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Corals exert a strong biological control over their calcification processes, but there is a lack of knowledge on their capability of long-term acclimatization to ocean acidification (OA). We used a dual geochemical proxy approach to estimate the calcifying fluid pH (pHcf) and carbonate chemistry of a Mediterranean coral (Balanophyllia europaea) naturally growing along a pH gradient (range: pHTS 8.07–7.74). The pHcf derived from skeletal boron isotopic composition (δ11B) was 0.3–0.6 units above seawater values and homogeneous along the gradient (mean ± SEM: Site 1 = 8.39 ± 0.03, Site 2 = 8.34 ± 0.03, Site 3 = 8.34 ± 0.02). Also carbonate ion concentration derived from B/Ca was homogeneous [mean ± SEM (μmol kg–1): Site 1 = 579 ± 34, Site 2 = 541 ± 27, Site 3 = 568 ± 30] regardless of seawater pH. Furthermore, gross calcification rate (GCR, mass of CaCO3 deposited on the skeletal unit area per unit of time), estimated by a “bio-inorganic model” (IpHRAC), was homogeneous with decreasing pH. The homogeneous GCR, internal pH and carbonate chemistry confirm that the features of the “building blocks” – the fundamental structural components – produced by the biomineralization process were substantially unaffected by increased acidification. Furthermore, the pH up-regulation observed in this study could potentially explain the previous hypothesis that less “building blocks” are produced with increasing acidification ultimately leading to increased skeletal porosity and to reduced net calcification rate computed by including the total volume of the pore space. In fact, assuming that the available energy at the three sites is the same, this energy at the low pH sites could be partitioned among fewer calicoblastic cells that consume more energy given the larger difference between external and internal pH compared to the control, leading to the production of less building blocks (i.e., formation of pores inside the skeleton structure, determining increased porosity). However, we cannot exclude that also dissolution may play a role in increasing porosity. Thus, the ability of scleractinian corals to maintain elevated pHcf relative to ambient seawater might not always be sufficient to counteract declines in net calcification under OA scenarios.

Citizen‐science projects vary extensively in subject matter, objectives, activities, and scale, but there is always one common goal: to collect reliable data that can be used for scientific and policy purposes. The quality of data collected by non-professional volunteers in citizen science programs is crucial to produce data that are usable by stakeholders to implement environmental management and protection plans. The aim of this study was to assess the quality of data collected by non-specialist volunteers during the citizen science project SCUBA Tourism for the Environment (STE), carried out in three touristic resorts of the Red Sea between 2007 and 2015. The project was based on the Recreational citizen science protocol that differs from the Traditional one because it does not change dives features (i.e. dive place, depth, etc.), do not require to follow a training course and to pass a final exam before participating in the project. For the recreational protocol, scuba instructors and divemasters were briefly trained during public events about project aims, methods and expected results and then they had directly involved volunteers in the project. STE project involved more than 14,000 volunteer recreational divers in data collection on biodiversity. Through a specifically designed questionnaire, volunteers indicated which of the seventy-two target marine taxa were sighted during their recreational dive, giving an estimate of their abundance. To assess the validity of collected data, a reference researcher randomly dove with the volunteers and independently filled in the project questionnaire. Correlation analyses between the records of the reference researcher and those of the volunteers were performed to assess their quality. The study was performed based on 513 sample dives (dives in which was present our reference researcher with at least three volunteers) with a total number of 3138 volunteers tested. Different parameters were used to analyze data reliability 1) Accuracy, the similarity between data collected by volunteers and those collected by the reference researcher, obtained with Spearman’s rank correlation coefficient; 2) Consistency, obtained correlating data collected only by volunteers during the same dive, without the reference researcher, using Spearman’s rank correlation coefficient; 3) Percentage of identified that is the percentage of taxa registered by volunteers compared to the taxa observed by the reference researcher; 4) Correct identification that is the percentage of volunteers that correctly identified individual taxa when the taxon was present; 5) Correctness of abundance ratings (CAR) that is the correctness in abundance ratings made by volunteers compared to those collected by the reference researcher; 6) Reliability obtained with correlation between data collected by volunteers and those collected by the reference researcher, using Cronbach’s alpha correlation; 7) measure of similarity between each volunteer and the reference researcher, using Czekanowski’s proportional similarity index). The influence of independent variables date, depth, dive time, diving certification level and group size of participants on volunteers’ accuracy was also analyzed. The lowest mean score (mean score 51.6%, 95% Confidence Interval CI 44.1-59.2%) was obtained for Consistency, indicating that, depending on personal interests, volunteers could give attention to different taxa and the highest one for the Reliability parameter (mean score 69.8%, 95% CI 62.8 – 76.9) indicating that volunteers are able to collect good quality data. A positive correlation was found between Accuracy and Correctness of Abundance Ratings (CAR) score and date indicating that long-term projects could achieve a higher quality of data collected by volunteers. Diving certification level and dive time resulted positively correlated with all parameters except for CAR indicating that more expert divers could collect better quality data than less expert ones and that spending more time underwater could have benefits on data quality. Overall, data quality in this study was comparable to that obtained in Traditional citizen science projects where strict training activities and protocols were followed. Independent variables revealed that long-term projects could achieve a higher Accuracy and CAR, this could be due to an improvement of the project with time, in terms of public training events, more clear description of tasks requested to instructors and divemasters and their consequent improvement in volunteers involvement. We also found that expert scuba divers (volunteers with higher diving certification level) were more reliable than the less expert, this could be due to their familiarity, not only with the marine environment, but also with the diving equipment, which allows them focus on the surrounding environment rather than on their balance or equipment. Finally, more time volunteers spent underwater the more reliable their data became. This study showed that Recreational citizen science could significantly support conventional research methods in monitoring biodiversity, notwithstanding careful planning for volunteer skills according to each specific project. The use of the Recreational citizen science protocol could enhance massive volunteers participation in citizen science projects because it do not require changes to the recreational activity in order to participate; this could also allow the collection of huge amount of data in a short period of time.

