Global Ocean Accounts Partnership Secretariat · GOAP Technical Guidance on Ocean Accounting · circular
TG-2.7 sits at the boundary between the residual flow accounts compiled in TG-3.4 Flows from Economy to Environment and the policy applications addressed in TG-1.6 OA and Environmental Impact Assessment and TG-2.8 Climate Change Indicators: the Circular converts accounting data on pollution flows into decision-relevant indicators. The indicators produced through this Circular feed directly into marine spatial planning, SDG 14.1 reporting, and environmental impact assessment processes.
This Circular provides operational guidance on compiling indicators of pollution and other flows from the economy to the marine and coastal environment. These indicators support evidence-based decision-making for marine spatial planning, pollution control programmes, environmental impact assessment, and SDG 14.1 reporting. Upon completing this Circular, readers will understand how to derive pollution indicators from the residual flow accounts compiled using TG-3.4 Flows from Economy to Environment, construct composite indices for marine pollution assessment, and calculate intensity and efficiency indicators that link economic activity to environmental pressures.
This Circular requires familiarity with:
The SEEA Central Framework supports indicator derivation through combined presentations that juxtapose physical flows with economic data. For marine pollution, this framework can be extended to address the specific characteristics of ocean-related residual flows, as in Figure 2.7.1.
· Figure 2.7.1
Source TG-2.7, Section 3 (accounts-to-indicators derivation) and Section 4 (indicator-family mapping).
Marine pollution indicators can be classified into the categories summarised in Table 3.1.1 below.
The derivation of indicators from accounts follows the structured process summarised in Table 3.1.2 below.
The FDES 2013 Basic Set of Environment Statistics identifies specific statistics related to emissions and waste that can inform indicator development, organised under Component 3: Residuals. These include emissions of greenhouse gases by sector, generation and pollutant content of wastewater, discharge of wastewater to the environment, and generation and management of waste. The FDES 2013 Core Set of Environment Statistics provides a prioritised subset of the Basic Set, and compilers should note which indicators in this Circular align with Core Set statistics, as the Core Set carries the priority for international comparability.
Scope boundary — physical disturbance flows: Physical disturbance flows (underwater noise, dredging, sediment disturbance, habitat modification) are outside the scope of this Circular. Indicator and compilation guidance for these flows is addressed in TG-2.1 Aggregate Biophysical Indicators and TG-3.4 Flows from Economy to Environment, Section 3.3.
The SEEA CF physical supply-use table for residuals records flows by substance or material type. For marine pollution indicators, compilers should extract the following categories from the PSUT:
Water emissions:
Air emissions with marine deposition:
Solid waste to marine environment:
The SEEA CF Table 3.18 provides the general structure for recording solid waste flows by source and destination. For marine litter accounting, the “waste to environment” category is disaggregated to distinguish waste reaching marine waters from other environmental destinations.
The physical supply table records residual generation by economic unit (industries classified by ISIC and households). For each pollutant category, compilers extract:
Example extraction for nutrient emissions:
Household residuals — boundary with municipal treatment systems: Household generation should be recorded gross (before treatment) under the HH row as the total nutrient load generated at the household level. Treated discharge should be attributed to the wastewater treatment plant operator (ISIC 3600) to avoid double-counting household flows that have already been captured in the treatment system. Where PSUTs do not disaggregate household flows from mixed municipal or residential categories, compilers should estimate household nutrient generation using population and per-capita nutrient excretion coefficients. National coefficients should be used where available. In their absence, indicative values from SEEA CF Box 3.2 provide a starting point. The resulting estimates should be flagged with the appropriate TG-0.7 quality codes to document the estimation method.
When extracting flows for maritime NOx indicators (used in the atmospheric deposition calculation in Step 3), compilers must exclude inland water transport (ISIC 5021—5022) from the maritime-destined atmospheric deposition sub-total. For the full scope definition of maritime NOx emissions, including the rationale for this exclusion, see the Maritime NOx indicator specification in Section 3.5.
The SEEA CF methodology for recording solid waste flows by source and destination is described in SEEA CF paras 3.268-3.277. For the general principles of attributing residual flows to source industries within the physical supply-use framework, see SEEA CF paras 3.99-3.109. Attribution should record flows to the industry that generates the residual rather than the industry that manages or treats it, and this attribution should be applied consistently across pollutant categories (unless treatment is incomplete and residuals are released).
