Eutrophication
Assessment of progress towards the achievement of Good Environmental Status for eutrophication.
The extent to which Good Environmental Status has been achieved
The UK has largely achieved its aim of Good Environmental Status for eutrophication. A small number of eutrophication problems remain in coastal and estuarine waters, representing 0.03% of the total UK Exclusive Economic Zone, and 0.41% of estuarine and coastal waters.
How progress has been assessed
Step 1: We agreed characteristics of Good Environmental Status
In the Marine Strategy Part One (HM Government, 2012), the UK set out the following “Characteristics of Good Environmental Status” for Eutrophication:
Human-induced eutrophication in UK seas is minimised and all UK marine waters are ‘non-problem areas’, where:
- nutrient concentrations do not lead to an undesirable disturbance to the balance of organisms present in the water or to the quality of the water concerned resulting from accelerated growth of algae
- the direct effects of nutrient enrichment associated with algal growth do not constitute or contribute to an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned
- indirect effects of nutrient enrichment associated with growth of macroalgae, sea grasses, and reductions of oxygen concentrations do not constitute an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned.
Step 2: We set targets to help assess progress
Based on our knowledge of the eutrophication status of UK marine waters, from the initial assessment of the eutrophication status of UK seas in 2012 (HM Government, 2012) and previous assessments, linked targets were set for the acceptable conditions of nutrient levels, chlorophyll, phytoplankton, macroalgae, oxygen and oxygen-related effects. The linked targets were different for the eutrophication ‘problem areas’ and ‘non-problem areas’ identified in the initial assessment reflecting the different risks. It was also stipulated that the targets must be considered holistically and that the overall goal is to ensure no undesirable disturbance. Failure to meet an individual target does not necessarily signify a eutrophication problem.
Targets for nutrient levels:
- Non-Problem Areas 2007/2010: No increase in the assessed dissolved inorganic nitrogen and phosphorus concentrations resulting from anthropogenic nutrient input using data from periodic surveys
- Problem Areas 2007/2010: A downward trend in dissolved inorganic nitrogen and phosphorus concentrations resulting from decreasing anthropogenic nutrient input over a 10-year period.
Targets for direct effects of nutrient enrichment:
- Non-Problem Areas 2007/2010:
- no increase in the chlorophyll 90 percentile in the growing season (linked to increasing anthropogenic input) based on periodic surveys
- and, if there is evidence of nutrient enrichment and accelerated growth, then
- no trend in a eutrophication-relevant plankton index that is attributable to increases in nutrient loading, winter nutrient concentrations or trends in nutrient ratios.
- Problem Areas 2007/2010:
- a downward trend in the chlorophyll 90 percentile in the growing season over a 10-year period (linked to decreasing anthropogenic input)
- changes in a eutrophication-relevant plankton index that is attributable to decreases in nutrient loading, winter nutrient concentrations or trends in nutrient ratios.
Targets for indirect effects of nutrient enrichment
- Problem Areas 2007/2010:
- Water Framework Directive (European Commission, 2000) macroalgae and seagrass tools at good status
- oxygen (concentrations/5 percentile) in bottom waters should remain above area-specific oxygen assessment levels (e.g. 4 to 6 mg/l), and
- there should be no mortality events in benthic animal species as a result of oxygen deficiency that are directly related to anthropogenic input of nutrients.
Step 3: We carried out the assessment of targets
We worked with OSPAR countries to produce the “Third OSPAR Integrated Report on the Eutrophication Status of the OSPAR Maritime Area, 2006-2014” (OSPAR Commission, 2017) which includes an assessment of the eutrophication status of UK waters. This assessment uses the common methodology set out in the OSPAR Common Procedure for the Identification of Eutrophication Status (OSPAR Commission, 2013) through which the Contracting Parties apply harmonised criteria of nutrient inputs, nutrient concentrations, chlorophyll concentrations, phytoplankton indicator species, macrophytes, dissolved oxygen levels, incidence of fish mortality events and changes in zoobenthos. It also includes an integration step which considers all these criteria to judge whether eutrophication has occurred. At the same time, we set up four OSPAR common indicators which the UK has used to contribute to an assessment of progress towards achieving our targets and characteristics of Good Environmental Status with an emphasis on trends for nutrient concentrations and chlorophyll.
The UK report submitted to OSPAR to was used to assess the eutrophication status in the Celtic Seas and the Greater North Sea. The UK contribution to this OSPAR initiative involved the submission of a UK national report (Painting and others, 2016) which shows, amongst other things, how the findings of the four UK indicator assessments are integrated using the principles of the OSPAR Common Procedure to show if eutrophication effects are occurring in UK seas. It also provides details of the assessment method and maps of the assessment results which show where the small number of problem areas are located.
Step 4: Review of further action required to move towards Good Environmental Status
This involves further refining the UK targets, and ongoing evaluation of the UK indicators.
Progress since 2012
The initial assessment in 2012 (HM Government, 2012) reported relatively few eutrophication problem areas in UK waters, and that these were only found in coastal and transitional waters. Since then, the number of problem areas has decreased (from 23 to 21) and the number of potential problem areas has increased (from 6 to 11). This results from the continued development of surveillance, monitoring and assessments being undertaken for transitional and coastal waters. Some water bodies are showing signs of improvement from problem area to potential problem area. Changes in nitrogen and phosphorus inputs, concentrations of contaminants, chlorophyll concentrations and oxygen levels generally show improvements.
