A Holistic One Health Assessment Framework for Coastal Areas

Abstract

Coastal ecosystems face intertwined challenges from environmental degradation, zoonotic spillover, and socio-economic pressures, which demand integrated assessment approaches. This paper proposes a tailored conceptual and methodological framework for evaluating One Health (OH) in coastal environments. The proposed framework extends the Drivers–Pressures–State–Impact–Response model by embedding human health, animal health, and environmental ecosystem quality into a unified structure. Within this approach, three composite indicators are introduced—the Human Health and Socio-economic Well-being Index, the Animal Health Risk Index, and the Environmental Ecosystem Quality Index. Based on an extensive literature review, we propose the variables and indicators that will theoretically underpin the construction of these indicators. While their empirical development and application will follow in a subsequent stage, the present work establishes their conceptual foundation and provides the full set of indicators to be integrated. In doing so, the framework lays the groundwork for future operationalization of OH assessments in coastal areas, supporting vulnerability evaluation, sustainable governance, and alignment with European directives and the UN SDGs.

1. Introduction

Coastal zones encompass some of the planet’s most critical and delicate ecosystems, yet they confront compounding threats from pollution, biodiversity decline, and the pressing need for climate change adaptation [1,2,3]. These ecosystems deliver a wide array of indispensable services that underwrite human welfare [4,5]. Despite their irreplaceable contributions, coastal habitats have suffered extensive deterioration, with documented worldwide reductions in seagrass meadows, salt marshes, and living shorelines [6]. Such ecosystem collapse erodes biodiversity and destabilizes the socio-economic foundations of neighboring communities [7,8].

Contaminant loading and climate-driven changes interact synergistically, intensifying the intrinsic fragility of coastal zones and compounding the urgency of risk mitigation. Accelerated nutrient loading from agricultural runoff, compounded by the release of untreated sewage and an array of chemical pollutants, promotes the eutrophication of coastal waters, facilitating the proliferation of toxic phytoplankton that consumes dissolved oxygen and disturbs the equilibrium of marine ecosystems [9]. The resulting shifts also compromise the microbiological quality of recreational waters, thereby elevating the probability of adverse health outcomes in populations exposed to affected bathing sites [10,11]. Concurrently, advancing climate change magnifies the magnitude and frequency of thermal and hydrological extremes, resulting in accelerated rates of sea-level rise, recurrent coastal inundation, and an intensified retreat of shorelines, thereby rendering low-elevation coastal zones increasingly vulnerable [12,13].

Extreme events not only reshape coastlines but also compromise ecosystem resilience and the services that underpin disaster risk reduction [14]. Together, these processes highlight that pressures on coasts are neither isolated nor linear but cumulative, requiring responses that bridge across ecological, health, and societal domains [15].

In terms of governance and assessment, established frameworks such as the Drivers–Pressures–State–Impact–Response (DPSIR) model [16,17] and the EU’s Marine Strategy Framework Directive (MSFD) [10,18,19] and the Global One Health Index (GOHI) [20] have provided structured approaches to link environmental pressures with ecosystem states and policy responses and provide valuable tools for environmental monitoring and integrative assessment. While these tools have strengthened integrative thinking in coastal and marine management, they remain predominantly ecosystem- and pressure-focused, with limited attention to human and animal health dimensions that are central to a One Health (OH) perspective, defined as an integrated approach that aims to sustainably balance and optimize the health of people, animals, and ecosystems [2]. The proposed Coastal One Health (C-OH) framework advances this field by embedding OH principles within a DPSIR logic, introducing composite indicators, specifically Human Health Outcome Index (HHOI), Aquatic Animal Health Risk Index (AAHRI), and Environmental Ecosystem Quality Index (EEQI). These indicators are tailored to coastal contexts and align outputs with European directives. Doing so bridges a persistent gap in governance by integrating ecosystem, human, and animal health metrics into a single evaluative system, designed for operational use at the local level.

Connections between environmental degradation, zoonotic risks, food safety, and human well-being are acknowledged in global initiatives [21,22], yet assessment frameworks rarely capture these intersections in practice. Indicators of ecosystem health are often disconnected from metrics of human health, even though both depend on the same coastal processes. As Cabrera et al. [23] emphasize, a comprehensive vulnerability assessment must weave ecological, social, and health perspectives into a single evaluative framework if it is to remain meaningful under accelerating global change. Against this background, the present study aims to advance a holistic OH assessment framework tailored to the needs of coastal areas. By drawing on established methodologies while extending their scope across the human–animal–environment interface, this work seeks to offer an applied structure for integrated coastal governance aligned with the Water Framework Directive (WFD) [18], the Bathing Water Directive (BWD) [10], the Marine Strategy Framework Directive (MSFD) [19], and the UN Sustainable Development Goals (SDGs) [21]. This study contributes theoretical value by explicitly operationalizing the OH perspective in coastal governance. Beyond coastal zones, the framework also has potential for application in urban planning, where cross-sectoral coordination is equally critical. The ultimate goal is to provide decision-makers with a tool that better reflects the complex realities of coastal systems, thereby supporting policies that enhance resilience, safeguard ecosystem services, and protect the health of both communities and nature.

The present study pursues three main objectives. It develops an interdisciplinary C-OH framework that integrates human well-being, animal health, and environmental quality beyond the DPSIR logic; it provides a policy-ready methodology for comparing risks and priorities at the local scale, and it is conceptually harmonized with European and global policy instruments (e.g., WFD, MSFD, BWD) and the SDGs. In this way, the framework advances integrative assessment while offering practical decision-support basis for policymakers, local authorities, and coastal managers. Figure 1 presents the C-OH framework, developed through an extensive literature review. The framework is organized around three composite indicators—HHOI, AAHRI, and EEQI—which represent the three main pillars of OH. It highlights the interconnectedness of human, animal, and ecosystem health in coastal contexts, providing the conceptual foundation for the present study.

