Title: Indicators for ecosystem services and vulnerabilities in the Mediterranean Sea. An initial application
Subject: Ecological Indicators, 178 (2025) 114110. doi:10.1016/j.ecolind.2025.114110
Author: Alessandra La Notte
Keywords: Ecosystem accounts,Natural capital accounts,Marine ecosystem services,Overfishing,Sustainability indicator

A.L. Notte et al.	E c o lo gic al I nd ic a to rs 178 (2025) 114110

Ecological Indicators 178 (2025) 114110

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Ecological Indicators
journal homepage: www.elsevier.com/locate/ecolind
Original Articles
Indicators for ecosystem services and vulnerabilities in the Mediterranean Sea. An initial application
Alessandra La Notte ^a,1,2, Anna Maria Addamo ^b,c,d,*,1 , Silvia Ferrini ^e,f, Gaetano Grilli ^f, Luca Polimene ^c, Diego Macias ^c
^a International Consultant on Natural Capital Accounting, Milano, Italy
^b Faculty of Biosciences and Aquaculture, Nord University, Bodø, Norway
^c European Commission, Joint Research Centre (JRC), Ispra, Italy
^d Climate Change Research Centre (CCRC), University of Insubria, Varese, Italy
^e University of Siena, Siena, Italy
^f University of East Anglia, Norwich, United Kingdom
ARTICLE INFO
ABSTRACT
Keywords:
Ecosystem accounts
Natural capital accounts
Marine ecosystem services
Overfishing
Sustainability indicator
Economy and society rely on a healthy marine ecosystem to meet a number of tangible and intangible needs. However, understanding the composition and trends in the exchange between the marine ecosystem and the socio-economic system is key to inform effectively the management of marine resources and the sustainable development of economies that depend on them. The accounting framework applied in marine ecosystems may be useful to calculate indicators that measure ecosystem services flows and vulnerabilities. This is the first INCA pilot study on the Mediterranean Sea applied on the following ecosystem services: biomass for nutrition (i.e. fish provision), biomass for materials (i.e. raw biomass), atmospheric composition and conditions (i.e. carbon sequestration), and physical and experiential interactions (i.e. nature-based recreation). Results include Supply and Use tables (SUTs) in physical and monetary terms, and the complementary tables referring to ES vulnerabilities. After computing two indicators, a few suggestions for the on-going research agenda are proposed for the accounting of ES in marine ecosystems, considering the great interest of developing this tool.

* Corresponding author at: Faculty of Biosciences and Aquaculture, Nord University, Bodø, Norway.
E-mail address: am.addamo@gmail.com (A.M. Addamo).
1		These authors contributed equally.
2		While undertaking this research Alessandra La Notte was Contractual Agent at the Joint Research Centre of the European Commission.
https://doi.org/10.1016/j.ecolind.2025.114110
Received 14 May 2024; Received in revised form 13 August 2025; Accepted 21 August 2025
Available online 1 September 2025
1470-160X/© 2025 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

1.		Introduction
Economy and society rely on a healthy marine ecosystem to meet a number of tangible and intangible needs, such as food provision, climate mitigation, protection against extreme events, opportunities for recreation. Because of rapidly growing technological advancements, marine ecosystems are considered increasingly as the new economic frontier that drives investments to support existing industries and to create new ones. This “blue acceleration” is bringing human activities toward remote parts once considered inaccessible (Jouffray et al., 2020).
Such acceleration on exploiting any kind of marine resources (for food, material and space) is intensifying pressures on marine ecosystems that may soon lead to its degradation and eventually collapse in supporting human activities (Jouffray et al., 2020; Halpern et al., 2019). The need to measure and monitor the interactions between ecosystems and human activities is therefore becoming urgent. In fact, understanding the composition and trends in the exchange between marine ecosystems and socio-economic systems is key to inform the management of seas and oceans to enhance the sustainable development of economies that depend on them.
The concept of ecosystem services (ES) is functional to bridge ecosystems and socio-economic systems, since it represents the ecosystem contribution to human activities (deGroot 2002, Burkard and Maes 2017, Potschin et al. 2019, Dasgupta 2021), in providing ecological inputs, removing negative externalities, offering protection against hazards, and supporting the overarching targets concerning climate change mitigation and halting biodiversity loss (La Notte, 2024). A way to mainstream this ecological content into the economic context is through the accounting framework: the United Nations Statistical Division has developed the System of integrated Environmental and
Economic Accounting – Ecosystem Accounting (SEEA EA) as an international standard to accounts for ecosystems and their services (UN, 2024). Integrated accounts are structured, consistent and comparable information concerning on the one hand marine and coastal ecosystems as providers of goods and services, and on the other hand socioeconomic activities as beneficiaries (Cummins et al., 2023). The advantage to use an integrated accounting system lies in establishing coherence and consistency between environmental information and economic data currently used by economists and financial analysts, and therefore creating an entry point in conventional economic models and tools. The interest and urgency in exploring how to undertake integrated environmental and economic accounting for oceans and seas is confirmed by the growing number of applications worldwide (Alarcon Balzquez et al. 2023; Cummins et al., 2023; Gacutan et al., 2022; Gomez Cardona et al., 2023; Mengo et al., 2022; Grilli et al., 2021). In addition, the Regulation (EU) 2024/3024 introduce ecosystem accounts among the mandatory accounts that member states have to compile.