Not all residuals recorded in the PSUT reach the marine environment. Spatial attribution requires:
Hydrological connectivity analysis — identify catchments that drain to coastal waters, and estimate nutrient transport coefficients accounting for in-stream retention:
Delivery ratios typically range from 0.05 to 0.40 depending on distance to coast, soil type, vegetation cover, and retention in waterways. Higher delivery ratios apply to short, steep catchments with limited riparian buffers. Lower ratios apply to flat, heavily vegetated catchments where significant in-stream retention occurs. Compilers should select the delivery ratio method from the following four-level tiered protocol, applied in order of preference:
Tier 1 — Modelled national or OECD ratios: Use ratios derived from national hydrological models or OECD Gross Nitrogen Balance guidance where these are available and applicable to the catchment hydrology. The OECD Gross Nitrogen Balance methodology provides guidance on estimating nutrient delivery from agricultural catchments to receiving waters. This tier applies primarily to temperate agricultural systems in OECD member states.
Tier 2 — Regional sea or river-basin studies: Where OECD or national modelled ratios are unavailable or not applicable (e.g., small island states, tropical coastlines, monsoon-dominated basins), use delivery ratios from regional sea assessments or peer-reviewed river-basin studies covering comparable hydrological and geomorphological conditions.
Tier 3 — Simplified export-coefficient approaches: Where neither Tier 1 nor Tier 2 sources are available, apply simplified export-coefficient methods — for example, USGS SPARROW model coefficients adapted for tropical catchments, or FAO Land and Water Division guidance on nutrient export coefficients for tropical agriculture. These methods are less precise but documented and reproducible.
Tier 4 — Low-confidence documented fallback: Where no validated source is available, assume a delivery ratio consistent with the general range (0.05—0.40), document the assumed value and its justification, and flag the resulting indicator as low-confidence using the appropriate TG-0.7 quality codes. Do not use undocumented or arbitrary coefficients.
Direct discharge identification — for point sources (wastewater treatment plants, industrial outfalls), use administrative records to identify facilities discharging to coastal waters versus inland waters.
Atmospheric transport modelling — for air emissions, use atmospheric deposition models (e.g., EMEP, GEOS-Chem) to estimate the fraction depositing to marine waters within the EEZ. Where atmospheric models are unavailable, compilers may use deposition budget outputs published by regional sea conventions — for example, HELCOM Pollution Load Compilation or OSPAR deposition budget assessments — as documented simplified sources applicable to their regional context. If no validated method is available for the compiler’s region, atmospheric deposition should be reported as “not compiled” rather than estimated with undocumented coefficients. Omitting this component is preferable to introducing unverifiable estimates, and the absence should be noted in the indicator metadata.
Marine litter leakage rates — estimate the fraction of mismanaged waste reaching marine waters using methodologies such as Jambeck et al. (2015), which incorporates coastal population, waste management infrastructure, and proximity to shore.
With marine-attributed flows identified, compute indicator values:
Absolute indicators:
Intensity indicators:
The ocean economy GVA denominator is compiled as described in TG-3.3 Economic Activity Relevant to the Ocean, ensuring consistency between the numerator (pollution) and denominator (economic activity driving pollution).
Spatial indicators:
Temporal indicators:
Pollution indicators inherit uncertainty from multiple sources: measurement error in residual flow accounts, uncertainty in spatial attribution (delivery ratios, atmospheric deposition fractions), and sampling variability in monitoring data. Indicators compiled via spatial attribution carry multiplicative uncertainty that compounds across the delivery ratio, deposition fraction, and leakage rate assumptions. Compilers should:
The SEEA CF principle of recording flows at the point of generation (rather than point of ultimate environmental impact) means that accounts-based indicators measure pressure rather than state. Compilers should clearly communicate that nutrient loading indicators, for example, represent inputs to marine waters, not resulting water quality. The link between loading (pressure) and concentration (state) depends on hydrodynamic dilution, biological uptake, and other factors addressed in ecosystem condition accounts.
Nutrient pollution (nitrogen and phosphorus compounds) contributes to coastal eutrophication and is addressed by SDG Target 14.1, with indicator 14.1.1 including a coastal eutrophication index, .
Recommended nutrient indicators:
The OECD/Eurostat Gross Nitrogen Balances and Gross Phosphorus Balances methodologies provide standardised approaches for calculating agricultural nutrient balances that can be applied to coastal catchments. The SEEA Agriculture, Forestry and Fisheries (SEEA AFF) guidance extends these methodologies within an accounting framework.
