• Energy Research

AbstractTheMediterranean hydrozoan fauna (Siphonophora excluded) comprises 400 species; most (68%) occur in theAtlanticOcean, 20% are endemic to theMediterranean, 8% are ofIndo‐Pacific origin, and 4% are non‐classifiable. There are 69 nonindigenous (NIS) species in the basin: 44% of these are casual (recorded just one or very few times), 28% established (widely recorded in the basin), 6% invasive (establishedNISthat are able rapidly or largely to disseminate away from the area of initial introduction, having a noticeable impact on the recipient community), and 22% questionable (of doubtful taxonomic status). Entry through theSuez Canal and range expansion through theGibraltarStrait, often enhanced by ship traffic, appear to be the main processes for recent species introductions, but uncertainties remain for manyNIS. Species additions immediately result in larger local or regional species pools, but the newcomers might impact on populations of native species, altering extinction probabilities. A more reliable evaluation of the species pool can be accomplished by adding new species when they enter the taxonomic record (i.e. the records of any taxon in all types of literature), and by removing species that have not been found for a ‘reasonable’ time (e.g. several decades). Of the 400 non‐siphonophoran hydrozoan species known to occur in theMediterraneanSea, positive records in the last 10 years are available for 156 species (39%), whereas records of the remaining 244 species are older than a decade: 67 species have not been recorded for 41 years, 13 for 31–40 years, 79 for 21–30 years, and 85 for 11–20 years.

The aim of this research is to set a successful strategy for engaging citizen marine scientists and to obtain reliable data on marine species. The case study of this work is the bearded fireworm Hermodice carunculata, a charismatic species spreading from the southern Mediterranean probably in relation to global warming. To achieve research objectives, some emerging technologies (mainly social platforms) were combined with web ecological knowledge (i.e., data, pictures and videos about the target species published on the WWW for non-scientific purposes) and questionnaires, in order to invite people to collect ecological data on the amphinomid worm from the Adriatic Sea and to interact with involved people. In order to address future fruitful citizen science campaigns, strengths and weakness of each used method were illustrated; for example, the importance of informing and thanking involved people by customizing interactions with citizens was highlighted. Moreover, a decisive boost in people engagement may be obtained through sharing the information about citizen science project in online newspapers. Finally, the work provides novel scientific information on the polychete’s distribution, the northernmost occurrence record of H. carunculata in the Mediterranean Sea and new insights on predatory behavior on other living benthic species.

In the Mediterranean Sea, as well as in other parts of the word, intense bottom trawling threatens deep and mesophotic assemblages, compromising mainly the survivorship of erect organisms and of the habitat complexity they shape. Protection of species able to affect their habitats, by increasing spatial complexity and enhancing interspecific interactions, is crucial for biodiversity conservation. It is urgent to highlight the occurrence of those species which act as ecosystem engineers and/or habitat former to enhance awareness on their ecological role and to develop focused conservation strategies. Lytocarpia myriophyllum is the largest Leptomedusan hydroid of the Mediterranean Sea, with colonies up to 1 m high, and the most abundant Aglaopheniid in the eastern part of the North Atlantic Ocean. This species creates wide forests on soft bottoms stabilizing sediments, providing refuge and food for several other associated organisms and could be defined both a habitat former and an ecosystem engineer. Thanks to trimix diving here we report on new insights on the morphological, biological and ecological features of L. myriophyllum meadows from the Mediterranean Sea furnishing a baseline for protection plans focused on these facies. This work demonstrates that direct studies of mesophotic habitats allow to collect far more detailed information than grabs, ROVs, or towed camera arrays and highlights the urgent need to redefine the vertical extension of several marine protected areas.

The patchy distribution pattern of benthic hydrozoans reflects high sensitivity of colonies to local and micro-scale environmental factors, which may affect the outcome of biodiversity inventories based on different sampling methodologies. We compared three quantitative sampling methods for benthic hydrozoans, differing for strategy (scraping standardized surfaces or picking visually located colonies) and tactics (extension of examined surface). Each of the three methods consisted of eight replicate samplings to compare relative and absolute method efficiencies, also in terms of minimum sampling area representative of the hydroid diversity in the study site. A single horizontal belt transect on a vertical rocky cliff was chosen at 15 m depth near Otranto (South Adriatic). A total of 37 species were identified by the three methods and their relative abundances were evaluated. The hydroid assemblage was dominated by generalist species with high polyp numbers able to colonize different substrata. We compared the outcomes of each of the three sampling methods, and by a cost-benefit analysis we identified the optimal sampling methods to be adopted according to the different targets of the investigations. On data standardized to the same total sampled areas, the three sampling methods did not originate significant differences in the number of polyps of each recorded species (PDA, Polyp Detection Ability), whereas the visually-oriented collection (VIS) and the scrapings over 20x20 cm standard surfaces (S20) were more effective in the detected number of species (SDA, Species Detection Ability) than over 10x10 cm squares (S10). For ecological purposes, samplings based on five S20 replicates can be considered an appropriate experimental design to get a statistically robust representation of the studied hydroid assemblage at Punta Palascia. However, variation in depth, exposure and geographical locations may require different sampling approaches, and pre-surveys should be always carried out before addressing taxonomical surveys of sessile organisms.

