Eutrophication Thematic Assessment

The response to eutrophication

Starting as early as 1988, the OSPAR Contracting Parties agreed to reduce nutrient emissions to the Greater North Sea by 50%. Since then, several OSPAR Recommendations as well as other management actions have been taken to combat eutrophication. These include measures targeting diffuse run-off from land, atmospheric nitrogen emissions, wastewater, and other point sources.

These responses have led to significant improvements in nutrient loadings to the OSPAR Maritime Area since the start of monitoring in 1990. During the last decade, improvements have slowed down, however, and waterborne nutrient inputs to Region I (Arctic Waters), have shown a significant increase caused mainly by nutrient inputs from the growing marine aquaculture industry.

The commitment to further reduce nutrient inputs is reinforced in the new OSPAR Strategy for the Protection of the Marine Environment of the North-East Atlantic (NEAES) 2030. The Contracting Parties have committed to determining maximum nutrient inputs and agreeing nutrient reduction needs for each Contracting Party. Under the MSFD, Contracting Parties take measures directed towards atmospheric emissions and shipping, emissions from ports and harbours, aquaculture and habitat restoration. Within the EU, the Urban Wastewater Treatment Directive is under revision. So is the Gothenburg Protocol. These will make important contributions to combating eutrophication in the North-East Atlantic. However, despite the ongoing and future responses, there are still many activities that will continue to discharge anthropogenic nutrients into coastal and marine waters.

The automated COMPEAT tool was successfully applied for the first time and the methodology should be further developed towards COMP5. It is also important to improve understanding of the interactions between eutrophication and biodiversity and between eutrophication and climate change. An improved understanding is needed in order to permit the follow-up of implemented measures and to further understand the ecosystem’s response to eutrophication pressures.

Measures implemented

The OSPAR Contracting Parties have made significant efforts in the past to reduce nutrient losses to the marine environment. Widespread eutrophication in the OSPAR Convention area and particularly the North Sea, led to the agreement of PARCOM Recommendation 88/2, wherein the Contracting Parties agreed to reduce nutrient emissions by 50% relative to 1985 values. PARCOM Recommendation 89/4 introduced a coordinated programme for the reduction of nutrients while PARCOM Recommendation 92/7 committed the Contracting Parties to better management of agricultural nutrient releases – both nitrogen and phosphorus - to both atmosphere (for ammonia) and water.

In addition to the OSPAR Recommendations, many OSPAR Contracting Parties that are EU Member States, and even some that are not, have adopted EU directives into national law. Although the EU and its predecessor, the European Community, introduced water quality directives in the 1970s, conditions continued to deteriorate throughout the 1980s. In 1991, the EC introduced Nitrates Directive 91/676/EEC to prevent water pollution from agriculture, which requires the definition of Nitrate Vulnerable Zones and the implementation of additional measures (restrictions) on agriculture in those regions. Many measures under the Nitrates Directive mirror those in PARCOM Recommendation 92/7. While measures required under the Nitrates Directive are binding and therefore not eligible for financial support, the EU’s Common Agricultural Policy includes an increasing amount of support for agri-environmental measures beyond the minimum requirements laid down in the Nitrates Directive.

In addition to tackling diffuse nutrient losses from agriculture, the EU has addressed pollution from point sources through the Urban Wastewater Treatment Directive (91/271/EEC) and several generations of industrial directives such as the Integrated Pollution Prevention and Control Directive (2008/1/EC) and the subsequent Industrial Emissions Directive (2010/75/EU). The Urban Wastewater Treatment Directive improved water treatment standards in many OSPAR Member States while the Industrial Emissions Directive developed the concept of agreed Best Available Techniques and Best Environmental Practice to drive down emissions to both air and water, with standards described in a series of sector-specific reference documents. Connected to the Industrial Emissions Directive, the National Emissions Ceiling Directives (2001/81/EC and 2016/2284) set binding reduction targets for atmospheric emissions.

In 2000, the EU agreed the Water Framework Directive (2000/60/EC) (WFD). This requires harmonised methodologies for regional status assessments in fresh and coastal waters and the implementation of programmes of measures aimed at raising the quality of water bodies to ‘Good Ecological Status’ – similar, but not identical to non-problem eutrophication status – over a six-year management cycle. Through this directive, water management in the catchment was connected administratively to coastal water status. Like the Water Framework Directive, the Marine Strategy Framework Directive (2008/56/EC) uses a six-year management cycle, albeit with separate deliverables for status assessments, monitoring programmes and programmes of measures. The aim of the MSFD is to achieve Good Environmental Status, and it includes an explicit focus on eutrophication as one of the descriptors, while acknowledging that the WFD water bodies (coastal waters up to 1 nm from the baseline) are to be assessed according to WFD threshold values.

