Search Results (3)

Stylasterid corals are known to be fundamental habitat-formers in both deep and shallow waters. Their tridimensional structure enhances habitat complexity by creating refuges for a variety of organisms and by acting as basibionts for many other invertebrates, including sponges. Porifera represent crucial components of marine benthic assemblages and, in Antarctica, they often dominate benthic communities. Here, we explore the sponge community associated with thanatocoenosis, mostly composed of dead stylasterid skeletons, collected along the Western and Northern edges of the Ross Sea continental shelf. Overall, 37 sponge species were identified from 278 fragments of the stylasterid Inferiolabiata labiata, of which 7 are first records for the Ross Sea, 1 is first record for Antarctic waters and 2 are proposed as new species. Despite the high biodiversity recorded in this and previous studies on Antarctic deep-sea communities, we are still far from capturing the true richness of Antarctic benthic assemblages. Long-term research programs designed to improve the knowledge of the deep-sea fauna inhabiting Antarctic waters are needed to support successful management and conservation plans, especially in this area, considered one of the main marine diversity hotspots worldwide. Full article

Coralligenous bioconstructions are biogenic calcareous formations developing at low irradiance on littoral rocky cliffs or on the deeper sub-horizontal bottom in the Mediterranean Sea. Unusually shallow coralligenous banks on the sandy coast of Sinuessa (Mondragone City, Gulf of Gaeta, SW Italy) were investigated. Their communities and the surrounding biogenic detritus were characterized. Geophysical and acoustic data revealed the presence of coralligenous banks between 7.5 and 15 m depth, showing constant thickness and sub-horizontal geometry, incised by sub-perpendicular channels. Sediment deposits ranging from silty sands to bioclastic gravel occur in the area. The biogenic detritus of the soft bottom sampled around the coralligenous banks is highly heterogeneous. Through the thanatocoenosis analysis of macrozoobenthos, different biocenoses were detected, among which the coralligenous and photophilic habitats are mainly represented, followed by the well-calibrated fine sands and the relit sands. A total of 16 different species and 10 epimegabenthic morphological groups (MGs) were detected on the coralligenous banks, of which 4 are included in European regulation for threatened species. The density of epimegabenthic organisms has an average of 10.34 ± 5.46 individuals or colonies/100 m². Cladocora caespitosa is the dominant species, with a height of 17 ± 5 cm. This and other structuring species (SS) were larger in size in the sampled sites than in the literature data. Overall, coralligenous had a “medium” health status, with 52% of the individuals or colonies in healthy conditions, compared to 47% with epibiosis phenomena and 1% with entanglement. Longlines were the most common anthropogenic litter, with a density of 2/100 m². Ad hoc monitoring programs and conservation measures would be desirable to protect and guarantee the well-being of these sensitive and rare shallow bioconstructions. Full article

Emerging evidence of rhodolith bed complexity and heterogeneity poses a challenge to monitoring strategies and questions about the role of abiotic factors in controlling the observed morphostructural diversity. Mollusk thanatocoenoses quickly respond to environmental conditions, expressing fidelity to biocoenosis and representing, thus, a useful ecological/paleoecological tool to unravel this heterogeneity. In this research, we studied three distinct rhodolith beds from the Tyrrhenian Sea (Italy), in a range between 40 and 100 m of water depth, together with their mollusk thanatocoenoses, sediment size, and oceanographic conditions. The beds are all heterogeneous and rarely correspond to a specific rhodolith morphotype and shape. On the contrary, the study of the associated thanatocoenoses led to distinguish at least five different assemblages within the known variability of the Coastal detritic (DC) association. DC and deep mud (VP) mollusk species dominate hanatocoenosis A, which is associated with mixed sediment and a low hydrodynamic regime. Thanatocoenosis B corresponds to an assemblage in which DC species mixed with species of adjacent vegetated bottoms in sandy sediment with a medium hydrodynamic. Thanatocoenosis C includes species related to muddy coastal detritic (DE) and offshore detritic (DL) associated with sand and a variable proportion of praline and branch morphotypes. Thanatocoenoses D and E include a wide range of detritic species (DE DC, DL) together with VP and coralligenous (C), associated with exclusive praline and gravelly sand (Thanat. D), or a mixed proportion of branch and praline and mixed sediment (Thanat. E). Our results demonstrate that the study of mollusk thanatocoenoses provides insights into the diversity within and among heterogeneous rhodolith beds. Moreover, rhodoliths, as part of the sediment, create microhabitats suitable for a wide range of mollusk species that contribute to the formation of complex thanatocoenoses. Full article