7. Preventing Pollution to Achieve Clean Seas

Achieving clean seas is a major ambition for the OSPAR Contracting Parties. This is a formidable challenge in the heavily-used North-East Atlantic, since pollution comes in many forms and from a multitude of sources. OSPAR assesses major groups of pollutants, including nutrient pollution leading to eutrophication, hazardous substances, radioactive substances, marine litter, marine noise and non-indigenous species (NIS) introduction (a form of biological pollution).

Pollutant monitored by OSPAR Contracting Parties with link to data sources, including links to several externally managed datastreams

Heavy Metal concentrations in Biota and Sediment    PAHs in Biota and Sediment

PCBs in Biota and Sediment   PBDEs in Biota and Sediment

TBT in Biota and Sediment   Mercury losses from the Chlor-alkali Industry*

Inputs of Heavy Metals    Inputs of Nutrients   Noise

Litter Ingested by Sea Turtles   Marine Litter Beach Monitoring

Plastic Particles in the Stomachs of Seabirds   Seabed Litter

Dumping and Placement of Wastes or Other Matter at Sea (Dredged Material)

Liquid Discharges from Nuclear Installations   Discharges of Radionuclides from the Non-Nuclear Sectors

Environmental Concentrations of Radioactive Substances

Discharges, Spills and Emissions from Offshore Oil and Gas Installations

*Monitoring ceased in 2019 when all mercury cell chlor-alkali plants in the OSPAR Maritime Area were phased out as a result of its Contracting Parties fully implementing PARCOM Decision 90/3 on reducing atmospheric emissions from existing chlor-alkali plants.

OSPAR Contracting Parties have made tangible progress in reducing all forms of pollution, but progress is variable across pollutants and regions. The reduction of all forms of pollution to achieve clean seas is a core OSPAR strategic objective and provided the initial impetus for creating the original Oslo and Paris Conventions which preceded the OSPAR Convention (1992) [About | OSPAR Commission]. However, while progress on this front has been made since the last assessment (the QSR 2010) and is quantified in the QSR 2023, much work remains before the goal of achieving clean seas is reached.

Different classes of pollution are assessed individually. For oil and gas activities, the QSR 2023 details the significant progress made in the industry to limit pollution, resulting in decreased discharges and emissions and a subsequent reduction in levels of contamination ( Offshore Industry Thematic Assessment ). A risk-based approach to the management of produced water discharges, the main source of crude oil contamination in the sea, has also been introduced to complement the OSPAR harmonised mandatory control system for offshore chemicals and promote the shift towards the use of less hazardous substances ( Offshore Industry Thematic Assessment ). Likewise, Contracting Parties have made significant progress towards fulfilling OSPAR’s aim of achieving concentrations in the environment near-background values for naturally occurring radioactive substances and close to zero for artificial radioactive substances ( Radioactive Substances Committee Thematic Assessment ). In the future, OSPAR will focus on gaining a better understanding of the cumulative effects of different pressures and the linkages between climate change and radioactive substances in the OSPAR Maritime Area.

Pollution of the OSPAR Maritime Area by a wide range of hazardous substances, excessive nutrients (leading to eutrophication) and marine litter has not been fully addressed. However, reductions have been seen in discharges of hazardous substances from the oil and gas sector and of radioactive substances from the nuclear sector. The QSR 2023 highlights that concentrations of many of the most serious hazardous substances, such as PCBs, PAHs and organochlorine insecticides, have decreased substantially compared with the 1980s and 1990s ( Hazardous Substances Thematic Assessment ). The 2008 ban on Tributyltin (TBT) in antifouling paints has similarly led to declining TBT levels in coastal areas. However, most OSPAR sub-regions (ten out of 12) in the OSPAR Maritime Area have a poor status for hazardous substances in marine indicator species, caused mainly by mercury and PCB 118. Nevertheless, concentrations of mercury are below European Commission maximum levels in foodstuffs in most areas, while for PCB 118 no maximum levels have been adopted by the European Commission. Moreover, current trends indicate that only one of the sub-regions may improve substantially during the next 10-20 years. The lack of progress towards the goal of ceasing pollution by hazardous substances is in part due to the re-release or bioaccumulation of long-lived compounds, meaning that many of these substances are legacy pollutants. For hazardous substances in sediment, the situation is somewhat better, as several OSPAR sub-regions are in good status.