As awareness of marine and aquatic pollution has grown, so has knowledge of the impacts of atmospheric pollution. In 1979, thirty-two countries signed the UNECE Convention on Long-range Transboundary Air Pollution. The Convention was a response to acid rain on forests and lakes, among other pressures. In 1988, the Convention adopted the Sofia Protocol concerning emissions of Nitrogen Oxides, and in 1999 the Gothenburg Protocol was adopted to abate acidification, eutrophication and ground-level ozone. The Convention also agreed in 1984 to create a monitoring and modelling organisation, the EMEP, for the monitoring and evaluation of the long-range transmission of air pollutants in Europe. The emission reduction goals agreed and revised under the Gothenburg Protocol form the basis of the National Emissions Ceilings (NEC) Directive targets, and thus have legal force among EU Member States.

Effectiveness of measures

By 2005, six out of nine reporting Contracting Parties had met the 50% reduction target for phosphorus. Only Denmark had achieved the reduction target for nitrogen although several Contracting Parties came close. Rapid input reductions occurred, particularly with the introduction of secondary, and in some areas tertiary, wastewater treatment, which in most countries occurred at the end of the 1980s and the start of the 1990s. The effects of these nutrient reductions are visible in declining trends for nitrogen and phosphorus inputs in most OSPAR Regions and in improvements in eutrophication status . Inputs of nutrients to OSPAR Regions I – IV have decreased significantly since the start of monitoring in 1990. Nitrogen inputs have decreased by 1 350 kt since 1990, while phosphorus inputs have decreased by 70 kt ( Common Indicator on Nutrient Inputs ). Waterborne nutrient inputs to Region I (Arctic Waters), however, have shown a significant increase, which is mainly caused by nutrient inputs from the growing marine aquaculture industry. Since the last QSR, significant but smaller annual decreases in nutrient loads of approximately 28 kt for nitrogen and 1,6 kt for phosphorus have continued in OSPAR Regions I-V as a whole ( Common Indicator on Nutrient Inputs ). For nitrogen, these reductions are due to reductions in atmospheric deposition, since no statistically significant trend has been observed in waterborne inputs during the last decade. Since the first application of the Common Procedure (1990–2001), the extent of the OSPAR Maritime Area classified as either a problem or a potential problem area has decreased steadily to 38 764 km² (≈1,5% of the assessed area) in COMP4.

Reporting on PARCOM Recommendation 88/2 was suspended in 2006 in expectation of better, ecosystem-based nutrient reduction targets. While, therefore, no reporting on nutrient sources currently takes place in OSPAR, examples from selected catchments ( INPUT report ) continue to demonstrate that agriculture is the main source of nutrient inputs , with sewage treatment plants, stormwater overflows, scattered dwellings, aquaculture and shipping constituting other important sources.

Ongoing and future actions

The commitment to further reduce nutrient inputs is reinforced in the new OSPAR strategy. More specifically, the Contracting Parties have committed to “determine the maximum inputs of nutrients for relevant assessment areas which prevent deterioration and enable the achievement of non-problem area status throughout the North-East Atlantic” by 2022 (objective S1.O2) and to “identify and quantify relevant sources, including transboundary transport, and agree nutrient reduction needs for each Contracting Party to stay at or below the maximum input levels” by 2023 (S1.O3). Fulfilling these objectives of the OSPAR NEAES will pave the way for scientifically founded, ecosystem-based nutrient reduction targets in OSPAR and possibly a revision of PARCOM Recommendation 88/2 to include regular reporting on sources and pathways.

Actions on land in the catchments are the principal tool to tackle eutrophication in coastal and marine waters. Most Contracting Parties take action under the Water Framework Directive or equivalent national legislation. In addition, the Nitrates Directive, the Waste Framework Directive, the Urban Wastewater Treatment Directive, the Industrial Emissions Directive or the National Emission Ceiling Directive have been identified as appropriate for defining measures associated with land-based sources of nutrient pollution. Despite the long history of the Urban Wastewater Treatment Directive, Contracting Parties have identified a need for intensified work, both in terms of higher levels of treatment where possible, but also in managing stormwater flows and reducing losses from the sewage pipe network. Within the EU, the Urban Wastewater Treatment Directive is under revision. The revised directive may address the concerns identified by Contracting Parties. Otherwise, joint action through OSPAR could be appropriate.

