A review of the effectiveness of solutions to achieve the good environmental status of the marine environment

1 Introduction

Europe’s seas are a dynamic, ecologically complex mosaic of interconnected marine regions, covering more than 11 million km² (EEA, 2015), each hosting distinct habitats and species. They deliver essential ecosystem services, such as seafood, climate regulation, and opportunities for recreation and leisure, which translate to key benefits for humans in terms of nutrition, habitable living environment, and well-being (Culhane et al., 2019; EEA, 2019; IPCC, 2019), while being attached to a key cultural and historical role.

However, the ever-increasing human activities and demand for marine resources have put Europe’s seas at the nexus of a “triple crisis” of biodiversity and habitat loss, climate change, and pollution, with each of these elements reinforcing the others (EEA, 2019; Andersen et al., 2026). Unsustainable resource extraction, nutrient and chemical pollution, seabed disturbance from infrastructure development, non-indigenous species, and increasing land- and sea-based activities have been increasingly pushing Europe’s marine ecosystems to the limits of their capacity to self-renew, eroding their resilience and capacity to provide ecosystem services (EEA, 2019). Climate change acts both independently and as a multiplier, through e.g., short- and long-term changes in temperature, oxygen loss and acidification (Andersen et al., 2026), accelerating and amplifying the severity and complexity of this impact (EEA, 2023, 2024).

To address these issues, over the past decades the European Union (EU) has gradually established an increasingly complex and integrated legal and policy framework, aiming to balance the protection of the marine environment with its sustainable use (Bigagli, 2015). This framework is centered around the Marine Strategy Framework Directive (MSFD; 2008/56/EC), which established an ecosystem-based approach to achieve the Good Environmental Status (GES)¹ of Europe’s seas, centered along 11 Descriptors (see Table 1). This framework includes several other legal instruments and policies aiming to protect key habitats or species (e.g., the EU 2030 Biodiversity Strategy, the Nature Restoration Regulation 2024/1991, and the Habitats and Birds Directives), ensure the sustainability of resource extraction (e.g., the Common Fisheries Policy, CFP), the sustainable planning of maritime activities (Maritime Spatial Planning Directive 2014/89/EU), and regulate and minimize the impact of specific pressures (e.g., contaminants, nutrients, wastewater discharges, waste and marine litter), such as the Water Framework Directive (WFD; 2000/60/EC). Although essential, these policies proved to be insufficient. Despite encouraging signs of improvement and recovery, the objective of the MSFD to achieve GES in all EU marine waters by 2020 was not reached. Gaps in GES definition, a lack of consideration of climate change, as well as uneven ambition, insufficiency of measures, gaps in monitoring and data comparability, and inadequate integration between the MSFD and other key policies, such as the CFP and the MSP Directive, have been identified as major factors behind this failure (EC, 2020, 2025).

Table 1. The 11 GES descriptors of the MSFD.

The aim of this study was to review the measures and solutions that have been implemented to address the ecological features and the pressures covered by the 11 MSFD GES Descriptors, and to assess their effectiveness, their benefits and trade-offs, as well as their implementation constraints. By providing a comprehensive picture of the current experience in addressing pressures and impacts and achieve GES, the findings of this study may support EU Member States in the implementation of the MSFD, by identifying the most effective measures to achieve GES for their marine waters, including their strengths and limits.

2 Materials and methods

This review was performed along the following steps (further details are provided in the Supplementary Materials):

Step 1. Identification of the relevant studies. Two online databases were employed to search for relevant scientific, peer-reviewed articles: Google Scholar and ScienceDirect. These databases were first queried in July-August 2025; a second query was performed in February-March 2026, and a third search in September 2026 following the first round of peer review, to integrate the results following reviewers’ comments. The queries employed combined general keywords related to effectiveness with specific keywords tailored to each MSFD Descriptor, using the Boolean “AND” operator. For example, to search for studies addressing the effectiveness of MPAs, the following combination of keywords was employed, among others: “effectiveness” AND “MPAs”. The full list of the two sets of general and specific keywords is presented in the Supplementary Materials.

Step 2. Selection of pertinent studies. Because of the structure and functioning of these two databases, the preliminary research retrieved several hundreds, or even thousands of scientific articles. These were screened to identify only those that were pertinent to our research, i.e., only those that focused on measuring and/or assessing the effectiveness of specific measures and solutions in relation to the MSFD Descriptors. The others were discarded.

Step 3. Extraction of the relevant data and information. Next, the text of the pertinent studies was reviewed to extract the following information: (i) the type of policy measure assessed; (ii) information on the quantitative/qualitative evaluation of its effectiveness; and (iii) the identification of co-benefits, trade-offs, possible implementation concerns and limits to its effectiveness.

Step 4. Backward and forward citation search. During the extraction of relevant information, a backward citation search was performed to include relevant research that was cited by the main studies analyzed. Moreover, a forward citation search was also performed, by using the “cited by” function in the two search engines, to check for newer studies covering a certain topic. Step 3 was repeated for these additional studies. At the end of this process, a total of 222 valid scientific articles were retrieved and analyzed across all MSFD Descriptors. The number of studies analyzed for each Descriptor, as well as those that were pertinent to more than one Descriptor, is presented in Table 2, while the full list of studies is presented in Supplementary Table SM1 in the Supplementary Materials.

Table 2. Number of pertinent studies analyzed for each MSFD descriptor, and number of studies pertinent to more than one descriptor.

The full list of pertinent studies is in Supplementary Table SM1 in Supplementary Materials.

3 Results

3.1 Descriptor 1: biodiversity

Existing measures proposed to achieve GES for biodiversity can be grouped in two main categories: conservation and restoration measures. In addition, the achievement of GES in the so-called pressure-related descriptors –D2, (partly) D3, D5, (partly) D6, D7, D8, D9, D10, and D11– will support the achievement of GES for D1.

3.1.1 Marine protected areas

MPAs are widely considered as the main pillar of marine conservation. Global (Hopf et al., 2016) and European-level (Fenberg et al., 2012) reviews have shown that MPAs lead to an increase in key biological variables (biomass, density, body size, species richness) of organisms within their boundaries, especially marine mammals such as harbor seals (Jensen et al., 2017; Grau Tomás and García Sanabria, 2022), narwhals and Hector’s dolphins (Gormley et al., 2012), and humpback whales (Calambokidis et al., 1997). Moreover, MPAs can promote the dispersal of larvae (Harrison et al., 2012) and adults of target and non-target species to areas outside their borders, potentially benefiting both fisheries and biodiversity outside the MPA (Di Lorenzo et al., 2016; Pendleton et al., 2018). MPAs were reported to allow for faster recovery and improve the resilience of benthic fauna after storm damage (Sheehan et al., 2021, as cited by Renn et al., 2024). Furthermore, they may help address both climate change mitigation, as the protection of seagrasses, kelp, and sediments may increase carbon storage (The Nature Conservancy, 2022), and adaptation (Davis et al., 2019). Ensuring a coherent and well-connected network of MPAs, based on an ecosystem function approach, and including sites in healthy condition, with positive reproductive rates, fosters the effectiveness of passive restoration (ICES, 2025). Positive effects are particularly evident for strictly protected MPAs (i.e., those that prohibit commercial activity and allow only light fishing) and fully protected, or “no-take” MPAs (i.e., those that prohibit also fishing; Lester and Halpern, 2008; Edgar et al., 2014; Gill et al., 2017), which showed to outperform multiple-use MPAs from an ecological standpoint (Rodríguez-Rodríguez and Martínez-Vega, 2022). Partially protected MPAs also proved to be effective in relation to specific features (Sciberras et al., 2013).