Ref.	https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=OJ:L 202403024.

The objective of this paper is to provide an integrated environmental- economic accounting application for the Mediterranean Sea to propose indicators that support in monitoring the blue acceleration. In order to be compliant with existing international guidelines, this application follows the Technical Guidance on Ocean Accounting v.1.0 (GOAP, 2021). Specifically, within the GOAP framework (reported in Fig. 1a), the focus is on the flow accounts (transactions) provided by the marine ecosystem to economy and society. Consistently with the SEEA EA framework (United Nations, 2021), and the Stock and Flow model (Loureiro et al., 2023), measurements concern selected ecosystem services (ES) flowing to the economic system. While the SEEA EA general framework provides context, rules and format for the accounting tables, it does not impose any specific approach or operational procedure to assess and value ES. The European Commission tested and implemented the SEEA EA framework in Europe through the INCA project (Integrated system for Natural Capital Accounting). INCA developed an approach able to measure both the ES actual flow and the ES vulnerability (La Notte et al. 2019). ES actual flows are part of the marine ecosystem accounts as proposed in SEEA EA and GOAP that flow into economic and social accounts. Along with the official SUT, as described in Technical Guidelines (GOAP, 2021; UN, 2021), complementary information reporting sustainability can widen our understanding of natural-economic capitals interactions, as demonstrated by a number of examples in INCA (La Notte et al., 2022). In fact, the INCA approach considers the generation of ES as the result of the interaction between the ES potential and ES demand when they match. The ES potential is in fact what ecosystems could deliver irrespective from humans’ demand. It becomes a service (in accounting terms) when there is a human need for it. There can be cases when mismatches occur, i.e. when the demand for ES is not covered by the availability of ES potential (Fig. 1b).

INCA platform available at https://ecosystem-accounts.jrc.ec.europa.eu/.