Ocean acidification may impact ecosystems reliant on calcifying organisms, potentially reducing thesocioeconomic benefits these habitats provide. This study investigates the response of growth and skeletalproperties of the non-zooxanthellate stony coral Astroides calycularis living in naturally acidified seawater ata Mediterranean CO2 vent (Ischia, Italy). Unexpectedly, contrasting patterns of calcification were found atpolyp and colony levels. Polyp linear extension rate, bulk skeletal density and net calcification rate increasedwith acidification (i.e., skeletal porosity decreased). At the colony level, a decrease of net calcification ratewas observed in acidified conditions, with colonies that extended less, were smaller, and were composed byfewer polyps, thus partitioning the available energy among less polyps. As a result, the single polyps had ahigher amount of resources available for calcification than in control conditions, and all their growthparameters had higher values. This unforeseen pattern of response to acidification was observed in this studyfor the first time, and contrasts with what previously observed in the Mediterranean solitary coralBalanophyllia europaea,whose polyps invest the calcification resources in linear extension rate to reach thesize at sexual maturity at the expenses of skeletal resistance (i.e. bulk skeletal density). In the colonial A.calycularis asexual reproduction is possible and corals may invest more on skeletal resistance without theurge to reach sexual maturity.

Corals exert a strong biological control over their calcification processes, but there is a lack of knowledgeon their capability of long-term acclimatization to ocean acidification (OA). We used a dual geochemicalproxy approach to estimate the calcifying fluid pH (pHcf) and carbonate chemistry of a Mediterranean coral(Balanophyllia europaea) naturally growing along a pH gradient. The pHcf derived from skeletal boronisotopic composition (11B) was homogeneous along the gradient, exhibiting an increased up-regulationcapability with increasing acidification. Also, carbonate ion concentration derived from B/Ca washomogeneous regardless of seawater pH. Furthermore, gross calcification rate (GCR), estimated by a “bio-inorganic model” (IpHRAC), was homogeneous with decreasing pH. This determined an apparentlyunresolved puzzle with the previously observed decrease in net calcification rates on the same specimensalong this gradient. However, on the contrary, the homogeneous GCR was in agreement with the previousresults in which the ‘building blocks’ produced by the biomineralization process were substantiallyunaffected by increased acidification. Furthermore, the pH up-regulation observed in this study provides asubstantial contribution in solving the puzzle. In fact, it confirms the previous hypothesis that less buildingblocks are produced with increasing acidification by showing thatB. europaea likely produces less buildingblocks because part of its energy is used to maintain elevated calcifying fluid pH with increasing acidity.Thus, the ability of scleractinian corals to maintain elevated pHcf relative to ambient seawater might notalways be sufficient to counteract declines in net calcification under ocean acidification scenarios.

The coral Astroides calycularis (Scleractinia: Dendrophylliidae) is endemic to the Mediterranean Sea (Terrón‐Sigler et al. 2016), where it can be reef forming (Musco et al. 2017: Fig. 1). In shallow water, it may cover up to 90% of rocky substrate from the surface down to 15 m depth where it is found in caves and on vertical walls. Astroides calycularis colonies frequently occur in dense aggregations (Goffredo et al. 2011), possibly favored by limited dispersion ability of both sexual (Goffredo et al. 2010) and asexual propagules (Serrano et al. 2017). High water movement promotes massive colony shapes with closely connected polyps usually forming continuous orange surfaces, leaving little space for the settlement of other benthic organisms (Casado‐Amezua et al. 2013). Astroides calycularis is “polystomatous,” forming small colonies composed of polyps connected to each other as a single organism bearing several mouths. Colony morphology is also strongly controlled by food availability (Goffredo et al. 2011). Polyps are typically 4–5 mm in length but larger polyps can grow up to 8 mm long. Like other azooxanthellate corals, A. calycularis is an obligate suspension feeder (Cebrian and Ballesteros 2004) and it is assumed to feed primarily on zooplankton transported by water movement, although the identity of its most preferred prey is unknown.

