Indicator Assessment

Nutrients in transitional, coastal and marine waters

Indicator Assessment
Prod-ID: IND-153-en
  Also known as: SEBI 015
Published 21 May 2010 Last modified 11 May 2021
6 min read
This page was archived on 09 Feb 2021 with reason: Other (Discontinued indicator)

In countries that reported data, 85 % of stations reported no changes in oxidised nitrogen levels in transitional, coastal and marine waters in the period 1985 - 2005 and 82 % reported no change for orthophosphate. At stations that identified changes, decreases were more common than increases.

Some 12 % of measuring stations reported a decreasing trend in oxidised nitrogen concentrations in 2005. Increasing trends were found at 3 % of stations whilst the majority of stations (85 %) indicate no statistically significant change.

Decreasing trends in orthophosphate concentrations were found at 11 % of stations, compared to increasing concentrations at 7 %. The majority of stations (82 %) reported no statistically significant change in orthophosphateconcentration.

Nitrogen (N) and phosphorus (P) enrichment can result in a chain of undesirable effects, starting with excessive growth of planktonic algae, which the seabed. This accumulation may be associated with changes in species composition and altered functioning of the pelagic food web, which may lead to lower grazing prospects for copepods. The consequent increase in oxygen consumption can cause oxygen depletion, changes in community structure and death of the benthic fauna.

For the EU, the Water Framework Directive will bring in better information on the ecological status of transitional and coastal waters, although not before 2010.


Supporting information

Indicator definition

The indicator illustrates trends in, and concentrations of, winter nitrate and phosphate (microgram/l), as well as Nitrogen/Phosphorous ratio in the seas of Europe.


Concentrations in micromol/l


Policy context and targets

Context description

Nitrogen (N) and phosphorus (P) enrichment can result in a chain of undesirable effects, starting from excessive growth of plankton algae that increases the amount of organic matter settling to the bottom. This may be enhanced by changes in species composition and functioning of the pelagic food web (e.g. growth of small flagellates rather than larger diatoms), which leads to lower grazing by copepods and increased sedimentation. The consequent increase in oxygen consumption can, in areas with stratified water masses, lead to oxygen depletion, changes in community structure and death of the benthic fauna. Eutrophication can also increase the risk of algal blooms, some of them consisting of harmful species that cause the death of benthic fauna, wild and caged fish, or shellfish poisoning of humans. Increased growth and dominance of fast-growing filamentous macroalgae in shallow sheltered areas is another effect of nutrient overload which can change the coastal ecosystem, increase the risk of local oxygen depletion and reduce biodiversity and nurseries for fish.

Measures to reduce the adverse effects of excess anthropogenic inputs of nutrients and protect the marine environment are being taken through various initiatives at all levels - global, European, national, regional conventions and Ministerial Conferences.

There are a number of EU Directives aimed at reducing the loads and impacts of nutrients, including the Nitrates Directive (91/676/EEC); the Urban Waste Water Treatment Directive (91/271/EEC); the Integrated Pollution Prevention and Control Directive (96/61/EEC); and the Water Framework Directive (2000/60/EC) which requires the achievement of good ecological status or good ecological potential of transitional and coastal waters across the EU by 2015.

The EU Thematic Strategy on the Protection and Conservation of the Marine Environment and its associated proposed Marine Strategy Directive are of key relevance with regards to the achievement of good environmental status in marine waters.

Additional measures arise from international initiatives and policies including: the UN Global Programme of Action for the Protection of the Marine environment against Land-Based Activities; the Mediterranean Action Plan (MAP) 1975; the Helsinki Convention 1992 (HELCOM); the OSPAR Convention 1998 (Convention for the Protection of the Marine Environment of the North-East Atlantic); and the Black Sea Environmental Programme (BSEP).

Relation of the indicator to the focal area

Undesirable effects caused by Nitrogen (N) and phosphorus (P) (have a direct impact on ecosystem integrity and functioning (e.g. changes in species composition, oxygen depletion, changes in community structure) and the delivery of ecosystem services (death of commercial fish species or shellfish poisoning).


No targets have been specified

Related policy documents

No related policy documents have been specified



Methodology for indicator calculation

Consistent time series are used as the basis for assessment of trends over time. The trend analyses are based on time series 1985-2004/2005 from stations having at least 3 years data in the period 1999-2004 and at least five years data in all. For nitrogen the combined concentrations of nitrate and nitrite are used, but gaps may be populated with nitrate alone to complete the time series.

Winter concentrations are used because in summer all inorganic nutrients are used for plankton growth.

The following steps are undertaken for the calculation. For a detailed description of methodology, reference is made to the EEA core set indicator 'Nutrients in transitional, coastal and marine waters' ( ISpecification20041007132008/full_spec).

1. Primary aggregation of sea water TCM data

The primary aggregation consists of identifying stations and assigning them to countries and sea regions and creating statistical estimates for each combination of station and year.

2. Geographical classification: sea region, coastal/offshore

All geographical positions defined in the data are assigned to sea region by coordinates, and classified as coastal or off-shore (> 20 km from coast) by checking them against the coastal contour.

3. Defining stations

Eionet-Water stations
TCM data reported directly from countries are assigned to station identifiers that are listed with coordinates. For these data, which are mostly along the coast of the reporting country, stations are kept as defined.

Marine convention data from ICES
The data reported through ICES has no consistent station identifiers (i.e. station names), only geographical coordinates (longitude and latitude).

Methodology for gap filling

No methodology for gap filling has been specified. Probably this info has been added together with indicator calculation.

Methodology references

No methodology references available.



Methodology uncertainty

No uncertainty has been specified

Data sets uncertainty

No uncertainty has been specified

Rationale uncertainty


  • Data for this assessment are still scarce considering the large spatial and temporal variations inherent to the European transitional, coastal and marine waters. Long stretches of European coastal waters are not covered in the analysis due to lack of data. Trend analyses are consistent only for the North Sea and the Baltic Sea (data updated yearly within the OSPAR and HELCOM conventions) and Italian coastal waters. The accuracy on regional level is largely influenced by the number of stations for which data are available.


The indicator is an EEA core set indicator. The information basis for the indicator and the assessments possible will improve in time as the WFD and Marine Strategy Directive assessments are implemented by Member States.

Data sources

Other info

DPSIR: Pressure
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • SEBI 015
Frequency of updates
Updates are scheduled every 2 years
EEA Contact Info


Geographic coverage

Temporal coverage


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