Condition of intertidal rocky shore macroalgae (seaweed) communities in coastal waters determined using Water Environment Regulations methods.
The targets covering the proportion of surveyed rocky shore macroalgae communities at an acceptable condition have been achieved in the Celtic Seas Marine Strategy sub-region and constituent Regional Seas. Data was absent for the Greater North Sea Marine Strategy sub-region. Data coverage is limited and there is low confidence in the assessment results.
Background
UK Target on rocky shore macroalgae quality
This indicator is used to assess progress against the Water Environment Regulations (WER) ecological status boundaries and areas of unacceptable impact which are components of the rocky habitats targets set in the UK Marine Strategy Part One (Defra, 2019).
Key pressures and impacts
The UK WER risk assessments identify those pressures that are likely to cause a failure for a WER water body to meet its environmental objectives. The risk assessment information used for the updated UK marine strategy (UKMS) assessments is based on those derived by the UK WER monitoring authorities to support the Cycle One River Basin Management Plan (RBMP) classifications.
Risk assessment information used in the UKMS assessments was derived by the UK WER monitoring authorities to support the Cycle One RBMP classifications by identifying pressures considered likely to cause water bodies to fail to achieve their WER environmental objectives. These identified 52 of the 467 coastal water bodies as ‘At risk’ or ‘Probably at risk’ of failing to meet their WER objectives due to point source pollution containing substances such as metals and hydrocarbons. Rocky shore macroalgae may be further impacted by habitat modification, other physical disturbances and organic/nutrient enrichment in severe cases.
Measures taken to address the impacts
Measures to protect benthic habitats are set out in the UK Marine Strategy Part Three. These include those related to the Habitats Regulations, WER RBMPs, Urban Wastewater Treatment Regulations, Nitrate Pollution Prevention Regulations, the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR) measures on species and habitats, Marine Spatial Planning, land management schemes, catchment sensitive farming and European Marine Site management schemes.
Monitoring, assessment and regional cooperation
Areas that have been assessed
Progress against the UK target was assessed for the Celtic Seas UK Marine Strategy sub-region and its constituent UK Regional Seas set out in Charting Progress 2 (CP2) (UKMMAS, 2010). There was insufficient data to assess the Greater North Sea UK Marine Strategy sub-region. These areas were assessed in the 2018 UK Marine Strategy assessments.
Monitoring and assessment methods
Routine monitoring of intertidal rocky shore macroalgae communities is undertaken for WER. The WER rocky shore macroalgae indicator combines species diversity measures and proportions of opportunistic taxa to derive an Ecological Quality Ratio (EQR).
Assessment thresholds
The indicator quality threshold is defined as the boundary for WER Good Ecological Status (EQR ≥0.60) or Good Ecological Potential (GEP) (for Heavily Modified Water Bodies (HMWBs)). The UK Marine Strategy assessment target is met where the proportion of survey assessments achieving the quality threshold meets the extent threshold of 75%.
Regional cooperation
The indicator was not used for the OSPAR Quality Status Report 2023. The boundary of WER Good Ecological Status has been set through Intercalibration with Member States of the North-East Atlantic Geographical Intercalibration Group (NEAGIG).
Further information
The Water Environment Regulations intertidal rocky shore macroalgae tool is a multi-metric indicator derived from the following measurements of the rocky shore macroalgae communities within a survey:
Number of macroalgal taxa: This is simply the number of different taxa found. This is “normalised” using the shore description score (or shore description factor) to take account of influence of the natural physical habitat.
Proportion of Chlorophyta taxa (green seaweeds): This is the number of green algae found expressed as a percentage of the total number of taxa found.
Proportion of Rhodophyta (red seaweeds): This is the number of red algae found expressed as a percentage of the total number of taxa found.
Proportion of opportunistic taxa: This is the number of opportunistic algae found expressed as a percentage of the total number of taxa found.
Ecological Status Group Ratio: This is a measure of how the macroalgae indicate a shift from a “pristine state” where late successionals or perennials are found to a degraded state where more opportunists or annuals are found. In high quality waters we would expect high species richness with a diverse community of perennial red and brown seaweeds and proportionally fewer opportunist seaweeds. However, a degraded site typically would have fewer taxa, and it is likely that ephemerals and opportunist species would be more dominant.