So far, INCA was applied only on terrestrial ecosystems. This pilot assessment on the Mediterranean Sea represents the first application of the INCA approach on the marine ecosystem. The accounting framework (and therefore its operational procedure) applied in marine ecosystems may present a number of differences if compared to terrestrial ecosystems, especially for what concerns the role of the spatial dimension. The focus of this application is on the European Mediterranean countries due to the lack of data that characterizes neighboring countries. However, the lessons learned in terms of operational procedures that could be adopted remain valid for any context, if data are or become available. The materials and methods section opens with the general accounting setting to move into the details of each of the four marine ecosystem services (ES), which follow the INCA approach. Results focus on Supply and Use Tables (SUTs) in physical and monetary terms for the year 2018. Also, the complementary tables referring to ES vulnerability are reported and commented. Finally, the discussion wraps up on the overall lessons learned. It will cover both the conventional ES accounts and the new ES vulnerability accounts and their implications in monitoring the blue acceleration, together with a few suggestions for the on-going research on marine ecosystem accounts.
2.		Material and methods
This pilot case study on the Mediterranean Sea is undertaken for the year 2018 and for the European countries bordering the Mediterranean Sea. This work complies with the building blocks of the Ocean Accounts (IDEEA Group, 2021), which acknowledge the need to set sustainability measurements (IDEEA Group, 2023). The procedure followed in this application is summarized in Fig. 2 and described through this section. Major details are provided in the Supplementary Material Methodology.
2.1.		The accounting setting
As reported in the Technical Guidelines (GOAP, 2021), the marine environment should be considered as an “asset” that contributes to human activities. The flows provided by environmental assets are represented by ES and are recorded as supply and use tables (SUTs).
To address the accounting setting, Ecosystem Types (the columns of the supply table) represent the building block on Environmental Asset and are described as:
•		Coastal: beaches, seagrass beds, mangrove forests, intertidal and subtidal rocky shores, oyster reefs, kelp forests, and tropical coral reefs (reported in the Regulation (EU) 2024/3024 as “coastal waters”);
•		Marine (to shelf): benthic soft-bottom habitats, phytoplankton and zooplankton communities (reported in the Regulation (EU) 2024/ 3024 as “shelfs”);
•		Marine (shelf to EEZ): aphotic benthic sessile communities, uninhabited soft bottom, uninhabited rock, pelagic phytoplankton and zooplankton communities, migratory pelagic species (reported in Regulation (EU) 2024/3024 as “open ocean” and, specifically in this study, as “open waters”).
To address the building block on environmental flows, we extract from GOAP/CICES the ES assessed for the Mediterranean Sea:
•		Provisioning services:
o Biomass for nutrition (corresponding to fish provision, CICES 1.1.5.1)
o Biomass for materials (corresponding to raw biomass, CICES 1.1.5.2)
•		Regulating and maintenance services:
o Atmospheric composition and conditions (corresponding to carbon sequestration, CICES 2.2.6.1)
•		Cultural services:
o Physical and experiential interactions (corresponding to naturebased recreation, CICES 3.1.1.1–3.1.1.2).
To address the building block on Economic Units, we identify the sectors that act as primary users in receiving ES from ET, by referring to the Statistical Classification of Economic Activities in the Europe.^5 Primary users are the sectors that receive ES directly from Ecosystem Types, e.g. from the ecosystem type “shelves” to the “marine fishing” sector (NACE A 03.11). Primary users can process and transform the ES and transfer the outcome to other sectors, which would be secondary users, e.g. from the “marine fishing” sector to the “processing of fish”
^5 Ref. NACE at https://ec.europa.eu/eurostat/web/metadata/classifications.

Fig. 1. General Framework of marine ecosystem accounts based on GOAP (Guidance on Ocean Accounting) (a) with a focus on Ecosystem Services JRC-INCA (Integrated system for Natural Capital Accounting) approach (b).

sector (NACE C 10.20 within Manufacture of food products). At each transformation step, the commercial value of product that is generated increases.
2.2.		The spatial setting
The spatial allocation and the subsequent intermediate allocation rule requires the compilation of an intermediate SUT that is pivotal in connecting the ecosystem supply side (marine areas disaggregated into GSA) with the economic use side (countries where economic units are located) (Fig. 3). All the details are described in the Supplementary Material Methodology.
For the use table, the allocation is straightforward:
•		fish provision is allocated to the primary sector, in particular to “Fisheries”;
•		raw biomass is allocated to “other sectors”;
•		carbon sequestration goes beyond national boundaries because it serves the overarching environmental target of climate change mitigation. For this reason, it is allocated to what the INCA approach (La Notte et al., 2023) identifies as “Global Society”;
•		nature-based recreation is assessed as daily recreation that residents have the opportunity to enjoy and should not be overlapped or mixed with nature-based tourism, that would be assessed with a different metric. The (primary and final) user of nature-based recreation are households.
The ability to allocate clearly and consistently flows results from a combination of the use of intermediate pivotal tables and of the transparency and granularity of ecosystem services identification and their assessment.
2.3.		Methodologies applied to assess and value ecosystem services
The biophysical assessment and valuation used in this study builds upon an existing work (Addamo et al., 2025) of which Supplementary Material Table SM2 summarizes the applied biophysical assessment and valuation techniques.
As a general introduction, the assessment of ES requires to choose a proxy able to measure the main characteristics of the ecological process under investigation. For some ES the choice of the proxy is straightforward. Specifically on fish provision, it refers to the provision of fish biomass for human consumption and the condition to grow it (see Grizzetti et al., 2019). For other ES, the choice of the proxy may require some moderate processing, e.g. blue carbon and nature-based recreation. Estimates on the tons of seagrass are used in isolation (raw biomass provision, part of carbon sequestration) or coupled with another indicator (i.e. density of marine mammals and turtles in nature-based daily recreation).
2.4.		Sustainability measurement
The mismatch between ES potential and the ES demand, and specifically when ES potential < ES demand, highlights a vulnerability of ecosystems in meeting human needs and therefore creates a risk for economy and society. Within the Stock and Flow models (Loureiro et al, 2023), the ES vulnerability accounts could contribute to delineate a part of the risk accounts (La Notte, 2024). Specifically, human needs that depend on ecosystems are at risk because the ES yearly flow are weak, vulnerable for a number of reasons. Our application considers two cases: (1) the overuse of fish provision flow; and (2) the missed flow of naturebased recreation.

