Colonization of Bryozoa on seagrass Posidonia oceanica ‘mimics’: biodiversity and recruitment pattern over time

Abstract

Artificial rhizomes (‘mimics’) mimicking Posidonia oceanica natural rhizomes were used to study colonization and successional patterns of bryozoan species over a 1-year period in a meadow off Ischia Island (Tyrrhenian Sea). Investigation of succession patterns at 3-, 6-, 9-, and 12-month intervals showed that the number of species and abundance increased significantly throughout the period, with Disporella hispida and Puellina hincksi as the most abundant species, both as earlier colonizers and dominating as late species. Succession occurred through progressive but not significant changes in species diversity. Seasonal recruitment pattern analyzed every 3 months over the 1 year reported that on the whole 84% of the species were in common with those found on mimics after the 3-, 6-, 9-, and 12-month immersion periods. April–July, corresponding to water temperature increase, was the period during which a significantly high number of species and diversity were found. The significantly high number of colonies per mimic found in the October–January period was mainly due to a recruitment peak of D. hispida. About 63% of the bryozoan species growing on natural rhizomes sampled in the P. oceanica meadow were in common with those settled onto mimics after 1 year of immersion, thus indicating the role of the surrounding assemblages as the basic pool of colonizers. Results suggest that more than 1 year would have been necessary to reduce differences between mimics and natural rhizomes in term of species dominance.