The effectiveness of MPAs depends on their objectives, the ecological and human contexts in which they are situated, the degree of involvement of stakeholders, and how well their management and enforcement is resourced (Pendleton et al., 2018). Fenberg et al. (2012) pointed out that the positive effects of marine reserves may take years, decades, or even longer to accumulate. Moreover, Smith et al. (2023) showed that MPAs may have a limited ability to mitigate the impacts of marine heatwaves on community structure. At the socioeconomic level, MPAs may entail economic losses for those stakeholders engaged in prohibited activities (Simons et al., 2023), greater fishing pressure on nearby fishing grounds, increased conflicts between fishers and possible shifting of pressure from one species to another (Sanchirico et al., 2002). In particular, restrictive measures, such as fishery no-take zones or no-anchoring zones, may conflict with existing uses of the marine environment and have negative impacts on the livelihoods of dependent communities (Herrera et al., 2021), potentially leading to overfishing in nearby areas and/or increase in accidental captures (Vivier et al., 2021). Also, if left uncontrolled, increased tourism driven by MPA attractiveness could have negative impacts, offsetting the biological and cultural benefits (Sanchirico et al., 2002).

3.1.2 Restoration measures

The numerous active (or direct) and passive (or indirect) ecological restoration projects implemented from 1950 have been successful in 64% of cases globally (Danovaro et al., 2025), providing benefits such as self-sustaining or expansion of the restored habitat-forming species over time, increased biodiversity including iconic and highly endangered species (van Katwijk et al., 2016; Thorhaug et al., 2020), and nursery and foraging areas for other marine species (Rogers et al., 2019). Restoration efforts showed to be viable for a large variety of marine habitats, scalable, and effective even in areas with persistent human impacts, provided the main pressures and stressors are removed (van Katwijk et al., 2016; Arnkil et al., 2024). Passive restoration measures may be the first step in a multi-tier strategy to abate pressures, paving the way for the implementation of active restoration measures as a second step (Manea et al., 2023). On the negative side, there may be trade-offs between long-term, large-scale passive restoration and small-scale, quick-gain active restoration measures, especially in case of limited funds, or of transboundary areas where coordination between different authorities and government levels is necessary. “Engineered” solutions are restoration measures that explicitly incorporate the design or modification of ecosystems or specific ecosystem elements. They include approaches such as the replacement of traditional built infrastructure with newly created or restored coastal ecosystems, or the design of new infrastructure (e.g., breakwaters) to add structural complexity and promote the settlement of marine organisms, such as seagrass (Tan et al., 2020). However, while promising, these approaches are extremely high-cost and have possible side effects, including seagrass disruptions due to loose sediments creating increase in turbidity, dredging and filling, or changing/increasing sediment transport away from shorelines (Thorhaug et al., 2020). Moreover, focusing on maximizing only one or a few ecosystem services may increase the risk of project failure, as it can lead to regime shifts with unfavorable and unexpected sudden loss of other services, and lead to conflicts among stakeholders on the perceived benefits/disbenefits (Unsworth et al., 2025).

3.1.3 Nature-based solutions

NbS partially overlap with active restoration, although they also include a wide variety of pressure-reduction measures, such as enhanced or artificial wetlands, erosion control zones and even harnessing wind and solar power to reduce noise and pollution. Positive effects of NbS have been reported for the passive and active restoration of coastal wetlands. These provide nursery and shelter places for numerous species (Zhao et al., 2016; Wang et al., 2022), successfully reduce substance flows from the catchment area, while also allowing to address climate change by increasing carbon sequestration rates and building long-term carbon stocks (Fennessy and Lei, 2018), an effect that is only partially offset by limited methane emissions (Taillardat et al., 2020). Positive effects of NbS on biodiversity have also been reported for measures such as the construction of artificial reefs by placing man-made underwater constructions (Higgins et al., 2022; Dinu et al., 2025); bivalve and seaweed farming, especially through low-trophic (LTA) or integrated multi-trophic (IMTA) aquaculture (Theuerkauf et al., 2022); the restoration of sub-tidal boulder structures (Støttrup et al., 2014; Kristensen et al., 2024) and seagrass meadows (van Katwijk et al., 2016), especially of species with significant seed banks and fast-growing species, such as Zostera spp. in the Atlantic Ocean and Baltic Sea, and Cymodocea spp. in the Mediterranean Sea (IUCN, 2021). Especially, seagrass restoration proved to increase the abundance of species of commercial interest (van Katwijk et al., 2016), although this is a slow, site-dependent process, and it may take decades or centuries for a successful recolonization and meadow establishment (Tan et al., 2020). Other techniques, such as phytoremediation, showed to have unclear or highly context-dependent results (Pinchin et al., 2012; Oliveira et al., 2024; Temmink et al., 2020; van der Heide et al., 2021). The NbS providing both pressure reduction and improvements in ecosystem state may have the best cost-efficiency. Most typical and well-studied examples are from the coastal wetlands, but also underwater structures, such as boulder reefs or vegetated zones have proven effective as NbS.

3.2 Descriptor 2: non-indigenous species

Non-indigenous species (NIS) are those species that have spread beyond their natural biogeographical range to new regions with the aid of human actions (Essl et al., 2018). Four main groups of solutions have been proposed to address and manage marine NIS: prevention, eradication, management, and other measures (Katsanevakis et al., 2023).

3.2.1 Prevention measures

These measures aim to address the main pathways of NIS introduction. For Europe, in terms of number of introduced species, shipping (through ballast water and biofouling) is the main pathway for over half of the species, followed by marine and inland corridors, mainly the Suez Canal, and aquaculture and aquarium trade (Katsanevakis et al., 2023). International regimes have been established for these pathways, including the International Maritime Organisation (IMO)’s Ballast Water Management Convention (BWMC) and 2011 Biofouling Guidelines, with growing support for a dedicated IMO Convention including surveillance optimization and hull cleaning (Katsanevakis et al., 2023). However, no studies so far have assessed their effectiveness in preventing the spread of NIS.

The release or escape into the environment of non-indigenous species is one of the most important issues affecting the aquaculture industry globally (FAO, 2016), as it can pose significant ecological risks, including the reduction of local biodiversity and the modification of ecological functions of local ecosystems (Ju et al., 2020). Several recommendations, guidelines and contingency measures have been formulated worldwide to address this issue (ICES, 1984; FAO, 1995, 2023), centered on biosecurity protocols and assessments as crucial tools to prevent the establishment of introduced populations (Atalah and Sanchez-Jerez, 2020, as cited by Oficialdegui et al., 2025). In Europe, the European Non-native Species in Aquaculture Risk Analysis Scheme (ENSARS) established protocols for the identification and evaluation of the potential risks of using non-native species in aquaculture, with a growing record of successful implementation both in Europe (Copp et al., 2016) and globally (Li et al., 2025; Tarkan et al., 2020). However, solutions such as biosecurity measures to minimize the chances of escape into the wild, should be consensual, given the considerable importance of these species in supporting livelihoods, food security, and economic sustainability (Oficialdegui et al., 2025).

