Marine reserves are areas where fishing mortality is reduced, and their effectiveness in enhancing fisheries depends on the magnitude of this reduction. We evaluated the effectiveness of two marine reserves in the Mediterranean that differed in enforcement levels using a dual approach that combined interviews with fishers and on-board sampling. Only the reserve with stricter fishing restrictions showed measurable stock enhancement. In areas adjacent to this reserve, catches were higher and body sizes were larger for some species. In addition, fishers adjusted their fishing gear when operating near this reserve, thereby targeting larger individuals. In contrast, no distance-related trends were detected around the reserve with weaker fishing restrictions. Both the interviews and on-board sampling produced consistent results regarding the effectiveness of the two reserves.

The recent growth of Blue Economy-related human activities has increased underwater noise pollution. Sound is a key factor in ensuring the well-being of marine animals as it allows them to communicate with each other and extract valuable information from the environment. Although the Marine Strategy Framework Directive requires monitoring programs to achieve good environmental status, there remains a significant deficit of information concerning three key domains: the characteristics of the underwater soundscape, its transformation due to anthropogenic activities, and the effects of noise on marine animals. This study aimed to evaluate the impact of anthropogenic activities on marine acoustic environments. Acoustic metrics and ecoacoustic indices were applied to characterise variability and assess daily, weekly, and seasonal patterns, as well as the effects of trawling restrictions. Three underwater soundscapes were compared in this study: two natural environments in the Mediterranean Sea and one artificial environment, a land-based fish farm tank. High anthropogenic noise levels were found, primarily due to fishing vessels near the selected locations. Similarly, the soundscape exhibited notable seasonal variations (annual and weekly), demonstrating a significant dependence on tourist activities. The results highlight the benefits of acoustic parameters as a tool for monitoring environmental conditions over time.

Climate change poses significant risks to Mediterranean aquaculture, with sea surface temperature (SST) identified as a critical stressor affecting cultivated species. This study aims to assess climate-related risks for coastal aquaculture in the Valencian Community (Spain) by analyzing SST spatiotemporal variability and predicting future trends. A multi-method approach was employed, combining ARIMA models for 10-year predictions at eight coastal locations, Bayesian hierarchical models (BHM) fitted via INLA for spatiotemporal analysis of maximum SST and temperature range (2000–2024), and Generalized Additive Models (GAM) to evaluate relationships with climate indices (NAO, AMO, ENSO). Results revealed a consistent warming trend since the 1990s, with ARIMA predictions indicating maximum SST values of 27.2 ± 0.1 °C in September over the next decade. The spatiotemporal model showed effective spatial correlation ranges of 246 km for maximum SST and 207 km for SST range. Anomalous warming years (2003, 2006, 2018, 2023–2024) coincided with documented marine heatwave events. The GAM explained 98.2% of deviance, with AMO showing significant influence (p<0.001), while ENSO was not statistically significant. Southern locations (Altea, Campello) currently experience the highest temperatures, but projections indicate Valencia and Sagunto will become the warmest areas. These findings provide essential information for marine spatial planning and recommend a precautionary approach when considering aquaculture relocation towards northern coastal areas.

Due to increased emissions of CO2 and other greenhouse gases, the oceans are warming under the global phenomenon of climate change. This effect is especially pronounced in semi-enclosed seas like the Mediterranean, where marine heatwaves have become more frequent and intense, destabilizing marine ecosystems. This study analyzes Mediterranean Sea thermal stratification trends using Copernicus Marine Service reanalysis data at 12 aquaculture facilities in Spain, Croatia, Tunisia, Greece, Türkiye, Cyprus and Egypt, covering 35 years (1987-2021). Data were averaged over approximately 14 × 14 km around each facility to evaluate water-column thermal structure across latitudinal and longitudinal gradients. Two periods were compared: a reference period (1987-2010) and a post-period (2011-2021). Depth anomalies of the 25°C isotherm (calculated as the deviation from the reference period mean) and the Thermal Anomaly Stratification Index (TASI) were calculated to quantify deviations from historical baseline conditions. A consistent deepening of isotherms between 20 and 28°C was detected across the basin, with the most pronounced changes in the eastern and southern Mediterranean, following a clear longitudinal and latitudinal gradient. Statistically significant isotherm deepening was confirmed at five stations by a Wilcoxon signed-rank test. These shifting thermal patterns represent a growing threat to Mediterranean aquaculture, increasing heat stress on farmed species and compromising growth and productivity. A provisional risk classification framework based on the TASI is proposed to support managers and regulators in translating climate indicators into specific adaptation strategies, including adjustments to feeding protocols, stocking densities and farming calendars.

