Eutrophication related monitoring tasks and WFD for coastal waters in Greece

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Eutrophication is addressed in several EU policies. Nutrient levels were introduced in several early pieces of EU water legislation (e.g. Freshwater Fish Directive 78/659/EEC) in order to describe the water quality. The main anthropogenic sources of nutrient loadings were addressed in two directives in 1991. The Urban Wastewater Treatment Directive (91/271/EEC) addresses the major point sources, in particular the municipal waste water discharges. The Nitrates Directive (91/676/EEC) deals with the diffuse pollution of nitrogen from agriculture. Both directives define the term “eutrophication”. In addition, the designation of sensitive areas or vulnerable zones (which suffer from eutrophication or may suffer from it if measures are not taken) in the UWWT and Nitrates Directives provide for measures to combat eutrophication. Furthermore, eutrophication is indirectly addressed in the Dangerous Substance Directive (76/464/EEC) that lists inorganic phosphorus and substances, which have an adverse effect on the oxygen balance, particularly ammonia and nitrites.

Water Framework Directive (WFD)

More recently, the Water Framework Directive (WFD, 2000/60/EC) establishes an integrated and co-ordinated framework for the sustainable management of water, including prevention of deterioration of water bodies (lakes, rivers, coastal and transitional, groundwater), promotion of sustainable water use, and ensuring “enhanced protection and improvement of the aquatic environment”. This last point requires that rivers, lakes, estuaries, coastal waters and groundwater achieve and/or maintain at least ‘good status’ by 2015. For surface waters this requires both Ecological Status and Chemical Status to be at least ‘good’. Good status will be achieved by implementing a programme of measures as reported in River Basin Management Plans (Articles 11 and 13 in WFD), and based on the results of river basin characterisation. The WFD stipulates detailed procedures for its implementation including the classification and monitoring of water bodies. The WFD requires Member States to classify the ecological status of surface water bodies into one of five ecological status classes: high (= nearly undisturbed conditions), good (=slight change in composition, biomass), moderate (=moderate change in composition, biomass), poor (= major change in biological communities) or bad (= severe change in biological communities) ecological status. The ecological status of a water body is an expression of the quality of the structure and functioning of its aquatic ecosystem. The Directive provides normative definitions (see Annex V of the WFD) for each ecological status class and for each surface water category. Ecological status is derived from Ecological Quality Ratios (EQRs), which reflect the deviation of observed values from type-specific reference conditions. The boundary between good and moderate ecological status is crucial because it determines when restoration measures need to be taken.

Biological quality elements (BQE)

The values for the biological quality elements (BQEs)set by Member States for the ‘high’ – ‘good’ class boundary and the ‘good’ – ‘moderate’ class boundary are being compared as part of the intercalibration exercise (GIGs), in which the member states participate. European Mediterranean Member States participate in the MEDGIG exercise. The BQEs set for coastal and transitional water bodies are: a) the composition, abundance and biomass of phytoplankton, b) composition and abundance of other aquatic flora, c) composition and abundance of benthic invertebrate fauna, and d) composition and abundance of fish fauna, this last one only for transitional waters. The WFD classification of water bodies in relation to type-specific reference conditions enforces the view of eutrophication as a process, where nutrient enrichment through human activities causes adverse changes in the aquatic environment, rather than as a particular level of productivity or trophic state. The definition of good ecological status for the BQEs ‘Phytoplankton’ and ‘Macrophytes and Phytobenthos’ uses very similar wording as the definition of eutrophication used in the UWWT and Nitrates Directives and by OSPAR. Good status includes an absence of eutrophication problems.

Management measures to control nutrient enrichment

Since nutrient enrichment may affect ecological status of water bodies require management measures to control nutrient enrichment in order to achieve the objectives of the Directive. The sensitivity of water bodies to nutrient enrichment may vary depending on their physical characteristics and on the extent of other anthropogenic alterations to them. Nutrients, as part of the physicochemical quality element, must be at a level to ensure the functioning of the ecosystem and the values specified for biological quality elements. For the purposes of monitoring water bodies at risk because of nutrient enrichment, Member States must monitor parameters indicative of the BQE or BQEs, most sensitive to the effects of nutrient enrichment as well as the nutrients that are being discharged into the water body in significant quantities (Table 1).