2.4.1.		
Fig. 2. Procedure for the accounting of marine ecosystem services.

ES vulnerability due to fish provision overuse
Fish provision is a “source” service (La Notte et al., 2019) characterized by a regeneration rate that determines whether actual fish catch is sustainable or not. If catches are below the regeneration rate, the biomass regeneration rate over time is not under threat. The spawning stock biomass (SSB) measures the status of fish stock and its reproductive capacity are only available for a few stocks (UNEP/MAP, 2017), and therefore cannot be used neither as potential validated reference point for sustainable use of marine living resources nor as a proxy of Good Environmental Status of commercially exploited fish.
Because of these data gaps, in this study we applied a “Fishing Sustainable Score” that combine the information on status of fishing mortality and stock biomass as indication of the status of fish stock. Fishing mortality is the removal of fish stock by fishing activities, a measure used in fisheries population dynamics to account for the loss of fish in a fish stock through death. Stock biomass is the number of fish individuals multiplied by their mass.
The score is created to estimate whether the current flow of fish provision (actual flow) in the SUT is “sustainable” or is overused. The possibility to measure sustainability based on scores is a common practice when no better specific measurements are available (Mace et al., 2012).
In order to enable the accounting of both (i) the actual flow and the (ii) sustainable flow, the score is computed according to the following procedure. The amount of catch in tons recorded for each species, country and GSA (FAO 2021) for the year 2018 is associated to a total score for the stock status based on (a) fishing mortality and (b) stock biomass related indicators reported in the GFCM Validated Stock Assessment Forms (SAFs) (FAO, 2022) for each target species. The total score for the stock status is computed using the scores reported in Supplementary Material Table 3 for each indicator used in the SAF report (see Supplementary Material Table SM3 and Table SM4 per further details) according to Eq.1.
Fishing Sustainable Score Range =	(Fish Mortality Score)_i
+ (Stock Biomass Score)_i	(1)

Fig. 3. Procedure underpinning the Mediterranean ecosystem services accounting structure applied in this study. FAO = Food and Agriculture Organization; STECF=Scientific, Technical and Economic Committee for Fisheries; FDI = Fisheries Dependent Information; GSA = Geographical subarea.

where i indicates the fish stock.
Based on the “Fishing Sustainable Score Range”, it is possible to identify a risk level and eventually estimate the percentage of the actual flow that can be considered as sustainable (Table 1, Supplementary Material Figure SM2). The estimate is based on the fact that a risk exists, and it is determined by both the fishing effort and the stock abundance. Such percentage is therefore applied to the fish provision actual flow: if there is no risk, all the actual flow can be considered as sustainable; if there risk only part of the actual flow may be considered as sustainable depending on how high the risk is. With a risk that is critical, any actual flow will be unsustainable.
The percentages reported in Table 1 (based on the “Fishing Sustainable Score Range”) applied to the GSA in the Mediterranean Sea generates the coefficients reported in Supplementary Material Table SM6.
There can thus be a fish provision actual flow, officially reported in SUT, and a fish provision sustainable flow, assessed by applying the score reported in Supplementary Material Table SM6. The mis-match account that reports the ES vulnerability is computed by subtracting the sustainable flow from the actual flow: the ES vulnerability is the overuse component of the ES actual flow, i.e. that part of the actual flow that is not sustainable.
2.4.2.		ES vulnerability due to the nature-based daily recreation missed flow
In the case of nature-based daily recreation, this ES could reach a higher economic impact when higher presence of seagrass and mammals

Table 1
Range values of the “Fishing Sustainable Score Range”, the risk level for the fish stock due to fishing activity and the associated percentage of the actual flow that can be estimated as “sustainable”.

