Late in summer 2003, extensive mass mortality of at least 25 rocky benthic macro-invertebrate species (mainly gorgonians and sponges) was observed in the entire Northwestern (NW) Mediterranean region, affecting several thousand kilometers of coastline. We were able to characterize the mortality event by studying six areas covering the main regions of the NW Mediterranean basin. The degree of impact on each study area was quantified at 49 sites by estimating the proportion of colonies affected in populations of several gorgonian species compared with reference data obtained in years without mortality signs. According to these data, the western areas (Catalan coast and Balearic Islands) were the least affected, while the central areas (Provence coast and Corsica-Sardinia) showed a moderate impact. The northernmost and eastern areas (Gulf of Genoa and Gulf of Naples) displayed the highest impact, with almost 80% of gorgonian colonies affected. The heat wave of 2003 in Europe caused an anomalous warming of seawater, which reached the highest temperatures ever recorded in the studied regions, between 1 and 3 degrees C above the climatic values (mean and maximum). Because this exceptional warming was observed in the depth ranges most affected by the mortality, it seems likely that the 2003 anomalous temperature played a key role in the observed mortality event. A correlation analysis between temperature conditions and degree of impact seems to support this hypothesis. Under the present climate warming trend, new mass mortality events may occur in the near future, possibly driving a major biodiversity crisis in the Mediterranean Sea

In the late summer of 1999, an extensive mortality of gorgonians and other epi‐benthic organisms was observed in the Ligurian Sea (Mediterranean Sea) from the Tuscan Archipelago to Marseille. Quantitative data from Tino Island and Portofino Promontory indicated that the proportion of affected gorgonians ranged from 60% to 100% in populations having a density of 9–27.8 colonies m−2, suggesting that millions of sea fans died along the coast of Liguria. This mass mortality episode coincided with a sudden increase of sea water temperature down to more than 50 m depth. Laboratory analyses showed that the colonies stressed by high temperature also underwent extensive attack by microrganisms (protozoans and fungi), which are interpreted as opportunistic pathogens.

Mass mortality events of benthic invertebrates in the temperate north-western (NW) Mediterranean Sea have been observed in recent seasons. A 16 month in situ study in the Ligurian Sea (NW Mediterranean Sea) demonstrated that the occurrence of Paramuricea clavata mortality episodes were concomitant to a condition of prolonged high sea surface temperatures, low chlorophyll concentrations and the presence of culturable Vibrio spp. in seawater. The occurrence of Vibrio spp. at the seasonal scale was correlated with temperature; with few vibrios retrieved on specific media when the temperature dropped below 18 degrees C and a sharp increase of vibrios abundance (up to 3.4 x 10(4) MPN l(-1)) when the temperature was greater than or equal to 22 degrees C. Phylogenetic and phenotypic analysis of Vibrio isolates associated with healthy and diseased P. clavata colonies collected during a mortality episode showed that these bacteria were significantly more abundant in diseased than in healthy corals and were related to the V. harveyi, V. splendidus and V. coralliilyticus groups, the latter only identified in diseased organisms. Inoculation of bacterial isolates from these groups onto healthy P. clavata in aquaria caused disease signs and death in a range of Vibrio concentrations, temperature values and trophic conditions consistent with those recorded in the field. It is concluded that Vibrio infections may act as an additional triggering mechanism of mass mortality events in the coastal Mediterranean Sea and that their occurrence is climate-linked. Predicted global warming leading to long-lasting hot summer periods together with stratification resulting in energetic constraints represent a major threat to the survival of benthic invertebrates in the temperate NW Mediterranean Sea due to potential disease outbreak associated with Vibrio pathogens.

