Latest Version, 2018 Assessment

Concentrations of dissolved oxygen near the seafloor

In UK marine waters of the Greater North Sea and the Celtic Seas, dissolved oxygen concentrations are above levels required for healthy marine ecosystems, indicating that targets have been met.

Background

UK target on dissolved oxygen

The UK targets for the indirect effects of nutrient enrichment include the indicator for dissolved oxygen. The target for eutrophication ‘problem areas’ is that oxygen concentrations in bottom waters should remain above area-specific oxygen assessment levels (4 to 6 mg l^-1); and there should be no benthic species mortality events as a result of oxygen deficiency that are directly related to anthropogenic input of nutrients.

Key Pressures and Impacts

In the UK Initial Assessment (HM Government, 2012), the key pressures associated with this indicator were the riverine and direct inputs of nutrients (nitrogen and phosphorus) from various industrial and diffuse sources and from atmospheric deposition. These are still relevant but, considering that eutrophication problem areas are generally limited to a small number of coastal waters, estuaries and embayments, the key pressures are likely to be related to local agriculture and wastewater treatment.

Measures taken to address the impacts

The UK Marine Strategy Part Three (HM Government, 2015) describes the robust UK legislative framework for controlling and reducing discharges, emissions and losses of nutrients from sources affecting specific eutrophication problem areas. Measures include the Water Framework Directive river basin management plans, which are particularly relevant for UK problem areas in coastal waters. There are improvements in some of the places where measures are in place, but it can take many years for those measures to take effect.

Monitoring and assessment

Risk-based monitoring of oxygen is carried out under the Clean Seas Environment Monitoring Programme, and assessments follow OSPAR guidance and procedures (OSPAR Commission, 2013).

Regional cooperation

The UK reports information on dissolved oxygen concentrations to OSPAR and has contributed to the monitoring and assessment of the OSPAR dissolved oxygen common indicator. The UK results have been used in the OSPAR Intermediate Assessment (OSPAR Commission, 2017).

Further information

Dissolved oxygen is necessary for healthy marine ecosystems. Excessive nutrient enrichment may cause accelerated growth of algae and/or higher forms of plant life (European Commission, 1991b), and may result in an undesirable disturbance to the balance of organisms present and overall water quality. Undesirable disturbances include depletion of oxygen due to decomposition of accumulated biomass. Such disturbances can have other effects, such as changes in habitats and biodiversity, blooms of nuisance algae or macroalgae, and behavioural changes or death of fish and other species. Low oxygen levels, for example, may result in increased abundances of species which are able to tolerate low oxygen conditions. Very low oxygen levels may result in death of marine organisms. Identifying causal links between disturbances and nutrient enrichment is often difficult and complicated by other pressures. Cumulative effects of global change, including climate change, may have similar effects on biological communities and dissolved oxygen, complicating efforts to demonstrate causal links. Although oxygen depletion can be an indirect effect of nutrient enrichment, other factors which influence oxygen concentrations include changes in water temperature and salinity. Additionally, some degree of seasonal oxygen depletion is a natural process, particularly where the water column stratifies seasonally.

For the UK Marine Strategy Framework Directive Article 8 (European Commission, 2008) Assessment of Eutrophication (HM Government, 2012), four eutrophication criteria have been assessed at a national scale: riverine inputs, nutrient concentrations and ratios, chlorophyll concentrations, and dissolved oxygen levels (see Figure 1). The individual assessment results of any one of these indicators do not diagnose eutrophication by themselves. However, the assessments provide useful information about trends and are important for informing management measures (Painting and others, 2016).

Figure 1. Three stages in the identification of eutrophication. The criteria marked ¹ are common indicators for the  OSPAR Intermediate Assessment.