2. Materials and Methods

The present work focuses on three main objectives. First, we aimed to develop an interdisciplinary C-OH assessment framework that integrates human and socio-economic well-being, animal health, and environmental ecosystem quality, structured by the DPSIR logic. The framework introduces three thematic indicators (Figure 1), HHOI, AAHRI, and EEQI, which together capture key dimensions of public health, animal health and ecosystem quality, and enables integrated monitoring, risk prediction, and adaptive decision-making in coastal areas. Second, we aimed to produce a policy-ready methodology at local scale to compare coastal municipalities and support prioritization. Third, we aimed to align evidence with European and global policy instruments (e.g., WFD, MSFD, BWD) and the SDGs (notably SDG3, SDG6, SDG14), ensuring that assessment outputs are interoperable with existing regulatory monitoring and reporting obligations. The framework is intended to be used by policymakers, local authorities, NGOs, and coastal managers as a decision-support tool for prioritizing interventions and guiding sustainable strategies.

An overarching objective is to include coastal stressors, pollution, biodiversity loss, and climate risks, with indicators and responses that reflect their interdependencies across the OH pillars. Regarding the thematic scope of this work, the framework spans three OH pillars: (i) human and socio-economic well-being, (ii) animal health, and (iii) environmental ecosystem quality. Each pillar is represented by thematic indicators that capture relevant risks and conditions. These indicators are briefly outlined here and are presented in detail in the Methodological Foundations section, ensuring that public health is not assessed in isolation but in relation to environmental exposures and ecosystem services.

The OH paradigm is structured around the integration of human, animal, and environmental health as interdependent pillars. Their intersections are schematically illustrated in Figure 2, offering a concise synthesis of the conceptual foundations of the proposed framework.

3. Results

3.1. Environmental and Ecosystem Health Dynamics

According to Destoumieux-Garzon et al. [2] combining different techniques and interventions should be developed by connecting the study of the factors underlying stress responses to their effects on ecosystem functioning and evolution for the OH approach to succeed. This can be achieved by simplifying and analyzing the barriers of the different sciences that separate human and veterinary medicine from ecological, evolutionary and environmental fields to form the OH approach. This information is necessary to create new management methods that are motivated by the environmental processes and result in the equilibrium and dynamics that are wanted in healthy ecosystems. It is also important to provide a clear framework for coordinated operational activities in the near future. The authors also stress the importance of the addition of ecological health to the “One Health” holistic approach. This is because so far documents and publications concentrate on addressing developing zoonozes from domestic [24] or wildlife sources [25], including their interactions [26], while largely not considering the significance of inclusive ecosystems [27].

These dimensions are directly connected to human and socio-economic well-being in coastal areas, where ecosystem degradation, bathing-water quality, HAB, and microplastic exposure not only increase health risks but also undermine tourism, fisheries, and local livelihoods. Incorporating such indicators within the C-OH framework ensures that public health is assessed in relation to environmental exposures and ecosystem services, rather than in isolation. Moreover, these metrics can be operationalized in practice through municipal health planning, early-warning systems, and alignment with EU directives on bathing-water quality and marine pollution.

Ecosystem degradation, climate change, and anthropogenic pressures, including habitat loss, globalization, intensive farming practices, and antimicrobial use, are strongly linked to pathogen emergence, AMR, and zoonotic spillover [28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47]. These processes highlight the need for integrated indicators (e.g., biodiversity, habitat integrity, pollution load, AMR incidence) to assess ecosystem health in relation to human vulnerabilities.

Some of the factors that have been considered important for the appearance of vector-borne and direct transmission agents are the density and diversity of hosts, migration, environmental persistence, and interaction within communities of infectious agents [2]. Changes in species abundance and food web topology, such as the extinction of regulatory predators, the role of super-predators, consumptive competition, impacts on keystone species, biological invasions, the proliferation of resistant disease reservoir species, and density effects related to the emergence of epizootics or zoonotic diseases, etc., coupled with pollution, substantially heighten the risk of disease [2]. Moreover, some important factors that have been confirmed as catalysts on the occurrence and geographic distribution of infectious agents are destruction and fragmentation of habitat, environmental pollution, and climate change. According to Bebber [37] and Vezzulli et al. [38], diseases that never appeared before, especially at northern latitudes, are caused by global warming by modifying the distribution of pathogens, their vectors, and their reservoirs.

Spatial and socio-ecological factors further influence pathogen emergence. Spatial heterogeneity can create mismatches that favor contagious disease dynamics [39], while spatial indicator systems can help model zoonotic disease escalation and regional vulnerability to OH risks [40]. At the same time, anthropogenic pressures intensify these dynamics: globalization, trade, and intensive agricultural practices facilitate the movement of hosts and pathogens [41], while extensive use of pesticides and antibiotics accelerates insecticide resistance in mosquitos [42,43] and antimicrobial resistance (AMR) in bacteria [44]. AMR has become a global health crisis, demanding innovative approaches informed by eco-evolutionary dynamics [45]. In addition, the spread and impact of epidemics are shaped not only by biological processes but also by political, economic, and cultural factors [46,47], reinforcing the importance of a holistic perspective that integrates ecological and socio-economic determinants of health.