This study investigates the effects of long-term exposure to OA on skeletal parameters of four tropical zooxanthellate corals naturally living at CO2 seeps and adjacent control sites from two locations (Dobu and Upa Upasina) in the Papua New Guinea underwater volcanic vent system. The seeps are characterized by seawater pH values ranging from 8.0 to about 7.7. The skeletal porosity of Galaxea fascicularis, Acropora millepora, massive Porites, and Pocillopora damicornis was higher (up to ~ 40%, depending on the species) at the seep sites compared to the control sites. Pocillopora damicornis also showed a decrease of micro-density (up to ~ 7%). Thus, further investigations conducted on this species showed an increase of the volume fraction of the larger pores (up to ~ 7%), a decrease of the intraskeletal organic matrix content (up to ~ 15%), and an increase of the intraskeletal water content (up to ~ 59%) at the seep sites. The organic matrix related strain and crystallite size did not vary between seep and control sites. This multi-species study showed a common phenotypic response among different zooxanthellate corals subjected to the same environmental pressures, leading to the development of a more porous skeletal phenotype under OA.

Basic information on the reproductive biology of many scleractinian corals species is limited or entirely lacking, particularly from temperate zones, though it is essential for a better understanding of their ecology. This study describes the morphological aspects and the annual cycle of gametogenesis and biometric parameterss of the papillose cup coral Paracyathus pulchellus collected at Palinuro (Italy, Southern Tyrrhenian Sea), filling a knowledge gap about the reproductive biology of a widespread Mediterranean and Northern Atlantic coral. Samples of P. pulchellus were collected by SCUBA diving between 5- and 10-meters depth during 18 monthly collections from June 2010 to December 2011. Sexually active polyps displayed either oocytes or spermaries, indicating that P. pulchellus was gonochoric. The sex ratio of sexually active polyps was 1:1. Gametogenesis began with undifferentiated germ cells arose in the gastrodermis that migrated towards the mesoglea of the mesentery where they completed the development. During spermatogenesis, spermary diameter increased from 25 to 83 µm. Oocyte diameter ranged from 9 to 146 µm and during oogenesis the nucleus/cytoplasm ratio decreased due to the accumulation of yolk. The nucleus migrated to the periphery of the oocyte adhering closely to the cell membrane. No embryo was observed in the coelenteric cavity of the polyps, suggesting an external development of planktotrophic larvae due to the small-sized mature oocytes and a possible broadcast spawning reproductive mode. Gonadal index of both females and males increased significantly from August until November and fertilization took place from November to January. Only sexually inactive individuals were observed from February to April, suggesting a quiescence period in both males and females. Seasonal variations in water temperature and photoperiod may have a key role in regulating gametogenesis. The analysis of the main biometric parameters (polyp width, height, dry skeletal mass, volume, surface/volume ratio and bulk skeletal density) showed a negative correlation between size and skeletal density, and no sexual dimorphism.

Larval settlement is a critical step for sessile benthic species such as corals, whose ability to thrive on diverse natural and anthropogenic substrates may lead to a competitive advantage in the colonization of new environments with respect to a narrow tolerance for a specific kind of substratum. Plastic debris, widespread in marine waters, provides a large, motile, and solid substratum supporting a highly diverse biological community. Here we present the first observation of a floating plastic bottle colonized by the deep-sea coral Desmophyllum dianthus. The density pattern and co-occurring species composition suggest a pioneer behavior of this coral species, whose peculiar morphologic plasticity response when interacting with the plastic substrate (i.e., low density polyethylene) has not been observed before. The tolerance of D. dianthus for such plastic substrate may affect ecological processes in deep water environments, disrupting interspecific substrate competition in the benthic community.

Tourism is one of the most important economic sectors worldwide, with significant overarching impact on the environment, including negative effects caused by tourist inappropriate behavior while on vacation. By providing informal educational activities, tourism also has an educative role that leads to positive learning outcomes and beneficial environmental effects. Here we present the short- and long-term outcomes of a project for environmental education (Glocal Education) carried out in three travel destinations, aimed at promoting sustainability variables (knowledge, attitude, and awareness) in participating tourists. Since psychological components can affect learning outcomes, we also considered tourist satisfaction in participating in the project and identification with its values, as well as the intention to travel with the hosting tour operator again in the future. Tourists were asked to complete evaluation questionnaires three times: before Glocal Education activities, right after activities (i.e., while still on vacation), and after at least one year from initial project participation. Short- and long-term learning outcomes were tested, and possible relations between these variables and psychological components (satisfaction, identification, and intention) of the learning experience were verified. Overall, knowledge, attitude and awareness increased in the short term, while in the long term, knowledge and attitude decreased, and awareness remained constant. In most cases, psychological components showed positive relation with sustainability variables, which suggested their important role in structuring and carrying out environmental education activities. This study suggests that informal environmental education activities can be advantageous for tourism stakeholders in terms of customer loyalty. Such activities can contribute to enhance environment literacy, by allowing tourists to observe the environmental impact caused by human activity, and understand how their day-to-day actions, even if small, might help address some of the current concerns for environmental conservation.