Monitoring is considered a preventive measure, because it is fundamental for early species identification, provided it is regionally harmonized and coherent and focuses on producing knowledge of species distribution, ecology, and evolution (Kleitou et al., 2021). The majority of countries globally rely on existing broader monitoring initiatives (Lehtiniemi et al., 2015), and only a few have national inventories of marine NIS, such as Greece (Zenetos et al., 2018, 2020), Italy (Occhipinti-Ambrogi et al., 2011; Servello et al., 2019), Portugal (Chainho et al., 2015), Malta (Evans et al., 2015), Norway (Sandvik et al., 2019), Denmark (Stæhr et al., 2020), and Belgium (Verleye et al., 2020). In particular, port monitoring is crucial for the early detection of new arrivals. A port sampling protocol has been developed by HELCOM (HELCOM, 2023; Outinen et al., 2021), while the use of environmental DNA (eDNA) has been adopted in Denmark (Knudsen et al., 2022) and piloted in the Mediterranean (Aglieri et al., 2023; Borrell et al., 2017), although their effectiveness has not been measured.

3.2.2 Eradication

Eradication showed limited success (6 out of 40 cases reviewed by Katsanevakis et al., 2023), only in case of early detection and rapid management response (Giakoumi et al., 2019). Success was reported on the commercial use of the invasive or alien species (Green et al., 2014; Usseglio et al., 2017), although long-term suppression required repeated removals; the eradication of silver-cheeked toad-fish Lagocephalus sceleratus in Cyprus, by compensating small-scale fishermen based on fish and incinerated species biomass (Katsanevakis et al., 2023; Michailidis et al., 2023); the targeted removal and commercial utilization of dead specimens inside MPAs from the Western Mediterranean and the Caribbean Seas (Barcelo et al., 2016; Usseglio et al., 2017; Giakoumi et al., 2019); and the use of Caulerpa taxifolia and C. cylindracea in biotechnological and pharmacological applications (Mollo et al., 2014; Matos et al., 2024). However, eradication measures may trigger the local community to protect their new source of income, contributing to the persistence and expansion of undesired species (Nuñez et al., 2012). Moreover, no known successful control efforts have been reported in scientific literature for the only two marine species included in the EU List of Invasive Alien Species² of Union concern, i.e., the fish Plotosus lineatus and the alga Rugulopteryx okamurae (Katsanevakis et al., 2023).

3.2.3 Management

The management of NIS through biological control actions showed to be effective for C. taxifolia in California (Anderson, 2005). However, it is widely acknowledged that the widespread use of biocides can impact non-targeted species and affect human health through the food chain (Terlizzi et al., 2001). Similarly, other options, such as biological control using alien predators, parasites, or viral diseases, are strongly opposed by experts and stakeholders, due to fears of irreversible effects on native biodiversity (Katsanevakis et al., 2023).

3.2.4 Other measures

Furthermore, awareness raising and legal revision are considered as effective measures. Public awareness raising of the problem of NIS and encouraging their commercial use was evaluated as having the highest applicability and acceptability, low cost, and a medium effectiveness (Kleitou et al., 2021). As for legal revision, Kleitou et al. (2021) and Katsanevakis et al. (2023) highlighted the need to revise of the EU IAS Regulation to adopt a proactive approach, prioritizing prevention and early eradication, including through the elaboration of pre-defined rapid response plans and faster assessment processes, to allow rapid decision-making and avoiding time-consuming species-specific evaluation. Moreover, these authors suggest to include additional marine IAS in the European List, and to revise existing regulation to allow physical removal and commercial utilization.

3.3 Descriptor 3: commercial fish and shellfish

Three measures have been identified in the literature as contributing to achieving GES for this Descriptor: no-take zones, fishing quotas, and the removal of harmful subsidies.

3.3.1 No-take zones

Existing studies (mainly from Australia, California, and Europe) showed that no-take zones may entail an increase in larval supply and catch (Bode et al., 2025), as well as in the population density and biomass of several species (Dimarchopoulou et al., 2018; Frid et al., 2022; Smith et al., 2023), such as coral trout Plectropomus spp (Evans and Russ, 2004; Russ et al., 2008; Emslie et al., 2015; Sweatman et al., 2015), reef sharks (Robbins et al., 2006; Ayling and Choat, 2008), rays (Cappo et al., 2010). Moreover, they may generate positive spillovers to adjacent fished areas (Williamson et al., 2004; Harrison et al., 2012; Wen et al., 2013; van Hoey et al., 2024), supporting catch per unit efforts and increased revenues as a result of reduced competition for space and resources among fishermen (Pantzar et al., 2018). However, no-take zones may also have a negative socioeconomic impact on dependent communities, at least until the area recovers. Hopf et al. (2016) reported that the socialization of the fishery cost of rezoning allowed to mitigate the negative impacts on individual fishers.

3.3.2 Fishing quotas

Branch (2009) reported that the setting of individual transferable fishing quotas (ITQs) may promote a general decline in the mortality of target species. By linking the value of quota shares to the future income stream, ITQs encourage fishers’ stewardship towards the resource, maximizing the quota share value at higher stock sizes and lowering catches below the Maximum Sustainable Yield (MSY)³ level. Moreover, they reported a decline in high-grading and discarding, which, however, may increase if landings (and not catches) count against ITQs and when there is little at-sea enforcement. Possible negative impacts include collapses, in case Total Allowable Catches (TACs) are set too high or if catches are routinely allowed to exceed TACs, and an increase in fishing pressure on non-ITQ species, because of spillover from ITQ fisheries.

3.3.3 Removal of harmful fisheries subsidies

Da-Rocha et al. (2017)’s model showed that the complete elimination of a subsidy on the industrial shrimp fisheries in Mexico would help rebuild the resource biomass, leading to increased levels of sustainable catches, income and wellbeing of fishers, and reducing inequities in income and consumption when fish stocks are not effectively managed (Villasante et al., 2022).

3.4 Descriptor 4: food webs

MPAs are a key tool to preserve or reestablish trophic cascades and community interactions, fostering trophic redundancy and increasing resilience to external shocks. In addition, restrictions on fishing effort, such as trawling bans and fishing effort displacement, may restore trophic roles and protect/enhance marine food webs (Agnetta et al., 2024; Binch et al., 2025). The achievement of GES in the pressure-related descriptors is expected to support achieving GES for D4.

Eisaguirre et al. (2020) investigated phase shifts in the kelp forest of the Northern Channel Islands, California, USA, which was perturbed by the loss of an important sea star predator due to a sea star wasting disease. They showed the importance of MPAs in harboring biodiversity and managing predator guilds to foster trophic redundancy, which can in turn contribute to limit ecosystem phase shifts. Moreover, Hamilton and Caselle (2015) examined the impact of exploitation and recovery of the California sheephead (Semicossyphus pulcher) on size-structure interaction with sea urchin prey in southern California. These authors highlighted the importance of management measures that reduce or remove fishing impacts, such as marine reserves or restrictions to fishing effort, which may serve to restore the historical trophic roles of key predators, resulting in increases in density, size and biomass. Furthermore, Kumagai et al. (2024) confirmed the importance of fully protected MPAs in preserving trophic cascades, promoting the resilience and recovery of kelp forests to marine heatwaves in California, although this effect depends on region-specific environmental and trophic interactions. In Europe, a study by Fenberg et al. (2012) showed the value of European MPAs in reestablishing trophic relationships and community interactions that are typical of unfished conditions, highlighting the importance of understanding the variety and complexity of indirect effects on non-target species and ecological processes in MPAs.

3.5 Descriptor 5: eutrophication

Eutrophication is a complex issue, with a long time required for system recovery (Duarte et al., 2009), and with baseline conditions that may be achieved even decades after the cessation or partial reduction of inputs (McCrackin et al., 2017). In some cases, complete recovery from eutrophication may not be realistic, because of non-linear pressure-response pathways and the interactions among multiple pressures, leading to shifts in baseline conditions and alternative stable regimes. Climate change is expected to exacerbate this situation, as more frequent and intense floods and droughts are expected to increase nutrient loss from agricultural land (Bezner et al., 2022), while rising water temperatures, changes in wind speed and atmospheric depositions will reduce oxygen solubility and increase the risk of oxygen depletion, with negative ecological and socioeconomic consequences (Bourbonnais et al., 2026).