Assessment method

Concentrations of dissolved oxygen in seawater near the seafloor (‘near-bed’) are used to assess the degree of oxygen deficiency in marine waters. Oxygen concentrations above 6 mg l^-1 are considered to support a healthy marine ecosystem (Best and others, 2007), while concentrations < 2 mg l^-1 are considered to be hypoxic (Levin and others, 2009). Assessment levels used range from 2-6 mg l^-1 to judge whether oxygen is scored as an undesired oxygen deficiency level for that particular area (OSPAR Commission, 2013). Percentage saturation, calculated from concentrations, temperature and salinity, is also reported in order to ensure comparability of assessments and presentation of results within the OSPAR maritime area (OSPAR Commission, 2013).

For this assessment, near-bed dissolved oxygen concentrations and percentage saturation in marine waters (salinity > 30) were analysed for the Greater North Sea and Celtic Seas and for the sub-regions/regional seas within the Greater North Sea and Celtic Seas. For the Greater North Sea, sub-regions are the northern North Sea, the southern North Sea and the eastern English Channel. For the Celtic Seas, sub-regions include the western Channel and Celtic Sea, the Irish Sea, Minches and western Scotland, the Scottish Continental Shelf, and the Atlantic North-West Approaches.

Data on dissolved oxygen concentrations and all supporting information (for example, latitude, longitude, water column depth, sample depth, temperature, salinity) were obtained from 1990 until 2014 (Figure 2). Data were obtained from the International Council for the Exploration of the Seas database and from national (the UK Marine Environment Monitoring and Assessment National database (MERMAN), National Oceanographic Database) and institutional databases (Cefas Sapphire and SmartBuoy, Marine Scotland Science). Duplicates between databases were removed. Data were filtered for analysis by selecting only data within 10 m of the seabed and total water column depth < 500 m during the stratification season (1 July to 31 October) and applying salinity filters to focus on coastal waters (salinity 30 - <34.5 in all sub-regions, except in the Irish Sea, 30 - <34) and offshore waters (salinity ≥34.5 in all sub-regions, except in the Irish sea, salinity ≥34). Only the deepest sample from each cruise/station was used, as determined from day and station number. If there were two samples on the same day at the same depth, both were retained. Continuous data from Cefas benthic landers were averaged over 7-day intervals to be equivalent to survey-based data (Capuzzo and others, 2015), these averages were included in the final data set. Thresholds of 6 mg l^-1 and 60 % saturation were used in the assessments. Where fewer than five data points were available in any given year in an assessment area, these data points were excluded in order to improve the robustness of the analysis.

Figure 2. Map showing where near-bed data (1 July-31 October) on dissolved oxygen were available, 1990 to 2014. X = sampling locations at coastal (red) and offshore (blue) sites. Locations of Cefas benthic landers (2007-2008 only) are shown.

Average values in the lowest quartile of the data per stratification season per year (‘stratified-season’ averages) were plotted to identify trends in the data. Where fewer than five data points were available in any given year in an assessment area, these data were excluded in order to improve the robustness of the analysis. Mann-Kendall non-parametric tests were used for trend analysis (Mann, 1945; Kendall, 1975; Barry and Maxwell, 2015). Where p-values are greater than 0.05, a trend cannot be detected statistically. Where p-values are less than 0.05, it is assumed that there is a significant trend. Where trends were significant, weighted least squares regression lines were calculated, using the 95% confidence intervals for the means.

For assessments of status (2006-2014), stratified-season means in the lowest quartile over the assessment period were compared against the assessment threshold (6 mg l^-1). For dissolved oxygen, the stratified-season means should be above the threshold to support a healthy marine ecosystem.

Confidence levels in the stratified-season means being above the threshold were calculated (2006-2014) using the approach described in Annex 8 of the OSPAR guidance (OSPAR Commission, 2013). The representativeness of the available data in space and time was calculated for sub-regions by following an approach similar to that described in the OSPAR guidance (OSPAR Commission, 2013). Overall confidence of representativeness is provided by the worst score in either space or time.