Values of these five metrics were calculated to determine what these would be for undisturbed waters (reference conditions). The observed results are then compared with the reference condition values and combined to calculate the Ecological Quality Ratio (EQR) which operates between zero and one. EQR values close to one indicate rocky shore macroalgal communities are close to their natural state; those near to zero indicate a high level of pollution or disturbance. The EQR is used to categorise a survey (or multiple surveys when aggregated to e.g. water body level) into one of the five Ecological Quality Status classes as required by the WER:
High status: ≥ 0.8
Good status: 0.6 ≤ 0.8
Moderate status: 0.4 ≤ 0.6
Poor status: 0.2 ≤ 0.4
Bad status: <0.2
Further details on the WER rocky shore macroalgal index are available at the WER UK Technical Advisory Group (UKTAG) website:
Assessment method
Baseline setting
The WER rocky shore macroalgae indicator reference conditions have been used for the UK Marine Strategy baseline. Reference conditions are based on a combination of expert judgement and data from undisturbed sites and historic records. The approach to setting reference conditions as defined for the WER rocky shore macroalgal index. This complies with the approach to setting baselines for UK Marine Strategy as outlined by the Intersessional Correspondence Group on Biodiversity Assessment and Monitoring (ICG COBAM) (OSPAR Commission, 2012) as “a state in which the anthropogenic influences on species and habitats are considered to be negligible”.
Quality and extent targets
The target of GES or GEP (where mitigation measures against the modification features are considered sufficient for HMWBs) as defined for the WER is being applied as the indicator quality threshold for the UK Marine Strategy assessments. The number of rocky shore macroalgae surveys within the WER assessments are approximately proportional to water body surface area. The extent target is met where ≥75% of the surveys (representative of surface area) within a UK Regional Sea meet this quality threshold. This conforms to the 2023 EU agreement under Descriptor 6 in the EU Marine Strategy Framework Directive (MSFD) “Seabed Integrity” where no more than 25% of the habitat should be adversely affected by human pressures to achieve GES for broad scale habitats (TGSeabed, 2023). The 25% threshold also aligns with the methodology implemented by the UK in 2019 Article 17 assessments, under the EU Habitats Directive (now Habitats Regulations), to determine “Unfavourable-Bad” condition for habitats (JNCC, 2019). The 2018 Marine Strategy assessments used an extent threshold of 85% (based on targets relating to the assessed surface area achieving an acceptable condition recommended by the UK Technical Advisory Group on the WER for Good Ecological Status) which was revised for the current assessment to align with the EU Descriptor 6 MSFD targets for broadscale habitats.
The quality and extent targets may be reviewed and revised in future assessment cycles.
Aggregation approach
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Rocky Shore Macroalgae WER classification results for coastal water bodies from the 2021 Cycle Three RBMPs were collated at the survey level from the UK WER monitoring authorities.
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The percentage of individual survey assessment results at each WER ecological status class were calculated within each UK Regional Sea. The assessments use data derived WER classification results for use in the WER Cycle Three RBMP and exclude those rolled forwards from previous classifications. Please note: UK Marine Strategy assessments are based on the data and processes used for the WER water body classifications within the RBMP assessments and exclude changes to the classifications as a result of subsequent investigations.
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Survey assessments at ‘Bad’, ‘Poor’ or ‘Moderate’ ecological status under WER were categorised as being below the indicator quality target, with those at ‘Good’ or ‘High’ ecological status categorised as being above the indicator quality target.
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The final assessment is based on the percentage of UK Regional Sea survey results that meets the indicator quality target, measured against an extent threshold of 75%.
Confidence assessment
The approach to determining confidence in the UK Regional Sea assessments is based on the extent to which the indicator and associated assessments fulfil certain criteria which impact the extent to which the assessment represents the available habitat relevant to the indicator, the extent to which the indicator can identify the overall effect of the relevant pressures and the confidence in the assessment result being above/below the indicator target. The confidence assessment approach has been developed for UK Marine Strategy assessments and differs to those applied during WER classifications to account for differences in spatial scales of the UK Marine Strategy assessment areas, the distribution of the WER classifications within the UK Regional Seas and the inclusion of the indicator extent targets. The confidence assessment method was developed for the 2018 Marine Strategy assessments. Confidence thresholds were arbitrarily set based on an equal division of the range of values for each criterion. Details of the criteria are provided in Table 1.
