Characterization of North-Western Mediterranean coralligenous assemblages by video surveys and evaluation of their structural complexity

A 3D Innovative Approach Supporting the Description of Boring Sponges of the Precious Red Coral Corallium rubrum

The carbonatic scleraxis of Corallium rubrum (L.), commonly known as red coral, is often found infested by excavating sponges. These boring organisms produce galleries inside the compact axis of the coral in a variety of shapes compromising the integrity of the skeleton and reducing its commercial value. Three sponge species, already known to bore into Corallium rubrum, have been identified in colonies collected from Cape Verde Archipelago—Alectona millari (Carter, 1879); Dotona pulchella mediterranea (Rosell and Uriz, 2002); and Thoosa armata (Topsent, 1888)—together with a new species belonging to the genus Alectona and here described. SEM analysis provided evidence of the microerosion patterns of these species, confirming the presence of radial scars overlapped with the concentric ones, in T. armata. For the first time, microcomputed tomography was employed to obtain three-dimensional reconstructions of sponge excavations inside the red coral scleraxis and to estimate the eroded volume.

Testing Transplantation Techniques for the Red Coral Corallium rubrum

Corallium rubrum has been exploited by humankind for centuries. The long-term exploitation dynamics of this species make it even more important today to increase protection and restoration efforts as it provides a significant range of ecosystem services. This becomes even more important in areas where natural recovery is hindered or unlikely. So far, only very few experiments have been carried out in the past, investigating suitable techniques for the successful transplantation of this species. For this reason, a review was conducted in order to synthesize previous results and identify the most promising methodologies. Additionally, six different transplantation techniques were tested and discussed in the context of the review. Five techniques used fragments for transplantation, while one used newly settled larvae on PVC-tiles. Shallow C. rubrum colonies often grow upside down under crevices and rims as well as in caves, making the transplantation of fragments comparatively challenging. Here, C. rubrum was transplanted upside down under crevices using a PVC-grid in combination with epoxy putty to hold fragments in place, and the results indicated the potential benefits of this technique. In a novel approach, shallow colonies, and larvae on settling plates were also transferred to deeper areas, suggesting that mesophotic populations can be restored to reconstruct pre-exploitation conditions. Attaching the colonies to the roof of crevices provided a level of survivorship consistent with conventional erect transplantations of colonies on rock bottom but had the advantage of being more removed from sedimentation and anthropogenic disturbance. Future work must develop permanent grid-mounting methods for use in the crevices before this approach can be further explored for large-scale restoration efforts.

Distribution of seafloor litter and its interaction with benthic organisms in deep waters of the Ligurian Sea (Northwestern Mediterranean)

The Mediterranean Sea is one of the most polluted marine basins and currently serves as a hotspot for marine litter. The seafloor represents the ultimate sink for most litter worldwide. Nevertheless, the knowledge about litter distribution and its interactions with benthic organisms in deep water is poorly understood. In 2018, we investigated spatial patterns of macro- and micro-litter distribution, and their effects on benthic communities in the Ligurian Sea. An oceanographic survey was carried out with a remotely operated vehicle and a multibeam echosounder on seven seamounts and canyons, at depths ranging from 350 to 2200 m. High litter accumulations were discovered at the mouth of the Monaco canyon, where estimated densities of up to 3.8 × 10⁴ items km^-2 were found at 2200 m depth. The highest abundance of urban litter items was found on the soft substrate, at the bottom of the deeper parts of the submarine canyons, which seem to act as conduits carrying litter from the shelf towards deeper areas. In contrast, fishing-related items were most abundant in the upper layer of the seamounts (300-600 m depths). Furthermore, more than 10% of the observed deep gorgonian colonies were entangled by lost longlines, indicating the detrimental effects of this fishing gear on benthic habitats. The discovery of new litter hotspots and the evaluation of how deep-sea species interact with litter contribute to increasing the knowledge about litter distribution and its effects on the deep ecosystem of the Mediterranean basin. All the observations recorded in this study showed substantial and irreversible changes in the deep and remote areas of marine environments, and these changes were found to be caused by humans. Our findings further stress the need for urgent and specific measures for the management of deep-sea pollution and the reduction of litter inputs in the environment.