occur. In fact, two indicators (ref. Supplementary Material Table SM2) are used as proxies for natural attractiveness. Supplementary Material Figure SM3 shows the GSA where high presence of seagrass and high density of mammals and turtles would determine an overall high monetary value being paid by households to enjoy diving and whale watching.
Ideally, the effects of worsening natural attractiveness should be measured directly as decreasing number of visits. However, this kind of information is currently not available and therefore an indirect assessment is undertaken to estimate this figure. Specifically, to a low value of the indicator mapped in Supplementary Material Figure SM3 is
attributed a lower end monetary estimate to the visitors’ visit following the range of values from the literature review (Supplementary Material Table SM2) (lower value because of lower attractiveness of journeys). To a high value of the indicator mapped in Supplementary Material Figure SM3 is attributed a higher end monetary estimate to the visitors’ visit (higher value because of higher attractiveness of journeys). The ES missed flow is estimated as the difference between a situation where there is a high presence of seagrass and high density of mammals and turtles and the current situation. Such flow can be measured in monetary terms and reveals whether (and how much) there is room for improvement. Proportionally, such difference between an ideal situation when

Table 2
Supply and Use table for the European countries of the Mediterranean Sea, year 2018.
(a) Supply table in physical and monetary terms Ecosystem Types Ecosystem Services in physical terms (in tonne or number of visits) | Coastal | Shelves | | Open waters | Total

Provisioning services
tonne
Fish provision
Raw biomass provision
Regulation & maintenance services
tonne
Carbon sequestration
Cultural services
number of visits
Nature-based daily recreation
Ecosystem Services in monetary terms
(in Euro)
Provisioning services
Fish provision
Raw biomass provision
Regulation & maintenance services
Carbon sequestration
Cultural services
Nature-based daily recreation
Total
Total per km^2

3,823
4,353
3,167,593
Coastal
30,414,412 133,681
377,006,958
275,055,298
682,610,350
1,484

12,131
6,156,394
Shelves
83,226,964
732,733,980
345,025,505
1,160,986,450
1,010

193,425
16,593,350
Open waters
320,848,160
1,974,940,560
345,025,505
2,640,814,225
2,967

209,379
4,353
25,917,337
21,260,864
Total
434,489,536
133,681.3
3,084,681,498
965,106,310
4,484,411,026
1,794

(b) Use table in physical and monetary terms
Macro-aggregation of economic sectors
Ecosystem Services in physical terms (in tonne or number of visits)
Primary sector | | Other sectors | Households | Global Society | Total
Provisioning services tonne Fish provision	209,379 Raw biomass provision | | 4,353 | | | 209,379 4,353
Regulating & maintenance services tonne Carbon sequestration | | | | 25,917,317 | 25,917,317
Cultural services number of visits Nature-based daily recreation | | | 21,260,864 | | 21,260,864
Ecosystem Services in monetary terms (in Euro) Primary sector Provisioning services Fish provision	434,489,536 Raw biomass provision | | Other sectors 133,681 | Households | Global Society | Total 434,489,536 133,681
Regulating & maintenance services Carbon sequestration | | | | 3,084,681,498 | 3,084,681,498
Cultural services Nature-based daily recreation | | | 965,106,310 | | 965,106,310
Total	434,489,536 | | 133,681 | 965,106,310 | 3,084,681,498 | 4,484,411,026

the value of natural attractiveness is high everywhere and the current situation is transposed also in physical terms on the number of the visits, as the potential flow of visits that is not taking place (and is thus “missed”).
3.		Results
The outcomes of this case study are reported in two sub-sections. The first sub-section refers to the official accounts, the official SUT (according to SEEA EA and GOAP). The second sub-section refers to complementary accounts measuring ES vulnerability, i.e. the mis-match between ES potential and ES demand that may generate a risk in terms of addressing human needs now and in the future. Both sets of tables are compiled in physical and monetary terms for the reference year 2018, which was chosen because of data availability.
3.1.		Official Supply and use tables
The SUT reports respectively the ecosystem types providing ES flows (supply side) and economic units that act as primary users of the ES flows (use side). Before compiling the official SUT, it was necessary to compile the intermediate pivotal tables based on GSA (according to FAO classification, Supplementary Material Figure SM1) and the GSA-EU country allocation (Supplementary Material Table SM1). The intermediate supply and use tables are available as Supplementary Material Table SM7. Although the accounting rule requires the perfect match between supply and use, there can be a slight discrepancy in this case because there are shares of GSA that belong to non-EU countries. This applies specifically to GSA 18 for a share of about 37 % (in fact, from an accounting allocation perspective, 12,165 km^2 are attributed to Albania and 6,383 km^2 are attributed to Montenegro).
The official Supply Table for the Mediterranean Sea Marine ES in EU is filled allocating all ES according to the rationale explained in Supplementary Material Table SM2. In interpreting the outcomes, readers and practitioners need to keep in mind that the extent of coastal ecosystems is very tiny compared to shelves and open water. In fact, when considering the value per Km^2, the flow provided by coastal ecosystems assumes a larger perspective and is more in line with the other ecosystem types (Table 2).
SUT on fish provision shows estimates that may be lower than expected (€ 435 m/year over € 4 bn/year), because fishing is the major economic activity that takes place in marine ecosystems, and at the basis of the food system together with agriculture.
The monetary value attributed to nature-based daily recreation is relatively high (€ 956 m/year). This ES is attributed to households, who are the final beneficiaries. Compared to fish provision, nature-based daily recreation is not going to enter a value chain transformation (manufacture, transportation, etc.) but it is provided by marine ecosystems directly to households. On the other hand, fish provision represents only the first entry point into a market system that is going to