Table 1: Confidence assessment criteria for the UK Regional Sea WER rocky shore macroalgae indicator assessments.
|
UK Regional Sea confidence assessment criteria |
Low |
Medium |
High |
|
Spatial coverage of classification data
This criterion indicates the extent to which WER water bodies within a UK Regional Sea are classified by the indicator. High proportion of water bodies classified within a UK Regional Sea corresponds to high confidence in the UK MARINE STRATEGY assessment. |
<33.3% of WER water bodies assessed |
33.3% - 66.6% of water bodies assessed |
>66.6% of water bodies assessed |
|
Spatial coverage of pressures
This criterion provides a measure of the extent to which the classified WER water bodies correspond to the presence of relevant pressures (as determined through the WER risk assessments), indicating the potential of the WER classifications to detect the associated impacts of such pressures. High coverage of the areas exposed to pressure (i.e. those considered at risk of failing to achieve GES under WER) by the WER water body classifications corresponds to high confidence within the UK Regional Sea scale UK Marine Strategy assessment. |
<33.3% of At Risk/Probably At Risk WBs assessed |
33.3% - 66.6% of At Risk/Probably At Risk WBs assessed |
>66.6% of At Risk/Probably At Risk WBs assessed |
|
Indicator level agreement (Cohen's Kappa) between assessment results and pressure from Risk Assessments
Cohen’s Kappa agreement provides an indication of the extent to which the indicator WER classifications correspond to the risk assessments at the water body level. Agreement between water bodies categorised as ‘At Risk’ or ’Probably At Risk’ and those at less than Good Ecological Status is calculated using all water body data. High confidence in the UK MARINE STRATEGY assessments corresponds to high agreement between the indicator classifications and risk assessment results. Low correspondence may be indicative of either low sensitivity of the indicator to the pressure or indicative of a low correspondence between the risk assessment results and the true extent of the pressure (further investigation recommended). |
<0.333 |
0.333 - 0.666 |
>0.666 |
|
Variability of assessment results
This criterion is a measure of the variability of the different WER water body classifications within a UK Regional Sea scale UK Marine Strategy assessment. Low variability in the WER classifications corresponds with high confidence in the assessment. |
<66.6% of assessment units (surveys) within same WER status |
66.6% - 83.3% of assessment unit (surveys) at same status |
>83.3% of assessment units (surveys) at same status |
|
Proximity of observed extent to extent threshold
This criterion is a measure of the magnitude of the difference between the observed extent meeting the quality target and the extent threshold. Large differences between the observed extent meeting the quality target and the extent threshold corresponds to high confidence in the UK Regional Sea scale UK Marine Strategy assessment. |
Broad scale habitats: assessment within 5% of target |
Broad scale habitats: assessment within 5% - 10% of target |
Broad scale habitats: assessment >10% of target |
The overall confidence assessment is based on the lowest extent to which the criteria are fulfilled (one-out-all-out).
Deviations by WER Monitoring Authorities
Rocky Shore Macroalgae data was collected for use in the WER Cycle Three RBMP classifications by the Department of Agriculture, Environment and Rural Affairs (DAERA) of Northern Ireland and Natural Resources Wales (NRW) only. Both monitoring authorities applied the assessment methods as described within the UKTAG method statement.
Results
Results and progress towards achieving the relevant UK target
Latest findings
Status assessment
Assessments are based on aggregated coastal water body classifications derived for the 2021 Cycle Three UK RBMPs. The results of the aggregated rocky shore macroalgae indicator assessment for the UK Marine Strategy sub-regions and UK Regional Seas are presented in Table 2 and Figure 1.
Table 2: Proportion of intertidal rocky shore macroalgae surveys meeting the indicator quality threshold with corresponding assessment result and confidence for each UK Regional Sea and corresponding Marine Strategy sub-region summary.
