The increasing intensity, frequency, and duration of extreme climatic events (ECEs) due to climate change pose additional pressures on seagrass habitats in lagoon ecosystems. Among these ECEs, this study investigates the impact of marine heatwaves (MHWs) on three seagrass species from Mediterranean lagoons: Cymodocea nodosa, Nanozostera noltei, and Ruppia cirrhosa. Using a near-natural mesocosm, we simulated a 20-day MHW at three intensities (+ 2 °C, + 4 °C, + 6 °C above control) during spring and summer, and assessed changes in growth, respiration, and gross primary production. Species and seasonal responses varied. C. nodosa exhibited enhanced net foliar growth in spring and stable growth in summer. N. noltei benefited from moderate warming in spring but was vulnerable to high-intensity heatwaves in summer. R. cirrhosa was resilient in spring and exhibited increased growth in summer, particularly at + 4 °C. Overall, all three species tolerated a single 20-day MHW, with relative adaptation ranked as N. noltei < R. cirrhosa < C. nodosa. A common response across species was the initiation and growth of new leaves, although less pronounced in R. cirrhosa. Our experimental approach reveals clear species- and season-specific responses to MHWs, highlighting the complexity of seagrass resilience in lagoon ecosystems. In particular, seagrasses from lagoon environments display robust short-term tolerance to MHWs, with only N. noltei showing vulnerability to the highest summer intensity. These results indicate that while lagoon species are adapted to variable environments, their resilience may be challenged by increasingly frequent and prolonged MHWs expected under future climate change.

Early observations and adequate monitoring of non-indigenous species are of paramount importance for conservation, as biological invasions are among the top five drivers for declines in biodiversity. This case study focuses on the Atlantic blue crab (Callinectes sapidus), which has unexpectedly become invasive since 2020 in French Mediterranean coastal lagoons. We analyse the development of its multi-actor monitoring, in which local actors mobilise multiple techniques to produce diversified knowledge, driven by both scientific and political considerations. We examine how the diversification of techniques shapes biodiversity monitoring practices, in order to understand why, despite successive innovations, novel techniques for monitoring aquatic species do not replace former techniques but rather accumulate and complement each other. We used qualitative methods combining multi-sited observation and 33 semi-structured interviews with scientists, fishers and public policy stakeholders to identify the drivers and barriers to multi-actor monitoring. On the one hand, multi-actor monitoring is facilitated by a strong alignment of aquatic conservation and socio-economic objectives for managing the Atlantic blue crab. This allows the exchange of environmental knowledge and technical know-how among stakeholders, therefore fostering their autonomy for implementing monitoring initiatives and subsequent adaptive management measures. On the other hand, several barriers hinder long-term engagement in multi-actor monitoring, as producing environmental data implies an unequal division of labour depending on geographical and social position. Placed in the context of the Europeanisation of environmental conservation policy, these results offer a more nuanced perspective on the thesis that standardising monitoring at the supranational level would lead to a decline in the diversity of local knowledge about nature.

The integration of ecosystem services into the impact assessment phase, through the development of characterization models that reflect potential impacts on ecosystems’ capacity to provide services, is gaining momentum within the life cycle assessment community. This integration requires reflection on the positioning of concepts related to ecosystem services such as ecosystem functions, ecosystem services potential and flow within the life cycle impact assessment framework and in relation to common indicators. This research posits that the concepts linked to ecosystem services are at the crossroads of most characterization models, and proposes a revamped vision of the conceptual life cycle impact assessment framework. Its use is exemplified for the IMPACT World+ methodology. Building on the areas of protection proposed by Verones et al. (2017), the framework introduces a revised “Ecosystem Services” area of protection, which aggregates potential impacts on the instrumental value of social-ecological systems. Here, the term “Ecosystem Services” follows the Common International Classification of Ecosystem Services (CICES v5.2) and is used as an umbrella concept encompassing both biophysical ecosystem services and geophysical ecosystem outputs, noting the deviation from definitions of “ecosystem” provided by the UN’s Convention of Biological Diversity and some ISO standards. The revamped life cycle impact assessment framework is structured around the ecosystem services “cascade model”. It identifies causal pathways linking human activities to changes across different stages of the cascade and, ultimately, to the areas of protection. The framework considers the consequences of replacement strategies in response to declining services flows: replacement costs, indirect impacts associated with boundaries’ expansion, deficit of services, and potential impacts on human health. Existing characterization models from the IMPACT World+ methodology are mapped within this new structure. The framework reconciles natural resources- and ecosystem services-oriented characterization models, helps identify priorities for the development of characterization models in the IMPACT World+ methodology, and offers perspectives for integrating ecosystem disservices into life cycle impact assessment. By rethinking the life cycle impact assessment structure through the perspective of ecosystem services and related concepts, this work establishes a conceptual basis for the development of more coherent, comprehensive, and operational life cycle impact assessment models and methodologies.

