Posidonia Oceanica Beds Research Articles

Areas of spatial overlap between common bottlenose dolphin, recreational boating, and small-scale fishery: management insights from modelling exercises.

Sustainable management requires spatial mapping of both species distribution and human activities to identify potential risk of conflict. The common bottlenose dolphin (Tursiops truncatus) is a priority species of the European Union Habitat Directive, thus, to promote its conservation, the understanding of habitat use and distribution, as well as the identification and spatial trend of the human activities which may directly affect populations traits, is pivotal. A MaxEnt modeling approach was applied to predict the seasonal (from April to September) habitat use of a small population of bottlenose dolphins in the north-western Sardinia (Mediterranean Sea) in relation to environmental variables and the likelihoods of boat and fishing net presence. Then, the overlapping areas between dolphin, fishing net and boat presence were identified to provide insights for the marine spatial management of this area. Three of the main factors influencing the seasonal distribution of bottlenose dolphins in the area are directly (boating and fishing) or indirectly (ocean warming) related to human activities. Furthermore, almost half of the most suitable area for dolphins overlapped with areas used by fishing and boating. Finally, relying on fishing distribution models, we also shed light on the potential impact of fishing on the Posidonia oceanica beds, a protected habitat, which received higher fishing efforts than other habitat types. Modelling the spatial patterns of anthropogenic activities was fundamental to understand the ecological impacts both on cetacean habitat use and protected habitats. A greater research effort is suggested to detect potential changes in dolphin habitat suitability, also in relation to ocean warming, to assess dolphin bycatch and the status of target fish species, and to evaluate sensitive habitats conditions, such as the Posidonia oceanica meadow.

Benthic Fish Communities Associated with Posidonia oceanica Beds May Reveal the Fishing Impact and Effectiveness of Marine Protected Areas: Two Case Studies in the Southern Tyrrhenian Sea

The effectiveness of a Marine Protected Area (MPA) is strongly related to its zoning design, management, and surveillance, and fish communities are considered indicators of conservation effects. Posidonia oceanica beds and fish assemblages were studied here to evaluate the fishing impacts and the effectiveness of the Marine Protected Areas (MPAs) of Santa Maria di Castellabate (SMC) and Costa degli Infreschi e della Masseta (CIM) in the South Tyrrhenian Sea, Italy. P. oceanica characteristics were estimated counting and collecting shoots, while fish communities were investigated by visual census. Multivariate analyses were performed to detect differences in fish assemblages among the MPA protection levels and seagrass characteristics. Significant differences in fish communities were observed between the depth and protection levels. The latter are probably due to the zoning design at SMC, which does not allow a spillover effect, and to fishing activities, as showed by the ABC curve results. Trophic analyses suggested the use of longlines at SMC, due to the dominance of planktivorous fish species, and of trammel nets at CIM, due to the great heterogeneity of the fish trophic groups. Shoot density and leaf length were significantly correlated with fish communities. CCA analyses showed omnivorous species, mostly belonging to the Sparidae family, correlated with the highest shoot densities, with their feeding habits mostly directed to crustaceans, while macro- and microinvertivores, mainly belonging to the Serranidae and Labridae families, correlated with the highest leaf lengths, where they sough shelter and feed. In conclusion, the data suggest that a zoning redesign at SMC and an increase in the surveillance of fishing activities at CIM might enhance the effectiveness of these MPAs, highlighting the role of fish community studies in identifying MPA efficiency issues and providing trustful guidelines for their management.

Marine mollusk thanatocoenoses along the coasts of the San Pietro Island (South-Western Sardinia): a first reasoning on species composition and biodiversity

We conducted a study on the taxonomic composition and diversity of thanatocoenoses of marine mollusks sampled at five sites on a circum-Sardinian island (San Pietro Island, South-Western Sardinia). The aim was to measure the differences in terms of biodiversity by analyzing shells >2 mm. We collected 71 taxa (level of diversity γ) at five different sites. Four species represented more than half of the sample: Bittium reticulatum, Glans trapezia, Lucinella divaricata and Truncatella subcylindrica. We observed a high difference in the number of taxa (level of diversity α) between sites (range: 18-41; after normalization using the Margalef index: 9.45-15.84). The turnover of β-diversity between low-energy sites was lower than that among high-wave energy sites; low-energy wave sites located near shallow and extensive Posidonia oceanica beds showed the highest values of diversity metrics. Climatic factors related to wave energy (exposure to prevailing West winds) and the presence of Posidonia oceanica beds could explain the diversity patterns. Although our diversity analysis conducted across mollusk thanatocoenoses may show some methodological weaknesses (the storage and accumulation time of the shells; the uncertainty regarding the taxonomy based exclusively on shells and the relative importance of the living populations in front of the sampling sites), we suggest that this "proxy" approach could allow for a rapid first assessment of the conservation status of coastal and marine ecosystems (i.e. Posidonion oceanicae habitat) when sampling time is short and there are several areas to explore.&nbsp

