Condition of Benthic Habitat Communities: Assessment of Coastal Habitats in relation to Nutrient and/or Organic Enrichment

D1 - Biological Diversity

D5 - Eutrophication

D1.6 - Habitat condition

D5.3 - Indirect effects of nutrient enrichment

Key Message

This assessment indicated that 89% of the coastal water bodies in the OSPAR Maritime Area, for which European Union Water Framework Directive assessment data were provided, have benthic habitats in good status in relation to nutrient and / or organic enrichment and with regard to macroalgae and angiosperms and 74% with regard to benthic invertebrates. However, there were wide regional variations and some data gaps.

Area assessed

Printable Summary

PLEASE NOTE: THIS PAGE WAS UPDATED ON 4/04/2018 TO ALIGN DATA IN TEXT WITH FIGURES. THE RESULTS HAVE NOT CHANGED.

Background

Benthic habitats are essential for marine life, because many marine species rely directly or indirectly on the seafloor to feed, hide, rest or reproduce. Benthic habitats are characterised by animal and plant communities with no or slow mobility compared to fish or marine mammals (Figure 1). The whole benthic community is therefore exposed when a pressure occurs. As a result, the condition (quality status) of benthic habitats is a reflection of the combined effects of all the pressures to which they are subject.

OSPAR agreed that a common indicator for the condition of benthic habitat defining communities should be applied in the Greater North Sea, Celtic Seas and the Bay of Biscay and Iberian Coasts. It is recognised that the indicator should be based on a series of multimetric indices each assessing the impact of different pressures on different benthic habitat defining communities. No single metric for benthic habitats can achieve this given the diversity and complexity of benthic habitats and their communities.

This assessment considers the impact of nutrient and / or organic enrichment on some benthic habitats in coastal waters, where land-based and riverine inputs mean these pressures can be most pronounced. This assessment takes advantage of progress made in assessing benthic invertebrates and macroalgae through the implementation of the European Union Water Framework Directive (WFD). Data on these elements of the WFD status classification have been compiled to present this assessment.

Figure 1: Marine benthic invertebrates

Coastal waters represent the interface between land and ocean and are defined under the European Union Water Framework Directive (WFD) as extending one nautical mile from a baseline defined by the land points where territorial waters are measured. ‘Water bodies’ are defined by European Union Member States by sub-dividing these coastal waters according to their hydrological characteristics. Some coastal waters of OSPAR Contracting Parties have, to a varying degree, been affected by nutrient and / or organic enrichment (either as a direct or indirect effect of nutrient inputs or of organic enrichment) and this may be a cause of nuisance and toxic algal blooms, loss of benthic vegetation owing to shading, and modification of benthic fauna communities due to specific sensitivities.

The biological quality elements required for the integrated assessment of ecological status (European Union Water Framework Directive (WFD), Annex V) of coastal waters are phytoplankton, macroalgae, angiosperms and benthic fauna (Solheim et al., 2012).

The WFD requires that standardised methods are used for monitoring biological quality elements, and that the good status class boundaries for each biological quality element are intercalibrated across Member States sharing similar types of water body.

The WFD requires that the overall ecological status of a water body is determined by the results for the biological or physicochemical quality element, with the worst class determined by any of the biological quality elements. This is called the ‘one out - all out’ principle. The rationale for this is to avoid averaging the impacts on different quality elements due to different pressures and therefore overlook some significant pressures, and also to provide sufficient protection for the most sensitive quality element to a significant pressure.

By definition, the WFD aims to assess ‘water quality’ of water bodies through quality elements such as benthic invertebrates or macroflora. Benthic habitat communities are thus mainly assessed for the WFD to reflect the main pressures in the coastal zone, such as direct or indirect effects of nutrient and / or organic enrichment as a result of nutrients inputs from land-based sources and through riverine inputs. Contaminants are generally assessed in sediment. For these reasons, WFD monitoring was generally designed to focus on the effects of nutrient and / or organic enrichment. This does not mean that the indices used are not in themselves sensitive to other pressure types. Currently several statistical indices that are used, notably those including a species sensitivity classification, have been developed and calibrated to assess nutrient and / or organic enrichment. The European Union Marine Strategy Framework Directive (MSFD) requires a reconsideration and adaptation of monitoring, to take into account and assess other pressure types (both inshore and offshore).

Diversity indices and species richness indices, as well as sensitivity / tolerance species classification systems, have long been used to assess the qualitative state of benthic habitat communities. The development of Benthic Indices (BI), combining these indices and classifications, was made mandatory by the WFD. Species composition and relative abundance of the benthic habitat community are basic common metrics. Multi-metric BI classically contains diversity indices, species richness indices and / or the proportions of sensitive, tolerant and opportunistic species. Species sensitivity is a proxy used to quantify disturbance for some pressures on a benthic habitat community: either as a direct or indirect effect of nutrient or organic enrichment, oxygen depletion, sand extraction or hydrological changes. This requires a good knowledge (for the communities and species assessed) of natural spatial and temporal scales of variation and sensitivity to a specific pressure gradient.

