BENTHIC COMMUNITIES AND GEOMORPHOLOGY OF THE TESORO ISLAND CORAL REEF, COLOMBIAN CARIBBEAN

Abstract

The benthic communities distribution in Tesoro Island (Colombian Caribbean) coral reef was determined by cartography of reef morphology and functional groups from aerial photographstheodolite triangularon, and bottom transects over depths ranging from Oto 30 m. Tesoro Island is a sand cay reef developed over an emerged reef platform whose basal cone possibly originated by mud diapirism on the continental shelf. The benthic communities are distributed as subzones of the geomorphologic units. The reef crest lies along the breaker zone, formed by Millepora spp. buttresses covered on their tops by Palythoa spp. and seawardly by a turf of Dictyota spp. The rear reef (varying from 0.5-1.5 m in depth) is composed of pavement and grooves with live Pontes pontes and P. astreoides. The foré-reef terrace (2 to 9 m in depth) shows a low relief spur and grooves, composed of Acropora pa/mata skeletons on the windward side and A. cervicornis on the leeward side; sandy accumulations with dense and tall colonies of the gorgonaceans Pseudopterogorgia spp. are also appreciated. In the sandy reef platform there are monospecific patches of Montastraea annularis, P. pontes, M. faveolata, dead Acropora cervicornis and wide sandy zoneswhere patches of Halimedamonile are found. The slope edge, (depths ranging between 7 to >30m) shows mixed corals and gorgonaceans, at the drop-off, laminar corals, especially Montastraea franksiand Agaricia spp., jointly with other deep water organisms such as ellisellid gorgonaceans and antipatharians are found. The benthic communities distribution is influenced by reef geomorphology, wave energy diffraction and the past mass mortality of Acropora.