| UK MS sub-region | Extent meeting quality threshold (EQR ≥ 0.6) | Extent threshold met (≥ 95%) | Assessment summary | Regional Sea | Extent meeting quality threshold (EQR ≥0.6) | Extent threshold met (≥ 95%) | Confidence |
| Greater North Sea | - | - | Unable to assess | 1. Northern North Sea* | No data | - | - |
| 2. Southern North Sea | No data | - | - | ||||
| 3. Eastern English Channel | No data | - | - | ||||
| Celtic Sea | 97.0 % | ✅ | Target met for the sub-region (low confidence). | 4. Western Channel and Celtic Seas | 100.0 % | ✅ | Low |
| 5. Irish Sea | 99.8% | ✅ | Low | ||||
| 6. Minches and Western Scotland | 100.0 % | ✅ | Low | ||||
| 7. Scottish Continental Shelf | No data | - | - | ||||
| 8. Atlantic North-West Approaches, Rockall Trough and Faeroe/Shetland Channel | Suitable habitat absent | - | - | ||||
| 9. Shared waters between N Ireland and Rep of Ireland | 100.0 % | ✅ | Low |
Figure 1: UK Regional Seas with corresponding assessment results indicating locations of coastal water bodies used for RBMP Cycle Three WER rocky shore macroalgae classifications with corresponding ecological status.
The proportion of survey results achieving the extent threshold has been met for the Celtic Sea Marine Strategy sub-region and all assessed constituent Regional Seas. Two Regional Seas within the sub-region have not been assessed due to either the absence of data or habitat required by the indicator. The Greater North Sea was not assessed due to the absence of WER RBMP Cycle Three classification data for all water bodies within the sub-region. In the Irish Sea, Minches and Western Scotland and Shared waters between N Ireland and Rep of Ireland, the quality threshold is met for all contributing water bodies. For the Irish Sea, three surveys failed to meet the quality threshold, however the proportion of surveys meeting the quality threshold remains above the extent threshold of 75%.
Low confidence has been assigned to all assessments, primarily due to low spatial coverage of the WER assessments and the low proportion of water bodies categorised as being ‘At Risk’ or ‘Probably At Risk’ from point source pollution sources within the WER Risk Assessments that were classified under WER. Agreement between the rocky shore macroalgae assessment results and risk assessment results is low, potentially indicating either a low correlation between the indicator to point source pollution pressures (either due to variability in the indicator or the criteria used for the risk assessments) or a discrepancy between the threshold required to trigger a water body being categorised as ‘At Risk’/‘Probably At Risk’ and the indicator quality target threshold.
Findings from the 2012 and 2018 UK assessments
This indicator was not considered within the 2012 UK Initial Assessment. The 2018 UK assessment concluded that targets covering the proportion of surveyed rocky shore macroalgae communities at an acceptable condition had been achieved in the Celtic Seas and Greater North Sea UK Marine Strategy sub-regions. Low confidence was assigned to the assessment results.
The detailed 2018 assessment is available via the UK Marine Monitoring & Assessment Strategy (UKMMAS) Marine Online Assessment Tool:
Trend assessment
The aggregated WER results were not considered as part of the 2012 Initial Assessment.
The absence of data for the Greater North Sea prevents a trend assessment for the sub-region. The result for the Celtic Sea sub-region rocky shore macroalgae assessment remains unchanged with the overall target being largely achieved in both the 2018 and current assessments. Assigned confidence remains low between the two assessments. Data availability has reduced, with the number of rocky shore macroalgae surveys decreasing from 313 (within 54 water bodies) in the 2018 assessments to 107 (within 21 water bodies) in the current assessments.
Further information
The assessment is based on aggregated results from the classifications derived for the UK Cycle Three RBMPs. The method is based on intertidal rocky shore macroalgae assemblages and considered responsive to contaminants from inshore activities.
The indicator determines the impact to the ecological quality of rocky shore macroalgae communities of intertidal habitats by combining measures of species diversity and proportions of opportunistic taxa. These measurements are compared to undisturbed reference conditions to calculate the Ecological Quality Ratio (EQR). These are calculated for each WER water body throughout a six-year period. The water body assessments indicate the average extent to which the water body deviates from reference conditions and relates this to the boundary between Moderate and Good Ecological Status (Ecological Quality Ratio ≥0.6 as set through WER intercalibration) to identify whether the water body has achieved the target of Good Ecological Status. The water body results are combined within each UK Regional Sea with the extent target being met where ≥75% (broad scale habitat threshold) of the surveys meets the quality target of Good or High Ecological Status or Good Ecological Potential.
A summary of the data used for each UK Marine Strategy sub-region and Regional Sea WER rocky shore macroalgae indicator assessment is provided in Table 3. Individual WER water body information with associated Third Cycle RBMP rocky shore macroalgae classification results is provided in Table 4.