Toxic exposures, including natural toxins, emerging contaminants, and diffuse pollution, are key OH concerns in coastal regions, where they weaken defense mechanisms, heighten susceptibility to multifactorial diseases, and contribute to chronic non-communicable disorders in humans [48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65]. These toxicological pressures also interact with pathogens and vectors, underscoring the need to integrate ecotoxicological variables (e.g., pollutant loads, exposure risk, biocidal use) into the EEQI. Incorporating such indicators ensures that the C-OH framework systematically addresses chemical stressors as part of ecosystem and public health assessment.

Socio-environmental contexts, including urbanization, population mobility, and lifestyle factors, also influence pathogen dynamics and chronic disease risks. These determinants highlight the need for integrated OH indicators that capture not only ecological and toxicological pressures but also social and behavioral vulnerabilities [66,67].

Zhang et al. [20] lay out GOHI as a systematic framework for evaluating OH performance at national levels. This work presents a five-step methodology. The first step consists of the formulation of the framework. The second includes the identification of key indicators. The third is the building of a foundational database. The fourth includes the definition of relative weights, and fifth is aggregation into composite scores. This work is based on defining C-OH framework using these foundational steps. Within the GOHI, the Intrinsic Drivers Index (IDI) embeds both environmental and ecosystem health dimensions. It highlights the nexus of human health, animal health, and ecosystem biodiversity, capturing the systemic interconnections among these domains. By evaluating variables such as biodiversity, land use indicators, and environmental contamination metrics, the IDI is anchored in the precepts of integrated environmental and ecosystem health governance. The GOHI architecture exhibits a multi-tiered indicator hierarchy ordered by assigned weights. The first tier consists of three indicators which are considered first level. Each representing a broad thematic pillar of OH. The second-tier indicators elaborate specific domains beneath each pillar. The third tier offers precise metrics for comparative analysis. Moreover, the authors highlight key areas assessed under the IDI. The first category refers to biodiversity. Secondly, land use. More specifically, it involves evaluating how urbanization and agriculture affect ecosystems. Last, environmental pollution regards measuring air and water quality, and exposure to pollutants.

Halpern et al. [11] developed and implemented a systematic approach for measuring the overall condition of marine ecosystems that treats nature and people as integrated parts of a healthy system. Specifically, the authors proposed a conceptual framework for calculating an index to assess the health and benefits of the global ocean. The index was calculated for every coastal country and consisted of ten public goals, including sub-goals. The main public goals contained food provision with two sub-goals (fisheries, mariculture), artisanal fishing opportunity, natural products, carbon storage, coastal protection, tourism and recreation, coastal livelihoods and economies with two sub-goals (livelihoods, economies), sense of place with two sub-goals (iconic species, lasting special places), clean waters and biodiversity with two sub-goals (habitats, species).

For measuring a region’s contribution Jato-Espino et al. [40] incorporates interactions and effects of human, animal and environmental indicators. The indicators are selected based on the five steps proposed by Jato-Espino et al. [40]. First literature review was incorporated on the use of indicators for OH purposes. Then indicators were selected, based on the outcomes of the literature review. For the third step, Geographical Information Systems (GIS) are used to characterize the indicators. Fourth, Multi-Criteria Decision Analysis (MCDA) is implemented for indicator weighting and aggregation.

Based on this evidence, the EEQI incorporates indicators such as biodiversity, habitat condition, pollution load, water quality, and climate-driven stressors. These variables provide measurable proxies for ecosystem integrity and resilience, enabling their integration into the broader C-OH framework alongside human and animal health indicators. This ensures that environmental and ecological health are not considered in isolation but systematically linked with public and veterinary health outcomes in coastal areas.

3.2. Human and Animal Health in Socio-Economic Context

Animal health is a critical pillar of the OH framework, since livestock, fisheries, and wildlife act as reservoirs and sentinels of emerging risks that directly affect both humans and ecosystems. The effective implementation of the integrated OH framework plays a pivotal role in promoting human well-being and fostering socio-economic development, particularly in vulnerable regions. Linking health outcomes with socio-economic advancement through a multidisciplinary lens is essential to address the complex challenges of modern societies [68].

Health outcomes are shaped not only by economic and cultural factors but also by the broader socio-ecological systems in which communities operate [69,70]. As such, advancements in public health are largely tied to the reduction in social disparities and the success of international cooperation [71].

Diverting from disease-centric paradigms towards an integrated OH framework in agriculture simultaneously affirms the sector’s contributions to national GDP and labor markets [72] and confronts the persistent drivers of environmental collapse, persistent biodiversity attrition, and emerging zoonostic burdens [73,74].

Mackenzie et al. [75] observe that emerging epidemics routinely coalesce at the interfaces occupied by human, animal, and environmental health, warranting articulately sustained and trans-sectoral synergies. Prevention and correction that avail themselves of synchronized surveillance, reciprocal data architectures, and coherent operational protocols rather than isolated, adjacent or temporally lagged governance attenuates the likelihood of spillover, accelerates the urgency of detection, and harmonizes the setting and enforcement of regulatory codes such that the protection of human populations and biophysical systems share a common attribute of precedence.

