Comparison between the sponge fauna living outside and inside the coralligenous bioconstruction. A quantitative approach

Abstract

Coralligenous habitat results from a multi-stratified accumulation of crustose coralline algae and animal builders in a dynamic equilibrium with disruptive agents. The result is a complex architecture crossed by crevices and holes. Due to this three-dimensional structure, coralligenous may host a rich and diversified fauna, more abundant than any other Mediterranean habitat. Unfortunately, very few data are available about the cryptic fauna that lives inside the conglomerate. As already reported for coral reefs, the cryptic fauna plays an important role in the exchange of material and energy between water column and benthic assemblages. Here we compare the sponge community present inside and outside the coralligenous framework of Portofino Promontory (Ligurian Sea) at different depths (15 and 30 meters) not only in terms of taxonomic diversity but for the first time also in term of biomass. Sponges present on the surface of each block were collected, weighed and identified; after blocks dissolution in HCl, target cryptic sponges were separated from other organisms, weighed, and identified. We recorded a total of 62 sponge species. The average number of sponge taxa occurring outside the coralligenous accretions is lower than the number of taxa identified inside. This pattern is confirmed also regarding sponge biomass. These results underlines that studies focused on coralligenous functioning should take in account the important contribution of cryptic fauna, as recently evidenced also for tropical reef habitats.

A Mediterranean mesophotic coral reef built by non-symbiotic scleractinians

“…Overall, from a taxonomic point of view, the MCR benthic assemblage showed a marked similarity with Mediterranean coralligenous communities. Indeed, more than 80% of the species censused here have been previously reported in the literature in relation to coralligenous communities, with large variations among different taxa (Cnidaria, 100%; Porifera, 88%; Bryozoa, 70%; Mollusca, 89%; Polychaeta, 79%) 19,42,56,59,76–79 .…”

Temporal variability of sedimentation rates and mobile fauna inside and outside a gorgonian garden

“…; Calcinai et al . ). There is an increasing interest in the characterization of the distribution of this peculiar habitat (Martin et al .…”

“…As highlighted by Ballesteros (2006), knowledge about the actual biodiversity hosted by this habitat has yet to be characterized. This lack of information has been reinforced by recent studies focusing on the diversity of Porifera (Bertolino et al 2014;Calcinai et al 2015). There is an increasing interest in the characterization of the distribution of this peculiar habitat (Martin et al 2014), but a shared monitoring approach has still not been developed yet.…”

Role of Recruitment Processes in Structuring Coralligenous Benthic Assemblages in the Northern Adriatic Continental Shelf

“…Structures of the assemblages are shaped by the growth patterns of the dominant algal species, together with lithification and biological and physical erosion processes. These habitats host the highest level of benthic species diversity in the Mediterranean Sea [ 3 ]. Given their ecological and economic importance, Mediterranean coralligenous habitats are included among the natural habitats of European Community interest, deserving the designation of special areas of conservation (European Habitat Directive, 92/43/EEC; [ 4 ]).…”