RECRUITMENT OF CIRRIPEDS AFTER PRESTIGE OIL SPILL Milagros PENELA-ARENAZ*, Gonzalo MACHO, Esther PÉREZ-FERNÁNDEZ and Elsa VÁZQUEZ Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo MATERIAL AND METHODS The recruitment of the intertidal cirripeds Chthamalus montagui, Balanus perforatus and Pollicipes pollicipes was studied at four locations (Segaño, Cabo Home, Couso and Caldebarcos) with different affectation level by the Prestige oil spill from February 2004 to February Caldebarcos was the heaviest oiled location, followed by Couso. Cabo Home was lightly affected and Segaño was chosen as the control site since no hydrocarbons from Prestige were detected. To study the recruitment of C. montagui and B. perforatus, fifteen 32 cm 2 plates were placed at each site (five in each mesolitoral level). These artificial substrata were collected and replaced by new ones with a monthly or fortnightly periodicity. In the case of P. pollicipes, seventy adult individuals were collected with the same periodicity to determine the percentage of adults that presented, at least, a recruit in the peduncle. Segaño Cabo Home Caldebarcos Couso Map showing study sites INTRODUCTION The most affected habitats by the Prestige oil spill are the benthic ecosystems, which have a huge biodiversity. Besides the inmediate impact, that is shown by an increase of the mortality rates by asphyxia and oil toxicity (e.g. Sanders et al., 1980), the chronic or sublethal effects can be as desvastating as the lethal ones, since they can produce a gradual change in the specific composition, abundance and diversity of the communities that can persist during years (Kennish, 1997). One of the most important sublethal effects of an oil spill is a change in recruitment patterns, which can be important as an influence on the community structure of rocky shores (e.g. Roberts et al., 1991). Recruitment is the process that establishes the patterns of abundance and distribution, while factors such as competition, predation, facilitation or disturbance modify these patterns (Menge, 2000). The specific objetive of this study is to determine if there are differences in the recruitment patterns of three species of barnacles (Crustacea Cirripedia), Chthamalus montagui Southward, Balanus perforatus Bruguiére and Pollicipes pollicipes Gmelin, in four localities with different affectation level by the Prestige oil spill. Caldebarcos Chthamalus montagui Couso Cabo Home Segaño Balanus perforatus Pollicipes pollicipes Average number (±S.E.) of C. montagui recruits per plate throughout the sampling period at the upper (----), middle (----) and lower (----) mesolitoral. Average number (±S.E.) of B. perforatus recruits per plate throughout the sampling period at the upper (----), middle (----) and lower (----) mesolitoral. Percentage (%) of P. pollicipes adults that presents, at least, a recruit in the peduncle (±S.E.) throughout the sampling period. RESULTS AND DISCUSSION REFERENCES -Kennish, M.J. (1997) CRC Press, Boca Raton, Florida. 524 pp. -Menge, B.A.(2000) Ecol. Monogr., 70: Roberts, D., Rittschof, D., Holm, E., Schimdt, A.R. (1991) J. Exp. Mar. Biol. Ecol., 150: Sanders, H.L., et al. (1980) J. Mar. Res., 38:265. (Control site) (The heaviest oiled location) (Heavy oiled location) (Lightly oiled location) Plates used to study the recruitment of C. montagui and B. perforatus. Our results pointed toward that recruitment period of C. montagui was affected by the Prestige oil spill. The recruitment period of the oiled localities (Cabo Home, Couso and Caldebarcos) at the three mesolitoral levels is during summer and autumn (June-October) and has a duration of 4-5 months. In the case of the control site (Segaño), we can differentiate between the upper and middle mesolitoral, where the recruitment is observed during 6 months, from spring to autumn (April-October), and the lower mesolitoral, in which recruits can be observed on the plates during almost all year (March-January). Highest recruitment level for C. montagui is reached at all localities during the summer, although in Segaño high values can be observed too at the lower mesolitoral in April-May and October-November. Maximum recruitment in Caldebarcos, the heaviest oiled locality, is significantly lower than in the other sites. Something similar occurs with the cumulative number of recruits over the year which is significantly lower in Caldebarcos and significantly higher in Segaño (control site) than in the other locations. The number of recruits collected throughout the year is higher at the lower mesolitoral than at the upper and middle one, except for Caldebarcos, that presents very low values at the three levels, not existing significant differences among them. In the case of B. perforatus the cumulative number of recruits over the year is significantly higher in Segaño (the control site) than in the other localities. Recruitment is only observed at the lower mesolitoral. Maximum recruitment is reached, in Segaño, during March-June and September-December, and in Caldebarcos, during September-December. In Couso and Cabo Home, there aren´t important peaks and just few recruitments were collected from March to December. Again, the cumulative number of recruits of Pollicipes pollicipes over the year is significantly higher in Segaño (the control site) than in the other locations. The recruitment patterns at the four locations are very similar. Two recruitment periods, one from February to May and another from July to February, can be clearly observed. Cumulative number of recruits of C. montagui and B. perforatus (±S.E.) collected per location. Annual percentage of P. pollicipes adults that presents, at least, a recruit in the peduncle (±S.E.) ACKNOWLEDGMENTS Project funded by “Ministerio de Educación y Ciencia” (VEM C04-02). MPA would like to aknowledge “Universidade de Vigo” for economical support. Thanks to the scientific staff of the “Estación de Bioloxía Mariña da Graña” for field assistance and to Julia Ameneiro for her help. PAHs concentrations Concentrations of the PAHs measured in the three studied species