Assessing the sources and accumulation patterns of polycyclic aromatic hydrocarbons (PAHs) in corals is critical, as they threaten coral ecosystem resilience in addition to other anthropogenic pressures. We determined acenaphthene, fluorene, fluoranthene, and pyrene concentration in the skeleton and soft tissue of 7 adult and 29 old specimens of the non-zooxanthellate coral Leptopsammia pruvoti from the Mediterranean Sea. Leptopsammia pruvoti accumulated 2–72 times higher PAH concentrations than the previously investigated zooxanthellate Balanophyllia europaea living at the same site at shallower depth, likely in relation to the different trophic strategy. Low molecular weight PAHs were preferentially accumulated compared to high molecular weight PAHs. Detected PAHs were mainly petrogenic, consistently with local pollution sources. Populations of L. pruvoti immobilized PAHs in the skeleton 3–4 orders of magnitude more efficiently than B. europaea. This highlights the need to investigate other non-zooxanthellate species, which represent the majority of Mediterranean scleractinians, but are widely overlooked with respect to the few zooxanthellate species.

Ocean acidification caused by shifts in ocean carbonate chemistry resulting from increased atmospheric CO2concentrations is threatening many calcifying organisms, including corals. Here we assessed autotrophy vs heterotrophy shifts in the Mediterranean zooxanthellate scleractinian coralBalanophyllia europaeaacclimatized to low pH/high pCO2conditions at a CO2vent off Panarea Island (Italy). Dinoflagellate endosymbiont densities were higher at lowest pH Sites where changes in the distribution of distinct haplotypes of a host-specific symbiont species, Philozoon balanophyllum,were observed. An increase in symbiont C/N ratios was observed at low pH, likely as a result of increased C fixation by higher symbiont cell densities. δ13C values of the symbionts and host tissue reached similar values at the lowest pH Site, suggesting an increased influence of autotrophy with increasing acidification. Host tissue δ15N values of 0‰ strongly suggest that diazotroph N2fixation is occurring within the coral tissue/mucus at the low pH Sites, likely explaining the decrease in host tissue C/N ratios with acidification. Overall, our findings show an acclimatization of this coral-dinoflagellate mutualism through trophic adjustment and symbiont haplotype differences with increasing acidification, highlighting that some corals are capable of acclimatizing to ocean acidification predicted under end-of-century scenarios.

The research leading to these results has received funding from Project AWARE Foundation, ASTOI Association, Milano, Ministry of Tourism of the Arab Republic of Egypt, Settemari S. p. A Tour Operator, Scuba Nitrox Safety International, Viaggio nel Blu Diving Center. Tourism is one of the largest economic sectors in the world. It has a positive effect on the economy of many countries, but it can also lead to negative impacts on local ecosystems. Informal environmental education through Citizen Science (CS) projects can be effective in increasing citizen environmental knowledge and awareness in the short-term. A change of awareness could bring to a behavioral change in the long-term, making tourism more sustainable. However, the long-term effects of participating in CS projects are still unknown. This is the first follow-up study concerning the effects of participating in a CS project on cognitive and psychological aspects at the basis of pro-environmental behavior. An environmental education program was developed, between 2012 and 2013, in a resort in Marsa Alam, Egypt. The study directly evaluated, through paper questionnaires, the short-term (after 1 week or 10 days) retention of knowledge and awareness of volunteers that had participated in the activities proposed by the program. After three years, participants were re-contacted via email to fill in the same questionnaire as in the short-term study, plus a new section with psychological variables. 40.5% of the re-contacted participants completed the follow-up questionnaires with a final sample size of fifty-five people for this study. Notwithstanding the limited sample size, positive trends in volunteer awareness, personal satisfaction regarding the CS project, and motivation to engage in pro-environmental behavior in the long-term were observed. Publisher PDF

Ocean acidification, due to the increase of carbon dioxide (CO2) concentration in the atmosphere and its absorption by the oceans, affects many aspects of marine calcifying organisms' biology, including reproduction. Most of the available studies on low pH effects on coral reproduction have been conducted on tropical species under controlled conditions, while little information is reported for either tropical or temperate species in the field. This study describes the influence of decreasing pH on sexual reproduction of the temperate non-zooxanthellate colonial scleractinian Astroides calycularis, transplanted in four sites along a natural pH gradient at the underwater volcanic crater of Panarea Island (Tyrrhenian Sea, Italy). The average pH values of each site (range: pHTS 8.07–7.40) match different scenarios of the Intergovernmental Panel on Climate Change (IPCC) for the end of the century. After 3 months under experimental conditions, the reproductive parameters of both oocytes and spermaries (abundance, gonadal index, and diameters) seem to be unaffected by low pH. However, a delay in spermary development in the pre-fertilization period and a persistence of mature oocytes in the fertilization period were observed in the most acidic site. Furthermore, no embryos were found in colonies from the two most acidic sites, suggesting a delay or an interruption of the fertilization process due to acidified conditions. These findings suggest a negative effect of low pH on A. calycularis sexual reproduction. However, long-term experiments, including the synergistic impact of pH and temperature, are needed to predict if this species will be able to adapt to climate change over the next century.

