Pelagic Habitats Thematic Assessment

Measures to address the status of pelagic habitats

There are no OSPAR measures that directly address pelagic habitats. 

Climate change remains the most significant factor affecting the health of the plankton communities that form the pelagic habitat at the scale of the OSPAR Maritime Area, but the responses required to address the source of this issue lie outside of OSPAR’s competence. Other significant human activities and pressures include nutrient inputs and living resource extraction (fisheries). Addressing some of these activities and pressures is within the remit of OSPAR, the most significant being the input of nutrients at a more local scale.  Improving the state of pelagic habitats will require OSPAR to continue to strengthen cooperation with relevant competent organisations in order to strengthen ecosystem resilience to climate change and to safeguard the marine environment in line with the ambition set out in S11.O1 of NEAES 2030.

The section development has been supported by the collation of relevant measures: measures of relevance to pelagic habitats included in this section

Section Overview

This section describes the responses to minimise the effect of human activities and their resulting pressures or impacts on ecosystem services, and which aim to improve the state of pelagic habitats in the North-East Atlantic. These responses can include the development of policy, legislation, measures to manage or regulate specific human activities, or to mitigate impacts on ecosystem services.

Plankton provide an important range of provisioning and regulation for ecosystem services, see: Impact section. They act as a CO₂ sink, form the basis of most marine food webs, and support production of higher trophic levels such as shellfish, fish, seabirds, and marine mammals (Tweddle et al., 2018). Understanding the health, dynamics and spatial distribution of plankton is important for informing (a) how pelagic habitat is used by higher trophic levels, including highly mobile species, (b) climate-related changes in prey availability (Nedstrom et al., 2020), (c) how pelagic habitats support exploited or potentially exploitable living resources, and (d) how the potential impacts of human activities might affect the natural dynamics and patchiness of plankton communities. This improved understanding of the health and function of pelagic habitats provides an opportunity to make better use of information about primary productivity and phytoplankton stock and composition so as to inform ecosystem-based management responses (Tweddle et al., 2018) and is linked to the consideration of eutrophication, harmful algal blooms, change in hydrographic conditions as well as food webs and trophic guilds, including commercial species.

The primary focus of this section is the responses that have been adopted by the OSPAR Commission for implementing the Contracting Parties’ commitments under the OSPAR Convention and the strategic objectives of the NEAES. There are no OSPAR measures that directly target the plankton community. However, this section considers management measures relevant to the pelagic habitats created by plankton communities and which target specific human activities and pressures impacting their status, such as eutrophication. This section aims to describe the progress made in the implementation of these measures and whether they are working in terms of achieving the ambitions set out in the North-East Atlantic Environment Strategy 2030 (NEAES).  Efforts are made to set OSPAR’s responses in the wider policy context and to look at responses by other competent organisations, where these are pertinent to improving the status of pelagic habitats in the North-East Atlantic.  

NEAES 2030 includes objectives for conservation and management actions that will ensure ecosystem function and resilience, taking account of changing climatic conditions. The pelagic habitat is fundamental to achieving such ambitions and is specifically referred to in the following operational objectives:

S5.O4: By 2025 at the latest OSPAR will take appropriate actions to prevent or reduce pressures to enable the recovery of marine species and benthic and pelagic habitats in order to reach and maintain good environmental status as reflected in relevant OSPAR status assessments, with action by 2023 to halt the decline of marine birds.

S11.O1: By 2025 OSPAR will develop a coordinated management approach to strengthening ecosystem resilience, including to the consequences of climate change and ocean acidification. 

There are several linkages to other thematic assessments, including:

The reader is referred to the following feeder reports for additional information on some of the key human activities affecting pelagic habitats:

Measures adopted by OSPAR 

As noted, OSPAR has not adopted any measures specifically aimed at improving the status of the pelagic habitat, beyond measures to combat eutrophication. This section focuses on measures adopted by OSPAR which have consequences for pelagic systems.  

The implementation status of all OSPAR measures was reported on in 2021.

