DYNAMICS OF ALGAE-CORAL INTERACTIONS IN TWO BAYS OF THE SANTA MARTA REGION (COLOMBIAN CARIBBEAN) WITH A DIFFERENT DEGREE OF ANTHROPOGENIC INFLUENCE

Abstract

As a contribution to understanding the potential impact of macroalgae on coral communities, this work evaluated the presence and dynamics of algae-coral interactions in two bays of the Santa Marta region. Two stations were sampled in Chengue Bay, located within the Tayrona Natural Park, and two other in the Santa Marta Bay which is adjacent to the city of Santa Marta. Three permanent 10 m belt transects were settled at each station, at which a total of 270 coral colonies were monitored monthly. Algae - coral interactions were recorded from each colony based on five categories defined by the distance between the coral tissue and the algal mat. A total of 1956 interactions were recorded, 67% of which corresponded to direct contacts, 22% to indirect contacts, 6% to algae overgrowths and 5% to no contacts. Likewise, 58% of the interactions were with algal turfs, 27% with frondose algae, and 15% with crustose algae. There were significant differences between the two bays on the frequency of interactions only for algal turfs and frondose algae. Some seasonal changes were observed for these two groups in Chengue, while in Santa Marta the interactions were dominated all the time by algal turfs. Significant differences were recorded also between the two bays for algae overgrowth and direct contact categories. Although direct contacts were the most common at both locations, Chengue showed a light increase of overgrowths in December when interactions with frondose algae were highest. On the contrary, overgrowths were absent and direct contacts were more frequent in Santa Marta. Frondose algae was the only algal group found growing over live tissues of coral colonies.