High pCO2 habitats and their populations provide an unparalleled opportunity to assess how species may survive under future ocean acidification conditions, and help to reveal the traits that confer tolerance. Here we utilize a unique CO2 vent system to study the effects of exposure to elevated pCO2 on trait-shifts observed throughout natural populations of Astroides calycularis, an azooxanthellate scleractinian coral endemic to the Mediterranean. Unexpected shifts in skeletal and growth patterns were found. Colonies shifted to a skeletal phenotype characterized by encrusting morphology, smaller size, reduced coenosarc tissue, fewer polyps, and less porous and denser skeletons at low pH. Interestingly, while individual polyps calcified more and extended faster at low pH, whole colonies found at low pH site calcified and extended their skeleton at the same rate as did those at ambient pH sites. Transcriptomic data revealed strong genetic differentiation among local populations of this warm water species whose distribution range is currently expanding northward. We found excess differentiation in the CO2 vent population for genes central to calcification, including genes for calcium management (calmodulin, calcium-binding proteins), pH regulation (V-type proton ATPase), and inorganic carbon regulation (carbonic anhydrase). Combined, our results demonstrate how coral populations can persist in high pCO2 environments, making this system a powerful candidate for investigating acclimatization and local adaptation of organisms to global environmental change.

Atmospheric carbon dioxide enrichment alters seawater carbonate chemistry, thus threatening calcifying organisms such as corals. Coral populations at carbon dioxide vents are natural acidification experiments that mimic organism responses to seawater pH values projected for 2100. Even if demographic traits are paramount information to assess ecological relationships and habitat suitability, population dynamics studies on corals thriving under acidified conditions are lacking. Here, we investigate the demography and reproduction of populations of the solitary, symbiotic, temperate coral Balanophyllia europaea naturally living along a pH gradient at a Mediterranean CO2 vent. Gametogenesis and larval production were unaffected while recruitment efficiency collapsed at low and variable pH, contributing to coral abundance decline and suggesting that life stages between larval release and early polyp growth are hindered by acidification. Exploring these processes is crucial to assess coral fate in the forthcoming acidified oceans, to preserve coral ecosystems and the socioeconomic services they provide.

Notwithstanding the importance of analyzing the variations of population dynamic traits along environmental gradients for assessing coral resilience to global climate change, temperate areas are more understudied than tropical regions. In the Mediterranean Sea, some studies are available for its western basin, while there is a lack of information for its eastern basin. This study starts to fill this gap, by determining the demographic characteristics of the solitary zooxanthellate scleractinian Balanophyllia europaea in the Dardanelles (Turkey) along a 1–21 m depth transect. The population dynamics of B. europaea from this site in the eastern Mediterranean Sea was compared with the populations in the NW Mediterranean Sea. In particular, the sites of Calafuria and Palinuro (Tyrrhenian Sea, Italy) were chosen for the comparison since their temperature and latitude, respectively, were similar to that of the Dardanelles population. The population density in the Dardanelles increased exponentially with depth, possibly due to lower current and wave action, and higher salinity at depth. Age structure in the Dardanelles was relatively overrepresented in younger age classes with increasing depth. Nevertheless, this difference in age structure was not strong enough to cause trends with depth for all derived demographic parameters. In comparison with Italian populations, age structure presented a higher frequency of young individuals and were more stable in the Dardanelles, likely due to the less intense wave action. Hosting different clades of symbiotic algae may also contribute to these differences, but molecular studies are necessary to verify this hypothesis.

Polycyclic aromatic hydrocarbons (PAHs) are widespread and harmful environmental pollutants that threaten marine ecosystems. Assessing their level and source is crucial to estimate the potential risks for marine organisms, as PAHs represent an additional threat to organism resilience under ongoing climatic change. Here we applied the QuEChERS extraction method to quantify four PAHs (i.e. acenaphthene, fluorene, fluoranthene, and pyrene) in three biological compartments (i.e. skeleton, tissue, and zooxanthellae symbiotic algae) of adult and old specimens of a scleractinian coral species (Balanophyllia europaea) that is widespread throughout the Mediterranean Sea. A higher concentration of all four investigated PAHs was observed in the zooxanthellae, followed by the coral tissue, with lowest concentration in the skeleton, consistently with previous studies on tropical species. In all the three biological compartments, the concentration of low molecular weight PAHs was higher with respect to high-molecular weight PAHs, in agreement with their bioaccumulation capabilities. PAH concentration was unrelated to skeletal age. Observed PAHs were of petrogenic origin, reflecting the pollution sources of the sampling area. By coupling PAH data with population age structure data measured in the field, the amount of PAHs stored in the long term (i.e. up to 20 years) in coral skeletons was quantified and resulted in 53.6 ng m−2 of acenaphthene, 69.4 ng m−2 of fluorene, 2.7 ng m−2 of fluoranthene, and 11.7 ng m−2 of pyrene. This estimate provides the basis for further assessments of long-term sequestration of PAHs from the marine environment in the whole Mediterranean, given the widespread distribution of the investigated coral species.