Nguyen-Viet et al. [76] highlight that the effective mitigation of livestock-linked and foodborne zoonotic hazards in low-capacity settings hinges upon sustained cross-sector linkages, tailored dialogue with legislative entities, and interventions framed by the specific socio-cultural and economic contours of the community. Echoing this, Cleaveland et al. [77] propose that forward-looking, OH approaches, particularly through targeted animal vaccination initiatives, deliver equitable, financially efficient human health returns, enhance community resilience, and reinforce underfunded health systems. Synthesizing these arguments, a cohesive response is constituted by the design and executions of geographically focused, community-engaged livestock vaccination programs, simultaneously guided by ongoing translational-policy initiatives that connect knowledge production with governance fora. Such an orientation cultivates institutional trust, strengthens peripheral health systems, and assures the replicability and endurance of preventative actions at the human–animal-environmental interface. Within this framework, animal health metrics notably zoonotic surveillance, AMR surveillance, and vaccination coverage serve the double function of anticipatory safeguards and integrators of ecosystem health with the broader vectors of sustainable development.

Consequently, animal health indicators calibrated through the C-OH paradigm emerge as both confirmatory sentinels and integrators that bridge human welfare and ecosystem resilience. Continuous scrutiny of zoonotic pathogen activity, AMR dynamics, and livestock–aquaculture health status safeguards food security, protects public health, and simultaneously registers earliest disturbances in ecosystem balance. These overlapping registries converge with the forthcoming discourse on environmental quality, ensuring that the health of animal populations occupies an informational and operational nexus at the human–environment interface.

Table 1. Comparative Insights on Human and Animal Health within the Socio-economic One Health Framework.

Dimension	Key Insights
Similarities	The literature consistently underscores the central role of animal health within the OH paradigm, recognizing livestock, fisheries, and wildlife as reservoirs and early indicators of emerging threats [68]. There is also a broad consensus that epidemics commonly arise at the interface of human, animal, and environmental systems [75]. Furthermore, most studies stress the necessity of cross-sectoral collaboration and the inclusion of socio-economic determinants in designing effective health strategies [69,70,71].
Differences	Research varies in terms of emphasis: some scholars highlight agriculture’s economic contributions to GDP and labor markets [72], while others focus on ecological sustainability and biodiversity loss [73,74]. Distinct contrasts are also observed between studies prioritizing institutional and policy frameworks [76] and those concentrating on technical instruments such as surveillance, data integration, and operational coordination [75]. Divergent approaches also exist in mitigation strategies, ranging from targeted livestock vaccination programs [77] to broader governance and policy measures [76].
Strengths	A significant strength lies in the holistic framing of human, animal, and environmental health, which enhances community resilience and improves the effectiveness of health systems [68,71]. International cooperation is often noted as a driver for reducing social inequalities and advancing public health outcomes [71]. Preventive mechanisms including zoonotic disease and antimicrobial resistance (AMR) monitoring [75], coupled with targeted vaccination schemes [77] are highlighted as cost-efficient and sustainable alternatives to reactive interventions.
Weaknesses	Several limitations are evident across studies. Dependence on political commitment and institutional coordination often undermines progress, particularly in low-resource settings [76]. Insufficient financial support for public health and veterinary services further constrains implementation [77]. The technical and organizational complexity of establishing synchronized surveillance and cross-sectoral mechanisms poses additional challenges [75]. Moreover, socio-cultural barriers within rural communities may slow the uptake of innovative health measures [76].

presents a comparative synthesis of the literature addressing human and animal health within the socio-economic OH framework. The analysis is organized into four dimensions: Similarities, Differences, Strengths, and Weaknesses which highlight areas of convergence, divergence, and evaluation across existing studies.

3.3. Cross-Sectoral Governance and Policy Integration

Cross-sector governance and policy integration form the principal axis of the Coordinated-One-Health (C-OH) framework, aligning anthropogenic and veterinary health dimensions with harmonized decision-making. In coastal contexts, this is operationalized through Marine Spatial Planning (MSP), supported by data-sharing mechanisms and standardized protocols, which enable collaboration among communities, agencies, and private actors to manage the multiple pressures on coastal systems [78,79,80].

The concerted integration of heterogenous epistemic and practice domains fortifies evidence-based governance, conditional upon the establishment of transparent procedural protocols, extensive capacity-building initiatives, and iterative adaptive learning systems. By operationalizing the most current empirical analyses [81], MSPs demonstrably enhance the resilience of marine ecosystems, bolster the conservation of biodiversity, and further the achievement of selected SDGs [82].

The incorporation of the OH paradigm into the European policy framework for the protection of marine ecosystems is increasingly non-negotiable, given the convergence of zoonotic diseases, escalating AMR, and climate perturbations [79]. Current policy pillars including the European Green Deal, the Farm to Fork Strategy, and the Biodiversity Strategy are exemplary frameworks amenable to OH-enhanced articulation [79].

The decisive execution of this agenda necessitates robust political guidance, interdepartmental synergy, and the fortification of surveillance protocols, alongside the institutionalization of best-practice sharing platforms, and sustained investment in transdisciplinary research. These measures are essential for pre-emptive and adaptive mobilization in the face of emergent, interlinked risks to human, animal, and marine systems.

An integrative approach to OH continues to hinge upon the systematic incorporation of diverse biological, physical, chemical, and socioeconomic datasets, thereby creating actionable knowledge that informs policy coherence and adaptive governance.

Leveraging Geographic Information Systems (GIS) along with complementary geospatial instruments facilitates real-time evaluation of ecosystem dynamics, enabling empirical mapping of habitat vitality and coastal deterioration and furnishing the empirical substratum indispensable for policy founded on verifiable scientific evidence [83,84]. Concurrently, the consolidation of synergy among data generators and recipients necessitates the adoption of uniform protocols, comprehensive metadata, and transparency-accountability frameworks that enhance data accessibility and interoperability, thereby reinforcing the reliability of policy decisions predicated on informed analysis [85].