The OSPAR Contracting Parties have significantly reduced the nutrients reaching the marine environment, particularly from agricultural sources, wastewater, and industrial and atmospheric sources. This has led to improvements in the most affected OSPAR Regions; however, eutrophication persists in river plumes and in some coastal areas, and increasing nutrient inputs in Arctic Waters are giving rise to concern ( Eutrophication Thematic Assessment ). The picture for marine litter is similarly mixed: the amounts of marine litter in the OSPAR Maritime Area remain high although there have been decreases ( Marine Litter Thematic Assessment ). Macroplastic litter on beaches in most OSPAR Regions has declined and there has been a decrease in floating litter in some, but seafloor litter is widespread, with fisheries-related and plastic materials predominating.

Drivers of pollution

Food production systems are a major driver of marine pollution. Agriculture accounts for the greatest land use in the majority of OSPAR countries and can affect marine systems by nutrient run-off (nitrogen and phosphorus) into the marine environment, causing eutrophication ( Human Activities Thematic Assessment ). Inputs of other substances (e.g. synthetic and non-synthetic substances, medicines) come from diffuse sources, point sources, atmospheric deposition, and acute events. Pesticides are routinely used in agriculture across OSPAR countries and are occasionally detected in aquatic systems as a result of run-off, particularly from arable land. While regulatory procedures are in place to govern pesticide use, and there have been successes in taking certain substances off the market, some concerns remain, since studies have indicated the potential negative effects of pesticides on marine ecosystems. Marine food production - fisheries and aquaculture - also contributes to pollution pressures ( Human Activities Thematic Assessment ). Aquaculture can release nutrients, litter and hazardous substances and could contribute to the accidental release of non-indigenous species or genotypes. Fisheries contribute diesel or other fuel emissions, fish processing waste, packaging waste and lost fishing gear. All food production systems can contribute to the input of litter and contaminants, especially plastics and microplastics, not only from production but also through processing and trade ( Marine Litter Thematic Assessment) . 

Energy development continues to drive activities and their pressures. The oil and gas sector contributes to pollution pressures, though this has followed a downward trend ( Offshore Industry Thematic Assessment) . Hydrocarbon production in the OSPAR Maritime Area decreased by 28% from 2009 to 2019, though it increased from 2014 to 2016 before levelling off. There has been a decline in drilling activity in Ireland, the Netherlands and Denmark, while activity in Norway and the United Kingdom has remained relatively stable over the period. Pressure from offshore oil and gas activities is greatest in the Greater North Sea Region, followed by the Arctic Waters and Celtic Seas Regions. The declining trend in production is expected to continue and, as older installations reach their end-of-life stage, increased decommissioning activity is anticipated over the coming decade.

Shipping and tourism meet society’s need for trade, commerce, and recreation, and also contribute to marine pollution. Both of these sectors are growing in some parts of the OSPAR Maritime Area ( Human Activities Thematic Assessment )). The loss of sea ice in Arctic waters is likely to trigger expanded use of this relatively unpolluted region, particularly by shipping as new sea routes across the pole become available. Given the sensitivities of many polar marine ecosystems and the compounding effect of climate change in the region, there may be need to expand the monitoring of pollution effects, including those from the offshore renewable energy subsector.

Finally, the production, use and disposal of plastics affect the cleanliness of the North-East Atlantic, and this driver impacts the extent to which the OSPAR Contracting Parties can reduce marine litter. Plastics production in Europe and demand from converters (manufacturers of plastic products) rose slightly between 2010 and 2019, which contrasts somewhat with the increased attention being paid to litter generally and the expanding regulations on waste management. To ensure that rates of marine litter decline even as plastics production and use grow, OSPAR’s 2014 Regional Action Plan for Marine Litter (RAP ML) included commitments to highlight waste prevention and management practices that impact significantly on marine litter; to encourage the recyclability and reuse of plastic products; to assess instruments for reducing single-use items; and to reduce inputs of microplastics. OSPAR will continue to address sea-based and land-based sources of litter through its new Regional Action Plan for Marine Litter (RAP ML 2) adopted in 2022.