Massive outbreaks are increasing all over the world, which are likely related to climate change. The North Adriatic Sea, a sub-basin of the Mediterranean Sea, is a shallow semi-closed sea receiving high nutrients inputs from important rivers. These inputs sustain the highest productive basin of the Mediterranean Sea. Moreover, this area shows a high number of endemisms probably due to the high diversity of environmental conditions and the conspicuous food availability. Here, we documented two massive mortalities (2009 and 2011) and the pattern of recovery of the affected biocoenoses in the next two years. Results show an impressive and fast shift of the benthic assemblage from a biocoenosis mainly composed of slow-growing and long-lived species to a biocoenosis dominated by fast-growing and short-lived species. The sponge Chondrosia reniformis, one of the key species of this assemblage, which had never been involved in previous massive mortality events in the Mediterranean Sea, reduced its coverage by 70%, and only few small specimens survived. All the damaged sponges, together with many associated organisms, were detached by rough-sea conditions, leaving large bare areas on the rocky wall. Almost three years after the disease, the survived specimens of C. reniformis did not increase significantly in size, while the bare areas were colonized by fast-growing species such as stoloniferans, hydrozoans, mussels, algae, serpulids and bryozoans. Cnidarians were more resilient than massive sponges since they quickly recovered in less than one month. In the study area, the last two outbreaks caused a reduction in the filtration efficiency of the local benthic assemblage by over 60%. The analysis of the times series of wave heights and temperature revealed that the conditions in summer 2011 were not so extreme as to justify severe mass mortality, suggesting the occurrence of other factors which triggered the disease. The long-term observations of a benthic assemblage in the NW Adriatic Sea allowed us to monitor its dynamics before, during and after the mortality event. The N Adriatic Sea responds quickly to climatic anomalies and other environmental stresses because of the reduced dimension of the basin. The long-term consequences of frequent mass mortality episodes in this area could promote the shift from biocoenoses dominated by slow-growing and long-lived species to assemblages dominated by plastic and short life cycle species.

The majority of Hydrozoa is represented by not readily noticeable, small species. In recent decades, however, taxonomic knowledge of the group has increased worldwide, with a significant number of investigations focused on the Mediterranean Sea. Over more than two decades, 115 species of hydrozoans were recorded from coastal waters along nearly 300 km of the Salento Peninsula (Apulia, Italy). For each species, records from different collections were merged into single sheets of a general database. For each species, the following information is reported: description, cnidome, biology, occurrence in Salento, worldwide distribution, and bibliography. Descriptions refer to the benthic hydroid stage and, when present, also to the planktonic medusa stage. The 115 species of Hydrozoa, recorded along the Salento coastline, represent 25% of the Mediterranean Hydrozoa fauna (totaling 461 species), and nearly 3% of 3,702 world's known species covered in a recent monograph. Four species are non-indigenous, three of them with invasive behavior (Clytia hummelincki, Clytia linearis, and Eudendrium carneum), and one species now very common (Eudendrium merulum) in Salento. The complete life cycle of Clytia paulensis (Vanhöffen, 1910) is described for the first time. 

Lytocarpia myriophyllum, the biggest hydroid of the Mediterranean, lives at soft bottoms. It is severely threatened by bottom trawling activities. To assess its possible influence on trophodynamics and biodiversity of surrounding sediments, we compared the organic matter content and biochemical composition, and meiofaunal biodiversity in sediments below L. myriophyllum colonies and in surrounding bare sediments. Below L. myriophyllum sediments, the protein to carbohydrate ratio, the lipid contents and meiofaunal abundance showed values higher than in bare sediments, suggesting that L. myriophyllum may influence the availability of resources for benthic consumers. The richness of meiofaunal taxa and nematode species generally decreased from below the colonies to bare sediments suggesting that the presence of L. myriophyllum colonies can have a certain influence also on benthic biodiversity. The possible influence of L. myriophyllum on trophodynamics and biodiversity of neighbouring soft bottoms claims for ...