Figure 1. Results of assessments of eutrophication status, 2006-2014. Insets show water bodies assessed as OSPAR problem areas (red). OSPAR non-problem areas (green) have achieved the UK aim for Good Environmental Status. Reproduced from Painting and others, 2016.
Programme of measures
Part three of the UK Marine Strategy (HM Government, 2015) detailed an extensive programme of measures, designed to record and manage human activities that might have adverse effects on marine ecosystems and animals. The main vehicle for implementing a broad range of measures are the River Basin Management Plans developed under the Water Framework Directive (European Commission, 2000). These aim to achieve the objectives for specific water bodies, particularly where high nitrogen concentrations have resulted in the classification of ‘moderate status’ and an additional assessment of the biological quality indicates that measures to tackle eutrophication are necessary.
The measures taken to reduce nutrient pollution and eutrophication problems in the last decades (for example under the Urban Waste Water Treatment, Nitrates, Habitats and Birds Directives and covered by Water Framework Directive River Basement Management Plans (European Commission, 1991a, 1991b, 1992, 2000, 2009) appear to be leading to beneficial change to the areas at risk in the marine environment. The full effect of these measures takes a long time to result in the desired outcome due to time lags between taking measures and change in the large reservoirs of nitrogen that have built up in soils and ground-waters in previous decades.
Improved monitoring
The use of remote smart buoys in key locations to track concentrations of nutrients and chlorophyll has led to greater monitoring efficiencies and more robust real-time results which give a much better picture of how these indicators are changing during the growing season. Remote sensing of chlorophyll using satellites has enabled a near-quantitative estimation of chlorophyll concentrations in real time, which has led to a much better appreciation of the risks of eutrophication occurring in specific areas.
Outstanding issues
There are no major outstanding issues for eutrophication, but the impact of a changing climate will need to be considered in future assessments.
Achievement of targets
Targets for nutrient levels
There has been no significant trend in the waterborne input of nitrogen to the Greater North Sea (1990 to 2014) but there has been a significant reduction in phosphorus input. There have been significant downward trends in both nitrogen and phosphorus inputs to the Celtic Seas.
There has been no increase in the concentration of dissolved inorganic nitrogen in the coastal and offshore waters of the Greater North Sea and Celtic Seas since 1990. Significant decreases have been observed in coastal waters in both regions. UK targets for nutrient concentrations in the sea have been met.
Targets for direct effects of nutrient enrichment
Chlorophyll concentrations in UK marine waters of the Greater North Sea and the Celtic Seas are generally below levels used in the diagnosis of eutrophication. Since 1990, there has been no significant change in chlorophyll concentration and this meets the target set for non-problem areas.
Targets for indirect effects of nutrient enrichment
In UK marine waters of the Greater North Sea and the Celtic Seas, dissolved oxygen concentrations are above levels required for healthy marine ecosystems.
Indicators used to assess targets
The eutrophication assessment is based the following four OSPAR common indicators which were developed through sharing of data from the OSPAR contracting parties (OSPAR Commission, 2017).
- Inputs of nutrients: shows whether measures put in place to reduce nutrient loads are working,
- Nutrient concentrations: shows how trends in nutrient concentrations are changing,
- Chlorophyll concentrations: shows whether phytoplankton biomass is below assessment levels and whether there is any change,
- Concentrations of dissolved oxygen near the seafloor: shows whether concentrations of oxygen are at levels that support a healthy marine ecosystem.
Moving forward
Seeing that eutrophication is only a problem in a few small areas in coastal waters, we will focus on implementing management measures to improve these.
References
Acknowledgements
European Commission (1991a) ‘Council Directive 91/271/EEC of 21 May 1991 concerning urban waste-water treatment’ Official Journal of the European Union L 135, 30.5.1991, pages 40–52 (viewed on 8 October 2018)
European Commission (1991b) ‘Council Directive 91/676/EEC of 12 December 1991 concerning the protection of waters against pollution caused by nitrates from agricultural sources’ Official Journal of the European Union L 375, 31.12.1991, pages 1–8 (viewed on 8 October 2018)
European Commission (1992) ‘Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora’ Official Journal of the European Union L 206, 22.7.1992, pages 7–50 (viewed on 8 October 2018)
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European Commission (2009) ‘Directive 2009/147/EC of the European Parliament and of the Council of 30 November 2009 on the conservation of wild birds’ Official Journal of the European Union L 20, 26.1.2010, pages 7–25 (viewed on 8 October 2018)
HM Government (2012) ‘Marine Strategy Part One: UK Initial Assessment and Good Environmental Status’ December 2012 (viewed on 5 July 2018)
HM Government (2015) ‘Marine Strategy Part Three: UK Programme of Measures’. December 2015 (viewed on 5 July 2018)
OSPAR Commission (2013) ‘Common Procedure for the Identification of the Eutrophication Status of the OSPAR Maritime Area’ Document reference number 2013-8 (viewed on 8 October 2018)
OSPAR Commission (2017) ‘Eutrophication Status of the OSPAR Maritime Area: Third Integrated Report on the Eutrophication Status of the OSPAR Maritime Area’ Third Common Procedure Task Team of the Intersessional Correspondence Group on Eutrophication. Publication Number: 694/2017 (viewed on 8 October 2018)
OSPAR Commission (2017) ‘Intermediate Assessment 2017: Pressures from Human Activities: Eutrophication’ (viewed on 8 October 2018)
Painting S, Garcia L, Collingridge K (2016) ‘Common Procedure for the Identification of the Eutrophication Status of the UK Maritime Area – UK Report’ (viewed on 8 October 2018)