Consequently, cross-sectoral governance represents the institutional and political substratum that undergirds the actionable execution of the C-OH paradigm. Through the embedding of OH precepts within European regulatory frameworks, the orchestration of maritime spatial planning, and the rationalization of data-sharing protocols, coastal governance can transcend classical sectoral siloing, thereby fortifying ecosystem resilience, safeguarding benthic and pelagic biodiverse compartments, and upholding the well-being of both human and animal populations within a coherent and integrated operational architecture. The conjunction of environmental, health, and governance parameters constitutes the methodological groundwork of the paradigm and is further operationalized by a quintet of rigorously defined indicators (details supra, Section 4) that transmute the conceptual undergirding into quantifiable instruments for the assessment of coastal resilience and the efficacy of the OH directive.

3.4. One Health in Coastal Environments: Indicator-Based Approaches for Human, Animal, and Ecosystem Health

Human health is strongly conditioned by water health, seafood hygiene, and climate-linked pressures. Incidents of E. coli and Vibrio, alongside pollutant and metalliferous adulteration of seafood, together with salt-water intrusion into phreatic layers, create pathways by which ecosystem decline is converted into enteropathic disorders, toxic exposures, and threats to potable-water security. These lines of evidence demonstrate the set-linked transfer of ecological perturbation into measurable morbidity, mortality and market degradation, as further established in the systematic reviews by Malone and Newton [85], Melet et al. [86], and Zamora-López et al. [87].

Animal health functions as an intermediary component within the broader OH paradigm. Shellfish and finfish assimilate pathogens, biotoxins, and contaminants, compromising both their own viability and the safety of humans who consume them [88,89]. Concurrently, the emergence of AMR, propelled by aquaculture and effluent sources; the recurrence of disease epizootics; and the elevated mortality rates observed in both farmed and wild stocks effectively illustrate how environmental perturbation is inextricably linked to animal health status, food security, and the potential for zoonotic transmission [90,91].

The environmental health status of marine ecosystems constitutes the bedrock of the OH framework. Accelerated nutrient loading, chemical contaminants, and the influx of plastic debris promote eutrophication, precipitate biodiversity decline, and disrupt the structural and functional integrity of marine food webs [92,93]. Concurrent impacts including the introduction of non-native species, habitat destruction, overfishing, and the modulation of sound regimes further erode ecological resilience and compromise the long-term viability of marine resources. Climate-mediated stressors specifically, rates of sea-level rise and the incidence of marine heatwaves magnify the cumulative effects of these anthropogenic pressures, thereby reinforcing the pressing necessity for governance strategies that are synergistic, multidisciplinary, and spatially expansive [85,94,95].

A systematic framework for OH assessment must be characterized by rigor and must articulate the complex interlinkages among human, animal, and environmental health. The indicator architecture hereby proposed is organized along three core dimensions: Human Health, Animal Health, and Environmental Health, which are each further subdivided into well-defined thematic fields and specific metrics. The three axes are calibrated in alignment with critical concern areas and prevailing barriers substantiated in the pertinent literature and further validated during stakeholder dialogues. The following table presents the systematic architecture of the indicator framework, illustrating the thematic scope and the precise sub-indicators recommended for each dimension. Table 1 presents the metrics and indicators deemed essential for a consolidated evaluation of C-OH in coastal ecosystems.

Currently, a detailed array of indicators (

Table 2. Integrated Indicators for Assessing One Health in Coastal Systems, Highlighting Human, Animal, and Environmental Pathways.