Marine sponges (phylum Porifera) are a diverse, phylogenetically deep-branching clade known for forming intimate partnerships with complex communities of microorganisms. To date, 16S rRNA gene sequencing studies have largely utilised different extraction and amplification methodologies to target the microbial communities of a limited number of sponge species, severely limiting comparative analyses of sponge microbial diversity and structure. Here, we provide an extensive and standardised dataset that will facilitate sponge microbiome comparisons across large spatial, temporal, and environmental scales. Samples from marine sponges (n = 3569 specimens), seawater (n = 370), marine sediments (n = 65) and other environments (n = 29) were collected from different locations across the globe. This dataset incorporates at least 268 different sponge species, including several yet unidentified taxa. The V4 region of the 16S rRNA gene was amplified and sequenced from extracted DNA using standardised procedures. Raw sequences (total of 1.1 billion sequences) were processed and clustered with (i) a standard protocol using QIIME closed-reference picking resulting in 39 543 operational taxonomic units (OTU) at 97% sequence identity, (ii) a de novo clustering using Mothur resulting in 518 246 OTUs, and (iii) a new high-resolution Deblur protocol resulting in 83 908 unique bacterial sequences. Abundance tables, representative sequences, taxonomic classifications, and metadata are provided. This dataset represents a comprehensive resource of sponge-associated microbial communities based on 16S rRNA gene sequences that can be used to address overarching hypotheses regarding host-associated prokaryotes, including host specificity, convergent evolution, environmental drivers of microbiome structure, and the sponge-associated rare biosphere.

The twilight or mesophotic zone is amongst the less explored marine regions. In coastal areas, investigations and manipulative experiments on benthic biodiversity and ecosystem functioning at depths up to [50 m have been recently made possible by the progress of SCUBA techniques. In this study, we tested the effects of the presence of a gorgonian forest characterised by a large and dense population of the gold coral Savalia savaglia (Bertoloni 1819) on the benthic biodiversity (nematode species richness, and meiofauna community structure and richness of taxa), trophic guilds state (molluscs) and ecosystem functioning in the surrounding sediments. The S. savaglia colonies create elevated and complex tertiary structures. Our results indicate that the presence of these colonies was associated with a significantly increased deposition of bioavailable substrates and enhanced biodiversity, when compared with soft bottoms at the same depth but without gold corals. The higher biodiversity and altered trophic conditions resulted in higher rates of ecosystem functioning (e.g., higher benthic biomasses). These results suggest that S. savaglia should be particularly protected not only for its specific rarity, endemism and vulnerability but also because it has a prominent role in sustaining high levels of biodiversity and ecosystem functioning in the surrounding benthos of the twilight zone.

1. The analysis, by means of line transects, of a Paramuricea clavata (Anthozoa: Gorgonacea) population forming a facies of the Mediterranean coralligenous community along the Portofino Promontory (Ligurian Sea, Italy) evidenced a high per cent of lesions inflicted to the gorgonian coenenchyme by anchoring and fishing activities.  2. This damage favours the development of aggregates of epibionts (mainly hydroids and bryozoans) which leads to greater mechanical stress through increased resistance of the colonies to water movement; where polychaetes and nematodes colonize the denuded skeleton, their burrowing activity weakens the colony.  3. In situ tissue regeneration experiments suggested that aggregation of epibionts can develop only if the injuries result, from continuing abrasion.  4. Injuries caused by anchoring and fishing can therefore be considered the major cause of mortality of Paramuricea clavata in the Portofino Promontory.  5. Paramuricea clavata re‐colonizes experimentally denuded areas slowly and colonies take many years to reach the size of existing individuals and can be damaged easily by fishing and anchoring.  6. Special protection is needed for this key species of Mediterranean coral at Portofino Promontory, which is proposed as a Natural Marine Park. © 1997 John Wiley & Sons, Ltd.