Compilation of nutrient indicators should:
The relationship between nutrient loading indicators (pressure) and marine ecosystem condition indicators such as dissolved oxygen levels, chlorophyll-a concentrations, and habitat quality scores is addressed in TG-2.1 Aggregate Biophysical Indicators. Understanding this pressure-state linkage is central to interpreting nutrient indicators in a policy context.
Recommended chemical pollution indicators, following the FDES basic set for releases of chemical substances:
For indicators of oil and petroleum product discharges to marine waters, see the Hydrocarbon pollution indicators sub-section below.
The measurement of chemical pollutants presents challenges due to the large number of substances, varying analytical methods, and difficulty in estimating diffuse sources. The European Pollutant Release and Transfer Register (E-PRTR) and similar national registries provide models for point source reporting. For ocean accounting, priority should be given to chemicals:
Data-scarce context — countries without a Pollutant Release and Transfer Register (PRTR): Many national statistical offices, particularly in developing countries and small island states, have no PRTR or equivalent national registry. In these contexts, a minimum compilation approach comprises: (1) use UNEP GEMS/Water global water quality monitoring data as a proxy for point-source chemical concentrations where available; (2) estimate emissions using sectoral activity data (mining output volumes, industrial production indices) combined with substance-specific emission factors from IPCC/EMEP emission factor compilations; (3) flag all estimates compiled without PRTR data using the appropriate TG-0.7 quality codes to communicate data source limitations. The UNEP Guidance on Developing National Pollutant Release and Transfer Registers (2006) sets out a capacity-building pathway toward establishing national systems. Even partial indicators compiled under this approach contribute to international comparability and SDG reporting coverage, and data scarcity alone is not grounds for omitting them.
Recommended hydrocarbon indicators:
The ratio of accidental spills to total oil transport provides an indicator of maritime safety performance, whilst the trend in operational discharges indicates progress in compliance with MARPOL regulations.
For offshore petroleum activities, additional guidance on accounting for operational discharges is provided in TG-3.10 Offshore Energy. The broader context of marine litter (including oil-contaminated debris) is addressed in TG-6.12 Marine Litter and Plastics Accounting.
SDG Target 14.1 addresses marine debris, with indicator 14.1.1 including floating plastic debris density. The Intergovernmental Negotiating Committee (INC) process under UNEA Resolution 5/14 has been working toward a global plastics treaty. Compilers should monitor the outcomes of INC sessions for potential new mandatory reporting requirements on plastic waste that may affect indicator specifications in future revisions of this Circular.
Recommended plastic pollution indicators:
The Taskforce on Nature-related Financial Disclosures (TNFD) framework identifies plastic footprint as a specific disclosure metric, defined as total weight of plastics used or sold, disaggregated by reusable, compostable, and technically recyclable categories.
For practical compilation, the approach developed by Jambeck et al. (2015) provides a methodology for estimating plastic leakage from waste generation, mismanagement rates, and proximity to coastlines. This methodology can be adapted to national contexts using locally-sourced waste statistics. Uncertainty in Jambeck-derived estimates: The Jambeck methodology carries substantial uncertainty — published estimates span approximately one order of magnitude across scenarios, reflecting uncertainty in waste generation rates, mismanagement rates, and coastal proximity assumptions. Compilers must accompany any plastic leakage indicator derived from this methodology with a stated confidence range reflecting the low and high scenarios. Presenting a single central estimate without bounds is not appropriate for official statistics. Assign TG-0.7 quality flags for modelled estimates to communicate the estimation basis. Where beach survey data, at-sea debris observations, or national waste audit data are available, these should be used to validate or constrain the modelled estimate. More recent global waste model updates (Borrelle et al. 2020; Lau et al. 2020) may provide updated coefficient ranges for sensitivity testing.
Microplastics boundary — accounting classification: The boundary between microplastics as a water emission and as a solid waste entry requires explicit treatment to prevent double-counting across TG-2.7 and TG-3.4 Flows from Economy to Environment.
This Circular adopts the following classification. Primary microplastics (industrial pellets, microbeads, and other microplastic particles released directly to water from industrial or consumer processes) are classified as water emissions and recorded as a flow entry in the residual flow accounts. Secondary microplastics (particles that fragment from macroplastic solid waste already present in the marine environment) represent stock changes within the marine litter account rather than new economy-to-environment flows, and should not be recorded as a new emission flow. Water column microplastic concentration is an environmental monitoring variable, a state indicator rather than an accounting flow, and should not be entered as a residual flow in the PSUT. Compilers implementing both TG-2.7 and TG-3.4 should apply this classification consistently.