Within each regional sea, estuarine and coastal water bodies within 1 nautical mile of baseline (3 nautical miles in Scotland) are assessed under the Nitrates Directive (European Commission, 1991b), Urban Waste Water Treatment Directive (European Commission, 1991a) and Water Framework Directive (European Commission, 2000). Water Framework Directive assessment methods used are comparable with those used for OSPAR and Marine Strategy Framework Directive assessments.  Assessment outcomes are used as the basis for reporting on eutrophication status.

Results

Findings from the 2012 UK Initial Assessment

The UK initial assessment (HM Government, 2012) showed that eutrophication problems in UK seas are restricted to a small number of estuaries, embayments and coastal waters.

Latest findings

Status assessment

For marine waters, average stratified-season dissolved oxygen values (in the lowest quartile of the data) over the assessment period (2006-2014) were at or above the assessment levels in the areas assessed (Figure 3). These findings indicate that the target for oxygen has been met.

Figure 3. Average concentrations of dissolved oxygen (mg l^-1, as average values in the lowest quartile of the data) near the seabed in the Greater North Sea and Celtic Seas, 2006-2014. The red line shows the threshold value (6 mg l^-1) used in assessments of status.

Confidence in the assessment methodology and in the data is moderate as there were limitations to the data available. Under the risk-based approach to monitoring, there is no requirement to monitor dissolved oxygen in areas previously assessed as ‘non-problem areas’.

For coastal and transitional waters, the overall outcome from assessments of estuarine and coastal water bodies within 1 nautical mile of baseline (3 nautical miles in Scotland) under the Water Framework Directive and related Directives, showed that 21 water bodies were Problem Areas in terms of OSPAR eutrophication status.

Trend assessment

Trend analysis showed no significant trends in concentrations of dissolved oxygen near the seafloor in the Greater North Sea and Celtic Seas.

Further information

Previous assessments of UK marine waters during the first and second application of the OSPAR Common Procedure (see Defra, 2010) classified all assessment areas as ‘non-problem areas’. Monitoring was therefore focused on measuring on parameters required for the other eutrophication indicators (for example: winter nutrient concentrations), with relatively few near-bed oxygen data were available for this indicator assessment.

Greater North Sea and Celtic Seas

Assessment of trends

Time series of available data on near-bed concentrations of dissolved oxygen (Figure 4) indicate that stratified-season averages in dissolved oxygen concentrations in the Greater North Sea and Celtic Seas were above 6 mg l^-1, except in one year (2003) in the Greater North Sea and three years (1991, 2005, 2008) in the Celtic Seas, when values were 5 to 6 mg l^-1. Mann-Kendall statistics (p >0.05, Table 1) showed no significant trends in the data.

Figure 4. Trends in concentrations of near-bed dissolved oxygen (DO; mg l^-1, as average values in the lowest quartile of the data) in the Greater North Sea and Celtic Seas from 1990 to 2014. Data are plotted separately for coastal (blue symbols) and offshore (orange symbols) water. No trendlines are shown as no significant trends are observed (using Mann-Kendall analysis, see Table 1). Assessment thresholds are 6 mg l^-1 for both coastal and offshore waters. Results are shown for years with five or more data points. A 95% confidence interval is provided for every mean value.

Table 1. Results of Mann-Kendall analyses for concentrations of dissolved oxygen (mg l^-1) in coastal and offshore waters in the Greater North Seas (GNS) and the Celtic Seas (CS). The sign of the Mann-Kendall statistic gives the direction of the trend. Where p-values are greater than 0.05, it is assumed that there is no significant trend. n = number of years with data.

Region	Coastal waters			Offshore waters
	n	MK Statistic	p-value	n	MK Statistic	p-value
GNS	10	0	1	17	0.1236	0.9016
CS	4	1.0607	0.2888	15	-0.3961	0.6921

Assessment of Status

Stratified-season averages in near-bed concentrations of dissolved oxygen (in the lowest quartile of the data) during the assessment period (2006-2014), were above the assessment thresholds (6 mg l^-1) in coastal and offshore waters of the Greater North Sea (Figure 5). In the Celtic Seas, stratified-season averages were at or above the assessment threshold in all years in offshore waters (Figure 5) and in all years except 2008, when the average was just below 6 mg l^-1, in coastal waters.