This paper presents the first study examining the relationship between angiosperms, their associated bivalves, and environmental conditions, with the aim of assessing the health of the El Mellah lagoon. The study was conducted monthly throughout 2019 at three stations selected for their continental and marine influences. The seagrass beds exhibit remarkable abundance, with biomass reaching up to 1313.32 +/- 132.73 g DW m-2 in September. The biomass of Zostera noltei is positively correlated with temperature, while that of Ruppia maritima is positively correlated with salinity. Bivalve density in El Mellah follows the variation in seagrass bed biomass. The densities of the native bivalve Loripes orbiculatus and the invasive species Arcuatula senhousia increase with both the aboveground and belowground biomass of Z. noltei, as well as with temperature. This suggests the existence of a tripartite mutualism between seagrass beds, lucinid bivalves, and their sulphide oxidising gill symbionts. These findings highlight the importance of investigating the factors influencing the mutualistic relationship between seagrasses and lucinid bivalves in the El Mellah lagoon, not only to improve the long-term success of seagrass restoration but also to strengthen their resilience to climate change.

A territory, which is a geographical area qualified by a legal affiliation or by a natural or cultural feature, presents an appropriate scale for establishing responsibilities and initiating sustainable development actions. At the same time, globalization implies constant interaction of territories with the rest of the world. The management of territorial projects therefore requires a revised set of environmental assessment tools that consider local and global issues with a multi-scale perspective. The environmental benefits of land use policies can, however, remain hidden behind global approaches such as life cycle assessment (LCA), which are generally product-oriented and tend to ignore ecosystem services (ES). This paper aims to propose new decision-making tools for land use planning based on the joint use of ecosystem services assessment (ESA) and territorial Life Cycle Assessment (T-LCA). Within the T-LCA framework, two main types of indicators were quantified. On the one hand, the services provided by land planning scenarios were computed by the ESA by considering provisioning, cultural and regulation ES. On the other hand, environmental impacts were characterized using the Impact World+ Life Cycle Impacts Assessment (LCIA) method.Two contrasting scenarios and a business as usual scenario (BAU) were studied and compared as a proof of concept. Scenario 1 focused on productive economy by maintaining and diversifying the shellfish farming sector, which is a strong component of the area's social identity. Scenario 2 favoured the development of tourism. Overall, the results indicated that environmental damages varied only slightly between scenarios, with tourism activities (i.e., transport and accommodation) emerging as the primary contributors. In contrast, there were very different profiles in terms of socio-economic benefits depending on the scenario. Provisioning ES were very high in scenario 1, while scenario 2 led to a clear increase in cultural ES. This research emphasizes the importance of developing integrated assessment approaches when creating local planning policies, in order to identify potential trade-offs between environmental impacts and benefits, and local and global issues.