Coral microbiomes, the complex microbial communities associated with the different anatomic compartments of the coral, provide important functions for the host's survival, such as nutrient cycling at the host's surface, prevention of pathogens colonization, and promotion of nutrient uptake. Microbiomes are generally referred to as plastic entities, able to adapt their composition and functionality in response to environmental change, with a possible impact on coral acclimatization to phenomena related to climate change, such as ocean acidification. Ocean sites characterized by natural gradients of pCO2 provide models for investigating the ability of marine organisms to acclimatize to decreasing seawater pH. Here we compared the microbiome of the temperate, shallow water, non-symbiotic solitary coral Astroides calycularis that naturally lives at a volcanic CO2 vent in Ischia Island (Naples, Italy), with that of corals living in non-acidified sites at the same island. Bacterial DNA associated with the different anatomic compartments (mucus, tissue and skeleton) of A. calycularis was differentially extracted and a total of 68 samples were analyzed by 16S rRNA gene sequencing. In terms of phylogenetic composition, the microbiomes associated with the different coral anatomic compartments were different from each other and from the microbial communities of the surrounding seawater. Of all the anatomic compartments, the mucus-associated microbiome differed the most between the control and acidified sites. The differences detected in the microbial communities associated to the three anatomic compartments included a general increase in subdominant bacterial groups, some of which are known to be involved in different stages of the nitrogen cycle, such as potential nitrogen fixing bacteria and bacteria able to degrade organic nitrogen. Our data therefore suggests a potential increase of nitrogen fixation and recycling in A. calycularis living close to the CO2 vent system.

Many calcifying organisms exert significant biological control over the construction and composition of biominerals which are thus generally depleted in oxygen-18 and carbon-13 relative to the isotopic ratios of abiogenic aragonite. The skeletal δ18O and δ13C values of specimens of Mediterranean zooxanthellate (Balanophyllia europaea and Cladocora caespitosa) and non-zooxanthellate corals (Leptopsammia pruvoti and Caryophyllia inornata) were assessed along an 8° latitudinal gradient along Western Italian coasts, spanning ~2 °C and ~37 W m-2 of annual average sea surface temperature and solar radiation (surface values), respectively. Seawater δ18O and δ13CDIC were surprisingly constant along the ~850 km latitudinal gradient while a ~2 and ~4 ‰ variation in skeletal δ18O and a ~4 and ~9 ‰ variation in skeletal δ13C was found in the zooxanthellate and non-zooxanthellate species, respectively. Albeit Mediterranean corals considered in this study are slow growing, only a limited number of non-zooxanthellate specimens exhibited skeletal δ18O equilibrium values while all δ13C values in the four species were depleted in comparison to the estimated isotopic equilibrium with ambient seawater, suggesting that these temperate corals cannot be used for thermometry-based seawater reconstruction. Calcification rate, linear extension rate and skeletal density were unrelated to isotopic compositions. The fact that skeletal δ18O and δ13C of zooxanthellate corals were confined to a narrower range at the most isotopically depleted end compared to non-zooxanthellate corals, suggests that the photosynthetic activity may restrict corals to a limited range of isotopic composition, away from isotopic equilibrium for both isotopes. Our data show that individual corals within the same species express the full range of isotope fractionation. These results suggest that metabolic and/or kinetic effects may act as controlling factors of isotope variability of skeleton composition along the transect, and that precipitation of coral skeletal aragonite occurs under controlling kinetic biological processes, rather than thermodynamic control, by yet unidentified mechanisms.

Ecotourism gives tourists the opportunity to improve knowledge and awareness of environmental issues while on vacation. Recreational environmental education has been proven an effective method to raise perception of human impact on ecosystems. “Glocal Education” is an education project aimed at developing environmental interest in tourists on vacation. The present study assessed the effectiveness of Glocal Education in improving tourist environmental interest. Using specific questionnaires, we evaluated project impact on tourists, tourist satisfaction regarding the project and customer loyalty towards the tour operator hosting the project. The study took place at three mass touristic facilities, where tourists were asked to fill a questionnaire before and after participating in educational activities (e.g., biology lessons, excursions). The average score of both questionnaires was then compared to evaluate possible improvement of tourist knowledge, attitude and awareness. Results showed that such activities had a significantly positive impact on tourist knowledge, attitude and awareness at all localities. High levels of satisfaction and loyalty towards the host tour operator were observed at all sites, which indicate that once a person is briefed about the correct approach to natural systems, they can become increasingly interested in taking action, developing an “advocate” role. This study shows how informal education activities can act as trigger for environmental awareness and behavior among tourists, providing them with the tools, knowledge, and motivation to critically discern what is and isn't environmentally friendly, not only in terms of products and services in their everyday life, but also when choosing their vacation spots.

Anthropogenic carbon dioxide (CO2) emissions and consequent ocean acidification (OA) are projected to have extensive consequences on marine calcifying organisms, including corals. While the effects of OA on coral calcification are well documented, the response of reproduction is still poorly understood since no information are reported for temperate corals. Here we investigate for the first time the influence of OA on sexual reproduction of the temperate azooxanthellate solitary scleractinian Leptopsammia pruvoti transplanted along a natural pCO2 gradient at a Mediterranean CO2 vent. After 3 months, future projection of pH levels did not influence the germ cell production, gametogenesis and embryogenesis in this azooxanthellate coral. These findings suggest that reproductive potential may be quite tolerant to decreasing pH, with implications for ecosystem function and services in a changing ocean.