Figure 5. Mean of the lowest quartile of near-bed concentrations of dissolved oxygen (mg l^-1) during the stratified season (July to October) in marine waters in the Greater North Seas and Celtic Seas (2006-2014). Results are only shown where 5 or more data were available over the assessment period.

Confidence levels in the assessments of concentrations of dissolved oxygen (Table 2) show that confidence in concentrations being above the assessment threshold was high (98 – 100 %) in coastal and offshore waters of the Greater North Sea and Celtic Seas.

Table 2. Confidence levels (%, 2006-2014) for assessing whether average stratified-season concentrations of dissolved oxygen (mg l^-1) were above the assessment threshold in coastal and offshore waters in the Greater North Sea (GNS) and the Celtic Seas (CS). n = number of available data points.

Assessment region	Coastal water		Offshore water
	%	n	%	n
GNS	100	66	100	202
CS	98.3	57	100	125

Sub-regions of the Greater North Sea and Celtic Seas

The UK sub-regions/regional seas of the Greater North Sea are the northern North Sea (Region 1), southern North Sea (Region 2), and eastern English Channel (Region 3). The sub-regions/regional seas of the Celtic Seas include the western Channel and Celtic Sea (Region 4), the Irish Sea (Region 5), Minches and western Scotland (Region 6), the Scottish Continental Shelf (Region 7), and the Atlantic North-West Approaches (Region 8).

Assessment of trends

Time series of available data on near-bed dissolved oxygen concentrations (Figure 6) indicate that stratified-season averages of oxygen concentrations in all sub-regions/regional seas were above 4 mg l^-1, and usually above 6 mg l^-1. Mann-Kendall analyses showed no significant trends (Tables 3 to 5).

Figure 6. Trends in near bed dissolved oxygen (DO) (mg l^-1, mean value in lowest quartile) in Regional Seas 1 to 8, 1990 to 2014, in coastal (blue symbols) and offshore (orange symbols) water. A 95% confidence interval is provided for every mean value. Results are shown for years with five or more data points. Obs = observation. Lines indicate assessment levels (6 mg l^-1) used as part of the overall OSPAR Common Procedure Assessment of eutrophication status. See Table c for names of each regional sea/sub-region.

Table 3. Summary of the trends per sub-region, obtained by applying the Mann-Kendall analyses (1990-2014) to stratified-season averages in the lowest quartile of the near-bed dissolved oxygen data. ↘ = decreasing trend, ↗ = increasing trend, - = no trend. nan = no data or insufficient data. N/A = not applicable.

Regional Sea		Dissolved Oxygen
		Coast	Offshore
1	Northern North Sea	-	-
2	Southern North Sea	-	-
3	English Channel	nan	nan
4	Western Channel & Celtic Sea	nan	-
5	Irish Sea	-	-
6	Minches & West Scotland	-	-
7	Scottish Continental shelf	nan	-
8	Atlantic North-West Approaches	N/A	-

Table 4. Results of Mann-Kendall (MK) analyses for dissolved oxygen (mg l^-1) in coastal areas. The sign of the Mann-Kendall statistic gives the direction of the trend. Where p-values are less than 0.05, it is assumed that there is a significant trend. For p-values greater than 0.05, a trend could not be detected statistically. n = number of observations, nan = no data or insufficient data. See Table 3 for names of each regional sea/sub-region.

Regional Sea	n	MK Statistic	p-value
1	5	0	1
2	6	-0.378	0.706
3	0	nan	nan
4	0	nan	nan
5	2	0	1
6	2	0	1
7	0	nan	nan
8	0	nan	nan

Table 5. Results of Mann-Kendall (MK) analyses for dissolved oxygen (mg l^-1) in offshore areas. The sign of the MK statistic gives the direction of the trend. Where p-values are less than 0.05, it is assumed that there is a significant trend. For p-values greater than 0.05, a trend could not be detected statistically. n = number of data, nan = no data or insufficient data. See Table c for names of each regional sea/sub-region.