Pollution pressures affecting the OSPAR Maritime Area

Nutrients and eutrophication

Eutrophication is the result of excessive nutrients reaching aquatic environments, leading to increased growth of algae (phytoplankton), macroalgae and plants, changes in the natural balance of the ecosystem and its biogeochemistry, and degradation of water quality. The decomposition of algal and plant material by microbes promotes increased oxygen consumption in bottom waters, which can lead to hypoxia (a reduction of oxygen in the water) and subsequent deterioration of marine habitats and loss of biodiversity, as well as reductions in the quality and quantity of many ecosystem services.

OSPAR’s Strategic Objective for eutrophication is to limit inputs of nutrients and organic matter to levels that do not give rise to adverse effects on the marine environment ( Eutrophication Thematic Assessment ). Nutrient inputs to the environment result from agricultural run-off, atmospheric emissions, and direct discharges related to industrial uses and municipal wastewater treatment. Atmospheric emissions from combustion relating to shipping and industrial sources and its subsequent deposition provide another route for nutrient input. Aquaculture releases nutrients through faecal matter and uneaten feed. Dredging of the seabed can also release nutrients into the water column.

In combating human-induced eutrophication, the Eutrophication Strategy 2010-2020 built on the commitment of Contracting Parties to achieve a substantial reduction at source. The threshold for reduction of phosphorus and nitrogen inputs is of the order of 50% compared with 1985, and is applied in ‘problem areas’ where these inputs are likely, directly or indirectly, to cause pollution. To assist Contracting Parties in identifying these areas consistently, OSPAR has developed a common assessment framework (the Common Procedure), which has been regularly updated. The assessment of eutrophication for the QSR 2023 differs from earlier reports in its improved levels of coherence and harmonisation. 

Regarding atmospheric emissions, fossil fuel combustion is a major source of oxidized nitrogen, which is then transformed in the atmosphere into nitric acid and then “rained out” as nitrate. Atmospheric inputs of nitrogen contribute about 40% of the total nitrogen entering the OSPAR Convention area ( Waterborne and Atmospheric Inputs of Nutrients and Metals Other Assessment ). Direct emissions from livestock are a major source of ammonia, which, through rapid and efficient atmospheric transport, can reach the open ocean within days, much faster and more effectively than through fluvial inputs.

The last four assessments have described a steady improvement in the eutrophication status of three OSPAR Regions (Greater North Sea, Celtic Seas and Bay of Biscay and Iberian Coast). The first assessment covering the period 1990 – 2000 was characterised by poor conditions in much of the North Sea ( QSR 2000 ). This latest assessment (QSR 2023) shows areas of moderate status outside the Loire and Seine estuaries, along the Dutch and German coasts, in the eastern North Sea and in the deep Kattegat, while poor conditions occur in the Coastal Kattegat and Elbe plumes and no areas are considered to be bad. This improvement can be explained by the trends in nutrient inputs. Wastewater treatment and industrial point sources have reduced their discharges of both nitrogen and phosphorus. Riverine inputs of phosphorus have decreased significantly, as have atmospheric nitrogen inputs. Waterborne nitrogen inputs have not decreased as much. Those to the Arctic, mostly from fish farming, have increased substantially, but the lack of data and threshold levels did not allow an assessment of eutrophication for the Arctic Waters Region during the QSR 2023.

Figure 7.1: Eutrophication assessment results for all assessment periods of COMP1 (1990-2000), COMP2 (2001-2006), COMP3 (2006-2014) and COMP4 (2015-2020) covering a time span of 30 years

The most dramatic improvements have come in atmospheric nitrogen inputs and in the reduction in fertiliser use since 1990. Atmospheric nitrogen deposition, which spreads far from coasts, lands directly on the productive surface waters and is completely bio-available, accounts for about one third to a half of the nitrogen input to the Greater North Sea, Celtic Seas and Bay of Biscay and Iberian Coast Regions. In the Arctic Waters Region the atmospheric component is about 75% of total nitrogen input; this has been reduced as a result of applying and reviewing the Gothenburg Protocol of the Convention on Long Range Transboundary Air Pollution and incorporating those targets in legally binding EU directives and national legislation ( Eutrophication Thematic Assessment ). The transition to less combustion in power generation, transport, heating and cooking has enabled emissions targets to be met and has reduced nitrogen inputs to the sea in this Region.