For the full treatment of marine litter stock-flow accounts, including the marine litter asset account within which secondary microplastic stock changes are recorded, see TG-6.12 Marine Litter and Plastics Accounting.
Beyond plastics, marine litter includes fishing gear, packaging, and other materials.
Recommended debris indicators:
ALDFG compilation method: Abandoned, lost or discarded fishing gear (ALDFG) is rarely collected systematically in national fisheries statistics. Compilers should apply the following tiered approach: (1) as the primary data source, use gear loss rate surveys conducted following the FAO Voluntary Guidelines on the Marking of Fishing Gear (2019) and associated FAO Technical Guidelines for Responsible Fisheries on ALDFG; (2) as a secondary method where surveys are unavailable, apply gear-specific loss rate coefficients to fleet activity data (vessel-days by gear type) — loss rate coefficients by gear type are available from the Global Ghost Gear Initiative data framework; (3) document minimum metadata requirements distinguishing survey-based from modelled estimates, including the survey coverage (percentage of fleet observed), gear types covered, and the coefficient source. Estimates derived from loss rate coefficients rather than direct surveys should be flagged with TG-0.7 quality codes indicating the modelled basis.
The SF-MST (Statistical Framework for Measuring the Sustainability of Tourism) provides guidance on tourism solid waste accounting relevant to coastal tourism waste generation.
Key substances include nitrogen compounds (contributing to marine eutrophication), sulphur compounds (affecting ocean chemistry), carbon dioxide (driving ocean acidification), and mercury (entering marine food webs via atmospheric deposition).
This pathway is addressed in TG-3.4 Flows from Economy to Environment, Section 3.1, which notes that “the accounting challenge is to link atmospheric emissions to their marine deposition, which requires integration with atmospheric modelling or use of deposition coefficients.” This Circular addresses the indicator derivation aspect of this challenge.
The SEEA Technical Note on Air Emissions Accounting provides guidance on air emissions accounts that form the basis for deposition estimates.
Recommended atmospheric deposition indicators:
The estimation of actual deposition requires atmospheric transport and deposition modelling, which may be beyond the capacity of many national statistical systems. A pragmatic approach is to report emissions from relevant sectors (agriculture, transport, energy) that contribute to deposition, whilst noting that the relationship between emissions and marine deposition depends on atmospheric conditions and distance to coast. Where deposition modelling capacity is unavailable, compilers should consult HELCOM Pollution Load Compilation or OSPAR deposition budget outputs as documented regional sources before concluding that atmospheric deposition cannot be estimated.
Ocean acidification is addressed by SDG Target 14.3, with indicator 14.3.1 tracking average marine acidity measured at representative sampling stations. Indicators linking economic activity to acidification drivers are relevant for ocean accounting.
Recommended acidification-related indicators:
The relationship between national emissions and ocean acidification is mediated by global atmospheric mixing, meaning that national emissions contribute to global rather than specifically national marine acidification. The full treatment of climate-ocean indicators is provided in TG-2.8 Climate Change Indicators, which addresses ocean acidification indicators in detail in Section 3.3.
Mercury enters marine food webs through atmospheric deposition and bioaccumulates in fish, posing human health risks. The Minamata Convention on Mercury establishes international reporting requirements.
Recommended mercury indicators:
Intensity and efficiency indicators relate pollution flows to measures of economic activity, enabling assessment of decoupling, . They link the economic activity data compiled under TG-3.3 Economic Activity Relevant to the Ocean to the residual flow data compiled under TG-3.4 Flows from Economy to Environment.
Recommended intensity indicators:
Intensity indicators should be calculated separately for key ocean-related industries as identified in TG-3.3 Economic Activity Relevant to the Ocean:
Decoupling indicators assess whether environmental pressure is growing slower than (relative decoupling) or declining absolutely whilst the economy grows (absolute decoupling).
Recommended decoupling indicators:
The interpretation of decoupling requires time series data. Single-period ratios provide intensity measures, but decoupling assessment requires comparison of percentage changes over multiple periods.
Additional guidance on resource efficiency indicators is provided in TG-2.11 Resource Efficiency.
Following the SEEA Central Framework approach, a combined presentation for marine pollution indicators would include:
The indicator categories derived from this combined presentation follow the five-category typology defined in Section 3.1. The structure aligns with that recommended in TG-3.4 Flows from Economy to Environment, Section 3.4, ensuring consistency between accounting and indicator frameworks.
Coastal Zone Alpha is a 50 km stretch of coastline with intensive aquaculture (5 farms producing 8,000 tonnes/year of finfish), one urban wastewater treatment plant serving a population of 120,000, and agricultural catchments draining 15,000 hectares of cropland to coastal waters. The zone experiences periodic algal blooms, and planners require a nutrient loading indicator to support marine spatial planning decisions.