Marine Functional Connectivity (MFC) is a dynamic ecosystem process encompassing all the flows (of individuals, genes, matter and energy) driven by changes in the distribution and movement of marine organisms at sea and across the land-sea-air interface. Continuing advances in MFC understanding enhance our ability to evaluate the status, trends, and variability in marine species abundance, the drivers of change, and the role of marine species movement in the functioning of the biosphere. Ultimately, good knowledge of MFC is fundamental to advance models and forecasts of species and ecosystem distributions and resilience, and to develop scenarios that are possible outcomes of policy decisions. This talk explores how MFC knowledge can best improve the design of effective strategies for the sustainable and equitable use of marine ecosystems and resources. It summarizes practical transdisciplinary findings from several expert groups, convened in 2024 by the European COST Action/UN-Ocean Decade project SEA-UNICORN, the O-CONNECT working group of the French OMER GDR, and the UN-Ocean Decade Programme Marine Life 2030 to initiate the co-design of “the connectivity science and decision-making tools we need for the ocean we want”. Bringing together over 80 scientists, policymakers, and stakeholders from 22 countries, this initiative led to the production of key recommendations on how best to advance MFC data production and use to enhance: (1) Marine Protected Area design and management; (2) fisheries management; (3) blue economy development; (4) integrated management at the land-sea interface; (5) coastal and marine restoration; and (6) deep seas and high seas exploration and management.

More than five decades before the introduction of "environmental filtering" in plant and vegetation sciences, Baas Becking proposed that the "environment selects" for studies in microbial ecology. He coupled this with the ubiquity law that he proposed for microbes to obtain the tenet "everything is everywhere, but, the environment selects". Nowadays, while this tenet is mostly used as a null hypothesis for studies of microbial biogeography, the latter part has large implications for niche assembly theories. In this respect, it is very similar to the idea of "environmental filtering", although some minor differences exist regarding how both concepts have been applied in macrobial and microbial ecologies. During the second decade of the 21st century, the usefulness of the latter has been questioned due to difficulties in disentangling the roles of environmental (abiotic) filtering and ecological interaction in community assembly. A new vision has emerged in the literature that considers the environmental filter as dynamic and continuously influenced by biotic communities. With a small modification, this scheme provides a solution that can accommodate the ecologies of both microbes and macro-organisms for a common niche assembly theory.

This paper focuses on the challenges for the co-implementation of two European Union Directives, i.e., the Habitats Directive and the Water Framework Directive, for the management of Mediterranean coastal lagoons as protected areas. Many of these ecosystems are included in the Natura 2000 network, the largest network of protected areas in the world. Based on semi-structured interviews with 45 stakeholders from 41 institutions, the study identified five main types of perceived barriers: economic, political and socio-cultural, historical, administrative, and ecological. The study confirmed that the co-implementation of the Habitats Directive (HD) and the Water Framework Directive (WFD) in Mediterranean coastal lagoons generated multiple and interrelated barriers. Beyond their regulatory complexity, these EU directives confronted managers with deep operational challenges. First, mismatches between administrative and ecological boundaries weakened their ability to control key ecological processes such as nutrient flows. Second, the proliferation of indicators, often perceived as disconnected from local realities, reinforced the critique of a management by numbers approach. Finally, the widespread use of regulatory exemptions, while intended to adapt EU rules to local contexts, frequently fueled persistent mistrust among stakeholders, especially in historically degraded environments. These challenges were further exacerbated by a siloed organization of administrations, limiting coordination and adaptive management. Overall, these findings call for more integrated governance frameworks, a more critical and context-sensitive use of indicators, and greater transparency in derogation procedures.

The increased intensity, frequency and duration of extreme climatic events (ECEs) in the context of climate change have been recognised as additional pressures for seagrass habitat in lagoon ecosystems. Among these ECE, this study focuses on the impact of marine heatwaves (MHWs) on seagrass species in Mediterranean coastal lagoons, i.e., the seagrasses Cymodocea nodosa, Nanozostera noltei, and Ruppia cirrhosa. We experimentally assessed with a near-natural mesocosm, the effects of a 20-day heatwave at three intensities (+2, +4, +6°C above control near-natural conditions) in spring and summer on these seagrass species and quantified changes in growth performance, respiration, and gross primary production. Responses to these MHW varied by species and season. C. nodosa responded differently to MHWs in spring and summer, its net foliar growth rate being stimulated and maintained, respectively. N. noltei responded positively to moderate MHWs (+2, +4°C) in spring but showed vulnerability to the high-intensity MHWs (+6°C) in summer. R. cirrhosa remained resilient in spring and benefited from MHWs in summer, particularly at +4°C intensity, to stimulate growth. Hence, all three species were able to tolerate a single 20-day MHW with the species being increasingly better adapted in the following order N. noltei, R. cirrhosa, and C. nodosa. Increase of the initiation and growth of new leaves was a common phenological response observed in all three species, albeit at a lesser extent for R. cirrhosa. Our near-natural experimental approach reveals species- and season-dependent responses to MHWs, highlighting the complexity of seagrass resilience in lagoon ecosystems. These findings provide valuable insights to inform conservation strategies and improve the management of coastal habitats under future climate scenarios. ### Competing Interest Statement The authors have declared no competing interest.