Regional Sea	n	MK Statistic	p-value
1	16	1.04	0.3
2	10	-1.07	0.28
3	0	nan	nan
4	2	0	1
5	2	0	1
6	4	0.11	0.29
7	7	1.21	0.23
8	3	0	1

Assessment of Status

Using available data, dissolved oxygen data were assessed in coastal and offshore waters. The stratified-season averages in the lowest quartile of the data showed that concentrations and percentage saturation were at or above the assessment thresholds used in coastal and offshore waters assessed (Figure 7), confirming no undesirable disturbance due to nutrient enrichment.

Confidence levels in the assessments of concentrations of dissolved oxygen are given in Table 6 (coastal water) and Table 7 (offshore water). These results show that confidence levels in concentrations being above the assessment threshold were high (53-100%) in coastal waters where there were sufficient data, that is in the northern North Sea, the southern North Sea, the Irish Sea, and Minches and western Scotland. Confidence levels were also high (97-100%) in offshore waters where there were sufficient data, that is Regions 1, 2, 6, 7 and 8. In Regions 3 and 5 offshore, insufficient data were available. In Region 4 offshore, confidence levels were low (43%, Table 7) due to low sample numbers (n=14, mostly from 2014).

Figure 7. Mean of the lowest quartile of near-bed Dissolved Oxygen (DO) during the stratified season (July to October) per sub-region, as DO concentration (top) and percentage saturation (bottom). Results are shown separately for coastal and offshore water. Assessment thresholds are shown for oxygen concentrations (6 mg l^-1) and percentage saturation (60% used here; range = 50-75%). Results are only shown where 5 or more data were available. See Table c for names of each regional sea/sub-region.

Table 6: Coastal areas - confidence levels (%, 2006-2014) for assessing if near-bed concentrations of dissolved oxygen were above the assessment threshold. n = number of available data points. X = no data. * indicates where confidence levels were < 50 %. Region 8 (Atlantic North-West Approaches) is an offshore region. N/A = not applicable.

Assessment region	Dissolved Oxygen
	%	n
1. Northern North sea	100	29
2. Southern North Sea	99.78	37
3. English Channel	x*	x
4. Western Channel & Celtic Sea	x*	x
5. Irish Sea	99.69	27
6. Minches & W Scotland	52.89	29
7. Scottish Continental Shelf	x*	x
8. Atlantic North-West Approaches	N/A*	N/A

Table 7. Offshore areas- confidence levels (%, 2006-2014) for assessing whether near-bed concentrations of dissolved oxygen were above the assessment threshold. n = number of available data points. X = insufficient or no data. * indicates where confidence levels were <50 %. Brackets ( ) = insufficient data to be statistically significant.

Assessment region	Dissolved Oxygen
	%	n
1. Northern North sea	100	166
2. Southern North Sea	99.46	33
3. English Channel	x*	(1)
4. Western Channel & Celtic Sea	42.45*	15
5. Irish Sea	x*	(1)
6. Minches & W Scotland	100	32
7. Scottish Continental Shelf	100	65
8. Atlantic North-West Approaches	97.1	8

Spatial and temporal representativeness (2006-2014) of concentrations of near-bed dissolved oxygen in time and space was low for dissolved oxygen data (1.57-46.30%, Table 8), with the highest scores (39.6-46.3%) observed in Regions 1 and 6. These scores should provide the final score for representativeness for eutrophication indicators. However, dissolved oxygen is not routinely monitored in Non-Problem Areas, and these scores were not used in recent assessments (see the UK National Report Painting and others, 2016) to describe the overall representativeness of the data.

Table 8. Spatial and temporal representativeness of available data (as a %) for near-bed concentrations of dissolved oxygen in each of the sub-regions. Note: these analyses use all data in an assessment region, and do not consider coastal and offshore waters separately.