The OSPAR network of Marine Protected Areas (MPAs) and their role in supporting pelagic habitats

Within OSPAR, MPAs are understood as areas for which protective, conservation, restorative, or precautionary measures have been instituted for the purpose of protecting and conserving species, habitats, ecosystems or ecological processes of the marine environment (as defined in Recommendation 2003/3 implementing Annex V of the OSPAR Convention). In 2003, OSPAR adopted a Recommendation to establish an ecologically coherent and well managed network of MPAs; this was then amended in 2010. By 1 October 2021, the OSPAR network comprised 583 MPAs, eight of which were collectively designated in ABNJs. The network of MPAs has a total surface area of 1 468 053 km², covering 10,8% of the OSPAR Maritime Area and achieving the spatial coverage component of Aichi Biodiversity target 11 of the United Nations Convention on Biological Diversity (CBD) and Sustainable Development Goal 14, target 14.5, “to conserve at least 10 per cent of coastal and marine areas by 2020.” (See: Report and assessment of the status of the OSPAR network of Marine Protected Areas in 2021 )

MPAs as a response for pelagic habitats:

The use of MPAs as a management tool is considered relevant for plankton communities (Tweddle et al., 2018). There is evidence of co-location of primary productivity patchiness and the presence of highly mobile species, including top predators (Tweddle et al., 2018), and of intermediate trophic levels which include species of commercial interest (living resources). It is essential that effective marine management take account of where and how patchiness occurs by identifying areas of high primary productivity or where there are particular physical features, such as bathymetry, which drive increased productivity. This could inform the development of management measures, including MPAs, to protect target species as well as the intermediate trophic levels and plankton they rely on (Tweddle et al., 2018).

There are challenges associated with using MPAs as a response for pelagic habitats owing to the dynamic nature of plankton across time and space (Maxwell et al., 2014) and the fact that pelagic ecosystems spread across multiple governance scales and jurisdictional boundaries (Game et al., 2009). Nevertheless, MPAs often include pelagic habitats, such as frontal zones, which are known to be highly productive and provide important feeding areas for a wide variety of species, thereby enhancing biodiversity (Mousing et al., 2016).

Is the measure working?:

Pelagic habitats are not explicitly addressed within the OSPAR MPA Status Assessment.  However, the evidence supporting the designation of OSPAR MPAs in areas beyond national jurisdiction includes reference to the importance of plankton communities, especially in relation to key pelagic features such as fronts, high energy eddies and seamounts, which aggregate primary productivity and zooplankton, providing a temporally and spatially reliable foraging zone for higher trophic level predators including marine birds and mammals, fish, and turtles. Examples include the meandering subpolar front associated with the Charlie-Gibbs Fracture Zone (OSPAR, 2010) within the designations of the Charlie-Gibbs South MPA and the Charlie-Gibbs North High Seas MPA.

Other OSPAR measures responding to relevant human activities and pressures

Human-induced climate change:
There is a strong climate coupling with changes in pelagic habitats, bringing wide-scale impacts. The principal response to address human-induced climate change is being implemented by other competent bodies. See: Climate Change Thematic Assessment , Climate Change section.

Eutrophication from nutrient input
Input of nutrients - diffuse sources, point sources, atmospheric deposition [Substances, litter and energy]:
The input of nutrients leading to eutrophication can originate from a number of human activities: agriculture [cultivation of living resources]; industrial uses [urban and industrial uses] and waste treatment and disposal [urban and industrial uses]. 

The OSPAR response to eutrophication and subsequent implementation of measures adopted by the EU, the European Economic Area and other international forums, including the Urban Waste Water Treatment Directive (91/271/EEC), the Nitrates Directive (91/676/EEC), the Water Framework Directive (2000/60/EC) and the Marine Strategy Framework Directive (2008/56/EC), have had some effect in improving the eutrophication status of the OSPAR Maritime Area. However, there remain regional variations and local problem areas, particularly in areas sensitive to nutrient inputs, such as estuaries, fjords, and bights, and in areas affected by river plumes. The work to “Tackle eutrophication, through limiting inputs of nutrients and organic matter to levels that do not give rise to adverse effects on the marine environment” remains a strategic objective for OSPAR within NEAES 2030 (Strategic Objective 1). The operational objectives S1.O2 and S1.O3 on “determining maximum nutrient inputs” and “agreeing on nutrient reduction needs for each Contracting Party” are the most relevant. Another operational objective of the NEAES focuses on the application of nature-based solutions to safeguard the natural capacity of the ecosystem to sequester nutrients through the conservation and restoration of estuarine, coastal, and marine habitats (S1.O6).