Figure 7.2: Time series of oxidised (blue) and reduced (orange) nitrogen deposition to all OSPAR Regions, showing small reductions in reduced nitrogen (ammonium) deposition compared with oxidised nitrogen (from Gauss et al., 2020)

A striking finding in the QSR 2023 has been the magnitude of the growth in aquaculture within the OSPAR area. Figures available for aquaculture production in the North-East Atlantic show that it increased from approximately 1,5 Mt in 2008 to approximately 2,2 Mt in 2018 (approximately 1,68 Mt of which was finfish, and 0,54 Mt molluscs). More than 1,35 Mt of 2018 production (worth over €6,7 billion in 2018) was in Norway, and mainly salmon, which is the largest single component of global trade in fish and fish products, driven by demand in developed and developing markets. The United Kingdom and the Faroe Islands were the next largest salmon producers ( Human Activities Thematic Assessment ). Reported inputs from aquaculture have increased significantly since 1990 ( Waterborne and Atmospheric Inputs of Nutrients and Metals Other Assessment ).

Aquaculture is now the primary source of direct nutrient inputs to the OSPAR area, contributing approximately as much nitrogen as industry and wastewater treatment combined. The phosphorus inputs from aquaculture exceed those from all other point sources. As a result of the growth of aquaculture, there was no decrease in total direct discharges of nitrogen to the OSPAR Maritime Area between 1990 and 2019 while phosphorus inputs have only decreased by approximately one sixth, despite industrial and wastewater inputs having together decreased by two thirds since 1990. It should be noted that the inputs from aquaculture are suspected to be underestimated, as not all Contracting Parties have reported aquaculture inputs from all their territories and aquaculture is expanding into previously unaffected areas where excessive nutrients may cause significant ecological impacts.

In summary, while the extent of eutrophication in the OSPAR Maritime Area has continued to decrease since 1990, it still occurs within the OSPAR Maritime Area. The Arctic was the only region to show significant increases in waterborne nutrients, owing to a growing aquaculture industry. However, since the eutrophication assessment did not cover Arctic Waters for technical reasons, it cannot be determined whether the substantial increase in nutrient inputs is causing eutrophication. In other OSPAR Regions, eutrophication is still in evidence, particularly in some sensitive areas including the south-east coast of the Greater North Sea and localised areas of the Celtic Seas.

Hazardous substances

Many different hazardous substances are released into the environment through industrial and other human activities; these substances can cause localised pressures but also contribute to the global pollutant load. OSPAR investigates hazardous substance inputs and effects on marine ecosystems, with a focus on toxic heavy metals (arsenic, cadmium, chromium, copper, lead, mercury, nickel, and zinc); organotins such as tributyltin (TBT) and persistent organic pollutants like PBDE, PAH, PCB and PFAS. Known hazardous substances enter the OSPAR Maritime Area through a number of human activities including watercourse modifications (resuspension of contaminated sediments), dumping of dredged sediments, mineral extraction, oil and gas extraction, fishing and fish and shellfish processing, aquaculture, shipping (including atmospheric pollution and discharges into seawater), air transport, land transport, urbanisation, industrial discharges, desalination, and waste treatment and disposal. The pathways thus include discharge at sea, riverine inputs, run-off from land and atmospheric deposition.

Human activities collectively contribute to the presence of hazardous substances in seawater, sediments and biota. Contaminants cause declines in water quality with associated losses to society (decreased ecological and economic value of marine resources and the livelihoods dependent on them, decline in aesthetic values, impacts on (eco)tourism, among other effects). The cumulative effects of contaminants in marine organisms can lead to behavioural changes, reduced species fitness, reduced breeding success and mortality. These effects in turn impact food web structure, causing declines in provisioning and regulating services and further declines in human wellbeing.

In most cases, the trends for assessed hazardous organic substances are downward, and most OSPAR Regions are also seeing a decline in heavy metal pollution. In some hotspot locations, concentrations in fish have decreased by a factor of 1 000 since the 1970s. In the last two decades the downward trends have been smaller than in former decades, when decreases were driven by the elimination of large industrial point sources of contamination. Most metals follow the same pattern, but in the more populated OSPAR Regions (Greater North Sea and the eastern parts of Celtic Seas and Bay of Biscay and Iberian Coast) upward trends are seen in some places for selected substances like mercury. Some areas are showing wide-ranging increases in the trends for substances in biota, or in the overall trend of pollution status (e.g. Southern North Sea). No downward trends have been seen in the Northern North Sea, the English Channel or the Northern Bay of Biscay, where ‘not good’ status persists. The state of the environment with regard to hazardous substances is poor in regions with high population and industry levels, particularly due to mercury and PCB ( Pilot Assessment of Status and Trends of Persistent Chemicals in Marine Mammals ).