Table 1: General overview of WFD requirements regarding eutrophication (Source: EC, 2005 [1]) Directive /Policy Requirement to assess eutrophication Minimum monitoring requirements relevant to eutrophication WFD Implicit in classification of Ecological Status where nutrient enrichment affects biological and physico-chemical quality elements. Protected Area’s support and upholds requirements of UWWTD and Nitrates Directive. Phytoplankton (once per 6 months), aquatic flora (once per 3 yrs), macro-invertebrates (once per 3 yrs), fish (once per 3 yrs). Hydromorphological quality elements (Hydrology continuous – once per 1 month; others once per 6 years). Physicochemical quality elements (once per 3 months).

Assessing the Ecological Status

Many of the quality elements that are used for assessing Ecological Status under the WFD, are traditionally used for assessing eutrophication, in particular ‘nutrient conditions’ as well as the ‘composition, abundance and biomass of phytoplankton and macrophytes’. Corresponding values for nutrients necessary to support the achievement of good ecological status was suggested to be estimated from response curves based on knowledge of the relationships between nutrient concentrations and the BQEs (the dose-response relationship, if applicable to all types of water bodies). High nutrient concentrations without any corresponding biological impacts may not necessarily result in down grading Ecological Status. Thus assessments of eutrophication consistent with the WFD should primarily focus on the biological effects resulting from elevated nutrient levels, taking also into account possible effect of transboundary transport of nutrients. Measures to reduce nutrient loading may still be needed.

The situation in Greece

Greece, in order to implement the requirements of the directives relevant to eutrophication introduced prior to WFD, adopted and applied the eutrophication assessment criteria described hereafter (as for most affected gulfs as are Saronikos and Thermaikos), in order to define eutrophication status, assign critical values and, consequently, evaluate water quality. A eutrophication scale was developed by IGNATIADES et al., (1992)[2] and KARYDIS (1999)[3], based on nutrient data from several Greek marine areas, coastal and offshore waters influenced or not, by industrial and/or domestic effluents. For this scale, concentration ranges from nutrient and phytoplankton data sets, specific for this region of the Eastern Mediterranean and characteristic of the different trophic levels in the Greek Seas were defined. Later the original eutrophication scale was modified in order to include phytoplankton parameters also (SIOKOU & PAGOU, 2000[4]; PAGOU, 2000[5]), which underwent the same statistical treatment. The derived eutrophication scale is given in Table 2.

Table 2: Trophic classification ranges based on nutrients (phosphates, nitrates, ammonium), chlorophyll α and total number of phytoplankton cells. Ranges are given for the oligotrophic, lower mesotrophic, higher mesotrophic and eutrophic system. Nutrients concentrations are given in μM, phytoplankton cells number in cells l-1 and chlorophyll in μg l-1.

Parameter Oligotrophic Lower mesotrophic Higher mesotrophic Eutrophic
Phosphates (ΡΟ4) <0.07 0.07-0.14 0.14-0.68 >0.68
Nitrates (ΝΟ3) <0.62 0.62-0.65 0.65-1.19 >1.19
Ammonium (ΝΗ4) <0.55 0.55-1.05 1.05-2.2 >2.2
Phytoplankton <6x103 6x103-1.5x105 1.5x105-9.6x105 >9.6x105
Chlorophyll α <0.1 0.1-0.6 0.6-2.21 >2.21

Four levels of eutrophication are defined in this scale: eutrophic, higher mesotrophic, lower mesotrophic and oligotrophic, though 5 classes are required for WFD. However, under the Common Implementation Strategy (CIS) of the WFD and the European Marine Strategy, an activity was initiated in order to provide guidance on the harmonisation of assessment methodologies and of criteria for agreed eutrophication elements/parameters/indicators and their suitable boundary values for each of them and the coordination of monitoring and reporting of eutrophication across different European and national policies (WFD Working Group: the WG 2.A ‘‘Eutrophication Activity’’ Greece will have to follow the guidance that results from these activities in assessing water quality and especially eutrophication and thus define five levels of eutrophication to harmonize with the five ecological status classes (see: EC, 2005[1]). Such a first effort (Table 3) was proposed in PAGOU et al. (2002)[6] and SIMBOURA et al. (2005)[7].