Restructuring of seabed morphology, including dredging and depositing of materials [Physical restructuring of rivers, coastline or seabed (water management)]:  
Activities which involve dredging and dumping at sea are regulated by the OSPAR Convention. OSPAR Agreement 2014-06 establishes guidelines for the management of dredged material at sea and refers specifically to the need to include the water column and pelagic species in the consideration of potential deposit areas, as well as potential impacts on the water column, such as turbidity and sediment suspension. These impacts could affect plankton communities in shallow waters and / or species living at the bottom of the water column. A 2020 report showed that the 2014 Guidelines are fully implemented by most Contracting Parties and considered to be well regulated.

Extraction of minerals (rock, metal ores, gravel, sand, shell) [Extraction of non-living resources]:
This activity is likely to have a very localised effect on plankton communities. OSPAR Agreement 2003-15 on sand and gravel extraction requires Contracting Parties which are coastal states of the Maritime Area to take the ICES Guidelines for the Management of Marine Sediment Extraction into account within their procedures for licensing the extraction of marine sediments (including sand and gravel). The agreement does not specifically reference pelagic habitats, but clearly encourages an ecosystem-based approach to management of human activities. The agreement also recommends that necessary steps should be taken to avoid adverse impacts on ecosystem functioning. This could include subjecting plans for extraction of sediments to strategic environmental assessment, and placing controls on the extraction of sediments from any ecologically sensitive site. The ICES Guidelines are subject to a forthcoming review. (See: OSPAR Feeder Report 2021 – Extraction of non-living resources ).

Fish and shellfish harvesting (professional, recreational) [Extraction of living resources]: 
Article 4, Annex V of the OSPAR Convention sets out that no programme or measure concerning a question relating to the management of fisheries must be adopted under that Annex. However, where the Commission considers that action is desirable in relation to such a question, it must draw that question to the attention of the competent authority or international body. Where action within the competence of the Commission is desirable so as to complement or support action by those authorities or bodies, the Commission must endeavour to cooperate with them. 

Please refer to ‘Other important measures’ for more information about measures implemented to address fisheries.

Renewables:
Significant upscaling of offshore renewable infrastructure is expected by 2050 and is likely to have fundamental impacts on the physical functioning of the North Sea, including local wind patterns, wave generation, tidal amplitudes, stratification of the water column, the dynamics of suspended particles and bedload transport of sediment. These changes may have far-reaching consequences for the ecosystem, including primary production, food availability across trophic levels, and habitat suitability (Deltares, 2018). Modelling has shown that phytoplankton concentrations may be affected by the presence of offshore wind farms, but how, or if, these changes are significant in terms of CO2 fluxes or animal populations is currently unknown (Van der Molen, 2014). A recent study has also demonstrated the positive effect of offshore wind farms on the abundance of meroplankton (Floeter et al., 2017), while effects on holoplankton (including copepods) have not yet been reported.

OSPAR published Guidance on Environmental Considerations for Offshore Wind Farm Development in 2008. The guidance provides that the erection, operation, and removal of wind turbines should not be a hazard to the marine environment, including water quality or by disturbing hydrodynamic processes. However, it does not specifically address the potential impacts on primary production or disruption of plankton communities. Similarly, within the EU context, the European Commission Guidance document on wind energy developments and EU nature legislation, document (C/2020/7730), does not make specific reference to plankton or pelagic habitats but again refers to the need to be aware of changes to water quality arising from suspended sediment, hydrodynamic changes or the introduction of contaminants through the construction of offshore developments, which will be locally important for pelagic habitats. (See: OSPAR Feeder Report 2021 - Offshore Renewable Energy Generation ).

Other relevant activities

Aquaculture has been identified as a human activity that could have relevance to pelagic habitats, but on which OSPAR has not taken any specific measures.

Other important measures

Climate change measures

There is a strong climate coupling with changes in pelagic habitats. The significance for society lies in the potential negative impacts on ecosystem services provided by plankton, such as support for higher trophic levels including top predators and commercial species. The principal response is the Paris Agreement, adopted at the 21st Conference of the Parties to the United Nations Framework Convention on Climate Change (COP21) in Paris on 12 December 2015. This is a legally binding international treaty on climate change adopted by 196 Parties with the goal to limit global warming to well below 2˚C, and preferably to 1.5˚C, compared to pre-industrial levels. To achieve this long-term temperature goal, countries aim to reach global peaking of greenhouse gas emissions as soon as possible to achieve a climate-neutral world by mid-century. The outputs of the IPCC sixth climate assessment cycle indicate that at the current rate of progress, the world is not on track to meet the Paris Agreement targets and climate change action needs to be massively increased if we are to do so. (See: Climate Change Thematic Assessment , Climate Change section).