The OSPAR objective to continuously reduce discharges, emissions and losses has been partially achieved. The bans on use and conventions restricting the use of certain metals (Minamata Convention on mercury) and organic persistent pollutants (Stockholm Convention), together with OSPAR initiatives and guidelines and both EU and national regulations of hazardous substances have all contributed to declines in hazardous substances, though not uniformly across the OSPAR Maritime Area. OSPAR has thus moved towards but not achieved the 2020 cessation target. The objectives have been partly fulfilled for many legacy contaminants, such as PCBs and PBDEs, with many time series showing downward trends and few showing upward trends. While concentrations of hazardous substances in the environment are declining, the retained concentrations within mammal populations remain very high. However, analyses show that inputs of mercury from air and rivers are decreasing, which is also reflected by the decreasing mercury concentrations found in sediment, but not in fish and shellfish, for which the majority of trends are upward ( Waterborne and Atmospheric Inputs of Nutrients and Metals Other Assessment ).

Pressures from Oil and Gas

The oil and gas sector is one of the largest industrial users of the marine environment in the OSPAR Maritime Area and can contribute to pollution pressure through routine operations as well as oil spills. Studies undertaken by OSPAR Contracting Parties looking at a wide range of potential pressures from oil and gas activities, including those from historical cuttings piles, and discharges of produced water, drilling fluids and chemicals, show that there has been a decrease in emissions and discharges. Impacts that were once widespread, for example from the discharge of untreated oil-based cuttings, have now ceased and the level of contamination has decreased over most of the OSPAR area. Where potential impacts might still occur, they have been reduced, examples being the amount of dispersed oil discharged in produced water, the phase-out of the discharge of added chemicals identified for priority action (OSPAR List of Chemicals for Priority Action) and the reduction in discharges of hazardous offshore chemicals.

Pressures from the oil and gas sector can potentially impact the marine ecosystem in several ways. Discharges of produced water and chemicals could expose fish and other pelagic organisms to contaminants, the construction of pipelines and installations, discharge of cuttings and disturbance of cuttings piles can have a localised and temporary negative effect on benthic organisms, the noise from seismic surveys can potentially harm fish and marine mammals, and platform lighting and flaring can affect migrating birds.

The QSR 2023 reports that a 16% reduction since 2009 in dispersed oil discharged in produced water has been achieved through the application of the standards set out in OSPAR Recommendation 2001/1 for the Management of Produced Water from Offshore Installations, as amended. There has been a decrease in the number of installations exceeding the agreed limits for dispersed oil in produced water discharged to sea. The phasing-out of the discharge of added chemicals identified for priority action, and the almost 50% reduction in the use and discharge of substances carrying substitution warnings were both achieved thanks to OSPAR recommendations setting environmental goals for discharges by the offshore industry. Much of the progress has been made as a result of a risk-based approach to managing produced water discharges including naturally occurring substances. The risk-based approach was introduced to complement the OSPAR harmonised mandatory control system for offshore chemicals and promote the shift towards the use of less hazardous substances. To date, 54% of installations have been assessed as having their discharges under adequate control, 39% require further action to be taken and the remainder are still under assessment.

The Contracting Parties have agreed to prohibit the dumping of disused offshore installations in the OSPAR Maritime Area, in accordance with OSPAR Decision 98/3 on the Disposal of Disused Offshore Installations. Since 1998, approximately 170 installations have been decommissioned and 10 installations granted derogations under OSPAR Decision 98/3, meaning that under defined conditions, certain categories of installations can be wholly or partly left in place on the seabed.