Table 3: Summary of the data used for the UK Marine Strategy WER rocky shore macroalgae indicator Regional Sea assessments.
|
Regional Sea |
Regional Sea |
RS Total Area (sq km) |
RS Total WB area (sq km) |
Assessed WB Count |
Assessed WB Area (Km2) |
Assessed Area (% of total) |
Assessed HMWBs |
Assessed 'At Risk' WER WBs |
|
Celtic Sea |
4. Western Channel and Celtic Seas |
93,959.8 |
5,086.4 |
2 |
558.9 |
11 |
0 |
4 |
|
Celtic Sea |
5. Irish Sea |
38,647.4 |
10,014.0 |
13 |
1589.7 |
15.9 |
5 |
0 |
|
Celtic Sea |
6. Minches and Western Scotland |
30,548.8 |
24,817.0 |
3 |
266.9 |
1.1 |
0 |
0 |
|
Celtic Sea |
9. Shared waters between N Ireland and Rep of Ireland |
353.5 |
271.7 |
3 |
271.7 |
100 |
0 |
0 |
Table 4: Summary of WER water body pressure information and WER rocky shore macroalgae index classification results aggregated to the UK Regional Sea UK MARINE STRATEGY assessments.
|
Regional Sea |
Agency |
Water body name |
HMWB |
At Risk/Probably At Risk from Point Source Pollution pressure |
Number of surveys |
Water body EQR |
WER status |
|
4. Western Channel and Celtic Seas |
NRW |
Carmarthen Bay |
No |
No |
3 |
0.71 |
Good |
|
4. Western Channel and Celtic Seas |
NRW |
Milford Haven Outer |
No |
Yes |
4 |
0.75 |
Good |
|
5. Irish Sea |
DAERA |
Ards Peninsula |
- |
No |
6 |
0.84 |
High |
|
5. Irish Sea |
DAERA |
Belfast Harbour |
Yes |
No |
4 |
0.55 |
Moderate |
|
5. Irish Sea |
DAERA |
Belfast Lough Inner |
No |
No |
6 |
0.77 |
Good |
|
5. Irish Sea |
DAERA |
Belfast Lough Outer |
No |
No |
4 |
0.83 |
High |
|
5. Irish Sea |
DAERA |
Dundrum Bay Outer |
- |
No |
6 |
0.80 |
High |
|
5. Irish Sea |
DAERA |
Larne Lough Mid |
No |
No |
6 |
0.79 |
Good |
|
5. Irish Sea |
DAERA |
Maiden Islands |
No |
No |
1 |
0.76 |
Good |
|
5. Irish Sea |
DAERA |
North Channel |
No |
No |
7 |
0.85 |
High |
|
5. Irish Sea |
DAERA |
Strangford Lough North |
No |
No |
7 |
0.82 |
High |
|
5. Irish Sea |
DAERA |
Strangford Lough South |
No |
No |
6 |
0.83 |
High |
|
5. Irish Sea |
NRW |
Cardigan Bay Central |
No |
No |
2 |
0.82 |
High |
|
5. Irish Sea |
NRW |
Cardigan Bay North |
No |
No |
3 |
0.81 |
High |
|
5. Irish Sea |
NRW |
Holyhead Bay |
Yes |
No |
1 |
0.84 |
High |
|
6. Minches and Western Scotland |
DAERA |
North Coast |
No |
No |
6 |
0.84 |
High |
|
6. Minches and Western Scotland |
DAERA |
Portstewart Bay |
No |
No |
6 |
0.83 |
High |
|
6. Minches and Western Scotland |
DAERA |
Rathlin Island |
No |
No |
6 |
0.84 |
High |
|
9. Shared waters between N Ireland and Rep of Ireland |
DAERA |
Carlingford Lough |
No |
No |
6 |
0.79 |
Good |
|
9. Shared waters between N Ireland and Rep of Ireland |
DAERA |
Lough Foyle |
- |
No |
6 |
0.80 |
Good |
|
9. Shared waters between N Ireland and Rep of Ireland |
DAERA |
Mourne Coast |
No |
No |
5 |
0.82 |
High |
The Greater North Sea Marine Strategy sub-region has not been assessed. This is largely attributable to the cessation of WER rocky shore macroalgae data collection and classification for England and Scotland for RBMP Cycle Three. As a result, the number of Regional Sea assessments has reduced from seven in 2018 to four in the current assessment resulting in an absence of data to assess the Greater North Sea sub-region.