Conservation measures

The Marine Strategy Framework Directive 2008/56/EC aims to “achieve or maintain good environmental status in the marine environment”. It does not explicitly acknowledge the role of plankton in the provision of many ecosystem services such as regulating carbon and nutrient cycles and other biogeochemical cycles. However, plankton community composition is used as an indicator of biological diversity in relation to MSFD Descriptor 1: “Biological diversity is maintained. The quality and occurrence of habitats and the distribution and abundance of species are in line with prevailing physiographic, geographic, and climatic conditions” (Tweddle et al., 2018). Pelagic habitats are specifically addressed as a dedicated theme by criterion D1C6 of the Good Environment Status (GES) Decision under the MSFD: “The condition of the habitat type, including its biotic and abiotic structure and its functions (for example, its typical species composition and their relative abundance, absence of particularly sensitive or fragile species or species providing a key function, size structure of species), is not adversely affected due to anthropogenic pressures”. Criterion D1C6 must be assessed as the “extent of habitat adversely affected in square kilometres (km²) and as a proportion (percentage) of the total extent of the habitat type”. There are also links to Descriptor 4 (Food webs) “All elements of the marine food webs, to the extent that they are known, occur at normal abundance and diversity and levels capable of ensuring the long-term abundance of the species and the retention of their full reproductive capacity”.  It has not been possible to determine whether any measures have been undertaken specifically to address the status of pelagic habitats under the MSFD.

Directive 2014/89/EU, which establishes a framework for maritime spatial planning, includes a general reference to "healthy marine ecosystems and their multiple services, if integrated in planning decisions, can deliver substantial benefits in terms of food production, recreation and tourism, climate change mitigation and adaptation, shoreline dynamics control and disaster prevention." Action under this directive is considered to be important to the regulation of nutrient inputs. Information on plankton community dynamics (spatial and temporal) would be a very useful input to the Marine Spatial Planning (MSP) process (Tweddle et al., 2018).

Eutrophication from nutrient input

The Water Framework Directive 2000/60/EC (WFD) is currently the principal document covering the management of inland, transitional, and coastal waters in the EU. It requires Member States to take measures to prevent deterioration of the ecological and chemical status of waters, restore polluted waters, reduce pollution and cease or phase out inputs of hazardous substances. Its scope includes coastal waters one nautical mile out to sea and, for chemical status, out to twelve nautical miles. It also contains requirements for the monitoring and management of shellfish protected areas. The WFD is the key legislative instrument for tackling phosphorus pollution from agriculture (along with all causes of poor water quality). The Directive establishes a framework for sustainable water management through the development of River Basin Management Plans and Programmes of Measures, with the objective of preventing deterioration of the aquatic environment and achieving good status of all water bodies by 2015. The WFD considers phytoplankton parameters such as abundance and community composition in assessing Good Ecological Status (Tweddle et al., 2018), with indicators to measure these parameters still under development by Member States. 

Council Directive 91/271/EEC of 21 May 1991 concerning urban waste-water treatment (Phosphates Directive) and Council Directive 91/676/EEC concerning the protection of waters against pollution caused by nitrates from agricultural sources (Nitrates Directive) are also both important for the regulation of diffused land-based pollution into the marine environment. The Nitrates Directive (91/676/EEC) and the Urban Waste Water Treatment Directive (91/271/EEC) are credited with having reduced the nitrate and phosphate input into rivers, and consequently the coastal North Sea (McQuatters-Gollop et al., 2007). (See: Eutrophication Thematic Assessment ).

Fisheries

The removal of fish from the ecosystem through fishery activities can alter the balance of food webs, leading to a trophic cascade. For example, if fisheries target higher trophic levels, thereby reducing predation on intermediate trophic levels, this can result in an increase in abundance of these species, which in turn can overgraze zooplankton and increase the grazing pressure on phytoplankton, whose stocks then decrease. A trophic cascade can also be observed from the bottom-up, where changes in lower trophic levels, often induced by a disequilibrium in nutrients, including cases of eutrophication, can impact fish populations.