The Nitrates Directive is also long-established and builds on the work of PARCOM Recommendation 89/4. The measures under this directive aim, for example, to better manage fertilizers and prevent emissions. Landscape restoration and nature recovery on land are also used as a tool to improve freshwater quality and reduce coastal eutrophication.

Under the MSFD, Contracting Parties take measures to address atmospheric and shipping emissions, emissions from ports and harbours, aquaculture, habitat restoration and what may be described as ‘knowledge’, including target setting and monitoring. Proposed actions connected to atmospheric emissions involve implementing and strengthening the Gothenburg Protocol under the UNECE CLRTAP. Some Contracting Parties have identified the need to reduce NOx discharges from shipping. Joint OSPAR work to reduce scrubber discharges is ongoing. Spain and Germany identify issues relating to the management of ports and harbours. Germany proposes the development of Best Available Techniques for bulk fertilizer handling, which has been identified as a potential pathway for large quantities of nutrients entering the Baltic Sea. Given the larger amounts of fertilizer handled by ports in OSPAR Contracting Parties, this could be a significant source. In addition to this source, Spain has identified a general need to better manage stormwater, sewage and greywater discharges in ports. Some Contracting Parties also recognise aquaculture as a source of nutrient inputs and are committing to setting conditions for sustainable mariculture, promotion of no-net-input and extractive aquaculture. The restoration of seagrass meadows, lagoons and estuaries is also foreseen to mitigate eutrophication effects.

About 35 - 40% of nitrogen input stems from atmospheric deposition (2015 - 2019) ( Input Other Assessment ). Atmospheric nitrogen emissions are addressed by UNECE CLRTAP and the EU NEC Directive, both aiming at limiting a number of air pollutants, among them nitrogen oxide (NOx) and ammonia (NH3), by setting emission reduction targets to be achieved in 2020 and 2030, respectively. Therefore, full implementation of the Gothenburg Protocol and the EU NEC Directive (2016/2284/EU) will make an important contribution to combating eutrophication in the North-East Atlantic. A prognosis by EMEP conducted in 2017 on the reduction of atmospheric nitrogen deposition achievable by implementing the Gothenburg Protocol until 2020 and the EU NEC Directive until 2030 indicated that an overall reduction of approximately 30% of the nitrogen deposition of 2005 was possible for OSPAR Region II (EMEP 2017). The prognosticated reduction in deposition for oxidised nitrogen was larger than for reduced nitrogen, reflecting the higher reduction commitments for the respective emissions. Recent EMEP modelling data has shown that the reduced emissions of nitrogen to air have led to a reduction of almost 600 kt in annual atmospheric nitrogen deposition to Regions I – IV, with the greatest reductions in the Arctic and Greater North Sea ( OSPAR Common Indicator on Nutrient Inputs ). This reduction constitutes 86% of the overall reduction achieved for total nitrogen inputs, highlighting the substantial contribution made by clean air policies to reducing eutrophication effects in coastal and marine waters. The Gothenburg Protocol reduction commitments consider, inter alia, human health aspects and the susceptibility of terrestrial and freshwater ecosystems, but not yet marine eutrophication. The Protocol is currently undergoing a review process with the aim of agreeing new emission reduction targets up to 2030. OSPAR has committed to cooperate with the UNECE Convention on Long-range Transboundary Air Pollution (CLRTAP) to promote consideration of marine pollution and eutrophication when setting emission targets. A prerequisite to achieving this is the setting of nutrient reduction needs in OSPAR. As soon as such targets are agreed in OSPAR, as foreseen in the NEAES, they can be considered in future revisions of the Gothenburg Protocol.

The Contracting Parties have committed under the NEAES to “ensure that sufficient measures are taken to achieve the necessary input reductions to prevent coastal and offshore eutrophication in the North-East Atlantic, working where appropriate with national and international organisations and authorities concerned” by 2028 (S1.O4). This commitment necessitates establishing an analysis of the sufficiency of measures, building on the portfolio of measures under MSFD and WFD. Based on this analysis, and building on the identified nutrient reduction needs, OSPAR could undertake to develop recommendations addressing nutrient inputs from selected sources of concern, such as aquaculture and agriculture. The newly established Intersessional Correspondence Group on Measures and Recommendations (ICG-MaRE) under HASEC will work on dedicated measures to further reduce nutrient inputs to the OSPAR Maritime Area so as to provide guidance over the next few years.