In this study, we apply a GIS-based proxy model to estimate the production carrying capacity within the official Spanish allocated zones for aquaculture (AZAs) designated for marine finfish in the Mediterranean region. The model used integrates georeferenced data on various factors such as distance between facilities, distance to priority habitats, depth, current velocity, and employment provided. The study area was divided into 1 x 1 km cells, each assigned a weighting value (V) based on the ranges identified in the proxy model. Prior to the capacity analysis, cells deemed unsuitable for aquaculture were removed in accordance with AZA zoning criteria, so estimates refer exclusively to already compliant sites. Additionally, three self-limiting factors (unit cost of production, tonnes of feed per hectare and cage arrangement) were analyzed separately as scenarios due to their dependence on existing and projected aquaculture facility data. The carrying capacity was classified according to the upper and lower values of the production granted to the Spanish facilities currently operating in the Mediterranean region as follows: low (LCC; < 10.6 t ha(-1) year(-1)), medium (MCC; 10.6(-1)87.5 t ha(-1) year-1) and high carrying capacity (HCC; >187.5 t ha(-1) year(-1)). Under the neutral scenario, 81.8 % of the AZA surface fell within the MCC class and Andalusia was the only region obtaining HCC (13.15 %). The Valencian Community and Catalonia showed larger shares of LCC (23.28 % and 16.17 %, respectively) while MCC dominated in all regions. The percentage of high-capacity areas increased when self-limiting factors were set to their maximum values, with 'tonnes of feed per hectare' having the most significant impact. These self-limiting factors are linked to best practices, such as reducing feed volume or improving spatial organization within concession areas. Our findings demonstrate how a proxy-based carrying capacity layer can support spatial planning and adaptative management of Mediterranean finfish aquaculture.

Environmental monitoring plans (EMPs) are essential for assessing and limiting the impacts of marine cage aquaculture. In the Mediterranean, EMPs are legally mandatory in many countries. However, inconsistencies in variable selection, analytical methods, and experimental designs limit regional comparability and hinder environmental assessments. This study evaluated EMPs from five finfish cage farms in southeastern Spain (2017-2022). We qualitatively compared sampling methodologies, measured variables, and experimental designs across physicochemical and biological components, and quantitatively assessed, using meta-analysis (logarithmic response ratios, random-effects models), which variables are most sensitive for detecting aquaculture-driven changes. Significant methodological inconsistencies were identified among consulting firms, particularly in variable measurement and analytical protocols. The meta-analysis identified suspended solids, chlorophyll-a, nitrate, ammonium, sediment organic matter, sediment redox potential, and dissolved oxygen as the most informative physicochemical indicators. Among biological variables, macrobenthic abundance showed the largest effect (substantially higher in impact areas), followed by faecal coliforms. Shannon-Wiener diversity and species richness were recorded across all farms but showed negligible effects, likely reflecting methodological inconsistencies rather than true ecological insensitivity. These results demonstrate the environmental effects of fish farming on surrounding ecosystems and highlight an urgent need for standardised EMP frameworks at the regional scale. Such frameworks must integrate both physicochemical and biological indicators with appropriate experimental design to enable reliable long-term assessment of marine aquaculture impacts.