Sponges (phylum Porifera) are the phylogenetically oldest metazoan animals, their evolution dating back to 600 million years ago. Here we demonstrate that sponges express ADP-ribosyl cyclase activity, which converts NAD ؉ into cyclic ADP-ribose, a potent and universal intracellular Ca 2؉ mobilizer. In Axinella polypoides (Demospongiae, Axinellidae), ADP-ribosyl cyclase was activated by temperature increases by means of an abscisic acid-induced, protein kinase A-dependent mechanism. The thermosensor triggering this signaling cascade was a heat-activated cation channel. Elucidation of the complete thermosensing pathway in sponges highlights a number of features conserved in higher organisms: (i) the cation channel thermoreceptor, sensitive to heat, mechanical stress, phosphorylation, and anesthetics, shares all of the functional characteristics of the mammalian heat-activated background K ؉ channel responsible for central and peripheral thermosensing; (ii) involvement of the phytohormone abscisic acid and cyclic ADP-ribose as its second messenger is reminiscent of the drought stress signaling pathway in plants. These results suggest an ancient evolutionary origin of this stress-signaling cascade in a common precursor of modern Metazoa and Metaphyta.A DP-ribosyl cyclase activity is expressed along the phylogenetic tree from unicellular protists (1) to mammals (2). It converts NAD ϩ to cyclic ADP-ribose (cADPR) (3), an intracellular calcium mobilizer that is being increasingly recognized as a pivotal signaling molecule, involved in such diverse functions as cell cycle regulation (1) (protists), oocyte fertilization (4) (invertebrates), insulin secretion (5), and cell proliferation (6) (mammals). The peculiar position of Porifera in the phylogenetic tree [they are the oldest known Metazoa, sharing a common ancestor with all multicellular animals (7)] and the presence of signaling pathways in these organisms (8) prompted us to investigate the presence, and the functional role, of the ADPribosyl cyclase͞cADPR system in marine sponges. Materials and MethodsSponges. Sponges were collected in the Ligurian Sea (Mediterranean Sea), at Gallinara Island (Genova, Italy) at a depth between 35 and 45 m. The temperature was maintained at 14°C during transfer of the animals to the lab. They were kept in an aquarium in natural seawater (SW) at 14°C for 5-7 days before utilization. All procedures involving sponge tissue were performed at 14°C. As the most ancient and simple metazoan animals, sponges lack a defined tissue organization. Cells are embedded in a collagenous matrix, impregnated with siliceous or calcareous spicules, surrounding a complex network of internal canals, through which water circulates. Intact sponge cells (Ϸ8 m diameter) could be easily obtained by gentle squeezing of cleanly cut Axinella polypoides fragments. Cell viability, as checked microscopically, was always Ն95% after mechanical dissociation and after exposure of the cells to heat stress or abscisic acid (ABA).HPLC and Fluorimetric Assays of Enzymatic A...

Marine bioconstructions are biodiversity-rich, three-dimensional biogenic structures, regulating key ecological functions of benthic ecosystems worldwide. Tropical coral reefs are outstanding for their beauty, diversity and complexity, but analogous types of bioconstructions are also present in temperate seas. The main bioconstructions in the Mediterranean Sea are represented by coralligenous formations, vermetid reefs, deep-sea cold-water corals, Lithophyllum byssoides trottoirs, coral banks formed by the shallow-water corals Cladocora caespitosa or Astroides calycularis, and sabellariid or serpulid worm reefs. Bioconstructions change the morphological and chemicophysical features of primary substrates and create new habitats for a large variety of organisms, playing pivotal roles in ecosystem functioning. In spite of their importance, Mediterranean bioconstructions have not received the same attention that tropical coral reefs have, and the knowledge of their biology, ecology and distribution is still fragmentary. All existing data about the spatial distribution of Italian bioconstructions have been collected, together with information about their growth patterns, dynamics and connectivity. The degradation of these habitats as a consequence of anthropogenic pressures (pollution, organic enrichment, fishery, coastal development, direct physical disturbance), climate change and the spread of invasive species was also investigated. The study of bioconstructions requires a holistic approach leading to a better understanding of their ecology and the application of more insightful management and conservation measures at basin scale, within ecologically coherent units based on connectivity: the cells of ecosystem functioning.