Spatial and temporal variation of motile macro-invertebrate assemblages associated with Posidonia oceanica meadows

The present study assesses the spatial and temporal distribution of motile invertebrates in Posidonia oceanica meadows located off the coast of Tuscany, in the northwestern Mediterranean Sea. A hierarchical sampling design was used to evaluate changes in composition and abundance of assemblages in relation to depth and to different periods over one year. A total of 136 taxa were determined, among them 34 Mollusca, 94 Arthropoda, 5 Annelida and 1 Echinodermata. Results of both multivariate and univariate analyses showed that the macro-invertebrate assemblage structure varied along a depth gradient but this pattern was not consistent in the two study periods. Results suggest that temporal and spatial differences in the structure of P. oceanica meadows are key drivers in determining the structure of associated macro-invertebrate assemblages, as values of richness and abundance decreased with a decrease in leaf length and shoot density.Original Abstract: Ova studija procjenjuje prostorne i vremenske raspodjele pokretnih makro-beskraljesnjaka u livadama Posidonia oceanica u blizini obale pokrajine Toskana, u sjeverozapadnom Mediteranu. Hijerarhijska uzorkovanja koristena su za procjenu promjena sastava i obilja u odnosu na dubinu i na razlicita razdoblja dulja od jedne godine. Ukupno 136 svojti je utvrdeno, medu njima 34 Mollusca, 94 Arthropoda, 5 Annelida i 1 Echinodermata. Rezultati multivarijantne i Uni-varijabla analize pokazali su da je struktura makro-beskraljesnjaka kolebala po dubini gradijenta, ali ovaj uzorak nije bio dosljedan u dva razdoblja istazivanja. Rezultati ukazuju na to da su vremenske i prostorne razlike u naselju livada P. oceanica kljucni pokretaci u odredivanju strukture povezane sa sastavom makro-beskraljesnjaka, kao sto su vrijednosti bogatstva i obilja smanjene sa smanjenjem duzine lista i gustoce izdanaka.