Pillars OH	Sub-Dimensions	Specific Indicators	Pathway of Transmission	Relevance C-OH Framework	References
Human Health Outcome Index (HHOI)	Bathing water quality	Enterococci, E. coli (Colony Forming Units (CFU)/100 mL)	Bathing waters become contaminated through untreated sewage, agricultural runoff, and combined sewer overflows, leading to the introduction of fecal bacteria. These organisms survive in coastal waters and are directly ingested or encounter humans during recreational activities.	This indicator reflects the risk of gastrointestinal and skin infections in local populations and tourists, and it is fundamental for public health management in coastal zones.	[85]
	Illness outcomes	Gastrointestinal, dermal, and ear infections (cases per 100k)	Illnesses are triggered by exposure to pathogens and pollutants in contaminated coastal waters. Monitoring reported cases provides evidence of the direct impact of waterborne hazards on communities.	Tracking illness outcomes translates environmental contamination into tangible human health burdens and supports risk-based management decisions.	[96]
	Vibrio risk	Vibriosis incidence; Vibrio suitability index	Rising sea surface temperatures combined with moderate salinity create optimal growth conditions for Vibrio species. These bacteria can infect humans via open wounds or through the consumption of raw or undercooked seafood.	Vibrio infections are an emerging climate-sensitive hazard, demonstrating how environmental change directly influences disease risk and public health.	[85]
	Seafood safety	Heavy Metals (Hg, Cd, Pb), PFAS, PCBs, PAHs; shellfish toxins (PSP, Diarrhetic Shellfish Poisoning (DSP), Amnesic Shellfish Poisoning (ASP), Ciguatera Toxin (CTX))	Contaminants and algal toxins are taken up by filter-feeding organisms and bioaccumulate in fish and shellfish tissues. Consumption of these seafood products leads to dietary exposure and poisoning incidents.	This indicator connects environmental contamination with food safety, nutrition security, and consumer protection. It also highlights the dependency of coastal communities on safe seafood.	[87,97]
	Harvest closures	Days per year of shellfish closures	Authorities’ close shellfish harvesting areas when monitoring shows microbial or toxin exceedances. Closures prevent intoxication but also disrupt livelihoods and local economies.	The frequency of closures reflects both environmental stress and the social-economic vulnerability of fishing communities, emphasizing the balance between public safety and economic resilience.	[87]
	Drinking-water intrusion	Salinity exceedances in aquifers	Sea-level rise, storm surges, and flooding lead to the intrusion of saline water into coastal aquifers. This degrades the quality of drinking water and reduces freshwater availability.	Safe and sufficient drinking water is essential for health. This indicator illustrates how coastal hazards undermine basic human needs and increase vulnerability to climate change.	[86]
Aquatic Animal Health Risk Index (AAHRI)	Shellfish hygiene	E. coli in shellfish flesh (MPN/100 g); Class A/B/C	Shellfish accumulate microorganisms by filtering large volumes of water. Elevated fecal contamination in shellfish indicates polluted waters and creates risks for consumers.	Monitoring shellfish hygiene protects food safety and provides an early-warning signal for zoonotic transmission pathways at the human–animal–environment interface.	[88]
	Biotoxin accumulation	PSP/DSP/ASP toxin concentrations (µg/kg)	HAB produce toxins that are concentrated in shellfish tissues. These toxins can cause mortality in marine organisms and poisoning in humans.	This indicator reveals how ecosystem disturbances, such as eutrophication, propagate through the food chain and compromise both animal health and human well-being.	[87]
	Pathogens in fauna	Prevalence of Vibrio, Salmonella, norovirus in bivalves and fish	Aquatic animals act as reservoirs of zoonotic pathogens. Infections in wildlife and aquaculture species create a risk of cross-species transmission to humans.	Surveillance of pathogens in marine animals is essential to identify reservoirs, protect aquaculture, and prevent foodborne and zoonotic outbreaks.	[89]
	AMR in isolates	Percentage of resistant E. coli; MAR index	Antibiotic residues from aquaculture and wastewater select for resistant bacteria in coastal waters. These resistant strains persist in wildlife and can spread to humans.	AMR in coastal environments represents a critical OH issue because it links environmental pollution to reduced treatment efficacy in human and veterinary medicine.	[91]
	Contaminant burden	Metals, POPs (mg/kg); microplastics ingestion	Marine fauna ingest microplastics and accumulate chemical pollutants. These substances induce sublethal effects and are transferred to higher trophic levels.	This indicator highlights how environmental pollutants impact animal welfare, ecosystem functioning, and indirectly human health through seafood consumption.	[93,97]
	Nutrients	TN, TP, Dissolved Inorganic Nitrogen (DIN), Dissolved Inorganic Phosphorus (DIP), N:P ratios; silica	Nutrient over-enrichment stimulates phytoplankton growth, leading to eutrophication, HAB, and oxygen depletion.	Nutrient indicators are foundational for linking agricultural runoff and land use with coastal ecosystem degradation, fisheries decline, and human health hazards.	[92,98]
Environmental Ecosystem Quality Index (EEQI)	Eutrophication status	Chlorophyll-a, dissolved oxygen, Secchi depth, hypoxic area	Excess primary production and decomposition lower oxygen levels and reduce water clarity, creating hypoxic or anoxic conditions that destabilize marine food webs.	Eutrophication status integrates multiple ecosystem processes and provides early warnings of fisheries collapse, biodiversity loss, and public health risks associated with HABs.	[85,99]
	Chemical contaminants	Metals, pesticides, PFAS, pharmaceuticals	Persistent contaminants accumulate in sediments and organisms, where they exert chronic toxic effects, disrupt endocrine systems, and bio magnify through food chains.	Monitoring contaminants addresses long-term threats to ecosystem resilience, animal health, and human food security.	[89,100]
	Marine litter and plastics	Macro-litter density; microplastics in water and sediment	Marine litter causes entanglement, habitat degradation, and ingestion hazards. Microplastics also carry pathogens and toxic chemicals into marine food webs.	This indicator bridges environmental pollution, animal welfare, and food safety, highlighting the pervasive cross-sector risks of plastic pollution.	[93]
	Non-indigenous species	Number of introductions; impact class	Invasive species are introduced by shipping and aquaculture, where they alternative biodiversity and ecosystem functions and may carry novel pathogens.	Invasions disrupt ecosystem stability, reduce fisheries productivity, and increase disease risks, demonstrating strong OH linkages.	[95]
	Coastal habitats	Extent and condition of seagrass, saltmarsh, coral reefs	Habitat degradation reduces nursery areas for fish, weakens coastal protection, and lowers carbon storage capacity.	Healthy habitats support biodiversity, fisheries, climate mitigation, and cultural services, all of which are essential to OH sustainability.	[87,94]
	Benthic quality indicators	AZTI Marine Biotic Index (AMBI), M-AMBI, SAV-IBI	Shifts in benthic communities occur under pollution and physical disturbance, with declines in sensitive species and dominance of tolerant taxa.	Benthic indicators capture the long-term condition of ecosystems, informing biodiversity conservation and sustainable resource use.	[89,101]
	Fish community and fisheries	Large Fish Index, mean trophic level, F/FMSY, SSB/SSBMSY	Overfishing reduces population size, alters trophic structure, and undermines stock sustainability.	Fisheries indicators reveal how ecological pressures affect food provision, economic stability, and nutritional health in coastal communities.	[102]
	Seafloor integrity	Swept-area ratio, benthic condition	Bottom-contact fishing and dredging damage benthic habitats, reduce biodiversity, and alter nutrient cycling.	Seafloor integrity connects human exploitation practices with ecosystem degradation and declining fisheries.	[85]

) which is the highlight of this study, distilled from a broad-ranging review of scholarly sources, elucidates the interrelation of human, veterinary, and ecological health within the context of coastal environments. After this synthesis, the articulated C-OH architecture will be operationalized within the Pagasitikos Gulf, a coastal basin that has recently experienced two destructive episodic flooding events. The case study will thus furnish a controlled setting in which to assess how the pronounced climate-induced shocks magnify existing vulnerabilities in all three health spheres and to affirm the architecture’s value for the purposeful enhancement of resilience and the adoption of risk-informed coastal governance.