The use of remote sensing for monitoring Posidonia oceanica and Marine Protected Areas: A systemic review

Posidonia oceanica is a priority habitat (Habitat Directive 92/43/CEE) that needs to be protected by conservation tools such as Marine Protected Areas (MPAs). Remote Sensing (RS) is a useful tool allowing for mapping seagrass meadows and other important marine habitats. In this study, we explore the global scientific literature on RS applied to both P. oceanica and MPAs tracking its evolution and trends by applying network analysis to bibliometric science. The software VOSviewer was used to create maps based on network data of scientific publications displaying relationships among authors and countries. In addition, specific keywords were used to explore the co-occurrence of different terms characterizing the application of RS in marine science. Results showed that France is the main country publishing on RS applied to Posidonia oceanica while Pergent Gerard and Pergent-Martini Cristine resulted the top authors. The co-occurrences analysis highlighted that RS is primarily used for seagrasses mapping, while few studies are focused on their monitoring. Furthermore, investigating RS in connection with MPAs the main country resulted Australia while the top author was Andrefouet. The network map of keywords showed that RS is widely applied to MPAs to study coral reefs and their biodiversity and for mapping marine ecosystems. The use of RS for monitoring Posidonia oceanica beds and MPAs resulted a poorly explored research area, probably due to the low resolution of available data determining large scale habitat mapping. In conclusion, we maintain that RS applications can provide useful information about the effects of local human activities and global climate change on marine ecosystems

Comparison of spatial scale variability of shoot density and epiphytic leaf assemblages of Halophila stipulacea and Cymodocea nodosa on the Eastern Coast of Tunisia

A study was undertaken to compare the patterns of spatial variability, epiphytic percentage cover, and distribution of epiphytic fauna and flora between the two adjacent seagrasses Cymodocea nodosa and the invasive species Halophila stipulucea. Samples were taken at six stations separated by 600 m and exposed to different current conditions. The stations G2 and G5 were affected by a high current tide, while G4 was directly exposed to the northern marine currents. The station G3 was situated in the middle of a Posidonia oceanica bed and was less exposed to hydrodynamism, whereas the other stations were relatively protected. Results indicate that for both H. stipulacea and C. nodosa, shoot density and epiphytic cover biomass decreased when exposed to high levels of hydrodynamic activity. In terms of epiphytic leaf assemblages, our results showed significant differences for the two host plants in their mean cover and for the six stations at the largest and smallest spatial scale. Our observations highlight the dominance of Rhodophyta and the low number of epiphytic species and the epiphytic cover on H. stipulacea compared to C. nodosa. In addition, results indicate the absence of two taxa Hydrozoans and Annelida in the epiphytic assemblage of H. stipulacea leaves.

Biomonitoring of Posidonia oceanica beds by a multiscale approach

In this study a multiscale biomonitoring approach, which encompasses multiple levels of observations (from ultra- to meso- and macroscale, photo mosaicing and SRS), was applied to evaluate the conservation status of a P. oceanica meadow. In particular, the approach included a combination of molecular and biochemical parameters associated to the assessment of plant phenology and large-spatial bed structure and heterogeneity, which have ecological relevance. The aim was to identify a toolbox of reliable and economically feasible indicators to efficiently monitor and manage seagrass meadows.At ultrascale level, the OJIP-test, a screening test based on the quantitative analysis of the chlorophyll a fluorescence, was used for the first time on P. oceanica. At molecular level we tested the expression pattern of a panel of genes involved in the stress and photosynthesis pathways, as fast and sensitive response to stress exposure. At the microscale level, phenological features of P. oceanica were considered; at mesoscale level, the morphology of the meadow was determined by a photomosaicing technique. Finally, at a macroscale level, a spatially extensive map was produced by Remote Sensing approach. An anticipatory signal of pressure impending on the P. oceanica meadows was provided by molecular and biochemical markers, thus confirming the importance of a multiscale approach to asses a risk conditions in a natural environment, before these have a long-term effect.