This paper presents spatio-temporal variations of angiosperms, bivalves associated with them, to the environmental and conditions of the El Mellah lagoon in 2019 under continental and marine influences. Our results showed significant changes in their distribution, which appear to be linked to fluctuations in the environmental conditions and climatic change, between Zostera noltei and Ruppia maritima, while the seagrass beds are remarkably abundant, with a biomass that can reach 1313.32 ± 132.73 g DW.m -2 during the summer period. we have identified macrofauna made up of five species of bivalves: Cerastoderma glaucum, Abra ovata, Ruditapes decussatus, Loripes orbiculatus, and Arcuatula senhousia. Our results also highlight for the first time, an invasive species A. senhousia, the species dominates the bivalve community. and two threatened edible species in this area, R. decussatus and C. glaucum, probably due to the climat change, the reduced distribution of the Ruppa maritima meadow and silting of the channel.

This paper discusses how ecological restoration has been pursued through projects financed by L'Instrument Financier pour l'Environnement (LIFE) of the European Commission in Mediterranean and Black Sea coastal lagoon sites affiliated with the Natura 2000 network. While the LIFE programme started in 1992, the first project focusing on ecological restoration in a coastal lagoon setting in this eco-region was attributed in 1995. In total, 50% (27) of the 54 LIFE projects in the Mediterranean and Black Sea coastal lagoons comprised a worksite on ecological restoration. Eighteen finalized projects, all realized after 2008, have been sufficiently documented for our analysis. The ecological restoration works included (i) removing solid waste and alien invasive species, (ii) re-building lagoons, (iii) creating islets for bird colonies, (iv) restoring the hydrodynamics of the lagoons, and (v) restoring and protecting vegetation. The latter includes submerged aquatic vegetation in the lagoons, halophytes on tidal flats and in fringing salt marshes, freshwater marsh plants, and dune vegetation. Abandoned salt works (Salinas), originally created within the coastal lagoons or on their shoreline, represent significant areas that can be managed for conservation or restoration. Coastal lagoons are transitional waters, and successful restoration of water quality and aquatic communities must include the concept of the aquatic continuum. Combating eutrophication requires managing the watersheds of the lagoons to drastically decrease nutrient loadings. Unfortunately, these issues have only been marginally addressed by the LIFE projects, as they were too often limited by the perimeter of the Natura 2000 sites. In principle, the Water Framework Directive takes care of these issues and, according to an integrative vision, links them with the protected Natura 2000 sites. In practice, however, the LIFE projects and the water policies in the member states still suffer from sectorial approaches.

Coastal lagoons have been recognised as a priority habitat for conservation and have benefited from several conservation plans. Under the Mediterranean climate, some of these lagoons might dry out during summer due to drought events. We propose the term Mediterranean Temporary Lagoons (MTLs) for these ephemeral water bodies and discuss their definition and characteristics. This term emerged in France among its coastal zone managers, who now commonly use it for conservation purposes. It is used in both natural systems as well as most artificial salt ponds in abandoned saltworks. In Europe, two directives have integrated lagoons as key targets to be preserved. Nonetheless, a certain discrepancy in the different definitions of lagoons has constrained joint actions. Indeed, while institutional definitions were originally derived from the scientific concept, their legislative and managerials meanings have been gradually modified and nowadays often differ from the original concept to create difficulties in the field. In addition, while it has been recommended to consider MTLs as a coastal lagoon habitat in the European Habitat Directive, its interpretation among EU member states is unsettled. Thus, clarifying lagoon habitats' terminology is required to ensure better management, monitoring and planning, and coordinate conservation actions. We discuss the inclusion of MTLs in habitat 1150 by confronting scientific and institutional literature and propose a new framework to better delimitate lagoon habitat around the Mediterranean basin, integrating MTLs. MTLs represent a specific habitat that hosts a pool of stenoecious macrophytes of conservation interest like Althenia filiformis, Riella helicophylla or Tolypella salina.