3.5.1 Input reduction

To address this issue, the inputs of nutrients and organic matter should be reduced to well below the original pollution threshold levels (Riemann et al., 2016). Numerous studies confirmed the effectiveness of measures for input reduction. In the Baltic Sea, integrated, long-term policies based on the limitation of industrial discharges, reduction of nutrient losses from agriculture, and improved wastewater treatment, effectively reduced nutrient inputs and initiated a shift towards a better environmental status, which is expected in the medium-long term (Meilholm and Jørgensen, 2025; Riemann et al., 2016; Andersen et al., 2017; Murray et al., 2019). In the North Sea, better wastewater treatment technology, reduction in fertilizer use and of industrial point-source discharges, led to a decrease of phosphorus inputs and of atmospheric nitrogen, leading to an improvement in the eutrophication status of a larger area of the Greater North Sea, although the limited reduction in diffuse nitrogen indicates the need for further efforts to reduce nitrogen inputs, especially from marine aquaculture (Devlin et al., 2023).

However, a review of 89 case studies on nutrient reduction in lakes and coastal marine ecosystems showed that only 24% of coastal marine areas achieved baseline conditions after the cessation or partial reduction of nutrient input (McCrackin et al., 2017, as cited by Devlin and Brodie, 2023). Similarly, a large variety of recovery times from eutrophication has been reported, ranging from >3–4 years in Hong Kong (Shin et al., 2008), Moa Point, New Zealand (Rogers, 2003), and Mondego Estuary, Portugal (Dolbeth et al., 2010), to incomplete recovery even after 15–20 years in Greifswalder Bodden, North Sea (Munkes, 2005) and Tampa Bay, Florida, USA (Greening and Janicki, 2006). This depends on the amount of nutrient reserves in marine sediments and water exchange of the given sea area (Murray et al., 2019), and requires a management approach that is consistent over the whole period.

Furthermore, apart from agricultural sources, marine aquaculture is another significant contributor to the direct discharge of waterborne nutrient inputs; however, this sector is not covered by Best Available Techniques Reference (BREF) documents (Devlin et al., 2023). The farming of bivalve shellfish, especially oysters, through LTA or IMTA, was effective to mitigate eutrophication (van der Schatte Olivier et al., 2020; Kotta et al., 2023). Similarly, mussel farms were reported to remove about 0.6-0.9 t of nitrogen, and 0.03-0.05 t of phosphorus, per hectare per year (Petersen et al., 2016). Seaweeds also take up nitrogen and phosphorus, with a potential total global nitrogen removal of 65,000 tons per year (Kim et al., 2017).

3.5.2 Innovative measures

Innovative measures have been piloted with varying degrees of success. Successful examples for locally implemented actions in catchment areas or at sea include: the construction of freshwater wetlands (Shutes, 2001; Vymazal, 2014; Santos et al., 2024; Gaballah et al., 2024); the use of winter-catch crops (Andersen et al., 2014); hydrological engineering projects, based on increasing flushing and dilution in semi-enclosed estuaries and lagoons, and in intermittently closed and open lakes and lagoons (Duarte and Krause-Jensen, 2018); changes in sluices practices (Duarte and Krause-Jensen, 2018); seaweed aquaculture (Xiao et al., 2017); actions to protect or restore seagrass meadows (Unsworth et al., 2025), oyster reefs (Smith and Pruett, 2024), and wetlands (Zhao et al., 2016; Liu et al., 2021), including mangroves and salt marshes (The Nature Conservancy, 2022), which allow to lock nutrients in sediments (Duarte and Krause-Jensen, 2018); and algal removal (Morrall et al., 2025). Recently, several methods for the dredging of surface sediments to remove excess nutrients, organic matter, and hazardous substances, the oxygenation of bottom waters, and adding thermally treated limestone to bind phosphorus were successfully tested by the Interreg SEABED project in the Baltic Sea, showing the quick recovery of macrophytes, invertebrates, and fish in lakes (Tammeorg et al., 2024; Härkönen et al., 2025).

3.6 Descriptor 6: seabed integrity

The few studies retrieved in relation to seabed integrity focused on the two main drivers of seabed impact: commercial bottom fishing by towed gears and coastal development.

3.6.1 Commercial bottom fishing

Commercial bottom fishing with trawls, seines and dredges is the main driver of impacts on seafloor integrity, inducing habitat loss and cascade effects at higher trophic levels, especially for biogenic and gravel habitats (Van Lancker et al., 2024). Bastardie et al. (2020) applied a spatial modelling platform to evaluate the effects of spatial fishery management measures in the Baltic Sea, with contrasting results. While the closing of areas to fisheries in the central Baltic Sea did not improve the benthic status of affected species, as it concentrated the fishing effort into core fishing areas, reducing fishing opportunities with further economic impacts, it had a substantial positive impact in the Kattegat, where measures combined the protection of long-lived benthic communities with the mitigation of high-impact fisheries. In the Belgian part of the North Sea, three areas have been designated as bottom integrity zones in the context of the current Marine Spatial Plan (2020-2026), with the aim to restrict bottom-disturbing fishing practices; however, results on the effectiveness of this measure are not yet available. Moreover, a study on the Norway lobster fishery in Sweden (Hammarlund et al., 2021) showed that replacing bottom trawls with passive gears, such as creels, increased the number of creel fishers and pushed some trawlers to leave the fishery, improving the net present value and the environmental performance of the fishery. Thus, the actions under this topic are interlinked with MPAs and maritime spatial planning.

3.6.2 Coastal development

This category encompasses tourism activities and infrastructure, nourishment to avoid coastal erosion, the building of seawalls and other coastal defense structures, dredging (including the dumping of excavated sediments at sea), and port activities (including port anchoring; Watson et al., 2022), exert multiple pressures on coastal seafloor (Winter, 2017). Some studies (Andresen et al., 2005; Galparsoro et al., 2010) demonstrated the usefulness of detailed seabed information (depths, sediment and bottom types, seabed structures and processes), translated into thematic maps, as a tool to support informed Integrated Coastal Zone Management (ICZM). Furthermore, Carreira et al. (2025) presented several options for the beneficial use of dredged marine sediments: (i) their use as construction material (e.g., cement); (ii) their use for eco-engineering projects, such as wetland (re)construction, beach and dune nourishment, seagrass meadows, artificial shoals and reefs, nature/coastal flood protection islands, bathymetric recontouring, and fill dead-end canals and basins; and (iii) their use on land to replace eroded soils or amend marginal soils for agriculture and forestry purposes. Moreover, Morris et al. (2018) showed that the restoration of seagrass and kelp beds entailed a reduction in wave height of 31-70%, thus demonstrating their effectiveness as an eco-engineering solution for coastal defense.

3.7 Descriptor 7: hydrographical conditions

The hydrographical regime of currents, waves, and sediments may be altered by large-scale human activities, such as coastal defense works, modifications of coastal wetlands and estuaries, damming of large rivers, land reclamation projects, and coastal or offshore infrastructures, such as wind farms, ocean energy device arrays, and large-scale aquaculture facilities (Le Moigne, 2014).