Assessment region	Dissolved Oxygen
1	39.63
2	25.77
3	4.17
4	8.33
5	10.81
6	46.30
7	7.66
8	1.57

Conclusions

Oxygen concentrations near the seafloor met assessment thresholds in marine waters of both the Greater North Sea and Celtic Seas, indicating that targets have been met. Eutrophication problems remain restricted to a small number of estuaries, embayments and coastal waters which represent a small proportion (0.03%) of the total area of UK waters. Measures are in place to reduce nutrient inputs.

Assessments of oxygen concentrations confirm the findings of the nutrient indicators which show no significant increases in nutrient inputs and decreasing trends in nutrient concentrations in marine waters. Confidence levels in assessments and data are moderate.

Knowledge gaps

Coupling between biological and physical processes near the seafloor is poorly understood. Robust assessments of oxygen deficiency require improved availability of near-bed data on oxygen concentrations paired with salinity, depth and temperature measurements.

Further information

Our understanding of the relative importance of biological and physical processes (mixing and advection) in controlling oxygen dynamics near the seafloor and, the impacts of climate change on physical processes, oxygen deficiency and oxygen consumption, is relatively poor. This understanding will need to be improved in order to distinguish between future effects of nutrient enrichment and changes in sea water temperatures as a result of climate change. Improved understanding of the impacts of climate change require further research (see discussion in, for example: Greenwood and others, 2010; Große and others, 2016; Topcu and Brockmann, 2015; and Queste and others, 2013, 2016) and assessments based on oxygen saturation levels. Robust assessments of oxygen deficiency would require improved availability of suitable data in many of the assessment regions.

References

Barry J, Maxwell D (2015) ‘Tools for environmental and ecological survey design and analysis’ (viewed on 31 October 2018)

Best M, Wither AW, Coates S (2007) ‘Dissolved oxygen as a physico-chemical supporting element in the Water Framework Directive’ Marine Pollution Bulletin 55: 53–64 (viewed 15 Ocober 2018)

Capuzzo E, Stephens D, Silva T, Barry J, Forster RM (2015) ‘Decrease in water clarity of the southern and central North Sea during the 20th century’ Global Change Biology 21: 2206–2214 (viewed 10 October 2018)

Defra (2010) ‘Charting Progress 2. The State of UK seas’ (viewed 27 July 2018)

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 (2008) ‘Directive 2008/56/EC of the European Parliament and of the Council of 17 June 2008 establishing a framework for community action in the field of marine environmental policy (Marine Strategy Framework Directive)’ Official Journal of the European Union L 164, 25.6.2008, pages 19-40 (viewed 21 September 2018)

Greenwood N, Parker ER, Fernand L, Sivyer DB, Weston K, Painting SJ, Kröger S, Forster RM, Lees HE, Mills DK, Laane RWPM (2010) ‘Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health’ Biogeosciences 7: 1357-1373 (viewed 16 October 2018)

Große F, Greenwood N, Keus M, Lenhart H-J, Machoczek D, Pätsch J, Salt L, Thomas H (2016) ‘Looking beyond stratification: a model-based analysis of the biological drivers of oxygen depletion in the North Sea’ Biogeosciences 13: 2511-2535 (viewed 16 October 2016)

HM Government (2012) ‘Marine Strategy Part One: UK initial assessment and Good Environmental Status’ (viewed 10 October 2018)

HM Government (2015) ‘Marine Strategy Part Three: UK Programme of Measures’ (viewed 10 October 2018).

Kendall, MG (1975) ‘Rank correlation methods’ 4th ed.; Charles Griffith: London.