The UK WER risk assessments identified a total of 11% (52 of the 467 assessed) of coastal water bodies are ‘At Risk’ or ‘Probably At Risk’ of failing to meet their environmental objectives as a result of pressures categorised as point source pollution pressures.
Detailed assessment results for each Marine Strategy sub-region are presented for each of their component UK Regional Seas. Marine Strategy sub-regions comprise of their component UK Regional Seas as follows:
Greater North Sea Marine Strategy sub-region:
1. Northern North Sea
2. Southern North Sea
3. Eastern English Channel
Celtic Sea Marine Strategy sub-region:
4. Western Channel and Celtic Seas
5. Irish Sea
6. Minches and Western Scotland
7. Scottish Continental Shelf
8. Atlantic North-West Approaches, Rockall Trough and Faeroe/Shetland Channel
9. Shared waters between N Ireland and Rep of Ireland
Western Channel and Celtic Seas
The overall risk of the Western Channel and Celtic Seas failing to meet the target for rocky shore macroalgae can be considered as low. Both WER assessments within the Western Channel and Celtic Seas indicate that rocky shore macroalgae communities are above the indicator quality target, with all seven constituent surveys being classified as WER Good Ecological Status (Figure 2). The quality threshold has been achieved for 100% of the survey level assessments for the Western Channel and Celtic Seas, therefore meeting the 75% extent target for the Regional Sea.
Figure 2: Outline of the Western Channel and Celtic Seas Regional Sea inshore indicating rocky shore macroalgae UKMS assessment result and location and ecological status of the corresponding WER water bodies.
The corresponding risk assessments for the water bodies indicate one water bodies categorised as ‘At Risk’ or ‘Probably At Risk’ of failing to achieve the indicator quality target as a result of point source pollution pressures, with the remaining one water bodies being ‘Not At Risk’ or ‘Probably Not At Risk’ of failing. However, the Western Channel and Celtic Seas regional sea intersects with a total of 25 water bodies, with six water bodies considered 'At Risk' or ‘Probably At Risk' from point source pollution pressures which have not been assessed with the rocky shore macroalgae indicator.
When considering indicator quality targets for HMWBs (WER Good Ecological Potential), none of the water bodies assessed as below the indicator quality target are categorised as HMWBs, so meeting a target of WER GEP is not considered.
The overall confidence in the Western Channel and Celtic Seas regional sea rocky shore macroalgae assessment is categorised as low. This is based on the low spatial coverage of the assessment data (two out of 25 water bodies within the region), the low spatial coverage of 'At Risk' or 'Probably At Risk' water bodies in terms of point source pollution pressures (one out of seven water bodies within the region), the lack of agreement between the rocky shore macroalgae indicator and point source pollution pressures (Kappa agreement of -0.05), the close proximity of the assessment results to the indicator target."
Irish Sea
The overall risk of the Irish Sea failing to meet the target for rocky shore macroalgae can be considered as low. The majority (10 out of 11) of WER assessments within the Irish Sea indicate that rocky shore macroalgae communities are above the indicator quality target, with constituent surveys predominantly being at WER High Ecological Status (39 of the 53 surveys) with the remainder at WER Good Ecological Status (Figure 3). The quality threshold has been achieved for 94.91% of the survey level assessments for the Irish Sea, therefore meeting the 75% extent target for the Regional Sea.
Figure 3: Outline of the Irish Sea Regional Sea inshore indicating rocky shore macroalgae UK Marine Strategy assessment result and location and ecological status of the corresponding WER water bodies.
The risk assessments for the Irish Sea water bodies indicate that none of the water bodies assessed by the rocky shore macroalgae indicator are categorised as ‘At Risk’ or ‘Probably At Risk’ of failing to achieve the indicator quality target as a result of point source pollution pressures, with all ten water bodies being ‘Not At Risk’ or ‘Probably Not At Risk’ of failing. However, the Irish Sea regional sea intersects with a total of 66 water bodies, including 16 water bodies which are considered 'At Risk' from point source pollution pressures which have not been assessed with the rocky shore macroalgae indicator.
Belfast Harbour is categorised as a HMWB which has been assessed as being below the indicator quality target. This may need to be considered in terms of whether GEP has been achieved. However, the outcome of this would not affect the assessment in terms of the Irish Sea meeting the extent target.