A predictive model based on multiple coastal anthropogenic pressures explains the degradation status of a marine ecosystem: Implications for management and conservation

During the last fifty years, there has been a dramatic increase in the development of anthropogenic activities, and this is particularly threatening to marine coastal ecosystems. The management of these multiple and simultaneous anthropogenic pressures requires reliable and precise data on their distribution, as well as information (data, modelling) on their potential effects on sensitive ecosystems. Focusing on Posidonia oceanica beds, a threatened habitat-forming seagrass species endemic to the Mediterranean, we developed a statistical approach to study the complex relationship between human multiple activities and ecosystem status. We used Random Forest modelling to explain the degradation status of P. oceanica (defined herein as the shift from seagrass bed to dead matte) as a function of depth and 10 anthropogenic pressures along the French Mediterranean coast (1700 km of coastline including Corsica). Using a 50 × 50 m grid cells dataset, we obtained a particularly accurate model explaining 71.3% of the variance, with a Pearson correlation of 0.84 between predicted and observed values. Human-made coastline, depth, coastal population, urbanization, and agriculture were the best global predictors of P. oceanica's degradation status. Aquaculture was the least important predictor, although its local individual influence was among the highest. Non-linear relationship between predictors and seagrass beds status was detected with tipping points (i.e. thresholds) for all variables except agriculture and industrial effluents. Using these tipping points, we built a map representing the coastal seagrass beds classified into four categories according to an increasing pressure gradient and its risk of phase shift. Our approach provides important information that can be used to help managers preserve this essential and endangered ecosystem.

Where not to fish – reviewing and mapping fisheries restricted areas in the Aegean Sea

An up-to-date systematic review and unofficial codification of the national fisheries legislation was performed, along with an up-to-date systematic review of environmental, archaeological and maritime legislation, about spatio-temporal restrictions of fishing activities by all fishing gears in the Aegean Sea. Spatio-temporal restrictions established by the European Union and the General Fisheries Commission for the Mediterranean were also reviewed. A database was built, including detailed information on the Fisheries Restricted Areas (FRAs) being identified. All FRAs were mapped, as polygons in Geographic Information System shapefiles. The national fisheries, environmental, archeological and maritime legal framework comprises of 32, 2, 37 and 43 legal acts respectively; EU and GFCM legislation consists of one Regulation and one Recommendation respectively. A total of 511 national (254 of fisheries, 21 of environmental, 85 of archaeological and 151 of the maritime legislation), 6 EU and 4 international FRAs were identified, out of which 85.2% are located in the Aegean Sea and 14.8% in Crete. Towed or mobile gears are restricted in 88.5% of the FRAs, while static gears are restricted in only 10.2% of FRAs. Fish stocks and Posidonia oceanica beds protection are the most common reasons for regulating fishing activities (25.3% and 25.0% respectively). Most of the FRAs (85.4%) impose permanent closures. National fisheries, environmental, archaeological, maritime, EU and international FRAs cover 25.8%, 1.0%, 1.1%, 0.4%, 13.5% and 22.6% of the study area, respectively. The present study provides valuable information for the Maritime Spatial Planning in the Aegean Sea.

Setting an ecological baseline prior to the bottom-up establishment of a marine protected area in Santorini island, Aegean Sea

Since 2010, a bottom-up initiative has been launched in Santorini Island (Aegean Sea, Eastern Mediterranean) for the establishment of the first fully-protected marine protected area in the Cyclades, aiming at improving fisheries and enhancing responsible recreational uses at sea. Following discussions with local small-scale fishers and divers, two sites along the southern and southeastern coasts of the island were suggested as suitable to this end. In 2012, a baseline study was conducted at these areas to assess their state and provide an ecological snapshot that would enable sound designation and monitoring. Several ad hoc indices and metrics were applied, taking into account structural and functional features of the upper infralittoral algae and Posidonia oceanica beds. An integrated assessment of the infralittoral fish assemblages and their associated benthic communities was also performed. Our most important findings were: (i) the low total fish biomass and the absence of adult top predators, indicating overfishing; (ii) the overgrazing effects of the overabundant alien herbivore spinefoot fishes (Siganus spp.), as reflected by the abnormal structure of the algal communities; (iii) the scarcity of signs of pollution or other direct anthropogenic pressures, as indicated by the good environmental status of the P. oceanica meadows and the upper infralittoral vegetation; and (iv) the presence of a rich diversity of species and habitats, especially along the Akrotiri Peninsula and the wider volcanic Caldera. These findings provide useful insights on strengths and weaknesses of the study area and are discussed together with their implications for protection and management.