Levin L, Ekau W, Gooday AJ, Jorissen F, Middelburg JJ, Naqvi SWA, Neira C, Rabalais NN, Zhang J (2009) ‘Effects of natural and human-induced hypoxia on coastal benthos’ Biogeosciences 6: 2063–2098 (viewed 15 October 2018)

Mann, HB (1945) ‘Non-parametric tests against trend’ Econometrica 13: 245-259 (viewed 9 October 2018)

OSPAR Commission (2010) ‘The North-East Atlantic Environment Strategy’ OSPAR Agreement 2010-3, Strategy of the OSPAR Commission for the Protection of the Marine Environment of the North-East Atlantic 2010–2020 (viewed 15 October 2018)

OSPAR Commission (2013) ‘Common Procedure for the Identification of the Eutrophication Status of the OSPAR Maritime Area’ OSPAR Agreement 2013-8, supersedes Agreements 1997-11, 2002-20 and 2005-3 (viewed 12 October 2018)

OSPAR Commission (2017) ‘Intermediate Assessment 2017’ (viewed on 21 September 2018)

Painting S and others (2016) UK National Report. Common Procedure for the Identification of the Eutrophication Status of the UK Maritime Area (viewed 12 October 2018)

Queste BY, Fernand L, Jickells TD, Heywood KJ (2013) ‘Spatial extent and historical context of North Sea oxygen depletion in August 2010’ Biogeochemistry 113: 53–68 (viewed 16 October 2018)

Queste BY, Fernand L, Jickells TD, Heywood KJ, Hind AJ (2016) ‘Drivers of summer oxygen depletion in the central North Sea’ Biogeosciences 13: 1209-1222 (viewed 16 October 2018)

Topcu HD, Brockmann UH (2015) ‘Seasonal oxygen depletion in the North Sea, a review’ Marine Pollution Bulletin 99: 5–27 (viewed 15 October 2018)