Figure 7.4: OSPAR 2019 Inventory of Offshore Installations; details of the location and status of Offshore Installations within the OSPAR maritime area, together with the water depth, operator, installation type and weight. Available at: ODIMS

Radioactive Substances

Society’s need for energy, industrial processes, health and wellbeing and national security have resulted in past and present human activities that introduced radionuclides to the marine environment. Activities linked to the production of energy (nuclear sector) have led to discharges of artificial radionuclides, while oil and gas extraction has resulted in the discharge of naturally occurring radionuclides. Industrial uses, research, survey and educational activities and medical uses have also produced discharges of radionuclides. Military activities such as atmospheric nuclear weapons testing and other sources such as the Chernobyl accident have contributed further inputs of radionuclides to the marine environment.

Radioactive substances can be harmful and are of high public concern. They are harmful because they can cause genetic, reproductive, cancerous as well as acute effects in living organisms (radiological impacts) and therefore have the potential to negatively affect marine organisms at the level of populations and to impact human health through, for example, seafood consumption. Radioactive substances can be transported far away from discharge points, and in some cases marine biota have the ability to accumulate levels of radionuclides to a relatively high degree, even if environmental concentrations in seawater are low. Economic and societal impacts can occur even if concentrations remain below levels known to cause radiological impacts, for example the reluctance to use coastal areas and amenities for fear of exposure to levels of radioactive substances.

OSPAR assessments show clear evidence of progressive and substantial reductions in discharges of radionuclides from the nuclear sector. Environmental concentrations of indicator radionuclides for the nuclear sector are close to or lower than historical levels. Discharges from the non-nuclear oil and gas sub-sector have mostly remained unchanged or have slightly declined; where discharges of produced water do occur, this is primarily where the option of re-injection is not possible. Neither the environmental concentrations from the nuclear sector nor modelled additional concentrations of naturally occurring radionuclides resulting from discharges of produced water from the oil and gas sub-sector are expected to result in any radiological impact to humans or the marine environment. The assessments carried out in the Fifth Periodic Evaluation show that Contracting Parties have successfully fulfilled the objectives of the Radioactive Substances Strategy for 2020 and have made significant progress towards fulfilling the ultimate aim of concentrations in the environment near background values for naturally occurring radioactive substances and close to zero for artificial radioactive substances.

Figure 7.5: Comparison of mean total alpha and total beta (excluding tritium) discharges for the baseline period 1995-2001 (black columns) and assessment period 2012-2018 (grey columns) for the different nuclear sub-sectors

Marine Litter

Marine litter (including microplastics) occurs throughout the OSPAR Maritime Area and is known to cause significant ecological impacts. The known adverse effects on marine animals are: ingestion of plastic particles either via filter feeding, suspension feeding, and consumption of prey exposed to microplastics or through direct ingestion in mistake for food, causing blockages and damage to the digestive tract; entanglement, especially with filamentous litter items (such as loops, packaging bands or net-like structures, e.g. from derelict fishing gear); smothering of benthic habitats; and generation of artificial hard substrate. Furthermore, floating litter may act as a vector for contaminants and biota, including microbes and non-indigenous species which can change or modify species assemblages.

The main direct sea-based sources of litter are fishing, aquaculture, shipping, and recreational boating. In addition, marine litter originates from offshore infrastructure (for example in the oil and gas industry). The major direct and indirect land-based sources of marine litter include poor waste management practices, general littering, untreated sewage, run-off and storm water discharges, sewage sludge applied to soils, land-based industry and construction, tourism and recreation, inland shipping, and agriculture, with rivers acting as significant pathways for marine litter to enter coastal waters. A rudimentary estimate of the total macro litter exported by six rivers (the Seine, Rhine, Meuse, Ems, Weser and Thames) to the Greater North Sea area (Region II) is 10,5 – 220,6 tonnes per year, most of it plastics.

OSPAR has been tracking marine litter in three different ways: 1) by assessing quantities and qualities of litter washed ashore or deposited on beaches; 2) by monitoring litter on the seabed to investigate spatial and temporal trends; and 3) by analysing floating litter using two indicator species that commonly ingest it: fulmars and loggerhead sea turtles. Overall, marine litter levels are still high and further efforts are needed. There is a predominance of plastics among the marine litter reported across all OSPAR Regions. Moreover, microplastics have been reported in sediments, surface waters, the water column and in biota in the OSPAR Maritime Area at different concentrations. Seafloor indicator assessments show increasing litter on the seabed in the Greater North Sea.