In sum, the proposed C-OH indicator architecture delivers a practical, decision-grade methodology that bridges long-standing silos between public health, veterinary science, and marine ecology. By translating ecosystem signals, pathogens, contaminants, eutrophication, heatwaves, into standardized human and animal health metrics, it establishes a transparent “common floor” for evidence generation, comparison, and accountability across coastal regions. The framework’s harmonized constructs enable early warning, longitudinal tracking, and benchmarking of interventions; guide risk-based management of seafood safety, potable-water security, and AMR; and support prioritization of investments where health returns and biodiversity co-benefits are highest. Operationalization in the Pagasitikos Gulf provides a transferable blueprint for climate-stress testing and policy evaluation that can be replicated and scaled, strengthening cross-sector governance and aligning with global sustainability and resilience agendas. In doing so, this methodology converts disparate data into actionable intelligence, accelerates learning across sites, and equips governments, communities, and markets with a consistent basis for safeguarding lives and livelihoods in an era of accelerating coastal change.

To ensure methodological transparency, the proposed indicators, HHOI, AAHRI, and EEQI, are designed as composite indicators that combine both quantitative and qualitative variables. Data sources include routine environmental monitoring programs (e.g., bathing water, shellfish hygiene, fisheries statistics), public health surveillance (e.g., gastrointestinal illness reports, Vibrio incidence), and socio-economic datasets (e.g., tourism, aquaculture outputs), aligned with existing EU regulatory frameworks (WFD, BWD, MSFD) and global initiatives (SDGs) [10,18,19,23]. Weighting and aggregation of sub-indicators follow a MCDA approach, consistent with methodologies applied in OH performance assessments such as GOHI [20] and coastal indicator studies [40]. Handling uncertainty remains a central challenge: differences in data availability and quality across regions can bias composite scores. To address this, sensitivity analysis, robustness checks, and scenario testing are recommended, following Borja et al. [1] and related studies [11,23]. In this way, the C-OH indicators are structured to be flexible, interoperable, and replicable across diverse coastal contexts, while retaining scientific rigor and policy relevance.

Weighting of the indicators will follow a hybrid approach combining expert elicitation (structured expert judgement), statistical techniques such as Principal Component Analysis (PCA) to reduce redundancy, and MCDA to balance trade-offs transparently across human, animal, and environmental dimensions, ensuring that aggregation reflects both scientific evidence and stakeholder priorities. The effectiveness of the C-OH framework will be benchmarked against EU directive standards (WFD, BWD, MSFD), WHO health guidelines, and global indicators such as OHI and GOHI, while also being validated against historical datasets from the case-study area (e.g., bathing-water quality, aquaculture outputs, public health records). This multi-layered benchmarking will allow refinement of weighting methods and enhance the transferability of the framework to other coastal and urban contexts. During the pilot in Pagasitikos Gulf, the effectiveness of the framework will be tested through in situ measurements and comparison with historical datasets, while the C-OH indicators will also be benchmarked against established tools such as the GOHI to ensure robustness and policy relevance.

4. Discussion

4.1. Applications of This Study’s Findings

Cumulative evidence across the reviewed literature supports adopting a C-OH framework to address the coupled problems of pollution, biodiversity loss, zoonotic risk, and climate-amplified hazards in coastal systems. Existing operational models, such as DPSIR and the EU MSFD, have strengthened integrated coastal governance by linking biophysical change to policy responses [1,17,19]. However, their limited and often implicit treatment of human and veterinary health weakens explanatory power and evaluative reach, obscuring key socio-ecological feedback that underpin resilience [2,21].

Integrating OH into the DPSIR framework via the C-OH construct makes the links between environmental degradation, human health, and animal well-being explicit, thereby bridging sectoral silos. This is increasingly salient amid rising zoonotic spillover at the human–animal–environment interface [34,75], the escalation of AMR [44,78], and the demonstrated fragility of aquaculture-reliant coastal economies [88,90]. Within C-OH, composite indicators, specifically, HHOI, AAHRI, EEQI, serve two purposes: (i) condense distributed, cross-domain indicators into coherent aggregates; and (ii) align those aggregates with binding policy commitments in the EU Water Framework and BWD and with the UN SDGs [10,18,21].

Ecological disturbance is a primary driver of altered infectious-disease dynamics in coastal systems. Recurrent pressures, nutrient enrichment, habitat simplification, and xenobiotic inputs, are consistently linked to intensified host–pathogen interactions, including HABs and episodic Vibrio outbreaks [38,48,92]. These stressors create pathways by which degraded ecosystems transmit harm to humans and co-occurring species, as evidenced by illness surveillance, fishery closures, and sustained bioaccumulation of enteropathogens in shellfish [85,87]. Beyond direct exposure, persistent ecological degradation erodes the socio-cultural and economic foundations of adjacent communities. The literature therefore supports management models that integrate environmental, public-health, and socio-cultural indicators within participatory stewardship arrangements, avoiding short-term exploitation in favor of coupled ecological and human well-being.