Table 3: Harmonization of eutrophication scale (according to KARYDIS, 1999[3] and PAGOU et al., 2002[6]) and ecological status in WFD, according to SIMBOURA et al. (2005)[7].

Eutrophication Scale Chlorophyll-α(μg l-1) Ecological Status (WFD)
Oligotrophic <0.1 High
Lower Mesotrophic-1 0.1-0.4 Good
Lower Mesotrophic -2 0.4-0.6 Moderate
Upper mesotrophic 0.6-2.21 Poor
Eutrophic >2.21 Bad

The Mediterranean subgroup MEDGIG

In the frame of WFD inter-calibration exercise already mentioned, and especially in the Mediterranean subgroup (MEDGIG) phytoplankton experts defined that for the chlorophyll as BQE (Biological Quality Element, related to phytoplankton and eutrophication), within the Mediterranean basin a new typology of coastal types has been developed, mainly focused on hydrological parameters characterizing water bodies’ dynamics and circulation. The typological approach was based on the introduction of the static stability parameter (derived from temperature and salinity values in the water column) having a robust numerical basis which can describe the dynamic behaviour of a coastal system: the surface density. (MEDGIG report, June 2007). According to the MEDGIG report (June 2007) it is stated that on the basis of surface density values (σt), three major water types have been defined, which in an ecological perspective, can be described as follows:

  • Type 1: coastal sites highly influenced by freshwater inputs (σt<25, annual mean salinity <34.5)
  • Type 2: coastal sites not directly affected by freshwater inputs (25<σt<27, annual mean salinity 34.5<S<37.5)
  • Type 3: coastal sites not affected by freshwater inputs (σt>27, annual mean salinity >37.5)

A further distinction has been suggested and approved by the Mediterranean MSs, regarding the splitting of the coastal water type 3 in two different sub basins, the Western and the Eastern Mediterranean one, according to the different trophic conditions. The Levantine Basin of eastern Mediterranean is characterized as nutrient-deficient and therefore ultra-oligotrophic in comparison to other oceans (BERMAN et al., 1984[8]; KROM et al., 1992[9]). The coastal waters of Cyprus and most of Greece are classified as Type III (no freshwater input – density greater of 27), due to their hydrographical features and the prevailed physicochemical characteristics. Among MSs, only Greece and Cyprus belong to the Eastern Mediterranean basin (Type III E) and ιntercalibration was performed between these 2 countries for this water type.


The following results of the intercalibration exercise apply to the countries sharing the Type IIIE. Parameter values are expressed in μg/l of Chlorophyll-α, as the 90%ile value, calculated over the year in at least five year period (the raw data consisted from, at least, monthly sampling frequency, in the surface layer; MEDGIG Technical Report, June 2007). Since there was not elaborated a common methodology based on a common data set for the whole Mediterranean, boundaries (on chlorophyll-α concentrations and EQRs) were compared, with those derived from national methods and specifically for Type IIIE the national method was the one described previously (eutrophication scale according to IGNATIADES et al., 1992[2] and KARYDIS, 1999[3]).

Type Ecological Quality Ratios Values (μg/l, 90%ile) High-Good boundary Good-Moderate boundary High-Good boundary Good-Moderate boundary Type IIIE 0.80 0.20 0.1 0.4

It must be noted that common statistical analysis on chlorophyll-α, nutrients and physico-chemical data and some multivariate techniques have been performed in order to facilitate a wide agreement for the intercalibration process and fulfill the requirement of application of dose-response relationship. This approach was not successful, thus the above reported “hybrid” option according to the Intercalibration Guidance was followed. However, further intercalibration activity is needed to improve the dose/response analysis correlating nutrients with trophic conditions.

Monitoring Networks Strategy

For the WFD, monitoring networks have to be designed “so as to provide a coherent and comprehensive overview of ecological and chemical status within each river basin and shall permit classification of water bodies into the five classes consistent with the normative definitions…” (EC, 2005[1]) using the above cited boundaries and EQRs. Member States were expected to finish the process of designing their monitoring networks for the Water Framework Directive and be operational by 22 December 2006. The best practice could be, where possible, to have integrated monitoring programmes that provide the data and information which will meet the needs of all the relevant policies, in this case, all those that deal with eutrophication. For example for Greece, where possible, the same monitoring stations, quality elements and sampling frequencies would be used for WFD (and/or other EU directives) and MED POL. It should also be noted that the European Marine Monitoring and Assessment (EMMA) group formed under the European Commission’s “Thematic Strategy for the Protection and Conservation of the European Marine Environment” is also considering ways of harmonising monitoring and assessments of marine waters including those for eutrophication.