Single-use plastics and maritime-related litter are frequently found among beach litter items throughout the OSPAR Maritime Area, with some important regional differences. Nonetheless, there are some positive signs: a decrease in the quantities of litter found on OSPAR beaches between 2015-2020 and in the floating litter in the North Sea between 2009-2018. When considered against the upward trend in plastic production and use in Europe over a similar period, this suggests that some progress has been made in preventing plastics from entering the marine environment.

At the same time, seafloor litter in the OSPAR Maritime Area is widespread, and has been monitored in the Greater North Sea (Region II), Celtic Seas (Region III) and Bay of Biscay and Iberian Coast (Region IV), with fisheries-related and plastic materials predominating. There are no clear trends in Regions III and IV, but the amount of seafloor litter in Region II appears to be increasing slightly. Additionally, a high density of floating litter has been identified in Region IV, especially in the south-east corner of the Bay of Biscay, as evidenced in ingestion by surface-feeding fulmars and sea turtles.

Marine litter is a pressure on ecosystem services, with important implications for both the economic and social aspects of human welfare. Litter, both visible debris and microplastics, can negatively impact economic sectors such as tourism, fisheries, aquaculture, navigation, and energy. Litter also affects the cultural and amenity services that the ocean offers, reducing the attractiveness and enjoyment derived from coasts and seas and affecting our psychological wellbeing.

Figure 7.6: Smoothed maps for the Greater North Sea of the probability that hauls contain a litter item, from 2012-2019. In general, the probability of a haul containing a litter item is lowest in the Northwest and then increases along a south-east gradient.The spatial components of the models are statistically significant (p <0,05) for all years.

Dredging and dumping

Dredging and dumping have been regulated by the Contracting Parties to the 1992 OSPAR Convention, which permits three main categories of materials to be legally disposed of at sea:

1. dredged material;
2. fish waste from industrial fish processing operations;
3. inert materials of natural origin, namely solid, chemically unprocessed geological material.

Since the implementation of the original OSPAR guidelines for disposal at sea, contaminant loads have decreased and have been levelling out since the mid-2000s.

Much material dredged from navigation channels within the OSPAR Maritime Area is either uncontaminated or only mildly contaminated by human activities (i.e. close to natural background levels). However, in some areas dredged material is contaminated to an extent that environmental constraints need to be applied when developing management options. OSPAR Contracting Parties monitor and report details of contaminant loads in managed dredged sediments, and also limit the disposal of contaminated material. The QSR 2010 identified a stabilisation in the previously downward trend observed throughout the 1990s for contaminant concentrations in dredged material from the southern North Sea. In the period from 2008 to 2020, no upward or downward trends were identified in the amounts of dredged material dumped or placed within the OSPAR Maritime Area; however, a slight downward trend was evident in the loads of TBT/DBT contained in dredged sediment.  Other contaminant loads did not display trends, thus confirming the findings of the OSPAR 2017 Interim Assessment.

The need for dredging may increase in future as growth in ship sizes necessitates deeper and wider navigation channels, and greater frequency and intensity of storm events cause infilling of channels and harbours. Some of this material may increasingly be put to beneficial use, partly mitigating the need for disposal at sea.

Figure 7.7: Locations of dumping or placement of waste or other matter activities in 2019. Available at ODIMS

Noise Pollution

Human activities at sea generate noise, a form of pollution that also impedes realisation of the goal of achieving clean seas. The assessments of anthropogenic noise in the OSPAR Maritime Area distinguish continuous noise (mainly from shipping) from impulsive noise (such as occurs in seismic surveys, explosions and pile driving).

Noise can interfere with the hearing or physiology of marine animals or cause behavioural disturbance or injury. Measures to mitigate impulsive noise have had some impact, but international guidelines on reducing continuous noise appear to have had little effect to date. Shipping noise and impulsive noise are particularly intense in the Greater North Sea Region. However, for both impulsive and continuous noise, it is not yet possible to establish any definitive long-term trends in noise levels, including trends in evidence since the Quality Status Report 2010 (QSR 2010). OSPAR has thus committed to producing a regional action plan of measures to reduce noise and to improve the monitoring of noise levels.

