New and Previous Records of Scleractinian Corals from Clipperton Atoll, Eastern Pacific!

Clipperton Atoll was visited from 23 to 25 November 1997. A total of 109 specimens of stony corals belonging to two orders, seven families, and 15 species was collected. Five taxa of Scleractinia represent new records for the atoll: Porites lutea, Porites australiensis, Psammocora superficialis, Astrangia sp., and Balanophylliasp. With these new records and species previously reported in the literature, the total number of scleractinians now known at Clipperton Atoll is 18 species. Observations on the fossil terraces on the island and on the dead coral fauna of the inner lagoon are presented. CLIPPERTON ISLAND IS the uppermost portion of a small coral atoll (3.7 km2 [Glynn et al. 1996]) located at lO 8'N and 109°13'W, approximately 1100 km off the Mexican mainland (Sachet 1962a) (Figure 1). Because of its position it is considered the easternmost atoll in the Pacific Ocean as well as the most remote shallow-water locale in the tropical eastern Pacific biogeographic region (Briggs 1974). Clipperton is characterized by its extreme isolation, small size, and low habitat diversity, which has probably contributed to its greatly impoverished coral fauna (Glynn et al. 1996). Nevertheless, it is a welldeveloped coral atoll, possessing the characteristic features of Pacific atolls: an interior lagoon and low topographic relief of its emerged portion (Sachet 1962a, Gonzalez Avelar 1992, Emerson 1994). Few works dealing with the marine flora and fauna of Clipperton Atoll have been published. Among the most important are those about collections of invertebrates in general (Hertlein and Emerson 1957) and on taxonomy and distribution of terrestrial and 1 Manuscript accepted 19 February 1999. 2 Departamento de Ecologia Acmitica, ECOSUR, Apdo. Postal 424, Chetumal, Quintana Roo 77000, Mexico (E-mail: [email protected]). 3 Universidad Autonoma de Baja California Sur, Apdo. Postal 19-B, La Paz, Baja California Sur 23080, Mexico (E-mail: [email protected]). marine vegetation (Sachet 1962b), stony corals (Glynn et al. 1996), mollusks (Salvat and Ehrhardt 1970, Emerson 1994), brachyuran crabs (Garth 1965), fishes (Robertson and Allen 1996, Allen and Robertson 1997), and seabirds (Howell and Webb 1995). In general, it can be said that the species of the atoll are mostly American colonists, with an important component of Indo-Pacific taxa also present (Robertson and Allen 1996). In this paper, some observations and new records of stony corals from Clipperton Atoll are presented as a result of a visit to the island during the oceanographic expedition SURPACLIP-I (17 November to 3 December 1997) on board the RV El Puma, organized by the Instituto de Ciencias del Mar y Lirnnologia, Universidad Nacional Aut6noma de Mexico (Mexico City). MATERIALS AND METHODS During the SURPACLIP-I cruise, Clipperton Atoll was visited from 23 to 25 November 1997. Stony corals were collected at the "pocilloporid thicket," the "poritid zone," and along the seaward slope (zonation sensu Glynn et al. 1996) at two stations located in the northeastern sector of the atoll in which divers surveyed the reef at depths from 10 to 40 m (Figure 1). In addition, samples of corals were taken from the inner lagoon and in a series of extruded fossil terraces located