Passive acoustics as a tool for assessment of seagrass ecosystems

Seagrass meadows are important coastal ecosystems, being the most productive biomes on Earth. The amount of produced oxygen is a key parameter for assessing the seagrass ecosystem metabolism and productivity. Several experiments conducted in Posidonia oceanica seagrass meadows have demonstrated that using active acoustic methods one can monitor the oxygen production. The acoustic method is sensitive to bubbles production and provides estimates at ecosystem level, what is an advantage to other methods. Healthy seagrass ecosystems are populated by several noisy marine taxa such as fishes and crustaceans, therefore the ambient noise can be used to assess the ecosystem metabolism and productivity. During two periods of one week in October 2011 and May 2013, acoustic and environmental data was gathered at several locations over a Posidonia oceanica bed in the Bay of Revellata in Corsica (France). The diurnal variability pattern of ambient noise characteristics (frequency band, power, directivity, and number of noisy sources) shows an evident correlation with oxygen production as measured by independent methods (optodes). The ambient noise data were dominated by impulse like waveforms associated with marine taxa. This work discusses the challenges faced on using these waveforms to invert for oxygen production.

The impact of 85 years of coastal development on shallow seagrass beds (Posidonia oceanica L. (Delile)) in South Eastern France: A slow but steady loss without recovery

Shallow Posidonia oceanica beds (0 to −15 m), the most common seagrass in the Mediterranean, were mapped from aerial photographs dating from the 1920's and from 2012 along 800 km of coastline in South-Eastern France (Provence-Alpes-Côte-d’Azur region). Changes in P. oceanica bed spatial distribution (limits and extent) during these 85 years were analyzed in terms of concordance (remaining areas), positive discordance (expanding areas) or negative discordance (lost areas). Lost areas were linked with direct or indirect impacts of coastal development (artificialized coastlines (namely harbours, ports of refuge, landfills, artificial beaches, groynes and pontoons, submarine pipelines and aquatic farms) visible on the photographs. The comparison showed that 73% of the shallow limits have declined. Considering spatial extent, remaining seagrass meadows areas accounted for the major part (85%), while lost areas accounted for 13% and expanding areas for 1.1%. Lost areas were mainly linked with artificial coastlines but 44% remained with undetermined causes (invisible pressures and/or mixed effects). The analysis of 96 coastal facilities creating the artificial (namely man-made) coastlines showed that the highest impact over the longest distance (5 km) was caused by harbours. Only artificial beaches had such a distant impact. Pontoons were the least surrounded by lost seagrass meadows areas. These quantitative data offer important information for marine conservation.

PILOT APPLICATION OF 3D UNDERWATER IMAGING TECHNIQUES FOR MAPPING POSIDONIA OCEANICA (L.) DELILE MEADOWS

Abstract. Seagrass communities are considered one of the most productive and complex marine ecosystems. Seagrasses belong to a small group of 66 species that can form extensive meadows in all coastal areas of our planet. Posidonia oceanica beds are the most characteristic ecosystem of the Mediterranean Sea, and should be constantly monitored, preserved and maintained, as specified by EU Habitats Directive for priority habitats. Underwater 3D imaging by means of still or video cameras can allow a detailed analysis of the temporal evolution of these meadows, but also of the seafloor morphology and integrity. Video-photographic devices and open source software for acquiring and managing 3D optical data rapidly became more and more effective and economically viable, making underwater 3D mapping an easier task to carry out. 3D reconstruction of the underwater scene can be obtained with photogrammetric techniques that require just one or more digital cameras, also in stereo configuration. In this work we present the preliminary results of a pilot 3D mapping project applied to the P. oceanica meadow in the Marine Protected Area of Capo Rizzuto (KR, Calabria Region – Italy).