Acknowledgements

Assessment metadata

Assessment Type	UK Marine Strategy Framework Directive Indicator Assessment
	D5
	Eutrophication
	In addition to links provided in ‘References’ section above: European Court of Justice (2009) ‘Judgment of the Court (Third Chamber) of 10 December 2009, European Commission v United Kingdom of Great Britain and Northern Ireland’ Failure of a Member State to fulfil obligations - Environment - Directive 91/271/EEC - Urban waste water treatment - Article 3(1) and (2), Article 5(1) to (3) and (5) and Annexes I and II - Initial failure to identify sensitive areas - Concept of ‘eutrophication’ - Criteria - Burden of proof - Relevant date when considering the evidence - Implementation of collection obligations - Implementation of more stringent treatment of discharges into sensitive areas. Case C-390/07, European Court Reports 2009 I-00214*, ECLI identifier: ECLI:EU:C:2009:765 (viewed on 12 January 2019) OSPAR Commission (2003) ‘OSPAR integrated report 2003 on the eutrophication status of the OSPAR maritime area based upon the first application of the Comprehensive Procedure’ OSPAR Eutrophication Series, publication 189/2003. OSPAR Commission, London (viewed on 12 January 2019) OSPAR Commission (2008) ‘Second OSPAR integrated report on the eutrophication status of the OSPAR maritime area’ OSPAR Eutrophication Series, publication 372/2008. OSPAR Commission, London (viewed on 12 January 2019) OSPAR Commission (2010) ‘The North-East Atlantic Environment Strategy: Strategy of the OSPAR Commission for the Protection of the Marine Environment of the North-East Atlantic 2010-2020’ 27 pages (viewed on 12 January 2019) Painting S and others (2016) UK National Report. Common Procedure for the Identification of the Eutrophication Status of the UK Maritime Area (viewed 12 October 2018)
Point of contact email	marinestrategy@defra.gov.uk
Metadata date	Monday, October 1, 2018
Title	Nutrient levels; chlorophyll concentrations; concentrations of dissolved oxygen near the seafloor
Resource abstract	Data on primary indicators for eutrophication status (nutrients, chlorophyll and dissolved oxygen) were assessed for the UK sector of the Greater North Sea and the Celtic Seas. Targets have been met for nutrients, chlorophyll and dissolved oxygen concentrations. Problem areas are limited to 21 areas in estuarine and inshore coastal waters.
Linkage	Painting S and others (2016) UK National Report. Common Procedure for the Identification of the Eutrophication Status of the UK Maritime Area (viewed 12 October 2018)
Conditions applying to access and use	© Crown copyright, licenced under the Open Government Licence (OGL). and OSPAR Data terms and conditions.
Assessment Lineage	Data were obtained for both OSPAR and Marine Strategy Framework Directive assessments. Data on chlorophyll concentrations, and all supporting information (e.g. latitude, longitude, water column depth, sample depth, temperature, salinity) were obtained from 1990 until 2014. Data were obtained from the ICES database and from national (MERMAN, NODB) and institutional databases (Cefas Sapphire and SmartBuoy databases, Marine Scotland Science). All available data were used, collected using all sampling platforms (e.g. ships and submersible sensors), and analysed by all analytical methods (e.g. fluorometry, spectrophotometry and pigment analysis). Duplicates between databases were removed. Data were averaged over the whole water column for each cruise station and day, with the exception of MERMAN data where datetime was used instead of day as there were multiple records in different locations (along transects) for the same station and day. Continuous data from SmartBuoys were averaged over 7-day intervals to be equivalent to survey based data; these averages were included in the final data set. Data were filtered by salinity, to assign to coastal waters (salinity 30 - <34.5) or offshore waters (salinity >34.5). For the OSPAR Common Procedure, salinity filters for the Irish Sea were 30 - <34 for coastal waters and >34 for offshore waters), and by season for chlorophyll (growing season, March to October inclusive). Chlorophyll 90th percentiles were calculated over the growing season. The 90th percentiles were plotted per year to identify trends in the data. Where fewer than five data points were available in any given year in an assessment area, these data points were excluded, in order to improve the robustness of the analysis. Mann-Kendall non-parametric tests were used for trend analysis (Mann 1945; Kendall 1975; Barry and Maxwell 2015). Where p-values are greater than 0.05, a trend cannot be detected statistically. Where p-values are less than 0.05, it is assumed that there is a significant trend. Where trends were significant, weighted least squares (WLS) regression lines (see http://statsmodels.sourceforge.net/) were calculated, using the 95% confidence intervals for the means. For assessments of status (2006-2014), growing season chlorophyll 90th percentiles were compared against assessment thresholds for coastal waters (15 µg l-1) and offshore waters (10 µg l-1, see Foden et al 2011). Determination of the reference values and thresholds used for chlorophyll in coastal and offshore waters is described in Foden et al (2011). For chlorophyll, 90th percentiles during the growing season should be below the assessment thresholds.
Dataset metadata
Dataset DOI	Collingridge and others (2019). Data for UK OSPAR Common Procedure - Eutrophication Assessment Cefas, UK. V1.doi: https://doi.org/10.14466/CefasDataHub.79

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MEDIN discovery metadata - a list of standardized information that accompanies a marine dataset and allows other people to find out what the dataset contains, where it was collected and how they can get hold of it.

Recommended reference for this indicator assessment

Suzanne Painting¹, Kate Collingridge¹, Luz Garcia¹, Jon Barry¹, Simon Leaf², Mike Best², Alison Miles², Michael McAliskey³, Mark Charlesworth⁴, Lucie Haines⁴, Rob Fryer⁵, Pamela Walsham⁵, Lynda Webster⁵, Eileen Bresnan⁵, Ashley Roberts⁶, Clare Scanlan⁶ and Clemens Engelke⁶ 2018. Oxygen. UK Marine Online Assessment Tool, available at: https://moat.cefas.co.uk/pressures-from-human-activities/eutrophication/dissolved-oxygen/

¹Centre for Environment, Fisheries and Aquaculture Science

²Environment Agency

³Department of Environment, Agriculture & Rural Affairs, Northern Ireland

⁴Natural Resources Wales

⁵Marine Scotland

⁶Scottish Environment Protection Agency