The overall confidence in the Irish Sea regional sea rocky shore macroalgae assessment is categorised as low. This is based on the low spatial coverage of the assessment data (ten out of 66 water bodies within the region), the low spatial coverage of 'At Risk' or 'Probably At Risk' water bodies in terms of point source pollution pressures (none of the 16 water bodies within the region), the lack of agreement between the rocky shore macroalgae indicator and point source pollution pressures (Kappa agreement of -0.05) and the close proximity of the assessment results to the indicator target.
Minches and Western Scotland
The overall risk of the Minches and Western Scotland failing to meet the target for rocky shore macroalgae can be considered as low. Both WER assessments within the Minches and Western Scotland indicate that rocky shore macroalgae communities are above the indicator quality target, with constituent surveys predominantly being at WER High Ecological Status (16 of the 18 surveys) with the remainder at WER Good Ecological Status (Figure 4). The quality threshold has been achieved for 100% of the of the survey level assessments for the Minches and Western Scotland, therefore achieving the 75% extent target for the Regional Sea.
Figure 4: Outline of the Minches and Western Scotland Regional Sea inshore indicating rocky shore macroalgae UK Marine Strategy assessment result and location and ecological status of the corresponding WER water bodies.
The corresponding risk assessments for the water bodies indicate the absence of any water bodies categorised as ‘At Risk’ or ‘Probably At Risk’ of failing to achieve the indicator quality target as a result of point source pollution pressures, with the three water bodies used in the assessment being ‘Not At Risk’ or ‘’Probably Not At Risk’ of failing. The Minches and Western Scotland regional sea intersects with a total of 187 water bodies, with 12 water bodies considered 'At Risk' from point source pollution pressures that have not been assessed with the rocky shore macroalgae indicator.
None of the water bodies assessed as below the indicator quality target are categorised as HMWBs, so meeting a target of WER GEP is not considered.
The overall confidence in the Minches and Western Scotland regional sea rocky shore macroalgae assessment is categorised as low. This is based on the low spatial coverage of the assessment data (one out of 187 water bodies within the region), an absence of data for 'At Risk' or 'Probably At Risk' water bodies in terms of point source pollution pressures, the lack of agreement between the rocky shore macroalgae indicator and point source pollution pressures (Kappa agreement of zero) and the close proximity of the assessment results to the indicator target.
Shared waters between Northern Ireland and the Republic of Ireland
The overall risk of the Shared waters between Northern Ireland and the Republic of Ireland failing to meet the target for rocky shore macroalgae can be considered as low. All three WER assessments within the Shared waters between Northern Ireland and the Republic of Ireland indicate that rocky shore macroalgae communities are above the indicator quality target, with a close to even division between constituent surveys classified as WER Good Ecological Status (nine of the 17 surveys) and WER High Ecological Status (the remaining eight surveys) (Figure 5).
Figure 5: Outline of the Shared Waters between Northern Ireland and the Republic of Ireland Regional Sea inshore indicating rocky shore macroalgae UK Marine Strategy assessment result and location and ecological status of the corresponding WER water bodies.
The corresponding risk assessments for the water bodies indicate none as being categorised as ‘At Risk’ or ‘Probably At Risk’ of failing to achieve the indicator quality target as a result of point source pollution pressures, with the three classified water bodies being ‘Not At Risk’ or ‘’Probably Not At Risk’ of failing.
None of the water bodies assessed as below the indicator quality target are categorised as HMWBs, so meeting a target of WER GEP is not considered.
The overall confidence in the Shared waters between Northern Ireland and the Republic of Ireland UK Regional Sea rocky shore macroalgae assessment is categorised as low. This is based on the lack of agreement between the rocky shore macroalgae indicator and point source pollution pressures (Kappa agreement of -0.05).
Conclusions
The targets for intertidal rocky shore macroalgae communities have been met for the Celtic Seas sub-region although confidence in the assessment is low. The Greater North Seas sub-region cannot be assessed.
The pressures which impact the rocky shore macroalgae communities operate over small spatial scales with their effect being relatively localised. In all UK Regional Seas, the rocky shore macroalgal communities of almost all water bodies meet the quality threshold. The greatest reduction in rocky shore macroalgae quality is observed within the Irish Sea although the proportion of surveys meeting the quality target remains markedly above the extent threshold. The intertidal rocky shore macroalgae communities are unlikely to be impacted by hazardous substance, physical disturbance or nutrient enrichment pressures at a level to cause a reduction in environmental status within the inshore waters of the assessed UK Regional Seas. The results cannot provide directional trends in quality due to the low frequency of the data.