Spatio-temporal variability of Borer Polychaetes in Posidonia oceanica beds and its relation to meadow structure

Posidonia oceanica forms an extremely productive and complex ecosystem in the coastal Mediterranean Sea providing a suitable habitat for hundreds of plant and animal species. Among motile invertebrates associated to Posidonia meadows, polychaete borers of the plant sheaths represent a unique group which exploit a peculiar microhabitat. They belong to the family Eunicidae with three dominant species, Lysidice collaris, L. ninetta and L. unicornis. Due to their strong association with Posidonia shoots, these animals are particularly suitable to study the plant and animal spatial relationships and their pattern of variability. The aim of this work was to evaluate the frequency of occurrence of these animals (Index of Borer, IB) at different spatial and temporal (summer vs winter) scales in two Posidonia meadows off the Ischia Island (Gulf of Naples, Italy), which are exposed to different degrees of human impact and of hydrological conditions. Results showed IB values of L. collaris (the most abundant species) significantly different between meadows and at scales from 10s to 100s of meters, as well as between summer and winter. The IB of L. ninetta showed significant differences only at scales of 10s of meters while, on the contrary, the IB of L. unicornis (the less abundant species) did not show variability at any spatial and temporal scales. Most of the variance was at the more impacted and less water movement exposed meadow, suggesting higher level of small and intermediate scales of patchiness of borers at this meadow. These variation patterns are discussed in relation to local environmental differences between the studied Posidonia beds.

Reprint of “Monitoring of a Posidonia oceanica bed (Punta Manara, Eastern Ligurian Sea, Italy) and the associated molluscs twenty years after: What's new?”

This research project by the Marine Biology Laboratory at Turin University determined the degree of conservation and measured the size of the Posidonia oceanica bed in the eastern Ligurian Sea off Punta Manara in 1985–1986, a bed that had also been examined in 1973. This project assessed the structure, dynamics, and organization of the foliar stratum malacofauna in relation to the most important space–time variables, the bathymetric gradients, and the seasons. In 2006 the laboratory investigated this bed with methods like the previous ones in order to evaluate the effect of anthropogenic disturbances and to assess any changes in the P. oceanica and mollusc-community dynamics. Our overall project has spanned many years, something unique in P. oceanica studies. Our structural analysis of the meadow found (i) a reduction in shoot density in all the bed's regions, particularly in the shallow and intermediate belts; (ii) a progressive reduction of the lower limit (now considered erosive–regressive). We sampled the foliar stratum molluscs using hand-towed nets, the means we used to collect semi-quantitative data. In 2006, there were 40% fewer specimens and 31.5% more species than in 1985–1986. The core-stock (sensu Russo) has remained the same over the years in terms of both the presence and the abundance of species (8 dominant species belonging to Cerithidae and Rissoidae). As in 1985–1986, Bittium latreillii is the dominant species, whose juveniles exhibited similar settlement dynamics on the foliar strata and whose samples had comparable peaks in reproduction and abundance. The multivariate approach was applied to both the 1985–1986 and the 2006 data set. The present results confirm those obtained through the Detrended Correspondence Analysis (DCA) in 1985–1986. Namely, time (the period or the season) is the main factor of variability, the one that influences the malacological assemblages the most. The composition of the stocks depends closely on the sampling period (ANOSIM, R=0.532, P<0.001) and hence is linked to the biological cycle of the seagrass. The development of P. oceanica affects the malacological assemblages and regulates them quantitatively, something most evident in the reproductive and settlement cycles of the two dominant families, Cerithidae and Rissoidae. Thus the spatial variations (the variations in depths or bathymetric gradient) play a major role in determining the species of the stocks, while the temporal variations – the changes in seasons – play a major role in determining the total number of molluscs.

Minimizing environmental risks on constructing marine pipelines: Aguilas desalination plant