Assessing the environmental status of Protected Areas (PAs) is a challenging issue. To indicate that status, the identification of a common set of variables that are scientifically sound, and easy to assess and monitor by the PA practitioners, is particularly important. In this study, a set of 27 Essential Variables (EVs) for PA management was selected in a bottom-up process from 67 harmonised variables that describe the status of Ecosystem Functions and Structures, Ecosystem Services, and Threats in PAs. This bottom-up process involved 27 internationally recognised PAs, mostly European, with different level of protection, different extent, and a wide range of human-nature interactions. The EVs were selected by more than 120 practitioners, i.e. PA managers and rangers, as well as scientists, working in terrestrial and aquatic PAs. Across both terrestrial and aquatic PAs, scientists and practitioners largely identified the same variables as important. Data availability for these 27 EVs varied between PAs and av eraged 67% across all studied PAs. As this set of EVs for PAs is defined through a bottom-up approach considering variables already in use both in management and research, it is more than for previous EVs likely to be adopted, applied and developed to record the status and changes in the ecological and socio-economic conditions of PAs and to forecast future changes. Thereby, the EVs for PAs present a common vocabulary and tool to enhance in a uniform way the (inter)national communication, exchange and comparison of information on the status of PAs between policy makers, scientists and PA managers. The perceived status of the EVs, on an average 3.6 on a scale to a maximum of 5, indicates the surveyed PAs are in a moderate to good environmental condition. Moreover, the EVs for PAs form a cost- and time-efficient tool for PA managers to monitor developments in essential elements of their PAs, including the potential for Societal Goods and Benefits (SG&B), and to (pro-)actively tackle the potential threats that may arise in their area. Likewise, for policy makers EVs for PAs may support decision making on ecosystem management, spatial planning, and predictive modelling on the future status and requirements of PAs in their country or region.

This paper describes an empiric study of aggregation and deliberation—used during citizens’ workshops—for the elicitation of collective preferences over 20 different ecosystem services (ESs) delivered by the Palavas coastal lagoons located on the shore of the Mediterranean Sea close to Montpellier (S. France). The impact of deliberation is apprehended by comparing the collectives preferences constructed with and without deliberation. The same aggregation rules were used before and after deliberation. We compared two different aggregation methods, i.e. Rapid Ecosystem Services Participatory Appraisal (RESPA) and Majority Judgement (MJ). RESPA had been specifically tested for ESs, while MJ evaluates the merit of each item, an ES in our case, in a predefined ordinal scale of judgment. The impact of deliberation was strongest for the RESPA method. This new information acquired from application of social choice theory is particularly useful for ecological economics studying ES, and more practically for the development of deliberative approaches for public policies.

Preferences elicitation can be a challenging exercise for citizens participating in assessment surveys. It is even more challenging when it comes to complex and unfamiliar ecosystems and the threatened ecosystem services they provide. Making people aware of the characteristics of the ecosystem services being valued is determinant for the assessment process. We investigated the impact of familiarity and academic information supply on people's preferences for twenty selected ecosystem services of French Mediterranean coastal lagoons. The results show that regardless of familiarity and information supply, there is a strong consensus about the highest importance of regulation and maintenance ecosystem services as well as environmental education and research opportunity ecosystem services. By contrast, nine of the cultural ecosystem services, together with two provisioning ecosystem services showed heterogeneous preferences among the different citizen groups. Using a combination of descriptive and inferential statistics these eleven ecosystem services split up into three clusters characterized as (i) contemplative leisure, (ii) heritage, and (iii) consumptive activities. Familiarity and academic information supply had a strong impact on the preferences for these three clusters of ecosystem services.