3.7.1 Limiting damaging human activities

The main measures to address these topographical changes focus on the limitation of damaging human activities and the return to a previous hydrographical state; however, this may imply a significant loss of invested capital and use benefits (OSPAR Commission, 2012). Hence, it is necessary to carefully consider hydrographical conditions in Environmental Impact Assessments (EIA) and Strategic Environmental Assessments (SEA), for example through modelling of hydrodynamic conditions, of sediment transport and morphological conditions, wave modelling, habitat mapping and modelling. Logically, this should be reflected in both maritime spatial plans (MSP) and Integrated Coastal Zone Management (ICZM) and related processes (Spiteri, 2015). In particular, MSP should include an integrated assessment of the cumulative impacts of human activities on any ecosystem component (OSPAR Commission, 2012), as well as measures for the minimization of the impact of the installation of new offshore structures on marine habitats and biota, e.g., through a licensing system or by requiring the application of the best available techniques during EIA. A successful example is the achievement of the so-called “zero solution” for the Øresund bridge connecting Denmark and Sweden, i.e., an unchanged water flow to Østersen thanks to compensation excavations of about 1.5 million cubic meters of soil and sand.

3.7.2 Eco-engineering and eco-design

The inclusion into local spatial plans of measures to foster fish migration between marine and freshwater areas, or to facilitate the development of habitats that were lost (OSPAR Commission, 2012), are proposed as potentially effective. To this respect, Strain et al. (2018) demonstrated the positive effects of common eco-engineering approaches (e.g. increasing texture, crevices, pits, holes, elevations and habitat-forming taxa) in enhancing the biodiversity of key functional groups of organisms, across a variety of habitat settings and spatial scales, although with a marked variation across groups and habitats. In the intertidal zone, interventions to provide moisture and shade had the greatest effects on the richness of sessile and mobile organisms, and water-retaining features had the greatest effects on species richness. In parallel, in the sub-tidal zones, small-scale depressions, providing refuge from predators and protection from waves, had higher abundances of sessile organisms, and elevated structures had higher numbers and abundances of fish. Furthermore, green eco-design helps avoid or offset the negative impacts of traditional construction practices, increasing the capacity of artificial structures to provide refuge, breeding sites and increased feeding opportunities to several species, including habitat-forming species such as macroalgae and corals, while protecting important habitats from trawling (Firth et al., 2024).

3.7.3 Restoration measures

Restoration measures proved to have positive effects on hydrographical conditions. The restoration of bivalve shellfish beds (zu Ermgassen et al., 2020) and seagrass meadows, as well as their farming through LTA and IMTA, may contribute to shoreline stabilization and protection from erosion, although with a high spatial and temporal variability (Liversage and Chapman, 2018). The restoration of sub-tidal boulder structures may also contribute to shoreline stabilization (Liversage and Chapman, 2018), although reefs located close to coastal areas may impact coastal erosion and deposition rates (Støttrup et al., 2017). Coastal wetlands restoration may improve hydrological connectivity and the recovery of underground hydrology, which can accrete sediment retention and lower soil erosion; in addition, coastal wetlands may provide storm buffering and protect from windstorm and shore erosion (Zhao et al., 2016). These results also highlight the need for coastal spatial planning (e.g., as a part of a maritime spatial plan) to prevent conflicts with other socioeconomic activities, excess modifications and foster the building of natural littoral habitats. Finally, the creation of artificial reefs also proved to enhance protection from coastal erosion (Bracho-Villavicencio et al., 2023; Dinu et al., 2025).

3.8 Descriptor 8 (contaminants) and descriptor 9 (contaminants in seafood)

While the reduction and prevention of inputs of hazardous substances to aquatic environment is the key measure to ensure the achievement of GES under D8 and D9, few measures for remediation and restoration have been proposed in the literature.

3.8.1 Contaminants

Polycyclic Aromatic Hydrocarbons (PAH) have been the object of several actions globally to remediate and restore contaminated sites using a wide array of techniques and technologies, which, however, proved to have significant limitations. Recently, bioremediation proved to be relatively cost-effective, environmentally friendly, and publicly accepted (Alegbeleye et al., 2017). Khalid et al. (2021) demonstrated the effectiveness of using halophilic bacteria to bioremediate diesel-contaminated water. Marine-derived fungi also proved their effectiveness in the bioremediation of saline environments from several types of PAH (Passarini et al., 2011).

To address heavy metals, El-Sharkawy et al. (2025) highlighted the importance of prevention, remediation, and restoration strategies, including: the sharing of Best Management Practices to minimize the influx of sediment-bound pollutants into ecosystems; remediation techniques such as sediment dredging and capping, phytoremediation (i.e., the use of plants to extract, stabilize, or degrade heavy metals in contaminated soils and sediments) through phytoextraction, rhizo-filtration, and phytostabilization, especially in coastal wetlands and constructed wetlands (Shutes, 2001); and stakeholder engagement and education towards adopting sustainable land use practices. In particular, Alabssawy and Hashem (2024) reviewed successful cases of detoxification of several types of heavy metals by macroalgae, fungi and bacteria, and identified the main factors influencing the effectiveness of such strategies. Constructed wetlands proved their effectiveness for landfill leachate treatment (Bakhshoodeh et al., 2020) and, more in general, for wastewater treatment, especially when compared with traditional methods, with lower maintenance costs (Parde et al., 2021) and suitability for small communities and remote locations (Wu et al., 2015). A report by the International Atomic Energy Agency (IAEA) demonstrated a reduction in the levels of lead in the Baltic Sea and of mercury in the Caribbean Sea, thanks to the implementation of effective measures to limit the release of these substances into the marine environment, namely through the banning of leaded petrol and the closure of mercury-discharging plants, respectively (Jones Couture, 2018). Additionally, the use of shells of bivalve mollusks as biomaterials showed to reduce heavy metals contamination in the Northern Adriatic (Pasti and Cavazzini, 2020 as cited by Riisager-Simonsen et al., 2022).

Per- and poly-fluorinated alkyl substances (PFAS) have been banned or restricted in the EU through the Persistent Organic Pollutants Regulation (2019/2012) and the REACH Regulation and are considered as hazardous priority substances under the WFD and Directive 2013/39/EU on priority substances in the field of water policy. Stricter regulations since the early 2000s in the Baltic resulted in an initial stabilization of PFAS concentrations, followed by a considerable decline; however, concentrations in biota are still 5–230 times greater than the recommended thresholds (Bilela et al., 2023). Programs for awareness raising among decision makers, improving data collection, regulation, and public-private collaboration have been launched recently in the Baltic, e.g., “PFASEout” and “NonHazCity” project (Bilela et al., 2023); however, no studies reported on their effectiveness.

No previous studies addressed the emissions of pharmaceutical substances into the environment, which is a very recent concern. Zandaryaa and Frank-Kamenetsky (2021) recommend raising public and stakeholders’ awareness through targeted programs as an effective way to foster a responsible consumption of pharmaceuticals and reduce their discharge into the environment. A good preventive measure is the take-back programs for unused medicines by pharmacies or other drop-off sites, which ensure the proper disposal of this hazardous waste, such as through incineration (Wang et al., 2024). Other experiences reported include HELCOM’s regional policy recommendations, the update of the Baltic Sea regional framework for hazardous substances, and the creation of a regional cooperation, the “Baltic Pharma Platform” (Zandaryaa and Frank-Kamenetsky, 2021) to bring together projects and stakeholders to facilitate knowledge-transfer and promote coordinated activities.