In the building of marine brine discharge pipelines from desalination plants, there are some technical and environmental conditions that require previous numerous studies to guarantee their viability. In the project of Águilas desalination plant with a production capacity of 180.000 m3/day, in Murcia, Spain, a marine emissary was designed. It was made up of various sections that entail different building complexities. The main difficulty was to build a tunnel in the rocky massif called “Peñon del Roncaor”; the tunnel was dug through a piling of 443 m of length and an exterior diameter of 2.400mm that would have come up at a depth of 12 m to join the submarine section of 290 m of length. These more detailed geotechnical studies showed a great heterogeneity in the composition of the materials to be excavated from the Peñon. In order to avoid any risk of affecting to the castle right above considered of cultural interest, a new tracing of the tunnel was designed. The new tracing runs the Peñon’s outer south borders right into the dumping area. This new tracing implies greater length of piping and greater seabed marine area occupation as well; it required carrying out additional bionomic studies to guarantee its environmental compatibility. We must bear in mind that the marine surroundings of Águilas are a protected area included in the Red Natura 2000 (LIC Submerged Costal Strip of the Murcia Region) whose predominant bionomic community is the Posidonia oceanica beds, limited to the Southwest by another less dense seagrass of Cymodocea nodosa. These seagrass meadows and rock communities suffer anthropic pressure for its proximity to the city of Águilas, as near-shore marine discharges, fishing activity, and others. And, there are other affections of natural condition: terrigenous sediments and nutrients that get to the dry riverbed name El Charco, having seriously affected the species of greater natural value and the implementation of those ubiquitous species, and thus impoverishing habitat in general. Due to the fact that P. oceanica seagrasses have very low tolerance to increased salinity in the western Mediterranean Sea; a hydrodynamic model was developed to estimate the likely dilution of the brine discharge for this new solution. Other works comprise a bathymetric survey to establish the profile of the ocean bottom—very important for pipeline construction—a sediment characterization, the study of the oceanographic conditions and a monitoring study of the marine water quality to settle the values of the water quality in the preoperation moment and the parameters needed for process designing. During the construction of the pipeline, an environmental surveillance program was developed. And at the end of the stage, a study was developed to know the impacts produced by the works carried out and to establish the “zero situation” before start of the operation phase. In addition to that, a very strict environmental legislation was applied along the process. These regulations included exhaustive and systematic controls of several environmental parameters when starting and during the plant operation.

Monitoring of a Posidonia oceanica bed (Punta Manara, Eastern Ligurian Sea, Italy) and the associated molluscs twenty years after: What's new?

This research project by the Marine Biology Laboratory at Turin University determined the degree of conservation and measured the size of the Posidonia oceanica bed in the eastern Ligurian Sea off Punta Manara in 1985–1986, a bed that had also been examined in 1973. This project assessed the structure, dynamics, and organization of the foliar stratum malacofauna in relation to the most important space–time variables, the bathymetric gradients, and the seasons. In 2006 the laboratory investigated this bed with methods like the previous ones in order to evaluate the effect of anthropogenic disturbances and to assess any changes in the P. oceanica and mollusc-community dynamics. Our overall project has spanned many years, something unique in P. oceanica studies. Our structural analysis of the meadow found (i) a reduction in shoot density in all the bed's regions, particularly in the shallow and intermediate belts; (ii) a progressive reduction of the lower limit (now considered erosive–regressive). We sampled the foliar stratum molluscs using hand-towed nets, the means we used to collect semi-quantitative data. In 2006, there were 40% fewer specimens and 31.5% more species than in 1985–1986. The core-stock (sensu Russo) has remained the same over the years in terms of both the presence and the abundance of species (8 dominant species belonging to Cerithidae and Rissoidae). As in 1985–1986, Bittium latreillii is the dominant species, whose juveniles exhibited similar settlement dynamics on the foliar strata and whose samples had comparable peaks in reproduction and abundance. The multivariate approach was applied to both the 1985–1986 and the 2006 data set. The present results confirm those obtained through the Detrended Correspondence Analysis (DCA) in 1985–1986. Namely, time (the period or the season) is the main factor of variability, the one that influences the malacological assemblages the most. The composition of the stocks depends closely on the sampling period (ANOSIM, R=0.532, P<0.001) and hence is linked to the biological cycle of the seagrass. The development of P. oceanica affects the malacological assemblages and regulates them quantitatively, something most evident in the reproductive and settlement cycles of the two dominant families, Cerithidae and Rissoidae. Thus the spatial variations (the variations in depths or bathymetric gradient) play a major role in determining the species of the stocks, while the temporal variations – the changes in seasons – play a major role in determining the total number of molluscs.

Timing and habitat preferences for settlement of juvenile fishes in the Marine Protected Area of Torre Guaceto (south-eastern Italy, Adriatic Sea)