This work describes a method to create submarine artificial structures based on light metallic structures covered by calcareous layers obtained by electrolysis in sea water, with full environmental safety of the process. For structures based on meshes of cylindrical steel wire, the thickness of the deposited layer increases linearly with time for widths up to 2 mm. In the case of thicker layers, mathematical modelization suggests that the evolution of the deposited layer width might not be linear. Under the experimental conditions of this work, the deposited layers were mainly composed of stable crystalline forms of calcium carbonate. No significant presence of magnesium containing minerals was found in the deposited layers. The composition and texture of the obtained surfaces might be deemed as optimum from the point of view of providing colonization sites for the sessile benthic organisms of interest. These structures may be used as elements that can be included in the design of environmental remediation applications. Regarding their potential applications, once deployed in the marine environment and colonized by sessile benthic filter-feeding species, the structures could contribute to the improvement of sea water quality in commercial ports or marinas, which might be affected by organic pollution.

Understanding species population trends is key for assessing their conservation status and proposing measures to ensure their future persistence amid recent biodiversity loss. However, studies are reporting contrasting biodiversity trends over time. These discrepancies can be partly attributed to biases in global datasets, which might not capture the representativeness of local processes. Here, we aimed to address this gap of knowledge by complementing data included in the Living Planet Database (LPD), one of the largest repositories of population time-series, with locally sourced data from the Iberian Peninsula. The study aim: (i) to assess the state of wildlife Iberian vertebrates using population time-series across taxonomic groups and (ii) to determine differences between locally sourced data and LPD (evaluating also the differences between data sources). To supplement LPD, we conducted a review, analysing over 6000 peer-reviewed manuscripts and grey literature documents. We obtained 999 population time-series for 294 vertebrate species compiled in an Iberian Vertebrate (IbeV) database, two times the number of populations as the LPD includes. Our results indicate contrasting population trends across taxonomic groups, with freshwater amphibians and bony fishes showing steep declines. Moreover, the LPD shows a positive trend and IbeV indicates no net change over time. Threatened species did not exhibit net changes in population trends, while non-threatened species showed positive trends. We showed that local databases can provide distinct population trends compared to global databases. This approach highlights the need to bridge the gap between global and local datasets, to support context-specific management and conservation programmes.

Farm sabotage can cause massive fish escape events with significant ecological and socio-economic risks. This study examined the fate of Mediterranean seabass Dicentrarchus labrax escapees following a large-scale escape event caused by sabotage in the Western Mediterranean Sea. We monitored the escapee density and size structure over 3 mo after the escape at increasing distances from the escape point, up to 45 km away. Fish density adjacent to the escape location 5 d after the sabotage was, on average, 114 ± 44.7 (SE) fish per 100 m2. Our analyses showed that fish density decreased by 17% for every km away from the location, dropping to 2 and 1% after 1 and 2 mo, respectively, following the escape event. As escapee density declined throughout time and space, the size distribution of seabass shifted towards larger sizes. The rapid decrease in fish densities highlights the need for contingency plans focusing on fishing efforts in the coastal areas near the escape location (<20 km) within the first 24 h. These results are paramount to mitigating the risks associated with escape events cost-effectively. We emphasise the importance of sabotage prevention measures, such as security systems that can quickly detect intruders and trigger an immediate response to deter them. Additionally, enforcing appropriate sanctions based on the severity of the damage caused could help to discourage future sabotage attempts.

Marine reserves are being established worldwide to conserve and manage marine resources, and are also often assumed to conserve the evolutionary potential of marine populations. However, comparisons of genomic patterns inside and outside marine reserves in multiple species are scarce. Here, we aim to fill this gap by 1) comparing genomic variation in protected versus unprotected areas in a network of eight reserves in the Mediterranean Sea, and 2) disentangling the effect of seascape, space and marine reserves on this genomic variation in 1297 individuals from four species genotyped at more than 10 000 SNPs each. We report homogeneous patterns of local genetic diversity within and outside reserves in three of the four species (the white seabream Diplodus sargus , the striped red mullet Mullus surmuletus and the European spiny lobster Palinurus elephas ). Surprisingly, the comber Serranus cabrilla shows lower genetic diversity in protected areas, highlighting an apparent conservation paradox that may be due to increased predation by protected fishes in the reserves. Multivariate analyses reveal that seascape factors (salinity, temperature and chlorophyll) and space exert a significant influence on genomic variation in some cases, while protection status has no detectable effect. Nevertheless, four marine reserves (Cabo de Palos, Cerbère‐Banyuls, Cap de Creus and Illes Columbretes) harbor singular genetic variation in one or two species. This pattern, observed in the four species, suggests that reserves contribute to preserve genetic variation locally. Our study illustrates that we can document key aspects of the genetic variation of marine species and their interaction with seascape factors, space and protection status in multiple species. It stresses the need for a multi‐species approach to inform marine conservation planning, opening up new perspectives at the community level.