From the national physical supply-use table for water emissions (compiled per TG-3.4), extract nitrogen discharge for Zone Alpha:
Not all generated nitrogen reaches marine waters. Apply delivery ratios:
The agricultural delivery ratio of 0.18 is applied as a Tier 1 estimate based on OECD guidance for mixed cropland catchments with moderate riparian buffers. A sensitivity analysis under Tier 1 uncertainty bounds gives delivery ratios ranging 0.12—0.25 depending on rainfall intensity and vegetative cover, and the resulting total marine load range is approximately 302,000—331,000 kg N/yr. This uncertainty range should be reported alongside the central estimate.
Absolute loading indicator:
Spatial intensity indicator:
Loading per unit coastal zone area:
Source attribution:
The OSPAR eutrophication strategy suggests coastal zones with loading exceeding 1.0 tonne N/km²/yr may be at elevated eutrophication risk. Zone Alpha exceeds this threshold, indicating policy intervention may be warranted (the OSPAR value is a regional threshold: compare against the ecological threshold that applies locally, as the nutrient loading intensity row in Section 3.3 requires).
From ocean economy accounts (TG-3.3), Zone Alpha aquaculture GVA is 12.5 million currency units per year:
This intensity can be compared across zones or tracked over time to assess whether nutrient loading is decoupling from aquaculture production.
The indicator compilation reveals that whilst aquaculture contributes the majority (58%) of nitrogen reaching coastal waters, agricultural sources represent 45% of gross generation but only 13% of marine load due to retention in the catchment-to-coast pathway. Policy interventions focused solely on aquaculture may achieve 58% reduction potential, whilst interventions targeting agricultural practices have lower marine impact due to natural attenuation. The indicator supports prioritisation of aquaculture best management practices (reduced feed conversion ratios, improved waste collection) and WWTP upgrades, whilst agricultural interventions may be warranted for broader environmental benefits beyond marine loading.
This circular uses an extended six-section schema (Sections 1-3 standard, Section 4 Data Sources and Compilation, Section 5 Implementation Considerations, Section 6 Acknowledgements, Section 7 References). The extension accommodates the multi-source compilation procedure and tiered implementation guidance required for pollution indicators. Cross-references from other circulars to “Acknowledgements” or “References” in TG-2.7 should target Sections 6 and 7 respectively. All other circulars follow the canonical four-section schema (Sections 1-3 substantive, Section 4 Acknowledgements, Section 5 References) defined in the GOAP Circular Style Guide.
Compilation of pollution indicators draws on the residual flow accounts established under TG-3.4 Flows from Economy to Environment, supplemented by additional data sources for indicator derivation. TG-4.2 Statistical Sources and Data Gaps provides a full inventory of monitoring data sources and quality assessment procedures for pollution indicators, including national accounts denominators, spatial data, and international reporting framework alignment.
Given resource constraints, compilers should prioritise indicators based on:
To translate these criteria into an actionable indicator shortlist, the following three-tier implementation framework maps all indicators in this Circular to implementation capacity levels. Tier 1 is the minimum set recommended for all countries. Tier 2 is an intermediate set for countries with established environmental monitoring infrastructure, and Tier 3 is the full set for countries with full PSUT and modelling capacity. All Tier 1 indicators align with SDG 14.1.1 components or the FDES 2013 Core Set of Environment Statistics.
Table 5.1: Tiered implementation framework for TG-2.7 pollution indicators
Countries at first implementation are recommended to compile all Tier 1 indicators before expanding to Tier 2 and Tier 3. Countries with partial monitoring infrastructure may selectively advance specific Tier 2 indicators where data are available without completing all Tier 1 indicators first, provided they document coverage gaps.
The combined presentation table in Section 3.6 provides a template that can be adapted for dashboard and report card formats. Guidance on integrating pollution indicators with other ocean accounting outputs for combined presentation and communication is provided in TG-3.8 Combined Presentations.
Authors: Gerald Singh, Kirsten Oleson
Reviewers: [To be confirmed]
Cite this report
Pollution and Other Flows to Environment (2026) (GOAP Technical Guidance on Ocean Accounting, TG-2.7, v0.7.2). GOAP Secretariat. https://guidance.oceanaccounts.org/circulars/section-2/2-7-pollution-flows/
guidance.oceanaccounts.org/circulars/section-2/2-7-pollution-flows
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