Multi-dimensional deviation in community structure from a reference condition, aims to link pressure (for management issues) and pressure-impact calibration of indices (level of disturbance / resilience). This is set up with various pressures types at the community level, by combining biological and pressure data. Analysis of sensitivity is then elaborated at community level rather than species level. This is an important distinction and a point of attention for further development by experts and implementation for management issues (i.e. specific parameters / metrics to be monitored).

The results of the assessment of Biological Quality Elements ‘Benthic Invertebrates’ and ‘Macroalgae and Angiosperms’ in coastal waters were requested through a data call to national contacts. Most of the status reports are from the second assessment cycle of the WFD (2010–2015), although assessment results for Ireland and Wales date from the first cycle (2009). Information was also requested on the indices used and the monitoring stations in coastal water bodies. Information on the methodology of the various benthic indices (sampling strategy, data evaluation, reference conditions, detected pressures) was mainly derived from the WISER (Water Bodies in Europe - integrative systems to assess ecological status and recovery) methods database and intercalibration reports (Birk et al., 2010; van Hoey et al., 2015). Detailed assessment methods and intercalibration exercise are available from the European Commission.

Guidelines for specific monitoring and assessment methods are described in Annex 2 of the CEMP guidelines (OSPAR, in prep.).

Results

Figure 2 and Figure 3present the status (condition) of benthic invertebrates, macroalgae and angiosperms in response to nutrient and / or organic enrichment in coastal habitats of the Greater North Sea, Celtic Seas, Bay of Biscay and Iberian Coast and Norwegian parts of Arctic Waters. The condition assessments are based on the European Union WFD data and classification information.

Figure 2: Status (condition) of benthic invertebrates in intertidal and subtidal sediments, in response to the (direct or indirect) effects of nutrient and / or organic enrichment

Figure 3: Status (condition) of macroalgae on intertidal and subtidal rocks and angiosperms, in response to the (direct or indirect) effects of nutrient and / or organic enrichment

From a total of 2 934 WFD coastal water bodies in the Greater North Sea, Celtic Seas, Bay of Biscay and Iberian Coast, and Norwegian part of Arctic Waters, 777 (26.5%) have been classified for benthic invertebrates and 299 (10.2%) for macroalgae and angiosperms. Due to a mismatch between the identification of water bodies and assessment results, another 125 (4.3%) assessment results for invertebrates and 45 (1.5%) results for macroalgae and angiosperms could not be assigned to a water body and were not included in the assessment.

The status of benthic invertebrates is classified as good or high in most of the assessed areas (Figure 2). According to data provided, the WFD objectives of good or high status are achieved for benthic invertebrates in 90% or more of the assessed water bodies of France (95%), the United Kingdom (92%) and Spain (100%). In Sweden (3%) and Denmark (5%) only a small proportion of the assessed water bodies in the OSPAR Maritime Area achieved a good or high status for benthic invertebrates.

According to data provided, 89% of the assessed water bodies are classified as good or high status for macroalgae and angiosperms (Figure 3). There are major differences between OSPAR Contracting Parties. Spain (95%), Ireland (95%) and the United Kingdom (97%) possess the highest proportion of coastal water bodies with macroalgae and angiosperms in good or high status, whereas no Danish water bodies have benthic habitats of good or high status. There is a large degree of expert judgement in the Swedish assessment. Results for French water bodies exist and were provided, but not in the correct format. Denmark has not submitted all their existing data relevant for this indicator assessment, potentially causing an uncertain assessment result for the Danish waters.

The results provide only a partial view of the status of benthic invertebrates, macroalgae and angiosperms in response to nutrient and / or organic enrichment given the limitations in data coverage or availability. Trends in the condition of benthic habitat communities are not available, however with further WFD reporting these should be assessed in future.

There is medium confidence in the assessment methodology and medium confidence in the data availability.

National assessment outcomes, according to available data at the time of writing, are presented in Figure a to Figure p, together with the location of monitoring stations. Data for benthic invertebrates (sediment) were provided from nine of the 11 OSPAR Contracting Parties with coastal water bodies in the North-East Atlantic. The assessment results for macroalgae and angiosperms were available from seven Contracting Parties. For the Netherlands and Belgium this quality element is not relevant due to prevailing conditions. France provided data for the sub-components (macroalgae and angiosperms) of the macrophytes assessment from different assessment periods, but no aggregated classification of the water bodies for this quality element was available. The majority of the status reports are from the second assessment cycle of the European Union Water Framework Directive (WFD) (2010–2015). Assessment results from Ireland and Wales date from the first cycle (2009). Norway, a non-European Union Member State, has implemented a monitoring and assessment programme of coastal water bodies, which enables them to contribute to this assessment of condition of coastal benthic habitat communities.