We provide a cartography of the current property regimes of permanent coastal lagoons along the coastlines of the Mediterranean Sea for continental France and Corsica, which include both private and public properties. In France, for the latter, the State Domain Code and the General Code of the property of public persons make a clear difference between Public Domain and private property of the different public entities. Public domain represents property that is imprescriptible and inalienable, i.e. the property rights cannot be changed in the future and neither transferred nor sold to somebody else. In contrast, private properties of public entities can be sold or transferred to thirds. Maritime Public Domain (DPM) was created since 1681. DPM has accommodated Public Domain for the French coastal lagoons following their legal definition as "salty ponds (French e & acute;tangs sale & acute;s) with a direct, natural and permanent connection with the sea". However, private landlords battled juridically with the State for centuries both by attacking the pertinence of this definition and claiming ancestral property rights. As a result, before 1980, more than half of the coastal lagoons comprised private properties, representing about a quarter of the lagoon surface. Twelve of 40 coastal lagoons comprise DPM, mainly the larger lagoons (e.g., SalsesLeucate, many lagoons close to Narbonne, Thau lagoon, Berre lagoon), representing 65% of the total lagoon surface. Since its foundation in 1975, the Conservatoire du Littoral, a public body in charge of coastal nature protection, has bought private coastal lagoons properties in twenty of 40 lagoons, representing 22% of the total lagoon surface. These have been designated as inalienable and imprescriptible "Public Domain of the Conservatoire", safeguarded for nature conservation purposes. Nowadays, private ownership still persists in 13 lagoons representing 3.3% of total surface. The Coastal lagoons in Roussillon (Etangs du Canet and Salses-Leucate), the He & acute;rault department, in the Camargue and in Corsica currently show variable and sometimes fragmented ownership (in addition to the Conservatoire, DPM, private ownership, municipalities, departments). Fragmented ownership is a clear difficulty for the integrated management of coastal lagoons. With currently, 87% of the coastal lagoons as Public Domain, public law and the environmental code have to evolve to tackle the challenges for the conservation and management of coastal lagoons and their connectivity with the other ecosystems on land and in the sea.

The impact of changes in nitrogen (N) and phosphorus (P) availability on the trophic strategies of planktonic protists was evaluated in a disturbed Mediterranean lagoon (Biguglia lagoon, France) using short-term bioassays. Natural communities were collected in three periods, i.e., autumn, spring and summer, to address the influence of the different environmental conditions. The responses of autotrophic plankton communities to experimentally induced N and/or P limitations were assessed as changes in chlorophyll a (Chl a) concentrations and in the abundances of potentially mixotrophic protists taxa. We observed blooms (> 105 cells l−1) of nanoflagellates in autumn, and of phycocyanin-rich picocyanobacteria in summer. Communities showed a co-limitation by N and P at the three sampling periods, despite high N:P ratios in autumn and spring. The high abundances of potentially mixotrophic dinoflagellates during these periods suggest the involvement of alternative trophic pathways for their maintenance in the lagoon. After bioassay incubations using different nutrient enrichment treatments, we often observed reduced abundances of mixotrophic protists containing Chl a with a concomitant increased abundance of protists without Chl a. This indicates a loss of chloroplasts and photoautotrophic abilities in protists cells, possibly reflecting a shift towards heterotrophy that could be sustained by phagotrophy.

This paper describes an empiric study of aggregation and deliberation used during citizens’ workshops for the preference elicitation of 20 different ecosystem services (ESs) delivered by the Palavas coastal lagoons located on the shore of the Mediterranean Sea close to Montpellier (S. France). The impact of deliberation for the preference elicitation of 20 different ecosystem services (ESs) was studied by gathering and aggregating individual preferences before deliberation that were compared to the collective aggregation after deliberation. The same aggregation rules were used before and after deliberation and we compared two different aggregation methods, i.e. Rapid Ecosystem Services Participatory Appraisal (RESPA) and Majority Judgement (MJ). RESPA had been specifically tested for ESs, while MJ evaluates the merit of each item, an ES in our case, in a predefined ordinal scale of judgment. The impact of deliberation was strongest for the RESPA method. This new information acquired from application of social choice theory is particularly useful for ecological economics studying ES, and more practically for the development of deliberative approaches for public policies.