3.8.2 Contaminants in seafood

Our review did not retrieve studies identifying clear temporal trends in the concentration of contaminants in seafood globally. Existing studies highlight the need to: (i) update measures to tackle the new contaminants and threshold levels set in the most recent EU legislation; (ii) consider the extension of assessment, monitoring, and management of contaminants of emerging concern, such as brominated flame retardants, endocrine disruptors, toxic element species, pharmaceuticals and personal care products, perfluorinated compounds, microplastics and marine biotoxins; and (iii) ensure a coordinated approach at marine region/sub-region level in tackling pressures from contaminants. The measures implemented under D8 will also support the achievement of GES for D9.

Climate change is expected to pose new threats through acidification, which affects shell formation, and rising temperatures. In particular, rising temperatures may facilitate mercury uptake in fish (Pack et al., 2014), threatening seafood survival, and, in combination with changes in precipitation patterns, may favor the growth, persistence, and transmission of bacteria, viruses, parasites, and fungi (Rowley et al., 2024), posing risks to marine fauna, seafood production, and food safety. Moreover, climate change is expected to promote the proliferation of toxic algae species, increasing in the frequency, severity, and geographic extent of shellfish poisoning events (Mol and Cosansu, 2022).

Scientific assessments have been performed on the presence of contaminants in seafood in Europe. Garofalo et al. (2025) found that 2.43% of samples were non-compliant with existing limits set in EU Regulations for cadmium, lead, and total mercury from 2014 to 2023, with concentrations exceeding the limits for cadmium in cephalopods, and high levels of mercury in marine fish, notably swordfish, sharks, and tuna species, while for lead, only one sample was found to exceed the maximum limits. Although encouraging, these results do not provide evidence of temporal trends. To this respect, Kammann et al. (2023) assessed the temporal trends of mercury levels in fish from the German part of the North Sea from 1995 to 2020, showing an average annual increase of 1.4%, leading to a 41% increase in mercury contamination level within 25 years of monitoring. In the Mediterranean Sea, Cinnirella et al. (2019) reported lower values for short-lived fish and higher values for large, long-lived species, which were always below EU requirements, although without providing compelling conclusions on the temporal trends of these concentrations, which seem unaltered across the study period (1975-2020).

Bonito et al. (2016) reviewed the global impact of regulations on the concentration of persistent, bioaccumulative and toxic pollutants (PBTs), including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides (DDTs and CHLs), and mercury (Hg, MeHg), in seafood from 1900 to 2013. The results showed a significant decline of approximately 15-30% per decade across all PBT groups, although with wide spatial and temporal variations in concentrations.

As for contaminants of emerging concern, i.e., those for which no maximum levels have been laid out in EU regulations, such as brominated flame retardants, endocrine disruptors, toxic element species, pharmaceuticals and personal care products, perfluorinated compounds, microplastics and marine biotoxins, adequate information is lacking, and the assessment of their concentrations and food safety issues is urgent (Vandermeersch et al., 2015). Danopoulos et al. (2020) performed a systematic review and meta-analysis of seafood (mollusks, crustaceans, fish, and Echinodermata) contamination from microplastics. Most of the studies reviewed reported microplastics contamination, with a content of 0–10.5 microplastics (MPs)/g in mollusks, 0.1–8.6 MPs/g in crustaceans, 0–2.9 MPs/g in fish, and 1 MP/g in Echinodermata, with higher values for mollusks from Asian coasts.

3.9 Descriptor 10: marine litter

Löhr et al. (2017) framed the impact of marine litter on the marine environment along multiple pathways, related to macroplastics and microplastics, proposing corresponding solutions:

• For macroplastics – in the short term: improve waste management; awareness raising; beach and ocean clean-ups; extend legislation on abandoned, lost or otherwise discarded fishing gear (ALDFG) to cover smaller fishing vessels. In the long-term: circular economy; phase-out non-recoverable plastics; and reduction of single-use plastics.
• For microplastics – in the short-term: avoid discharge and spills/accidental losses; improve wastewater treatment facilities; ban microbeads. In the long term: circular economy; develop new technologies (e.g., filters for washing machines) and alternative materials.

3.9.1 Tackling macroplastics

However, previous studies have focused only on assessing the effectiveness of some of these measures only. For macroplastics, the effectiveness of bans or taxes on certain plastic products, especially single-use plastic bags were assessed (Luis and Spinola, 2010; Dikgang et al., 2012; Dikgang and Visser, 2012; He, 2012; Jakovcevic et al., 2014; Martinho et al., 2017). One of the first examples was the plastic bag levy introduced in Ireland in 2002, which resulted in a gradual reduction in plastic bag use by 90%, and a reduction in the share of plastic bags in total litter from 5% to 0.22% by 2004 (Oosterhuis et al., 2014). Also, other market-based instruments, such as bottle and container deposit-refund schemes, have been indicated as effective (Hardesty et al., 2014, as cited by Löhr et al., 2017), although their impact on waste reduction may not be clearly established, because of a lack of data and because it is hard to separate their impact from that of other policies or initiatives (OECD, 2016, as cited by Kirk and Popattanachai, 2018). Awareness raising campaigns can effectively put pressures on plastic producers. For example, the “Beat the Microbead” campaign launched in the USA resulted in the issue of a federal law banning microbeads in rinse-off personal care products (Löhr et al., 2017). Willis et al. (2018) reported on the effectiveness of educational programs in successfully reducing waste in Europe (Hartley et al., 2015; Veiga et al., 2016), Malaysia (Pudin, 2015) and the USA (Hasan, 2004).

3.9.2 Tackling microplastics

A review by Fiore et al. (2022) identified two main types of actions: the removal of microplastics from the environment, and their interception at source, reviewing existing technical measures and showing their effectiveness: (i) seabins, able to catch nearly 4 kg of debris per day and remove an estimated 1.5 tons per year; (ii) filters of wash water from shipboard exhaust gas cleaning systems, with a removal efficiency between 79% and 99% (Bayo et al., 2020; Lares et al., 2018; Talvitie et al., 2017, as cited by Fiore et al., 2022); the main drawback is that it does not eliminate microplastics but discharges it in sewage sludge; also, it suffers from rapid clogging and cannot be easily implemented in size-based treatment plants (Hou et al., 2021); (iii) Magnetic Seeded Filtration for the separation of microplastics from dilute suspensions, reaching a separation efficiency of 95% (Rhein et al., 2019); and (iv) a buoyancy separation method for beaches, which proved to be able to recover microplastics up to 10 μm (Fiore et al., 2022). As for marine coatings, some products have been developed, which ensure dust-free abrasive vacuum blasting of surfaces, preventing the release of microplastics (Fiore et al., 2022). For city dust, the “Tyre Collective” developed a device to be combined with vehicle tires, intercepting 60% of microplastics emissions. Finally, washing machine filters proved to have an efficiency of 26-100% in blocking microplastics from clothes (Fiore et al., 2022).

3.10 Descriptor 11: energy including underwater noise

Increasing levels of underwater noise have multiple impacts on marine fauna (Halliday et al., 2020), affecting the ability of marine animals to hear and use sound (Clark et al., 2009; Erbe et al., 2016), possible hearing damage (Southall et al., 2007, 2019; Finneran, 2016), while representing a chronic stressor for individuals (Rolland et al., 2012) and causing behavioral disturbance (Nowacek et al., 2007; Southall et al., 2007, 2019; Gomez et al., 2016). The main sources of underwater noise are commercial shipping, which generates lower to medium levels of continuous noise, and the offshore oil and gas exploration industry (Cruz et al., 2021), which creates high-intensity impulsive noise that can injure marine species. Moreover, noise produced from offshore wind farms (especially pile driving) may be harmful and disturbing to marine wildlife (Nehls et al., 2007).