A fine-tuned analysis conducted in OSPAR Region II (Greater North Sea excluding the English Channel) gives some indication of the continuous noise in this heavily used part of the OSPAR Maritime Area. Mapping of Excess Level shows that almost all over the North Sea shipping noise is at a median Excess Level of 6 dB or more, with shipping noise of over 20 dB concentrated in the southern part of the North Sea and along the major shipping routes. The areas with high median Excess Level are exposed to continuous noise for a high percentage of time, and in these areas shipping noise can obscure natural sounds. Analysis of the overlap of high continuous noise and marine protected areas (MPAs) shows the same type of disturbance for these areas as for the southern part of the North Sea where they are mostly located, suggesting that MPAs do not mitigate continuous noise.

( Underwater Noise Thematic Assessment ).

By contrast with this picture of overall continuous noise, the OSPAR Common Indicator on Pressure from Impulsive Noise shows increased numbers of ‘pulse block days’ in all five OSPAR Regions. This expression refers to the number of days in a calendar year that anthropogenic impulsive sound (pulse) occurs within a specified area (block), and thus provides detailed resolution at regional scale. Only impulsive sounds above a minimum intensity are included, below which the risk of impact on marine animals is judged to be insignificant.

Despite these overall trends in impulsive noise, the QSR 2023 reported some reduction in noise exposure for harbour porpoise – a species particularly vulnerable to impulsive noise, both because of its distribution in heavily used marine areas and due to its threatened population status. This decrease in noise exposure is a result of measures taken to reduce noise from piling activity. Other measures to reduce impulsive noise, as well as continuous noise, are described in the text box below.

Noise abatement

The International Maritime Organization (IMO) has produced voluntary guidelines on reducing noise from commercial ships. It is possible to reduce noise from shipping through technical measures, such as hull and propeller design, and by reducing propeller and machinery vibrations. Operational measures include spatial restrictions and reducing shipping speeds, and many of these approaches are adopted in the national standards for noise management that have been put in place by several OSPAR Contracting Parties. Area time limits for impulsive noise have been recently implemented in some marine mammal protected areas.

Technical measures to abate impulsive noise also exist. Measures to mitigate the adverse effects of percussive pile driving include the use of bubble curtains, isolation casings and hydro sound dampers. These measures are very effective in reducing levels of impulsive noise from pile driving in the OSPAR Maritime Area. Alternative, quieter, installation methods such as suction buckets and drilling can also be used in some areas. Bubble curtains can be used to reduce noise from the detonation of unexploded ordnance (UXO), although this is unlikely to be practical in most situations. More recently, quieter technologies for clearing unexploded ordnance from the seabed have been made available to the commercial market. In geophysical surveying, noise from seismic surveys can be reduced slightly by changing the design and configuration of airgun arrays. To achieve significant reductions, alternative technologies are needed; marine vibrator technologies are under development. Operational measures can also be taken to reduce the risk of adverse effects from impulsive noise on sensitive species, such as using acoustic deterrent devices, choosing less critical times or areas for activity (e.g. avoiding feeding areas, reproductive sites or migration routes) and using marine mammal observers or acoustic monitoring to detect animals in the vicinity of operations.

Pressures from non-indigenous species

Non-indigenous marine species (NIS) are organisms that enter new areas outside their natural range of distribution and dispersal potential. Their introduction is facilitated by human activities such as the transfer of ships’ ballast water, biofouling (accumulation of organisms on the hulls of ships), the aquaculture trade, and long-distance travel involving human marine litter. Species that naturally increase their range are not taken into consideration. However, NIS that spread to neighbouring areas by natural means or by human-mediated transport following their primary introduction are still considered to be NIS. These organisms, though not all, can become invasive and negatively impact ecosystems. Through competition for resources and space, as well as hybridisation with native species, invasive species can alter population and species composition, species’ potential adaptation to environmental changes, food webs, biogeochemical cycles, and water quality.

While the rate of new NIS introductions in the OSPAR Maritime Area appears to have decreased over the assessment period, the trend is uncertain due to inconsistent reporting. Nonetheless, many of the management measures adopted since QSR 2010 seem to be having a positive effect. Whether that situation can be sustained is unknown, as new introductions from aquaculture, ballast water, and biofouling are expected to continue and will require additional management measures. Given the knowledge gaps concerning which NIS are, or will become, invasive and the difficulty in controlling NIS spread in the marine environment, the focus is on preventing NIS introduction and on early detection so as to prevent the economic and health impacts of invasions.