Marine reserves are being established worldwide to conserve and manage marine resources, and are also often assumed to conserve the evolutionary potential of marine populations. However, comparisons of genomic patterns inside and outside marine reserves in multiple species are scarce. Here, we aim to fill this gap by 1) comparing genomic variation in protected versus unprotected areas in a network of eight reserves in the Mediterranean Sea, and 2) disentangling the effect of seascape, space and marine reserves on this genomic variation in 1297 individuals from four species genotyped at more than 10 000 SNPs each. We report homogeneous patterns of local genetic diversity within and outside reserves in three of the four species (the white seabream Diplodus sargus , the striped red mullet Mullus surmuletus and the European spiny lobster Palinurus elephas ). Surprisingly, the comber Serranus cabrilla shows lower genetic diversity in protected areas, highlighting an apparent conservation paradox that may be due to increased predation by protected fishes in the reserves. Multivariate analyses reveal that seascape factors (salinity, temperature and chlorophyll) and space exert a significant influence on genomic variation in some cases, while protection status has no detectable effect. Nevertheless, four marine reserves (Cabo de Palos, Cerbère-Banyuls, Cap de Creus and Illes Columbretes) harbor singular genetic variation in one or two species. This pattern, observed in the four species, suggests that reserves contribute to preserve genetic variation locally. Our study illustrates that we can document key aspects of the genetic variation of marine species and their interaction with seascape factors, space and protection status in multiple species. It stresses the need for a multi-species approach to inform marine conservation planning, opening up new perspectives at the community level.

The use of marine protected areas can be an effective way to simultaneously achieve both conservation and fisheries management objectives. The creation of marine protected areas, in addition to many benefits, also entails several costs, including the need for financing to maintain adequate surveillance and conservation. The recent economic crisis significantly lowered budgets for the maintenance of Spanish Marine Protected Areas, that may have had serious consequences for the marine resources sustainability. In this study we evaluated the indirect impact of the 2008 economic crisis on the conservation of fish stocks in Marine Protected Areas. We compared the number of species, abundance and biomass levels of the ichthyofauna, and abundance and biomass of selected species in two marine reserves (Cabo de San Antonio and Tabarca Island) with control areas, two years before (2008 and 2010) and two years after (2014 and 2015) the budget cut. Results in San Antonio revealed a decrease in total abundance, total biomass and number of species after the crisis, which translates into a decrease in the reserve effect. While in Tabarca no reduction has been observed in these variables, so the reserve effect was maintained after the crisis. We have found that of the 18 species analyzed, in San Antonio the abundance and biomass of 8 and 6 species respectively have decreased after the crisis, while in Tabarca the abundance and biomass of 6 and 8 species respectively have decreased after the crisis. Therefore, surveillance in marine reserves is necessary for the conservation of the species.

