Coral reefs of Huatulco, West México: reef development in upwelling Gulf of Tehuantepec

Abstract

Numerous pocilloporid coral reef occur along lhe 26 km coastline of Huatulco, Gulf of Tehuantepec. México. Twelve species of zooxanthellate corals belonging to four genera (Pocillopora, Pavona, Porites, Psammocora) are presen! in this area with three species of pociHoporid corais Jarge!y responsible for red framework construction. Seventeen fringing reefs, with mean depths ranging from 2 to 14 rn, displayed maximum, horizontal framework dimensions rangíng from 58 x 85 m (width x lcngth) lO 283 x 355 m. Recf topographic pro files suggest that vertical framework buildups range from about 1 to 5 m. Most reef developrnent occurs in bays or along protected shores with hillocky Ol' gently sloping pocillopodd frameworks. At sorne exposed sites, 2-3 rn high surge channels dissect seaward-facing reef slopes. Sudden cooling of nearshore waters, from 24°C lo 20°C, was detected al lhe reef base (8 m) on a Huatulco reef in February 1996, during the usual upwelling season (November-April) in the GulJ of Tehuantepec. Three of 17 reefs were dead, largely in an erosional state and with high populatíon densities of Diadema mexicanum. Sexual recrujts of Pavona gigamea were abundant at the seaward reef bases of sorne dead reefs. These colonies, dominant!y 5 lo g cm high, probably began (o settle in 1989 and later, possibly in response lo newly-created substrates following widespread coral mortality during the 1987 El Niño-Southem Oscillation (ENSO) event.