No trends are available because data were only provided from one WFD reporting cycle. In the future it should be possible to compare data between reporting cycles.

Confidence Assessment

The assessment methodology has been applied over successive WFD cycles, however intercalibration of results between EU Member States is not totally solved and therefore it has moderate confidence. For the data there is generally good coverage, but with gaps in some areas, and there is large degree of expert judgment in the results of one country. Therefore there is also moderate confidence in the data.

Figure a: National marine invertebrates assessment (Denmark)

Figure b: National marine macroalgae and angiosperms assessment (Denmark)

Figure c: National marine invertebrates assessment (France)

Figure d: National marine benthic invertebrates assessment (Germany)

Figure e: National marine macroalgae and angiosperms assessment (Germany)

Figure f: National marine invertebrates assessment (Ireland)

Figure g: National marine macroalgae and angiosperms assessment (Ireland)

Figure h: National marine invertebrates assessment (Netherlands)

Figure i: National marine invertebrates assessment (Norway)

Figure j: National marine macroalgae and angiosperms assessment (Norway)

Figure k: National marine invertebrates assessment (Spain)

Figure l: National marine macroalgae and angiosperms assessment (Spain)

Figure m: National marine invertebrates assessment (Sweden)

Figure n: National marine macroalgae and angiosperms assessment (Sweden)

Figure o: National marine invertebrates assessment United Kingdom)

Figure p: National marine macroalgae and angiosperms assessment (United Kingdom)

Conclusion

This assessment has focused on the status of coastal habitats in relation to nutrient and / or organic enrichment as one component of a more comprehensive indicator of the condition of benthic habitat defining communities (Condition of Benthic Habitat Communities). The results indicate that 90% of water bodies in the OSPAR Maritime Area for which data were provided have benthic habitats classified as being of good status according to the European Union WFD. However, data are lacking for many water bodies and the results showed wide regional variations, with localised problem areas for nutrient and / or organic enrichment. 

Knowledge Gaps

For this OSPAR assessment of coastal benthic habitats in relation to nutrient and / or organic enrichment, use of the already implemented WFD monitoring and assessment programme is relevant, and improves coherence and dataflow. However, even with this already implemented regional scale monitoring programme, some issues with the coherence and availability of data where highlighted. Data flow and availability should be improved, including quality assurance and quality control for methods and results. This should be optimised to cover the needs of several reporting processes (WFD, OSPAR and MSFD), both at national and European Commission level.

Most OSPAR Contracting Parties undertake large-scale marine benthic monitoring, at least for the European Union Water Framework Directive (WFD). Finer scale networks of state-pressure relationship assessment areas are more heterogeneous and should be further investigated. Developing coordinated monitoring (or better still, joint monitoring) would be more cost-efficient and would ensure coherence and robustness for an assessment at (sub)regional scale.

Each country currently stores its own monitoring data, so common methodology (and tools) still needs to be developed. Development of data flow arrangements to access and analyse data, compute indicators, and compare / intercalibrate results, is still in progress for the WFD. The need for these steps should be anticipated and relevant work should be coordinated at a (sub)-regional scale to ensure coherence and facilitate the data flow for this specific assessment to be used for each reporting requirement (WFD, OSPAR and MSFD).

Owing to limitations in accessing European Union WFD assessment results and other data at the time this assessment was undertaken, no trends can be established. This indicator will therefore require further development before the next OSPAR assessment cycle as part of the overall indicator on Condition of benthic habitat defining communities.

Birk S., Strackbein J. & D. Hering, D. (2010): WISER methods database. Version: March 2011. Available at http://www.wiser.eu/results/method-database/

OSPAR (in prep) BH2 CEMP guidelines for all references of generic and specific (BH2-A and BH2-B) monitoring and assessment methods

Solheim, A.L., Peterlin, M., Kodeš, V., Spiteri, C., Collins, R.P., et al. (2012). Ecological and chemical status and pressures in European Waters – Thematic assessment for EEA Water 2012 Report. EEA/NSV/10/002. 146p.

Van Hoey G., Bonne W. & Salas Herrero F. (2015): Intercalibration report for benthic invertebrate fauna of the North East Atlantic Geographical intercalibration group for Coastal Waters. (NEA 1/26), ILVO MEDEDELING 191.