A response to the management of fishery activities is outside the mandate of OSPAR, as set out in section 2.2. Within the OSPAR Maritime Area, the principal response is made through the Common Fisheries Policy for those Contracting Parties that are EU Member States. For non-EU Member States this is achieved through the relevant national fisheries management legislation as well as measures taken at a regional scale by the regional fisheries management organisations. These include the North-East Atlantic Fisheries Commission, which is the mechanism for fisheries management in areas beyond national jurisdiction within the North-East Atlantic. The principal objective of such measures is the sustainable management of stocks and not the preservation of ecosystem health, despite the introduction of amendments to apply an ecosystem approach.

Regional differences

As noted previously in this section, there is no policy specifically focused on the management of plankton communities. However, there are some important responses which address the main pressures and drivers of change, such as the management of carbon emissions, nutrient inputs (including through the WFD, MSFD, UWWTD and Nitrates Directive) as well as fisheries management measures at the regional and national scales which can have a top-down impact on plankton. Many of the policies are applicable to EU waters, although some such as the WFD are limited to the coastal zone.  Fisheries management in non-EU Member States that are OSPAR Contracting Parties is also applied at the national level. 

The biggest driver of change for plankton communities at the OSPAR Maritime Area scale is climate. The actions to address these impacts are being taken at a global scale and will have wide-ranging impacts, including in the open ocean. 

So far, the assessment of pelagic habitats within the OSPAR Maritime Area has focused on the Greater North Sea (Region II), Celtic Seas (Region III), and the Bay of Biscay and Iberian Coast (Region IV).

Gaps and opportunities

Are we doing enough?:

The ability to assess the state of pelagic habitats and support decision making is advancing rapidly. There is a greater understanding of what a healthy, functioning or “good” pelagic system looks like (Dickey-Collas et al., 2017). Responses to achieve the climate change goal, reduce nutrient inputs and increase measures to achieve sustainable fisheries remain the most significant in terms of ensuring the health and dynamics of plankton communities. Other activities may only result in localised effects.  

Very few responses specifically address pelagic habitats. With the increasing success in being able to assess this ecosystem component there comes a need to better connect the loop between the ecological consequences and physical drivers of plankton production (Tweddle et al.,2018) as a part of the information being used to inform management responses.

Many of the physical processes affecting the patterns of primary production are able to produce predictable patches of plankton concentration. However, climate change is affecting this predictability and such changes, often occurring across multiple temporal and spatial scales, are important to take into account in the development and adaptation of marine management processes, so as to effectively and adaptably plan towards, and manage for, future conditions (Tweddle et al., 2018). Technological improvements in remote sensing and automated in situ data acquisition, at higher frequency than the classical monthly or fortnightly monitoring, will facilitate an improved understanding of important changes and impacts on the state of pelagic habitats. 

The movement of highly mobile species often takes place between predictable locations that are important for key life histories, such as feeding or breeding. There is, however, an increasing level of variability in the areas being used by these species, due to the impacts of climate change (Nedstrom et al., 2020). Predators will aggregate and spend more time in areas of high prey density and so, if there are changes in the composition, abundance or distribution of pelagic prey species, this will affect the important aggregation sites for highly mobile species and therefore the management of these areas. Climate-driven changes to organisms low in the food chain can propagate to higher levels. If these higher species have different reliance on the range of prey species available in the system, changes in relative abundance may occur. This is relevant to MPA designation and effective management.

Are there other types of responses that could be undertaken by OSPAR to improve the status of pelagic habitats?

For OSPAR the biggest opportunity is offered by the NEAES strategic objective to “tackle eutrophication, through limiting inputs of nutrients and organic matter to levels that do not give rise to adverse effects on the marine environment” (SO1). 
There may also be opportunities to: 

• Explore how to consider plankton communities that form pelagic habitats within the MPA status assessment;
• Include consideration of plankton community dynamics in EIA guidance; 
• Include consideration of plankton dynamics in the scaling-up of offshore renewable infrastructure;
• Include the trophic cascade concept within OSPAR’s work so as to be able to continue developing linkages across trophic levels (top-down and bottom-up), including between plankton health, food web function and derived ecosystem services;
• Quantify the effects of plankton change on ecosystem services and integrate into policy development (OSPAR Science Agenda/ OSA / Knowledge gap);
• Quantify the effects of pressures on plankton as natural capital and integrate into policy development (OSPAR Science Agenda/ OSA / Knowledge gap);
• Improve the frequency and spatial coverage of plankton observations by integrating both remote sensing products, but also automated in vivo/in situ approaches at high spatial and temporal resolution.