Increasing human pressure has strongly impacted the littoral environment, altering the habitats and population parameters of some species. The Mediterranean Sea is one of the regions that have been highly affected by these events. In response to these events, marine protected areas (MPAs) have emerged as one of the main conservation tools for marine habitats and species. In this regard, harvesting of limpets (Patella spp.) is a good example of the impact of human activity on the coast. Limpets are mollusks that are collected as food or fishing bait, and their exploitation causes an immediate decrease in the density and size structure of individuals. In the Mediterranean Sea, the genus Patella is represented by five species: Patella rustica, P. caerulea, P. ulyssiponensis, P. ferruginea, and P. depressa. To verify the effectiveness of the MPAs, a deep review of 75 studies on Patella spp. in the Mediterranean Sea was conducted to analyze the spatial and temporal distribution of studies. Data extracted from these articles were used to assess the effect of protection on the density and size of P. ferruginea. Regarding spatial distribution, the studies reviewed were performed at 67 sites in 13 countries, of which 23 were in MPAs and 44 in non-protected or control areas. The findings of this study show that P. ferruginea is the species most studied, because it is one of the most threatened marine invertebrates in the Mediterranean Sea. This explains the temporal distribution of the studies, which coincides with the establishment of the conservation status and the concern about the population status of P. ferruginea. Analysis of the effect of protection on the density and mean size of P. ferruginea individuals revealed no significant difference in mean density between the control sites and MPAs. However, mean size between individuals was significantly higher in MPAs than control sites. This pattern may be related to intra- and interspecific competition between individuals.

Coastal marine lagoons are environments highly vulnerable to anthropogenic pressures such as agriculture nutrient loading or runoff from metalliferous mining. Sediment microorganisms, which are key components in the biogeochemical cycles, can help attenuate these impacts by accumulating nutrients and pollutants. The Mar Menor, located in the southeast of Spain, is an example of a coastal lagoon strongly altered by anthropic pressures, but the microbial community inhabiting its sediments remains unknown. Here, we describe the sediment prokaryotic communities along a wide range of environmental conditions in the lagoon, revealing that microbial communities were highly heterogeneous among stations, although a core microbiome was detected. The microbiota was dominated by Delta- and Gammaproteobacteria and members of the Bacteroidia class. Additionally, several uncultured groups such as Asgardarchaeota were detected in relatively high proportions. Sediment texture, the presence of Caulerpa or Cymodocea, depth, and geographic location were among the most important factors structuring microbial assemblages. Furthermore, microbial communities in the stations with the highest concentrations of potentially toxic elements (Fe, Pb, As, Zn, and Cd) were less stable than those in the non-contaminated stations. This finding suggests that bacteria colonizing heavily contaminated stations are specialists sensitive to change.

Marine protected areas (MPAs) are globally important environmental management tools that provide protection from the effects of human exploitation and activities, supporting the conservation of marine biological diversity, habitats, ecosystems and the processes they host, as well as resources in a broad sense. Consequently, they are also expected to manage and enhance marine ecosystem services and material, non-material, consumptive and non-consumptive goods, and benefits for humans. There is however certain confusion on what constitutes an ecosystem service, and it is not always easy to distinguish between them and societal benefits. The main nuance is that an ecosystem service is the aptitude an ecosystem has or develops naturally or as consequence of a management action, and that manifests through its own properties (productivity, diversity, stability, quality of its key parameters, etc.), while a societal benefit is the economic or other profitability (emotional, educational, scientific, etc.) that humans obtain from said service or quality. In this work, 268 publications, together with our own experiences in the different investigations carried out in the MPAs that are part of the BiodivERsA3-2015-21 RESERVEBENEFIT European project, have been selected, reviewed and discussed to analyze the knowledge status of the expected ecosystem services of MPAs and the societal benefits derived from them, sometimes providing information on their evidence, when they exist. We define and classify the effects of protection, ecosystem services and societal benefits and elaborate a conceptual model of the cause-effect relationships between them.

How far do marine larvae disperse in the ocean? Decades of population genetic studies have revealed generally low levels of genetic structure at large spatial scales (hundreds of kilometres). Yet this result, typically based on discrete sampling designs, does not necessarily imply extensive dispersal. Here, we adopt a continuous sampling strategy along 950 km of coast in the northwestern Mediterranean Sea to address this question in four species. In line with expectations, we observe weak genetic structure at a large spatial scale. Nevertheless, our continuous sampling strategy uncovers a pattern of isolation by distance at small spatial scales (few tens of kilometres) in two species. Individual-based simulations indicate that this signal is an expected signature of restricted dispersal. At the other extreme of the connectivity spectrum, two pairs of individuals that are closely related genetically were found more than 290 km apart, indicating long-distance dispersal. Such a combination of restricted dispersal with rare long-distance dispersal events is supported by a high-resolution biophysical model of larval dispersal in the study area, and we posit that it may be common in marine species. Our results bridge population genetic studies with direct dispersal studies and have implications for the design of marine reserve networks.

