Eutrophication

Eutrophication in marine, coastal and estuarine ecosystems is a consequence of nutrient over-enrichment, mostly inputs of nitrogen, phosphorus and organic matter from land-based sources (agriculture, urbanisation), marine activities (aquaculture) and from atmospheric deposition (e.g. from road transport and shipping emissions to the air). Eutrophication has been a problem in Europe’s coastal and marine waters for decades.

Eutrophication leads to increased plant or algae growth, changes in the balance of organisms and water quality degradation. This can lead to shifts in species composition and species displacement (Figure 1). As vegetal material decays, increased oxygen consumption in bottom waters is promoted, potentially leading to a reduction of oxygen in water (hypoxia). Hypoxia results in the deterioration of the impacted ecosystems and the loss of marine life. The environmental problems created by eutrophication lead to the loss of aquatic biodiversity and a reduction of ecosystem services related to fisheries, aquaculture, and recreation. Toxins released from potential harmful algal blooms have socio-economic impacts causing shellfish poisoning in humans.

Europe's four marine regions have different sensitivities to nutrient enrichment and eutrophication due to difference in natural characteristics, such as the depth of the ocean, the internal mixing properties of the water, and fresh water inputs to the marine region. Seawater warming due to climate change would make it more difficult to naturally process nutrient inputs.

In relation to 'Eutrophication', the Marine Strategy Framework Directive considers that 'good environmental status' is achieved when 'Human-induced eutrophication is minimised, especially adverse effects thereof, such as losses in biodiversity, ecosystem degradation, harmful algae blooms and oxygen deficiency in bottom waters'.

General outcomes from the regional assessments

The eutrophication in the North-East Atlantic has decreased continuously since 1990, but it still remains a problem in areas sensitive to nutrient inputs. There is a high eutrophication pressure along the south eastern coast of the Greater North Sea and some localised areas of the Celtic Seas. Concerns about atmospheric and riverine inputs of nutrients identified in OSPAR’s Quality Status Report 2010 still remain.

At least 97 percent of the Baltic Sea region was assessed as eutrophic in 2011–2016. 12% is assessed as being in the worst status category. Nutrient inputs from land based sources are decreasing, but the effect of measures has not yet been detected by the integrated status assessment.

Black Sea is exposed to many threats that need to be addressed urgently. There is a large number of riverine discharges into the Black Sea, the largest of them being Danube, Dniepr and Dniestr, that discharge into the north-western coastal waters. The eutrophication in the basin is caused by sources such as agriculture, municipal waste and industry. Between 1955 and 2015, the oxygenated layer depth decreased from 140 m in 1955 to 90 m in 2015 as a consequence of the eutrophication process that affects the Black sea north-western shelf.

On the other hand, the offshore waters of the Mediterranean are extremely oligotrophic, with an increasing tendency for oligotrophy eastwards. The main coastal areas in the Mediterranean which are historically known to be influenced by natural and/or anthropogenic inputs of nutrients are the Alboran Sea, the Gulf of Lions, the Gulf of Gabès, the Adriatic, Northern Aegean and the SE Mediterranean (Nile–Levantine).

Outcomes from the MSFD assessments

In 2018, Member States had to update the Good Environmental Status (GES) assessments performed under Marine Strategy Framework Directive Article 8. The present dashboard displays the overall status reported by countries for the features, where the results show which is the percentage of assessments where GES has been achieved, not achieved or is unknown or not assessed.