Timing and habitat preferences for settlement of juvenile fishes were investigated at the Marine Protected Area (MPA) of Torre Guaceto (SE Adriatic Sea) from April 2005 to March 2006. Data were obtained by visual census (on a fortnightly basis) in 10 habitat types identified within the depth range 0–6 m. A total of 22 taxa of juvenile fish was recorded: juveniles of 14 taxa were analysed for settlement timing and habitat preferences, whereas the other 8 taxa were only occasionally observed. Diplodus vulgaris and Sarpa salpa showed two settlement peaks, while the other 12 species displayed a single annual peak. Most species (10 out of 14) settled between late spring and early autumn. Juvenile labrids and Oblada melanura were mostly associated with exposed shallow rocks, while Diplodus sargus, D. vulgaris, D. puntazzo and S. salpa chiefly settled in shallow sheltered coves. Juveniles of Chromis chromis were found in sublittoral rocks and Posidonia oceanica beds. Spondilyosoma cantharus, Diplodus annularis and Dicentrarchus labrax mostly associated to P. oceanica and small-sized seagrasses for settlement, while Mullus surmuletus chiefly used sublittoral sands. This study provides evidence of clear coherence during settlement of many fishes in terms of habitat for settlement, while some discrepancy was found in terms of timing across the year. In addition, this study provided suggestive evidence of the potential of the MPA, relative to the habitats included within its borders, in hosting juvenile fish stages and thus contributing to sustain local diversity of the coastal fish fauna. Similar data would deserve to be properly considered to design MPAs and refine conservation targets.

Spatial and temporal patterns in Serranus cabrilla habitat use in the NW Mediterranean revealed by acoustic telemetry

We used acoustic telemetry to describe the spatial and temporal patterns of habitat use of one of the species most targeted by recreational anglers in the NW Mediterranean, Serranus cabrilla (Linnaeus, 1758). Temporal patterns and fish position were determined using a fixed-receiver array located in a marine protected area (MPA) in Palma Bay (Balearic Islands). Fish position as cen- tre of activity (COA, the centre of the area the fish uses during a specific time) and space utilisation preferences could be described due to a receiver array design with a high range detection overlap (more densely distributed near the COA). There were significantly more detections per time unit dur- ing the day, which was interpreted as increased activity possibly related to feeding habits and social behaviour. S. cabrilla spent 95% of its time in an average area of 0.77 ± 0.17 km 2 , with a core area (50% of the time) of 0.10 ± 0.29 km 2 . The home range size was not related to fish size or diel pattern (i.e. the size of the daytime home range was not significantly different from the night range). The lin- earity index and the index of reuse (proxies of site fidelity) also demonstrated that this species has high site fidelity, which suggests that it is sedentary with a limited adult dispersal capacity. Two main habitats were observed in the study area, and S. cabrilla spent on average much less time in seagrass meadows (Posidonia oceanica beds) compared to soft, gravel and detritus bottoms. A relatively small MPA would be a useful management tool for establishing sustainable exploitation levels of this species.

The first record of Cladocora caespitosa (Linnaeus, 1767) (Anthozoa, Scleractinia) from the Marmara Sea

The Scleractinian Cladocora caespitosa is reported for the first time from the Marmara Sea, Turkey. Five colonies of the elliptical Cladocora caespitosa were discovered at 7 m by scuba divers around Posidonia oceanica beds colonising a substrate of sand and rock. The colonies' characteristics were recorded with underwater apparatus with a close-up device and with a video system. The present paper provides the new updated area of the species on the Turkish coast.

Spatial pattern of coastal fish assemblages in different habitats in North‐western Mediterranean

AbstractVariability of fish assemblages across habitat structures can depend on spatial scales. A hierarchical sampling design was used to assess the spatial variability of temperate fish assemblages in different habitats and at multiple scales. Underwater visual censuses were carried out along the coasts of Elba Island (NW Mediterranean) on Posidonia oceanica beds, rocky algal reefs and sandy habitat at three spatial scales, namely tens of metres (individual replicates), hundreds of metres (sites) and tens of kilometres (locations). At the assemblage level, there was a clear relationship between fish and habitat type and the observed habitat‐related differences were largely dependent on species identity. Fish assemblages on P. oceanica beds and rocky reefs shared a high number of species, whereas overlap with sandy assemblages was negligible. Multivariate analyses revealed significant differences in fish assemblages among habitats, although there was also a significant habitat × site interaction. These differences relied mainly upon assemblage composition and species richness. Assemblages on rocky reefs and P. oceanica meadows usually harboured a higher number of species and individuals compared with sandy assemblages. Nevertheless, the patterns of habitat‐related differences in species richness and, especially, in the total number of fish, changed significantly from site to site. Eight species showed significant differences over habitats, but they were not consistent due to the interaction of habitat with site. Predictability of fish at both assemblage and population levels decreased with the scale of observation, and the spatial pattern of fish observed at the smallest scale was likely dependent on factors other than habitat type.