Sponges from rhodolith beds surrounding Ustica Island marine protected area (southern Tyrrhenian Sea), with a comprehensive inventory of the island sponge fauna

Caterina Longo,Frine Cardone,Maria Mercurio,Cataldo Pierri,Giuseppe Corriero,Carlotta Nonnis Marzano

doi:10.3989/scimar.04991.29a

Caterina Longo, Frine Cardone + Show 4 more

Open Access

https://doi.org/10.3989/scimar.04991.29a

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Abstract

The sponge fauna colonizing rhodolith beds from Ustica Island marine protected area was studied. Moreover, an inventory of the sponge species present along the island’s coasts was carried out for the first time. Analysis of rhodoliths trapped in nets used by local fishermen at two sites and data obtained from underwater video images were used to identify 25 sponge taxa, 22 of them at species level. The classes Demospongiae and Homoscleromorpha were present with 24 and 1 species, respectively. Most of the specimens were small-sized and represented by thick crusts or short erect branches. Few specimens were insinuating or excavating. Furthermore, qualitative sampling was performed on Ustica’s coralligenous formations, photophilous hard substrates and in marine caves, and the results obtained were added to the literature data. The overall checklist of sponges from Ustica encompassed 97 taxa, 90 named at species level, subdivided into 6 taxa of Calcarea, 3 of Homoscleromorpha and 88 of Demospongiae. Eleven of the species were endemic to the Mediterranean Sea, mainly concentrated on rhodoliths and in marine caves. This research adds a fundamental element to the knowledge of invertebrates associated with rhodoliths, and updates the checklist of sponges colonizing Ustica’s waters, facilitating its future monitoring.

Highlights

The marine habitats recently inserted in Annex 1 of the Habitat Directive (92/43/EC) include rhodolith beds (RBs), biogenic bottoms formed by free calcareous nodules mostly composed of unattached coralline algae of different species (Bosellini and Ginsburg 1971)
Analysis of rhodoliths trapped in nets used by local fishermen at two sites and data obtained from underwater video images were used to identify 25 sponge taxa, 22 of them at species level
Qualitative sampling was performed on Ustica’s coralligenous formations, photophilous hard substrates and in marine caves, and the results obtained were added to the literature data

Summary

Introduction

The marine habitats recently inserted in Annex 1 of the Habitat Directive (92/43/EC) include rhodolith beds (RBs), biogenic bottoms formed by free calcareous nodules mostly composed of unattached coralline algae of different species (Bosellini and Ginsburg 1971) This substrate, formerly known as maërl in the northeast Atlantic (Irvine and Chamberlain 1994), may have a nucleus of non-algal material (e.g. dead coral pieces, shells) and incrustations of other calcified epibionts (Horta et al 2016). The faunal component of the associated biocoenosis includes epibionts living on algal surfaces, cryptic organisms hiding in the crevices and small invertebrates exploiting the sediment pockets present within the rhodolith structure (Gondim et al 2014) Scientific interest in these environments started in the second half of the 20th century, when several researchers (Huvé 1956, Jacquotte 1962, Pérès and Picard 1964) pointed out the high species richness of the communities associated with these living substrates. In the Mediterranean Sea, the diversity of the overall associated assemblage places RBs among the richest communities, after coralligenous bottoms and Posidonia oceanica meadows (Ballesteros 2006, Sciberras et al 2009)

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