CORAL AND MACROALGAE INTERACTIONS: DEPENDENCE BETWEEN INVOLVED SPECIES

Abstract

Macroalgae proliferation on coral reefs has been a recognized phenomenon for the past two decades and is generally entitled to the human activities on the coasts. Even thought, the role of competition in this process is not clear and it has been assumed that algae are competitively superior to corals, even when it has been demonstrated that this is not always the case. It is probable that the result of coral-macroalgae depends upon the species involved. The goal of this study was to demonstrate that there is a dependence relation between interaction category and interacting species. In order to resolve this, quantifications of interactions per category along 20 m transects were done on three representative localities at the Archipielago de San Bernardo. The results show a significant dependency between interaction category and coral-macroalgae combinations. The highest percentage of encounters at the R (overgrowth) category was that one between Halimeda opuntia, and the coral species Montastrea annularis, Porites astreoides and Porites porites, as well as this last coral with the alga Lobophora variegta. Halimeda discoidea was the macroalgae with the highest percentage of interactions on the categories CP (peripheral contact), CT (tissue contact) and NC (no contact). At the CP category, it was common to find the interactions between the coral M. annularis and the algae H. opuntia and Dictyota bartayresiana besides the interactions with the red calcareous algae group. All this have led us to conclude that the intrinsic factors, those inherent to the coral and macroalga species involved in interactions, have the potential to determine the category of interaction or the way these two benthic components relate to each other.