A preliminary obstacle in effectively addressing marine underwater noise is the existence of gaps in scientific knowledge around soundscapes and their variability in time, and also regarding noise-related impacts on biota at population level, which imply the difficulty to define the problem in terms of its magnitude and spatial distribution (Bosi et al., 2023), limiting the possibility to determine internationally agreed threshold values. Other major obstacles identified include legal fragmentation at international level, weak enforcement and supervision, and accountability gaps (Wang and Bao, 2026).

3.10.1 Commercial shipping

As for ship-generated noise, the main measures reviewed include technical/design and operational measures. Technical/design measures for new ships include an improved design of the propellers, the isolation of any piece of machinery from the ship structure (Cruz et al., 2021), the reduction of the power requirement, or the installation of devices to generate air bubble curtains around the aft part of the ship hull (Cruz et al., 2021). Vakili et al. (2025) highlighted the efficacy of wind-assisted propulsion and air lubrication systems in reducing underwater radiating noise. For existing ships, retrofitting, for example through elastic mounting devices or improved propellers with higher cavitation inception speed, proved to be effective (Gassmann et al., 2017). In particular, Audoly et al. (2017) reported a 21% reduction in behavioral response risk for harbor porpoise and a -30% reduction for cod relative to the baseline situation. Operational measures consist of mandating speed reduction, especially for the noisiest vessels. Joy et al. (2019) reported a median reduction in sound pressure level of 3.1 dB at speed limits of 11 knots, and up to 11.5 dB for containerships (MacGillivray et al., 2019). Leaper (2019) estimated that a 10% speed reduction of all ships would result in about 40% lower emission of sound energy, assuming equivalent total cargo carrying capacity (Cruz et al., 2021). Other operational measures, although less effective, include the regulation of ship traffic by concentrating or diluting traffic, grouping vessels in convoys or modifying traffic schemes, especially to foster awareness and behavior change in shipowners (Audoly et al., 2017).

3.10.2 Offshore hydrocarbon activities

To address the emissions of impulsive noise from offshore hydrocarbon exploration and extraction, some measures have been identified as appropriate, based on the source, site, and species of concern. These include: the use of gravity foundations and suction buckets in offshore construction; techniques such as vibroseis, to perform seismic explorations; low-order deflagrations for the clearance of unexploded ordnances; and temporal and spatial restrictions when source mitigation is more challenging, for example in case of sensitive areas, as successfully demonstrated in the UK for harbor porpoise (Thomsen et al., 2021). Especially, marine vibroseis was successfully trialed in different marine environments, showing to generate lower sound levels and less noise at extraneous frequencies (>100 Hz), although there are no in situ studies of its effects on marine life (Thomsen et al., 2021). To reduce underwater noise in offshore wind farms, arising from offshore pile driving, Nehls et al. (2007) proposed the construction of a permanent noise barrier around the piles made up from foam or air, which can reduce the radii of physical damage by more than 90% and the radii of disturbance by two-third, thus contributing to a substantial reduction of the negative impacts on marine fauna.

3.10.3 Land-based activities

Other established sources of underwater noise are port-based activities, such as pile driving, explosions, compressed air guns, sonars, echosounders, and acoustic deterrent devices (Enguix et al., 2019). Several studies assessed the presence and intensity of these sources (Marley et al., 2017; Enguix et al., 2019; Lalander et al., 2021) or provided guidelines for noise-source characterization in ports (Fredianelli et al., 2022). Especially, Virto et al. (2022) proposed practical measures to reduce underwater noise from ports, including discounted port fees and reduced ship waiting times. However, no studies were found providing concluding evidence on their impacts on marine fauna, especially on noise-sensitive fauna.

Measures to address underwater noise may be included in MSPs, as they allow to tackle multiple use demands and related conflicts and coexistence possibilities, and integrate multiple policies, improving connections between planners and noise experts, thus contributing to reach GES targets (Bosi et al., 2023). Moreover, it is important to address cross-border impacts, given the transboundary nature of this pressure, and target recreational crafts, which may dominate certain soundscapes.

4 Discussion

The status of the marine environment is deteriorating worldwide, including in Europe. EU legislation for the protection of the marine environment and the sustainable use of maritime activities is among the most comprehensive in the world. Over the past few decades, it has progressively broadened from the species-centered protection of wild birds under the Birds Directive (1979), toward the conservation of vulnerable species and natural habitats under the Habitats Directive (1992), to more holistic, ecosystem-oriented management of coastal water bodies under the WFD (2000), and the explicit application of an ecosystem-based approach to marine management under the MSFD (2008). However, effective solutions are needed to address the increasing pressures on the marine environment, including climate change, and help translate the legal requirements into actionable practices. Our review showed that numerous measures have been identified and their effectiveness has been assessed, pointing to their limits, positive and negative aspects, trade-offs and multiple benefits; they are summarized below and detailed in Table 3. However, it also identified their limitations, including the need to adapt them to local circumstances, consider the synergistic effects with other measures, as well as some gaps in the assessments of effectiveness, such as for waste management and circular economy, and for contaminants of emerging concern.

Table 3. A synthesis of the solutions reviewed for each MSFD descriptor, their expected impact and contribution to other descriptors, and the possible limits, negative effects and trade-offs.

Commission Regulation (EU) 2023/915 of 25 April 2023 on maximum levels for certain contaminants in food and repealing Regulation (EC) No 1881/2006.

Our review identified 222 studies, covering the global ocean or specific areas of the globe, especially Europe, North America, and Australia. A substantial imbalance was found in the number of studies focusing on solutions across the topics addressed by the MSFD Descriptors (Table 2). While there are numerous studies on D1-biodiversity and D2-NIS (37 studies each), D5-eutrophication (32), and D11-underwater noise (25), a few studies were retrieved on the effectiveness of measures to address D4-marine food webs (3 studies), D7-hydrographical conditions (7) and D6-seabed integrity (9). In addition, an important gap was observed in relation to the assessment of the effectiveness of some key measures, such as improved waste management or circular economy, or on emerging contaminants. Furthermore, our review confirmed the existence of several marine NbS, focusing on the restoration of specific ecosystems (e.g., wetlands, mangrove, seagrass, saltmarsh, kelp, bivalve reefs, seaweed), the creation of artificial structures (e.g., reefs, sub-tidal boulders, eco-engineered coastal structures), or management practices such as LTA and IMTA. However, their number is significantly lower compared to terrestrial and freshwater ecosystems, and few of them have been developed to explicitly achieve GES (Riisager-Simonsen et al., 2022).

Across MSFD Descriptors, the horizontal role of climate change clearly emerged, exacerbating certain conditions and triggering potential regime shifts, worsening the ecological status of marine habitats and hindering the achievement of GES. However, despite the significant efforts worldwide to reduce greenhouse gas emissions and mitigate climate change in the framework of the Paris Agreement, very few measures have been found to explicitly address the impacts of climate change on the marine environment.

Moreover, it was observed that measures formulated in the context of other EU legal requirements have benefits for the marine environment. This is the case, for example, of measures such as the re-establishment of seagrass meadows, seaweeds, or reefs, established in the context of the Habitats and Bird Directives, but which indirectly also enhance food webs and ecosystem functioning in the context of the MSFD. Some measures also have added value for the source-to-sea approach, such as passive and active restoration in forests, marshes, pastures and coastal wetlands to reduce substance flows. These mainly address the WFD and the Habitats Directive, as well as the Nature Restoration Regulation and the Ramsar Convention objectives. A different method with constructed wetland designs may be more appropriate for treating point-source effluents from small industrial or municipal sites. Such a design may respond to environmental impact assessments (the EIA Directive) and permit requirements.