The proposed C-OH framework advances systemic resilience by coupling cross-sectoral governance with deliberative, co-management practices. Evidence shows that multi-stakeholder platforms, when paired with MSP, act as “living laboratories” that reconcile sectoral trade-offs and cultivate adaptive governance cultures [80,81]. European policy architectures, the European Green Deal, Farm-to-Fork, and the Biodiversity Strategy, provide mature scaffolding for institutional uptake [79]. Real-time, interoperable data pipelines that bridge agency silos are a prerequisite for actionable analytics [83,84].

C-OH complements higher-scale assessment tools by operationalizing OH at municipal and coastal-basin scales. The GOHI is methodologically robust at national level yet less sensitive to spatially and temporally nested local dynamics [20]. The OHI aggregates marine ecosystem status effectively but treats human and veterinary health only implicitly, limiting guidance on human–animal–ecosystem interfaces [11]. C-OH closes this gap by co-embedding epidemiological, veterinary and ecological variables in place-based diagnostics, thereby linking insights from global observatories to the day-to-day needs of coastal administrations facing concurrent bacterioplankton risks, zoonotic spillover and episodic storm-driven stratification.

Building on these governance and policy foundations, agroecological practices have also been highlighted as a pathway to reinforce systemic resilience within the OH framework. Baquero [103] contends that the enhancement of resilience may be pursued through the deliberate embedding of agroecological practices within OH, a modality capable of mediating ecological externalities and of knitting tighter synergies between food production, human health, and the sustainable governance of natural services. Under such a reframing, the continuous protection of livestock welfare transgresses veterinary, legal, and moral dimensions to command sustained attention from the economic and food-security contingents, a requirement that assumes force in coastal peripheries where aquaculture and small-scale fishing represent the chief livelihood anchors. These frameworks, together with Integrated Coastal Zone Management (ICZM) approaches, provide important governance baselines but remain limited in integrating explicit human and animal health dimensions, a gap that the proposed C-OH framework seeks to address.

Stakeholder platforms can be operationalized through municipal–regional partnerships and EU-funded initiatives, while data sharing is enabled via interoperable monitoring systems linking environmental, health, and socio-economic data. Cross-border cooperation may be advanced under existing EU marine governance frameworks, providing practical entry points for the C-OH approach.

4.2. Limitations and Possible Solutions

Operationalizing a C-OH assessment comprises several enduring challenges. Key among them is the patchy availability of cross-domain datasets, which constricts the assembly of composite indicators at a sufficiently localized scale [11,98]. Equally problematic, the governance of weighting, aggregation, and data uncertainty can affect both the interpretability of indicators and their acceptance by decision-makers [1,20]. Fragmentation of institutional mandates across municipal, regional, and national levels often postpones the full adoption of integrative OH evaluations [77]. Overcoming these impediments requires bolstered institutional capacities, interoperable data platforms, and dedicated, transdisciplinary research and training investments. Moreover, this study remains at a conceptual stage, as the proposed indicators (HHOI, AAHRI, EEQI) are theoretically defined and require empirical construction, weighting, and validation. These limitations underscore the importance of piloting and iterative refinement to ensure robustness and policy relevance.

4.3. Future Development of This Study

Applying C-OH to Pagasitikos Gulf (Figure 3) offers a timely benchmark characterized by chronic water-quality pressures and acute climate shocks. Recent catastrophic flooding illustrates how transient extremes compound persistent vulnerabilities across environmental, public-health and economic domains [13,86]. The pilot will test the adaptive capacity of the coastal governance network and refine indicator design for aligning ecosystem integrity, community well-being and regional livelihoods. Future work will also focus on refining the weighting and validation of indicators, developing interoperable data platforms for cross-domain monitoring, and exploring the transferability of the C-OH framework to other coastal and urban contexts.

In addition, several hot topics in current OH research further underscore the need for continuous refinement of the C-OH framework. Particular attention is being directed to the monitoring and mitigation of AMR at the human–animal–environment interface, the impacts of climate change on pathogen dynamics and ecosystem services, and the integration of emerging contaminants such as microplastics and nanomaterials into risk assessments. At the same time, advances in data-driven approaches, including AI and big-data analytics, are opening new possibilities for real-time OH surveillance and decision support. Incorporating these frontiers will enhance the empirical strength and policy relevance of OH assessments in rapidly evolving coastal and urban contexts.

Beyond Pagasitikos Gulf, the framework will be applied in other Mediterranean coastal regions facing climate, biodiversity, and pollution pressures. Variation in data capacity and EU directive implementation will test its robustness and support more harmonized coastal health governance under shared risks.

5. Conclusions

This study highlights the urgent need for integrated approaches to the complex challenges of coastal zones, where pollution, biodiversity loss, climate change, and zoonotic risks converge. By extending the DPSIR framework and embedding the three pillars of OH—human, animal, and environmental—into a unified C-OH framework, it advances a system-based tool that links scientific evidence with actionable governance.

The framework’s composite indicators (HHOI, AAHRI, EEQI) provide a structured, policy-ready means to monitor and prioritize risks. In doing so, they support adaptive decision-making, transparent resource allocation, and alignment with European directives and the SDGs. The main contribution lies in the operationalization of OH for coastal management at the local scale, bridging disciplinary divides and embedding socio-economic dimensions.

Next steps will focus on completing the development, weighting, and validation of the indicator set and piloting the C-OH framework in the Pagasitikos Gulf (Greece), in order to deliver a municipality-scale, policy-ready assessment and refine its transferability to other coastal systems. Ultimately, the framework lays the groundwork for more resilient coastal zones, safeguarding both communities and ecosystems amid accelerating global change.