Anthropogenic CO2 is a major driver of current environmental change in most ecosystems1, and the related ocean acidification (OA) is threatening marine biota2. With increasing pCO2, calcification rates of several species decrease3, although cases of up-regulation are observed4. Here, we show that biological control over mineralization relates to species abundance along a natural pH gradient. As pCO2 increased, the mineralogy of a scleractinian coral (Balanophyllia europaea) and a mollusc (Vermetus triqueter) did not change. In contrast, two calcifying algae (Padina pavonica and Acetabularia acetabulum) reduced and changed mineralization with increasing pCO2, from aragonite to the less soluble calcium sulphates and whewellite, respectively. As pCO2 increased, the coral and mollusc abundance was severely reduced, with both species disappearing at pH < 7.8. Conversely, the two calcifying and a non-calcifying algae (Lobophora variegata) showed less severe or no reductions with increasing pCO2, and were all found at the lowest pH site. The mineralization response to decreasing pH suggests a link with the degree of control over the biomineralization process by the organism, as only species with lower control managed to thrive in the lowest pH.

The anthropogenic increase in atmospheric CO2 that drives global warming and ocean acidification raises serious concerns regarding the future of corals, the main carbonate biomineralizers. Here we used transcriptome analysis to study the effect of long-term gradual temperature increase (annual rate), combined with lowered pH values, on a sub-tropical Red Sea coral, Stylophora pistillata, and on a temperate Mediterranean symbiotic coral Balanophyllia europaea. The gene expression profiles revealed a strong effect of both temperature increase and pH decrease implying for synergism response. The temperate coral, exposed to a twice as high range of seasonal temperature fluctuations than the Red Sea species, faced stress more effectively. The compensatory strategy for coping apparently involves deviating cellular resources into a massive up-regulation of genes in general, and specifically of genes involved in the generation of metabolic energy. Our results imply that sub-lethal, prolonged exposure to stress can stimulate evolutionary increase in stress resilience.

The IUCN Red List of Threatened SpeciesTM – Regional Assessment, This report presents the conservation status of the anthozoans occurring in the Mediterranean Sea, based on the assessment of 136 species using the IUCN Red List methodology. It identifies those species that are threatened with extinction at the regional level to guide appropriate conservation actions in order to improve their status

Organisms that accumulate calcium carbonate structures are particularly vulnerable to ocean warming (OW) and ocean acidification (OA), potentially reducing the socioeconomic benefits of ecosystems reliant on these taxa. Since rising atmospheric CO2 is responsible for global warming and increasing ocean acidity, to correctly predict how OW and OA will affect marine organisms, their possible interactive effects must be assessed. Here we investigate, in the field, the combined temperature (range: 16–26 °C) and acidification (range: pHTS 8.1–7.4) effects on mortality and growth of Mediterranean coral species transplanted, in different seasonal periods, along a natural pH gradient generated by a CO2 vent. We show a synergistic adverse effect on mortality rates (up to 60%), for solitary and colonial, symbiotic and asymbiotic corals, suggesting that high seawater temperatures may have increased their metabolic rates which, in conjunction with decreasing pH, could have led to rapid deterioration of cellular processes and performance. The net calcification rate of the symbiotic species was not affected by decreasing pH, regardless of temperature, while in the two asymbiotic species it was negatively affected by increasing acidification and temperature, suggesting that symbiotic corals may be more tolerant to increasing warming and acidifying conditions compared to asymbiotic ones.

While knowledge of the reproductive biology of tropical scleractinian corals is extensive, information from temperate zones is limited. The aim of this study is to describe the reproductive biology of Caryophyllia inornata, a temperate species, and to increase the understanding of the reproductive strategies of Mediterranean corals. Samples of C. inornata were collected during SCUBA surveys at Elba island. Sexually active individuals displayed either male or female germ cells, showing a gonochoric sexuality. C. inornata exhibited an unusual pattern of embryogenesis. Embryos appeared throughout the whole year in males and in sexually inactive individuals, and they did not show a seasonal pattern of development, as usually expected for sexual reproduction. This observation suggests the possibility of asexual origin. These embryogenetic sexually inactive individuals were larger in size than the embryogenetic sexually active ones, and they might be senile polyps that preserve the ability to produce embryos only by agamic reproduction.

The correlation between solar radiation and sea surface temperature (SST) and growth was assessed along a latitudinal gradient. Extension rate and skeletal density were both correlated with calcification rate, indicating that calcium carbonate deposition was allocated evenly between skeletal density and linear extension. Unlike most studies on other tropical and temperate corals, in which calcification was positively correlated with solar radiation and SST, in the present study calcification was not correlated with solar radiation, whereas it was negatively correlated with SST. We hypothesize that photosynthesis of the symbiotic algae of Balanophyllia europaea is inhibited at high temperatures, consequently causing an inhibition of calcification. The regressions between calcification and SST predicted that the calcification of B. europaea would be depressed at 20.5–21.0uC mean annual SST. The scenarios of the Intergovernmental Panel on Climate Change conclude that by 2100, SST will exceed this physiological threshold for most of the populations considered in this study. This study comprises the first field investigation of the relationships between environmental parameters and calcification of a Mediterranean coral and highlights the risks of losing Mediterranean marine biodiversity over the course of future decades.