There are still many activities that will continue to discharge anthropogenic nutrients into coastal and marine waters. The marine aquaculture sector is projected to further expand, especially in Norway, where the FAO anticipates an increase of 20% between 2018 and 2030 ( Aquaculture Feeder Report ). The consequences of such an increase are evident from the well documented significant increases to nutrient inputs in Region I ( Common indicator on nutrient inputs ). There are growth strategies for the aquaculture sector in a number of other OSPAR Contracting Parties, highlighting the urgent need to work on guidelines for a sustainable aquaculture that minimises nutrient pollution. So far, OSPAR has taken few specific measures on aquaculture, but they include the guidelines on reporting nutrient discharges/losses from marine and freshwater aquaculture plants issued in 2004 and revised in 2018 (OSPAR, 2018). PARCOM Recommendation 94/6 covers the reduction of inputs from potentially toxic chemicals used in aquaculture. In 2006, OSPAR agreed that, for the time being, implementation reporting on PARCOM Recommendation 94/6 could cease. Since there are now significant developments in the aquaculture industry giving rise to concern about pollution, OSPAR decided in 2020 to initiate a new reporting round under Recommendation 94/6 and compile the results in 2022.

Concerning the agricultural sector, across the OSPAR Regions there was a decrease in the agricultural nitrogen balance between 2000 and 2015, indicating an improving trend ( Feeder report on agriculture ). However, the main decrease occurred between 2000 and 2010, with the trend remaining relatively constant or decreasing only marginally from 2010 (Eurostat, 2019). The phosphorus surplus in 2015 was less than half of its value in 2000 in most OSPAR countries (Eurostat 2019); however, phosphorus fertilizer use has also been increasing since 2010 ( Feeder report on agriculture ). Since 2010, ammonia emissions from OSPAR countries, stemming mainly from animal husbandry, have been rising again after a 20% decrease before 2010 ( Feeder report on agriculture ). Overall, these increasing trends point to the need for a common approach in OSPAR to curb nutrient inputs from agriculture. Under the EU Green Deal published in 2020, the European Union committed itself to a series of agri-environmental goals, including reducing nutrient losses by 50% by 2030. To complement this commitment there is a growing interest in recycling nutrients from livestock manure and other organic sources. Furthermore, volatility in the natural gas market is encouraging the development of mineral fertilizer substitutes that use other sources of nitrogen, such as recycled manure products.

Lessons learned and future developments

The automated COMPEAT tool has been successfully applied for the first time and should be further developed for COMP5, adding additional properties and revising the status and confidence assessment methodology if needed. Currently, eutrophication effects are primarily diagnosed by means of elevated dissolved nutrient concentrations, elevated levels of chlorophyll-a and oxygen depletion, and to fully substantiate the evidence it is important to spatially widen the application of additional indicators such as total nutrient concentration and Secchi depth in COMP5.

Furthermore, it is important to improve understanding of how eutrophication affects biodiversity, in particular the quality of pelagic habitats and food webs. The linkage between the eutrophication assessment and the OSPAR pelagic indicators PH1 , PH2 and PH3 needs to be better understood and strengthened in order to allow for ecosystem-based management. Confidence in the eutrophication assessment could be further strengthened by improving monitoring, particularly in those areas where the temporal and/or spatial coverage is currently inadequate. The application of satellite data for eutrophication assessment should be further developed. Future assessments could be conducted based on a gridded approach, in order to obtain better spatially resolved information on eutrophication problems that could guide management decisions. Concerning oxygen concentrations near the seafloor, in situ data alone will not adequately capture the high spatial and temporal variability of depletion events. The use of automated monitoring devices and modelling of the spatial extent of depletion events should be developed for application in COMP5.

Lastly, climate change is leading to more frequent and intense floods and droughts which result in stronger variations in nutrient inputs. Understanding the ecological effects of this larger variability and how to adequately monitor and assess such extreme events for future eutrophication assessments needs to be solved in order to permit the follow-up of implemented measures and to further understand the response of the ecosystem to eutrophication pressures.