While some solutions are effective as stand-alone interventions, in many cases they are insufficient on their own and need to be implemented in combination with other measures. This is particularly relevant in areas characterized by multiple uses, complex local geography (e.g. fragmented coastlines or archipelagos), or where land-based activities exert multiple pressures on the marine environment. Under these conditions, it is essential to evaluate the potential synergistic effects of combined measures, including both positive and negative interactions.

The MSFD includes both pressure-related and state-related GES Descriptors. Therefore, there is an inherent synergism, where measures to reduce pressures and achieve targets of pressure-related Descriptors, will also benefit the state-related Descriptors. Obvious examples of this are the measures to reduce hazardous substances, nutrients, noise, litter, invasive species and habitat degradation (included in Descriptors 2, 5-11). This raises the management question of what measures are cost-effective and should be prioritized in management schemes. Prioritization can also be made within the pressure reduction measures; some pressures have wider ecosystem effects (such as habitat degradation) than others (e.g., mortality of a single species). However, synergism is also found within the measures directly improving the MSFD state Descriptors. For instance, measures improving habitat-forming species will benefit the associated community and, hence, have positive biodiversity consequences.

The effectiveness of certain solutions depends on the implementation of prerequisite actions. For instance, revegetation efforts are unlikely to be successful unless organic enrichment is first reduced. Likewise, constructed wetlands may not effectively retain target effluents if inflow volumes exceed their treatment capacity or if the systems are undersized, necessitating upstream measures to reduce nutrient inputs or modifications to wetland design and scale. Scale is also a critical consideration, as most solutions are implemented at the local level and may, therefore, be insufficiently effective at larger spatial scales. This limitation can be overcome by deploying a sufficient number of measures across the target area.

Several success and failure criteria were identified for each measure. Previous studies identified common success criteria for all solutions, which include the setting of specific, measurable, assignable, realistic, and time-bound (SMART) goals and project’s performance criteria in addition to careful site selection, supported by community assessment, and considering environmental factors (Smith and Pruett, 2024). For NbS, ICES (2025) listed the following common success and limit factors:

• Apply a hierarchical management approach by first reducing pressures, then protecting environmental features, and, where necessary, restoring degraded ecosystems;
• Restoration is meaningful only if the pressures that caused degradation are removed or mediated, and the physical environment is in a suitable condition;
• Often, hysteresis (i.e., the existence of different stable states under the same variables or parameters) can prevent the natural recovery of a system to its original state, even after removing the stressors;
• Suitable habitats are the key factor to determine the success of species recovery;
• Monitoring is fundamental to assess the effectiveness of action, and should match the spatial/temporal scale of the key habitat feature and/or target species;
• Objectives and targets of action should be clearly defined, and monitoring should be formulated accordingly;
• The timeline for restoration is usually longer than the timeframes of policy evaluation, and it may be difficult to evaluate policy or intervention effectiveness during the cause of a single EU policy cycle;
• A strategic and inclusive approach is important for successful restoration, including a top-down approach to planning, which is necessary to ensure adherence to scientific methodology, and the social acceptability of stakeholders and the wider society, especially through early engagement for implementation and support throughout the entire duration.

The combination of passive and active restoration with MPAs, particularly at historically polluted or abandoned sites, has proven to be especially effective in restoring marine ecosystems degraded by past industrial activities (Puig et al., 2024). In this context, successful restoration depends on three key principles: (i) re-establishing and maintaining the values of the protected area in accordance with its original purpose and conservation and/or cultural objectives; (ii) maximizing ecological, socioeconomic, and cultural benefits while minimizing associated costs; and (iii) engaging partners, rights holders, and stakeholders throughout the planning and implementation process to promote mutual learning and ensure that the perspectives and knowledge of local communities are incorporated (ICES, 2025).

Nevertheless, MPAs alone are generally insufficient to prevent pollution originating beyond their boundaries, highlighting the need for complementary preventive measures. These may include (i) passive or (ii) active wetland designs, (iii) the removal of historically contaminated sediments, or (iv) the active restoration of seabed anoxia, although evidence supporting the latter remains limited in marine environments. The effectiveness of these measures can be further enhanced through catchment-scale interventions aimed at reducing pollution, including sedimentation ponds, buffer zones, and restored wetlands.

Similarly, habitat restoration or the reintroduction of habitat-forming species is unlikely to succeed if the underlying drivers of degradation, such as bottom trawling, dredging, high-speed vessel traffic, aquaculture, or excessive nutrient inputs, remain unaddressed. Consequently, these pressures must first be reduced or eliminated, although in some cases NbS can contribute to achieving this objective. For example, the successful restoration of a coastal lagoon may require a sequence of interventions, including (i) restoring the lagoon entrance, (ii) banning, reducing, or re-routing boating activities, (iii) restoring upstream wetlands (or implementing alternative measures) to retain nutrients, and (iv) re-establishing the original lagoon species (Arnkil et al., 2024).

Another common element emerging from our review is the need to ensure early, inclusive and sustained stakeholder engagement, as it can strengthen the knowledge base, legitimacy and ownership of marine governance decisions, thereby improving their acceptance and implementation (Pomeroy and Douvere, 2008; Twomey and O’Mahony, 2019). This is especially valid in the context of participatory planning processes (i.e., MSP and ICZM), where early and effective participation can improve planning quality and build acceptance, ownership and support for implementation (Twomey and O’Mahony, 2019).

The EU has a comprehensive marine policy framework, the necessary scientific knowledge and experience with practical solutions to face, and perhaps even mitigate, some of the effects of the ‘triple crisis’ (Andersen et al., 2026). However, what is lacking is a more coherent implementation of existing policies at the relevant ecological scale and necessary speed linking the individual solutions presented here together. As such, the recent European Ocean Pact and the upcoming Ocean Act may be the last real chance to bring the needed shift towards a more holistic, ecosystem-based governance. A governance approach which integrates community actions on biodiversity loss, pollution and climate change across sectors and borders focused on closing persistent implementation gaps. The pace of pressure reduction, protection, and restoration measures must match, and outpace, the use and associated degradation of Europe’s seas.

The number of studies reviewed depended on the specific keywords employed. Although these were carefully chosen to provide the widest possible coverage, some studies may have been excluded, especially the most recent ones, limiting the comprehensiveness of this review. Future work should integrate the missing references, to provide a more complete picture and stronger support for MSFD implementation.

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Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmars.2026.1966019/full#supplementary-material

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Footnotes

Edited by: Tomaso Fortibuoni, Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), Italy

Reviewed by: Laura Sordo, Portuguese Institute for Sea and Atmosphere (IPMA), Portugal

Elliot Dreujou, Institut Nordique de Recherche en Environnement et en Santé au Travail, Canada

Chuanliang Wang, Shandong Normal University, China

Footnotes

Art. 3 of the MSFD defines GES as “the environmental status of marine waters where these provide ecologically diverse and dynamic oceans and seas which are clean, healthy and productive within their intrinsic conditions, and the use of the marine environment is at a level that is sustainable, thus safeguarding the potential for uses and activities by current and future generations”.

The EU Invasive Alien Species (IAS) Regulation 1143/2014 defines IAS as “alien species whose introduction or spread has been found to threaten or adversely impact upon biodiversity and related ecosystem services” (European Union, 2014).

MSY is defined as the highest theoretical equilibrium yield that can be continuously taken from a stock under existing (average) environmental conditions (FAO, 2001).