OCEAN WARMING AND ACIDIFICATION SYNERGISTICALLY INCREASE CORAL MORTALITY CO2-driven ocean warming (OW) and acidification (OA) has prompted urgent research to assess their potential effects on the marine environment, with strong emphasis on calcifying organisms. To correctly predict how these stressors will affect marine organisms, their synergistic effects must be assessed. Here we investigate the interactive effects of OW and OA on the mortality and growth of three Mediterranean coral species: the solitary zooxanthellate Balanophyllia europaea, the solitary non-zooxanthellate Leptopsammia pruvoti and the colonial non-zooxanthellate Astroides calycularis. Corals were transplanted, in different seasons, in proximity to a volcanic CO2 vent where water is naturally acidified to levels matching future IPCC scenarios. We show a strong synergistic adverse effect on mortality rates of the three species. Net calcification rates of the zooxanthellate species were not affected by reduced pH, while those of the two non-zooxanthellate species were negatively affected, indicating that different levels of resilience/resistance to OW and OA among species in symbiosis with photosynthetic algae or asymbiotic ones may be related to different modes of nutrition and/or biomineralization processes. Natural CO2-leaking marine sites can provide essential information on the combined effects of OA and OW on Mediterranean scleractinian corals, which may help understand to which extent different corals will be threatened by increasing atmospheric CO2 pollution.

In contrast with the number of studies on tropical species, analyses of the variation of growth parameters with environmental variables in temperate areas are very scarce. Notwithstanding the importance of obtaining information on coral population dynamics, few studies have quantifi ed demographic parameters of scleractinian corals, partly because of the processes of fragmentation, fusion and partial colony mortality, which cause corals of similar size to be of widely different ages, thus distorting the age-size relationships. Available literature on growth and population dynamics of natural populations of temperate scleractinians is reviewed in the present work. As general trends, it seems that: (1) solitary species have a defi nite growth pattern, in contrast with colonial species; (2) symbiotic species are more sensitive to increasing temperatures and more vulnerable to global warming; (3) non-symbiotic species are more tolerant to increasing temperature, but may be negatively affected by the indirect effects of increasing solar radiation; and (4) even if the energy resulting from photosynthesis may increase as a consequence of ocean acidifi cation, the growth and abundance of symbiotic corals seem to be negatively affected by acidifi cation and the negative response of non-symbiotic corals is expected to be even stronger.

Correlations between environmental parameters (depth temperature and solar radiation) and growth parameters (bulk skeletal density, linear extension rate and net calcification rate) of the solitary azooxanthellate coral, Caryophyllia inornata, were investigated along an 8 latitudinal gradient on the western Italian coasts. Net calcifi- cation rate correlated positively with both bulk skeletal density and linear extension rate, showing that C. inornata allocates calcification resources evenly to thickening the skeleton and increasing linear growth. Overall, the three growth parameters did not follow gradients in the two environmental parameters, showing a different trend compared to most studies on zooxanthellate corals. However, the results are in agreement with the only previous analysis of an azooxanthellate coral, Leptopsammia pruvoti, studied along the same latitudinal gradient. In a comparison of the response to temperature of all Mediterranean species whose growth has been investigated to date, azooxanthellate corals were more tolerant to temperature increases than zooxanthellate corals.

The ecology of scleractinian corals may be understood through comparisons between population demographic data and environmental parameters. Growth (growth constant and maximum size) and demographic parameters (population structure stability, instantaneous mortality rate, average age of individuals, percentage of immature individuals, age at maximum biomass, and average age of biomass) of the solitary, non-zooxanthellate, and temperate coral Caryophyllia inornata were investigated at six sites along an 8° latitudinal gradient of temperature and solar radiation (SR) on the western Italian coasts. Growth parameters were homogeneous among populations across the investigated latitudinal range. While demographic parameters were not correlated with depth temperature, populations were progressively less stable and showed a deficiency of young individuals with increasing SR, likely as a result of the lowered energetic resources due to reduced zooplankton availability. These results contrast with data from another Mediterranean non-zooxanthellate solitary coral, Leptopsammia pruvoti, investigated along the same gradient, which shows no correlation between population demography and temperature or SR.

Ocean acidification is expected to significantly affect calcifying marine organisms, such as corals. While ocean acidification effects on coral calcification have been widely investigated, the effects on coral gametogenesis are almost unknown. A volcanic vent at Panarea Island (Mediterranean Sea, Italy) characterized by continuous and localized CO2 emission, generates a stable pCO2 gradient from the centre to its periphery, providing a unique natural laboratory for ocean acidification studies. Here we assessed the effects of ocean acidification on gametogenesis and embryogenesis of the Mediterranean non-zooxanthellate coral Leptopsammia pruvoti transplanted along this natural pCO2 gradient. After 3 months under experimental conditions, increasing pCO2 seemed to negatively influence spermary production and development. In the control Site, all spermaries showed the latest (most advanced) maturation stage while in the most acidic Sites they also displayed earlier stages, indicating a delay in spermatogenesis and consequently of fertilization and planulation processes. Considering the negative response showed by this species after a short-term exposure, an even stronger negative effect on sexual reproduction is hypothesized under a long-term exposure.