Types of monitoring programmes

The WFD defines different types of monitoring programmes of surface waters (operational or may be investigative monitoring programmes and surveillance programmes). Operational monitoring for the WFD will be carried out for all those water bodies identified as being at risk of failing their environmental objectives (for example, achievement of good ecological status or good ecological potential, or no deterioration of status). Surveillance monitoring for the Water Framework Directive must be carried out of sufficient surface water bodies to provide an assessment of the overall surface water status within each catchment or subcatchments within the river basin district. This implies that water bodies across a range of statuses will be included and in particular those identified as not being at risk of failing their environmental objectives (good and high status water bodies, no risk of deterioration of status). The WFD furthermore focuses on managing whole river basins on a European scale, thus a downstream water body failing the WFD objective of good status e.g. being eutrophic, may require measures to be taken, in the entire upstream catchment or even in other river basins including coastal water bodies or exporting coastal water bodies, even if upstream water bodies meet the objectives (transboundary transport of nutrients).

Spatial coverage

Regarding spatial coverage, the WFD covers all waters, including inland waters and transitional and coastal waters up to one sea mile (in terms of monitoring ecological status and hence eutrophication - and for the chemical status also territorial waters which may extend up to 12 sea miles) from the territorial baseline of a Member State, independent of the size and the characteristics. These water bodies will need to be included in surveillance, operational or investigative monitoring programmes, whereas guidance is given for the selection of monitoring points for inclusion in surveillance and operational monitoring for the WFD. As an example, for operational monitoring selection of monitoring points in each water body must be sufficient in order to assess the magnitude and impact of the point source pressure or the diffuse source or the hydromorphological pressures. Annex V, (Table 1.1 of the annex) in the WFD, explicitly defines the quality elements that must be used for the assessment of ecological status (e.g. composition, abundance and biomass of phytoplankton). Quality elements include all BQEs elements and elements supporting the biological elements. These supporting elements are in two categories: ‘hydromorphological’ and ‘general chemical and physicochemical’. Also priority list pollutants and other pollutants must be monitored (Table 4).


Annex V of the WFD also provides tabulated guidelines in terms of the minimum monitoring frequencies for all the quality elements. The suggested minimum frequencies are applicable to both surveillance and operational monitoring and are generally lower than currently applied in some countries (Table 1 of this document). More frequent monitoring will most likely be necessary in many cases to achieve a reliable assessment of the status of the relevant quality element, but also less frequent monitoring is justified when based on technical knowledge and expert judgment. Member States are also able to target their monitoring to particular times of year to take into account variability due to seasonal factors. The CIS Monitoring Guidance recommends measurement frequencies for each parameter used in the assessments of Ecological Status. These frequencies are higher than the minimum frequencies specified in Annex V of the WFD, for many of the parameters relevant to eutrophication, such as phytoplankton and nutrient parameters (monthly or bi-weekly during growth season in the guidance as opposed to once every 3-6 months in Annex V).


From all the above, is obvious that, as it is stated in the Guidance Document on Eutrophication Assessment (EC 2005[1]), all the necessary tools, guidance and mechanisms are available or in development in the frame of European policies, in order to develop and decide upon the measures aiming at elimination of eutrophication in water bodies/ catchments/ marine areas. The challenge for Greece specifically will be to (be able to) apply these tools etc. in practice.

