Comunidades coralinas asociadas al infralitoral rocoso en Santa Marta y el Parque Nacional Natural Tayrona, Caribe colombiano

The rocky shore is subjected to extreme environmental conditions, yet it harbors a great variety of organisms. In the area of Santa Marta and Tayrona National Natural Park (TNNP), numerous small coral colonies develop in the infralittoral zone of the rocky flanks (< 5 m) that apparently fail to grow into reefs, forming a transition zone towards the deeper reef in a marginal environment for coral development. This research aimed to characterize this transition zone to begin understanding the factors that limit reef development in these environments and their possible role as biodiversity reservoirs. Along a gradient of continental discharge influence from SW in Santa Marta towards NE in PNNT, in the bays of Santa Marta, Granate, Concha, Chengue, and Gayraca, band transects were marked and evaluated using photo-quadrants, to determine differences in community structure from wave exposure, type of littoral (blocks, terraces) and the position along the gradient. The infralittoral zone was dominated by macroalgae (mainly turfs, 66.4 %), followed by stony corals (24.2 %), represented by 16 species. The highest coral richness (15 species) and cover (25.3 %) were recorded on rocky blocks and in the protected sides of the bays (11 species, 24.2 %). Regarding the disturbance gradient, a higher number of species was observed at the beginning of the disturbance gradient in the bays of S. Marta (12 species) and Granate (13 species), while coral coverage was high in the central zone of the disturbance gradient (B. Concha = 41.3 %) and lowest at the extremes (Gayraca = 6.9 % and S. Marta = 12.9 %). The coral formations in the area show great variability in their coverage due to coast configuration and wave exposure; conditions that are accentuated in shallow environments. The high coral diversity in these marginal environments highlights their importance for coral diversity conservation, as they could act as refuge and/or genetic reservoir for species adapted to extreme conditions.