The environmental impact of desalination is the most important concern related to its sustainable development. We present the results of a long-term environmental plan to monitor brine discharge (BD) from a desalination plant located in a high environmental value area in Spain. Generalized additive models were used to analyze the biological parameters of biological communities. Results of 17 years of BD monitoring show how its environmental impact can be minimized through well-planned decision-making between scientists and industry. The brine dilution prior to its discharge into an artificial channel of low ecological value significantly reduced the brine influence area. P. oceanica shoot production and echinoderms abundances were relatively stable across historical series and similar values in control and impacts locations were observed. Conversely, there was a higher abundance and species richness of fishes in the BD area. The important findings reported here should be considered for future applications in similar projects.

Long-distance (>40-km) dispersal from marine reserves is poorly documented; yet, it can provide essential benefits such as seeding fished areas or connecting marine reserves into networks. From a meta-analysis, we suggest that the spatial scale of marine connectivity is underestimated due to the limited geographic extent of sampling designs. We also found that the largest marine reserves (>1000km2) are the most isolated. These findings have important implications for the assessment of evolutionary, ecological, and socio-economic long-distance benefits of marine reserves. We conclude that existing methods to infer dispersal should consider the up-to-date genomic advances and also expand the spatial scale of sampling designs. Incorporating long-distance connectivity in conservation planning will contribute to increase the benefits of marine reserve networks.

Despite the Mediterranean being both a hotspot for recreational boating and for non-indigenous species (NIS), no data currently exists on the recreational boating sector's contribution to the spread of NIS in this Sea. To improve the basis for management decisions, a wide-scale sampling study on the biofouling communities of recreational vessels and marinas was undertaken. Specifically, we surveyed over 600 boat owners and sampled the same boat hulls for NIS in 25 marinas across the Mediterranean, from France to Cyprus, to determine which factors (i.e. boat characteristics, travel behaviour, home marina) are associated with higher NIS richness on boat hulls. Among the surveyed boats, we found recreational vessels to travel considerably, averaging 67 travel days and 7.5 visited marinas per annum. This results in a high potential for spreading NIS, especially as 71% of sampled vessels host at least one (and up to 11) NIS. Boats with high NIS richness strongly correlate with home marinas with high NIS richness. Over half of the vessels were carriers of NIS which were not yet present in the marinas they were visiting. The presence of biofouling in niche areas of the hull (i.e. in the cavities and metallic parts) emerges as the best predictor for NIS richness on boats, along with longer times since their last cleaning and antifouling applications. Interestingly, colonization of NIS occurred rapidly, even on boats that had recently had their hulls cleaned professionally. Synthesis and applications. We demonstrate that recreational boating has a very high capacity for the spread of non-indigenous species (NIS) in the Mediterranean, due to both high NIS richness on boats and extensive travel. To counteract the spread of NIS, routine monitoring for new NIS needs to be established for both marinas and vessels, along with frequent pontoon cleaning. Additionally, policy should require preliminary screenings for incoming vessels from new countries, especially those emanating from high-risk marinas. The niche areas of the boat hulls should be checked first for biofouling, which was the best predictor for NIS richness since they often go overlooked with in-water cleanings are rarely have antifouling applied to them.

• Factors shaping non-indigenous species (NIS) richness are tested in the Mediterranean. • There is a higher trend of NIS richness going from east to west in the Mediterranean. • NIS richness in marinas is mainly influenced by proximity to other major vectors. • NIS similarities between marinas are more influenced by environmental factors. • The Suez Canal exerts a very strong influence for NIS in Mediterranean marinas.