Table 4: Checklist for a holistic assessment in coastal/transitional waters according to EC (2005)[1]. The qualitative assessment parameters are:

a. The causative factors: The degree of nutrient enrichment: With regard to inorganic/organic nitrogen With regard to inorganic/organic phosphorus With regard to silicon Taking account of: Sources (differentiating between anthropogenic and natural sources) Increased/upward trends in concentration Elevated concentrations Changes in N/P, N/Si, P/Si ratios Fluxes and nutrient cycles (including across boundary fluxes, recycling within environmental compartments and riverine, direct and atmospheric inputs)

b. The supporting environmental factors: Light availability (irradiance, turbidity, suspended load) Hydrodynamic conditions (stratification, flushing, retention time, upwelling, salinity gradients, deposition) Climatic/weather conditions Zooplankton grazing (which may be influenced by other anthropogenic activities) Coastal morphology Typology factors for coastal waters

c. The direct effects of nutrient enrichment: i. Phytoplankton; Increased biomass (e.g. chlorophyll a, organic carbon and cell numbers) Increased frequency and duration of blooms Increased annual primary production Shifts in species composition (e.g. from diatoms to flagellates, some of which are nuisance or toxic species) ii. Macrophytes including macroalgae; Increased biomass Shifts in species composition (from long-lived species to short-lived species, some of which are nuisance species) Reduced depth distribution iii. Microphytobenthos; Increased biomass and primary production

d. The indirect effects of nutrient enrichment i. organic carbon/organic matter; Increased dissolved/particulate organic carbon concentrations Occurrence of foam and/or slime Increased concentration of organic carbon in sediments (due to increased sedimentation rate) ii. oxygen; Decreased concentrations and saturation percentage Increased frequency of low oxygen concentrations Increased consumption rate Occurrence of anoxic zones at the sediment surface (“black spots”) iii. zoobenthos and fish; Mortalities resulting from low oxygen concentrations iv. benthic community structure; Changes in abundance Changes in species composition Changes in biomass v. Ecosystem structure; Structural changes e. Other possible effects of nutrient enrichment i) Algal toxins (still under investigation - the recent increase in toxic events may be linked to eutrophication)


  1. 1.0 1.1 1.2 1.3 1.4 EC, 2005. Towards a guidance document on eutrophication assessment in the context of European water policies. Interim report in the frame of the “Common implementation strategy for the Water Framework Directive, 133pp.
  2. 2.0 2.1 IGNATIADES, L., VOUNATSOU, P. & KARYDIS, M., 1992. A possible method for evaluating oligotrophy and eutrophication based on nutrient concentration scales. Mar. Poll. Bull., 24: 238-243.
  3. 3.0 3.1 3.2 KARYDIS, Μ. (1999). Evaluation report on the eutrophication level in coastal greek areas. Univ. of Aegean, Mytilini, February 1999 (in greek).
  4. SIOKOU-FRANGOU, I. & PAGOU, K. (2000). Assessment of the trophic conditions and ecological status in the Inner Saronikos Gulf. Technical Report for the Ministry of Environment, Planning and Public Works, NCMR, Athens, March 2000,43pp. (in greek and english edition).
  5. PAGOU, K. (2000). Assessment of the trophic conditions in the Inner Thermaikos Gulf. Technical Report for the Ministry of Environment, Planning and Public Works, NCMR, Athens, December 2000, 11pp.
  6. 6.0 6.1 PAGOU K., SIOKOU-FRANGOU I. & PAPATHANASSIOU E. (2002). Nutrients and their ratios in relation to eutrophication and HAB occurrence. The case of Eastern Mediterranean coastal waters. Second Workshop on "Thresholds of Environmental Sustainability: The case of nutrients", 18-19 June 2002, Brussels, Belgium.
  7. 7.0 7.1 SIMBOURA N., PANAYOTIDIS P. & PAPATHANASSIOU E. (2005). A synthesis of the biological quality elements for the implementation of the European Water Framework Directive in the Mediterranean ecoregion: The case of Saronikos Gulf. Ecological Indicators, 5: 253–266.
  8. BERMAN, T., D.W. TOWNSEND, S.Z. EL-SAYED, G.C. TREES & Y. AZOV (1984). Optical transparency, chlorophyll and primary productivity in the Eastern Mediterranean near the Israeli Coast. Oceanol. Acta, 7: 367-372.
  9. KROM, M.D., S. BRENNER, N. KRESS, A. NEORI & L.I. GORDON (1992). Nutrient dynamics and new production in a warm-core eddy from the Eastern Mediterranean Sea. Deep-Sea Research, 39: 467-480.

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The main author of this article is Pagou, Popi
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Citation: Pagou, Popi (2019): Eutrophication related monitoring tasks and WFD for coastal waters in Greece. Available from [accessed on 25-05-2024]