Table 3
Complementary Supply and Use table for the European countries of the Mediterranean Sea on ES vulnerability, year 2018.
(a) Supply table in physical and monetary terms
Ecosystem Types
Ecosystem vulnerabilities in physical terms
(in tonne or number of visits)
| Coastal | Shelves | Open waters | Total

Provisioning services tonne
Fish provision

1,304

2,376

96,658

100,378

Cultural services number of visits
Nature-based daily recreation

10,858,844

13,621,181

13,621,180

38,101,205

Ecosystem vulnerabilities in monetary terms (in Euro) | Coastal | Shelves | Open waters | Total
Provisioning services Fish provision | 20,107,891 | 60,142,992 | 234,634,394 | 314,885,276

Cultural services
Nature-based daily recreation

450,390,537

564,963,568

564,963,568

1,580,317,674

(b) Use table in physical and monetary terms
Macro-aggregation of economic sectors

Ecosystem Services in physical terms (in tonne or number of visits)
| Primary sector | Other sectors | Households | Global Society | Total
Provisioning services tonne Fish provision | 100,378 | | | | 100,378
Cultural services number of visits Nature-based daily recreation | | | 35,025,573 | | 35,025,573

Ecosystem Services in monetary terms (in Euro)

Provisioning services 5 fish species provision

Primary sector 314,885,276

Other sectors

Households

Global Society

Total
314,885,276

Cultural services | | | | |
Nature-based daily recreation | | | 1,580,317,674 | | 1,580,317,674
Total | 314,885,276 | | 1,580,317,674 | | 1,895,202,950

Actual flow =

(2)

Vulnerability =

(3)

Fig. 4. Relative values of marine ecosystem services in the Mediterranean Sea, year 2018 (left): nature-based daily recreation (21%); fish and biomass provision (10%), and carbon sequestration (69%). Ecosystem Services actual flow and vulnerability indicators in the Mediterranean Sea, year 2018 (right).