Broader spatial coverage of surveys and of ‘At Risk’ and ‘Probably At Risk’ water bodies from point source pollution pressures would be required for a more comprehensive evaluation of the level to which pressures may be impacting UK rocky shore macroalgae communities.
As the rocky shore macroalgae assessments are based on intertidal communities, conclusions drawn relating to the effects of pressures within each UK Regional Sea should therefore be limited to inshore pressures only.
The results may inform data collection and research requirements to improve confidence of future assessments.
Knowledge gaps
From the current results, it is not possible to provide a full assessment of the target for all UK inshore waters because of the following gaps:
-
The WER assessments represent a small proportion of the UK coastline with assessments provided for 16 out of 467 coastal water bodies.
-
Assessments are based on communities characterised using the Reduced Species List (RSL). Full Species List (FSL) data is recommended but has not been used for surveys underlying the current assessment.
-
The assessments use WER classification data only and exclude additional relevant data (e.g. UK Conservation Agency condition assessment data). Such information should be incorporated into future assessments.
-
It is recommended that the results of WER investigations are considered in future assessments.
References
Defra (2019). Marine Strategy Part One: UK Updated Assessment and Good Environmental Status. 23 October 2019. Accessed 10 July 2025. https://www.gov.uk/government/publications/marine-strategy-part-one-uk-updated-assessment-and-good-environmental-status.
JNCC (2019). The UK Approach to assessing Conservation Status for the 2019 Article 17 reporting under the EU Habitats Directive. Joint Nature Conservation Committee, Peterborough. October 2019. Available from JNCC: https://data.jncc.gov.uk/data/6420776d-2a25-4575-8b6f-1922a6a13806/Article17-UK-Approach-2019-A.pdf
Technical Group on Seabed Habitats and Seafloor Integrity (TG Seabed) (2023). Marine Strategy Framework Directive (MSFD) – Common Implementation Strategy: Setting of EU threshold values for extent of loss and adverse effects on seabed habitats. Recommendations from the Technical Group on Seabed Habitats and Seafloor Integrity (TG Seabed) (Deliverable under Task h of the TG Seabed work programme). European Commission, DG Environment. Seabed_D6C4_D6C5_Threshold_Values_Endorsed_2023.pdf
Authors
Graham Phillips1
1Environment Agency Assessment metadata
Assessment metadata
| Assessment Type | UK Marine Strategy Assessment Part 1 (2024) |
|---|---|
Benthic habitats | |
| Point of contact email | marinestrategy@defra.gov.uk |
| Metadata date | Tuesday, July 1, 2025 |
| Title | Condition of intertidal rocky shore macroalgae (seaweed) communities in coastal waters determined using Water Environment Regulations methods. |
| Resource abstract | |
| Linkage | Water Framework Directive Cycle 3 River Basin Management Plans: England: Northern Ireland: Scotland: Wales: |
| Conditions applying to access and use | © Crown copyright, licenced under the Open Government Licence (OGL). |
| Assessment Lineage | |
| Dataset metadata | Please contact marinestrategy@defra.gov.uk |
| Dataset DOI | Please contact marinestrategy@defra.gov.uk |
The Metadata are “data about the content, quality, condition, and other characteristics of data” (FGDC Content Standard for Digital Geospatial Metadata Workbook, Ver 2.0, May 1, 2000).
Metadata definitions
Assessment Lineage - description of data sets and method used to obtain the results of the assessment
Dataset – The datasets included in the assessment should be accessible, and reflect the exact copies or versions of the data used in the assessment. This means that if extracts from existing data were modified, filtered, or otherwise altered, then the modified data should be separately accessible, and described by metadata (acknowledging the originators of the raw data).
Dataset metadata – information on the data sources and characteristics of data sets used in the assessment (MEDIN and INSPIRE compliance).
Digital Object Identifier (DOI) – a persistent identifier to provide a link to a dataset (or other resource) on digital networks. Please note that persistent identifiers can be created/minted, even if a dataset is not directly available online.
Indicator assessment metadata – data and information about the content, quality, condition, and other characteristics of an indicator assessment.
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.