PRELIMINARY STUDY ON THE EPIPHYTIC COMMUNITY OF TRANSPLANTED POSIDONIA OCEANICA (L.) DELILE SHOOTS STUDIO PRELIMINARE DELLA COMUNITÀ EPIFITA DI FASCI TRAPIANTATI DI POSIDONIA OCEANICA (L.) DELILE

In October 2006 an experiment on Posidonia oceanica (Angiospermae) cuttings was undertaken. In March 2009, several transplanted cuttings were removed to study if the epiphytic community of transplanted shoots and autochthonous shoots seemed different. In this paper we show the preliminary results. Key-words: epiphytic community, Posidonia oceanica, restoration. Introduction In October 2006, an experiment on new materials for marine restoration with Posidonia oceanica (L.) Delile was undertaken. Several transplantation devices were placed in Cavo Bay (Elba Island), for each device about 20 cuttings of P. oceanica were taken away from the nearby natural meadow and placed overtop (Cinelli et al., 2007). Materials and methods – In March 2009, several transplanted cuttings of P. oceanica were removed to study in the laboratory the shoots’ epiphytic community and to verify if the epiphytic community of transplanted shoots and autochthonous shoots were different. In the same site at 7 m deep, 6 areas were selected at random: 3 areas in natural meadow of P. oceanica and 3 areas in the transplantation devices. In each area, 3 vertical shoots were collected at random by SCUBA diving and preserved in 4% formalin seawater until the time of examination in the laboratory. The whole internal and external faces of the two external leaves per shoot were observed utilizing a dissecting microscope and a binocular stereomicroscope. All the organisms (both animal and vegetal ones) were identified at species level where possible and the coverage for each species was expressed as percentage cover. Analysis of variance (2 way ANOVA) was used to test the hypothesis that the percentage cover of the most abundant species (percentage cover >1%) and richness of species differed between transplanted shoots and autochthonous shoots. Multivariate analysis of variance based on permutations (PERMANOVA) (Anderson, 2001) was used to test the hypothesis that epiphytic assemblages differed between transplanted shoots and authocthonous shoots. A graphical representation of multivariate patterns was obtained by non-metric multidimensional scaling (nMDS). Results A total of 34 macroalgae (7 Heterokontophyta, 3 Clorophyta, 24 Rhodophyta) and 23 sessile animal taxa (3 Anellida, 3 Foraminifera, 7 Cnidaria, 8 Bryozoa, 1 Tunicata, 1 Porifera) were found. The most abundant macroalgae species were the Phaeophyceae Ascocyclus orbicularis (J. Agardh) Kjelman and Sphacelaria sp. , the Rhodophyta Acrothamnion preissii (Sonder) E.M. Wollaston and Gayliella flaccida (Harvey ex Kutzing) T.O. Cho & L.J. McIvor; the most abundant species among the fauna were the Hydrozoa Plumularia obliqua (Johnston, 1847), the Bryozoa Electra posidoniae (Gautier, 1957), Preliminary study on the epiphytic community of transplanted P. oceanica Delile shoots 291 Fenestrulina malusii (Audouin, 1826) and Tubulipora flabellaris (O. Fabricius, 1780) and the Foraminifera. Concerning the red encrusting algae, it was very difficult to define the percentage cover of each present species (Hydrolithon boreale (Foslie) Y.M. Chamberlain, Hydrolithon cruciatum (Bressan) Y.M. Chamberlain, Hydrolithon farinosum (J.V. Lamouroux) D. Penrose & Y.M. Chamberlain, Pneophyllum fragile (Kutzing, 1843), so we defined one group (Hydrolithon-Pneophyllum spp.) which included all species of both genera (Giovannetti et al., 2006). The results showed that the macroalgal epiphytic assemblage (specific percentage cover) is more developed on transplanted shoots than on natural shoots; the result was opposite for the animal epiphytic assemblage. Concerning the epiphytic assemblage in its totality, the results highlighted that the specific richness was more abundant on transplanted shoots. ANOVA analysis showed a significant difference between natural and transplanted shoots only for Foraminifera and Electra posidoniae. PERMANOVA analysis showed a significant difference among natural and transplanted shoots and the nMDS ordination of epiphytic assemblage showed 2 separate groups. Conclusions – The results illustrated a possible difference in the structure of assemblages of P. oceanica epiphytes between natural and transplanted shoots. However, it is necessary to highlight the different shoot density in the two studied conditions. Competition for light plays an important role in structuring marine communities and there is circumstantial evidence to indicate that light is a primary factor influencing algal recruitment and growth (Trautman & Borowitzka, 1999): it is likely that the reduced shoot density of artificial meadow (20 shoots/m2) has permitted a higher irradiation on the transplanted shoots, which may have influenced the epiphytic algal community’s abundance and composition. The results obtained suggest that future studies aimed at detecting epiphytic community’s difference between natural and transplanted shoots should specifically be focused on density shoots and seasonality of sampling.