transform, trade and sell a biological resource. All the added values that characterize fish provision from the production to the consumption stages (which will remarkably increase the final purchasing price) do not apply to nature-based daily recreation whose value could already be considered as the very final “purchasing price”.
Based on the pilot case study, carbon sequestration represents almost 70 % of the total value of the marine ES considered, followed by naturebased daily recreation (about 20 %) and the provisioning services (about 10 %) (Fig. 4). Although all the limitations just described, it is however important to consider the key role of marine ecosystems in climate change mitigation.
Mitigation of climate change through the sequestration of carbon in an ES that is attributed to the global society because the beneficiaries of this service are not restrained into the boundaries of individual countries. The opposite applies to the other ES, whose beneficiaries can be allocated to specific economic units (economic sectors or households) in specific countries.
3.2.		Complementary tables on ES vulnerability
There are complementary supply and use tables that can be compiled, based on the intermediate pivotal table as reported in the Supplementary Material Table SM8. The first of the two ES for which the mis-match accounts are produced is fish provision. The sustainable flow estimated for this ES is almost 1/3 lower than the actual flow (-26 %) and therefore determines a monetary value of the sustainable flow that is lower than the monetary value of the actual flow: 285 million Euro/ year Vs. 435 million Euro/year (Supplementary Material Table SM9). The difference between the two values represents the overuse of the fish provision service, reported as ES vulnerability in Table 3.
For nature-based recreation, as already explained in Section 2.4.2, high presence and density of seagrass for diving and marine mammals for whale watching would be worth €43, rather than €15.42 (for the moderate density) or €8 (for the low density). Therefore, the ES missed flow is calculated as the difference between an ideal situation with a high score for all biophysical indicators and the current situation. This difference (proportionally replicated also on the number of visits in physical terms) is reported as ES vulnerability in Table 3.
The ES vulnerability shows that there is an important gap to fill in terms of both sustainable fishing and appreciation of nature-based recreational activities. Moreover, the combined processing of both ES actual flow and ES vulnerabilities enables to monitor over time:
•		the productivity of the Mediterranean Sea in providing the selected ES, by computing the following indicator
ES actual flow
(~~ES actual flow~~ + ~~ES vulnerability~~)
•		the vulnerability of the Mediterranean Sea in providing the selected ES, by computing the following indicator
ES vulnerability
(~~ES actual flow~~ + ~~ES vulnerability~~)
It is, in fact, important to not only record the ES actually provided but also to measure and monitor over time whether this flow is sustainable and/or how far this flow is from a desirable level (see Fig. 4). This information could be useful for policy makers to setting targets, to plan restoration actions, to control the pace of the blue acceleration.
4.		Discussion
Accounting for marine ES is an opportunity to bridge ecosystem and socio-economic systems in a quantitative way. The flows are assessed in biophysical terms, translated in monetary terms and accounted in a way that bridges economic accounts. The estimates provided by the pilot application are meant to unhide ES flows and makes them available for further processing in economic and financial contexts, to unlock a series of integrated environmental-economic applications that currently underestimate and neglect the role and importance of ecosystems for economy and society. There are analyses and processing in the economic domains that necessarily require figures expressed in monetary terms, such as adjustment of macroeconomic indicators and cost-benefits assessments. However, it is important to specify that ES valuation (“monetary benefit”) should not be confused with “monetary profits”: the former measures the richness with which ecosystems support economic sectors and the overall society; the latter measures the excess of revenues in a purely business perspective.
As an overall comment, the premises to be made is that what reported for fish provision in the SUT only refers to five species out of the around 100 commercial species caught in the Mediterranean. For raw biomass provision, it is here only accounted for seagrass leaves that represent a tiny part of marine biological resources (excluding fisheries).
The same underestimate applies in general for the yearly flows of the ES accounted here: it is only four ES out of the 48 marine services currently listed in CICES. Therefore, these estimates are only a minor part of all services that marine ecosystems can provide.
This pilot application on the Mediterranean Sea highlights a number of features (as novelties) on marine ecosystem accounting, but also show current limitations.
From an accounting perspective, this pilot application showed us that a number of differences occur between terrestrial and marine ecosystems. First, as novelty for marine ecosystem accounting, there is an “intermediate step” that does not necessarily occur for terrestrial ecosystems: the spatial allocation. In fact, users of marine ES are not geographically placed where ES are provided. Therefore, we need to establish a political-economic “allocation rule” which can be consistent with ecological processes. For this application, we used the FAO zoning (i.e. GFCM-GSAs) to allocate ES to countries. This could be one possibility. Maybe other options could be explored to find advantages and drawback and eventually suggest a series of viable alternatives worldwide. Nevertheless, it should be considered that some data need to be processed at the appropriate disaggregated geographical level before being aggregated by ET and by country. The risk of skipping this step may lead to a remarkable underestimation of the ES flow because averaged values (in such a varied and dynamic environment) may hide key features. For example, to consider the whole Mediterranean Sea as a unique zone, or to consider only two or three sub-areas within the Mediterranean Sea would generate a figure that is totally different from the one we have calculated, in terms of order of magnitudes.
