Caribbean (Undaria tenuifolia)

Abstract

The Caribbean coral community structure is changing, particularly species dominance. The Acropora die-off, at many southern and western Caribbean reefs, has allowed the branching scleractinian coral Undaria tenuifolia Dana to become one of the dominant species in these shallow reefs. In this study, colonies of U. tenuifolia were followed for a year using digital imagery. We developed a size class model that allowed us to estimate population fluctuation and growth strategies (colony growth rates and clonal processes). Growth rates varied with colony size; mid-sized colonies doubled their size in a year, while larger colonies often undergo fission. The clonal strategies, i.e., fusion and fission, allow U. tenuifolia to compensate for the low survival rates of early larval post-settlement thus being able to become a dominant coral species in the current reef scenario. The size matrix model formulated on the basis of a relative colony growth rate offered a practical approach for a short-term observation situation, generating a time- invariant transition model. Mortality patterns were not correlated to size classes and were variable by location and time. Overall, population abundance was stable over the monitored period of time. The high survivorship of U. tenuifolia after clonal fragmentation, as well as its high growth rate, suggests that this is a potential species to be cultured, which could be a solution given that this species has become the most common coral being extracted and sold as a souvenir in Cartagena, Colombia.