Second, as novelty, in measuring sustainability we consider the mismatches between ES potential and ES demand, as suggested by the INCA approach (La Notte et al. 2019, 2022). The assessment of mis-matches enables to calculate not only the ES actual flow that measures the richness of ecosystems in providing services, but also the ES vulnerabilities that measures the risks for those human activities that depends on ES.
Third, as novelty, with a specific reference to fish provision, it is important to specify for which species it is being undertaken. The number and types of species may create difference in terms of order of magnitude; therefore, the comparison among countries may only occur for the same number of the same species.
Fourth, as limitation, about the accounting setting per se, the current available classification of marine Ecosystem Type (Supply Table) still very general and/or confused, mixing ecosystem and habitat types. For example, the IUCN Global Ecosystem Typology (see Keith et al, 2020) use a broad classification for the marine realm that lead to neglect the main role of each marine functional ecosystem and habitat in providing a variety of specific services.
Fifth, as limitation, about the calculation of fish provision sustainable flow, the methodology proposed (which is based on a score) should be considered only as a “temporary solution”. In fact, it is desirable to use data on sustainable yield based on effective measurements and robust modelling. Moreover, how to assess sustainability for blue carbon is still an open research question. In theory, any carbon sequestration decrease with respect to the background level (i.e. carbon sequestration in a pristine area) would result in a carbon “debit” which would require actions to be “repaid”, so is not sustainable. In practice, a given year may be chosen as “reference” and then any changes with respect that reference can be assessed. Positive or zero changes with respect to the reference could define the sustainability threshold (Johannessen et al., 2022).
Finally, the major limitations are mainly due to the lack of data. Therefore, about future developments, e.g. for fish provision, it is desirable to increase the number of species to account for, and also to add aquaculture that is a key ES in terms of economics and food system analysis. Overall, it is important to increase the number of marine ES by including also sink services (i.e. the ones concerning pollution removal) and source-suitability services (i.e. habitat and species maintenance). The latter would be particularly important to assess the importance of interconnectivity in marine ecosystems (Addamo and La Notte, 2023) which is different from the intermediate services supporting the delivery of other ES (see for an example Addamo et al., 2025).
5.		Conclusion
This study represents the first INCA pilot study on the Mediterranean Sea applied on the following ecosystem services, and proposes a novel approach highlighting both novelties and limitations due to the lack of knowledge or adaption to existing approaches applied for terrestrial ES. Therefore, the marine (or ocean) accounting, as emerging field, needs to have a common approach, in line with the general standards adopted by SEEA EEA but adapted to the complex realm that differ deeply from the terrestrial.. This initial application shows the feasibility of the approach, but many more applications are needed to drive its implementation toward a systematic accounting. In addition, the research agenda on marine accounts needs to be completed by further exploration of policy uses.
Authors contributions
This work was realized under the collaboration of all authors. AMA and ALN conceived and designed the analysis; AMA collected the data and performed the analysis on biophysical assessment; LP and DM collected the data and performed the analysis on biophysical assessment on phytoplankton; SF and GG reviewed literature and performed the analysis on monetary valuation; ALN performed the analysis on accounting. All authors participated in the discussion of the results and in the writing of the manuscript. All authors approved the final version.
The views expressed are purely those of the writers and may not in any circumstance be regarded as stating an official position of the European Commission.
CRediT authorship contribution statement
Alessandra La Notte: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Methodology, Formal analysis, Data curation, Conceptualization. Anna Maria Addamo: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Methodology, Formal analysis, Data curation, Conceptualization. Silvia Ferrini: Writing – review & editing, Formal analysis. Gaetano Grilli: Writing – review & editing, Formal analysis. Luca Polimene: Writing – review & editing, Formal analysis. Diego Macias: Writing – review & editing, Formal analysis.
Funding
AMA is supported by Horizon Europe MPA Europe (Grant Agreement 101059988).
Declaration of competing interest
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Anna Maria Addamo reports financial support was provided by European Commission Joint Research Centre Ispra. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors would like to thank Chiara Piroddi (JRC) for providing input to preliminary brainstorming and data on food web in the Mediterranean Sea. The authors are grateful to the anonymous reviewers for their comments and suggestions that improve the quality of the manuscript.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi. org/10.1016/j.ecolind.2025.114110. Supporting evidence for the supplementary material is drawn from several studies (Addamo et al., 2024; Ban˜olas et al., 2020; Buesseler et al., 2007; Camin˜as et al., 2020; Collier et al., 2021; Eppley and Peterson, 1979; Grammatikopoulou et al., 2023; Keith et al., 2020; Masri et al., 2018; Monnier et al., 2020; Partnership, 2021; Pindyck, 2019; Ro¨hr et al., 2018; Sousa et al., 2012; Wang et al., 2019; ACCOBAMS, 2021; Commission, 2022; Haines-Young and
Potschin, 2018; O’Keefe and Lillis, 2019; United Nations, 2014).
Data availability
All data are available in the supplementary materials
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