North Coast SMR

Location and physical characteristics

Figure 1: North Coast Scottish Marine Region.The thicker white line delineates the extent of the North Coast SMR. For a map of all SMRs and OMRs, see Figure 5 here

Coastline length (km) 544
Sea area (km2)    2,443
Deepest point (m) 124
Shallowest point (m)  coastline
Average depth (m)  68
Tides (m) 2.1 – 4.3
Salinity 34.49 – 34.85
Sea surface temperature (°C) 7.8 – 13.7

The North Coast SMR extends along Scotland’s north coast (Figure 1). Strong tidal currents run through the Pentland Firth, situated between the mainland and the Orkney Islands, in an east-west direction with the residual to the east and into the North Sea. These are some of the fastest tidal currents in the world, reaching over 8 m/s. The region only has a small amount of freshwater input. The north facing coast is exposed to wind and waves, mostly from the north and east.

Seabed sediments between Cape Wrath and Dunnet Head consist of a zone up to 15 km wide of gravels and sandy gravels. The strong currents that flow through the Pentland Firth result in patchy sediment cover with rock outcrops on the seabed. Sandbanks and sand-wave fields occur to the west and south east of the Pentland Firth. In most areas offshore, bedrock is covered by seabed sediments and infill sediments, but isolated rock outcrops may occur.

Productive

The North Coast SMR stretches the length of the north coast of the Scottish mainland. The border between this SMR and the Orkney Islands SMR passes through the Pentland Firth where the annual mean-depth average peak tidal current speed at spring tide can exceed 4.5 m s-1 (See Scotland’s Tidal Stream Resource case study). This predictable energy resource, although it fluctuates with four peaks every day, is being explored as part of Scotland’s future energy supply. 

The North Coast SMR, has a major ferry route running from the north coast (Scrabster) to Orkney (Stromness). In 2018 153,000 passengers were carried by ferries operating in the North Coast SMR.

As well as being a ferry port, Scrabster had a total fish landings of 20,665 tonnes in 2018, the bulk of which is demersal fish.

The Productive Assessment has been undertaken, with a focus on 2014 – 2018, on a sectoral basis. As mentioned, for some Sectors, including oil and gas, carbon capture and storage and aggregates, there was no activity within the North Coast SMR during the period 2014 – 2018.

However, for many sectors, there were changes over the period 2014 – 2018 (Figure 2). Atlantic salmon production, the length of subsea active power cables and the rod and line catch all decreased. In contrast, fish landings and marine passenger transport increased.

Figure 2: Changes that have taken place in the North Coast SMR by Sector.

Although the period 2014 – 2018 inclusive has been used where possible, there are some entries when a slightly different time period has been used. Information on Atlantic salmon production, mussel production and pacific oyster production for the North Coast SMR has been merged with the West Highlands SMR to avoid disclosure. Information on seaweed harvesting for the North Coast SMR has been merged with the Moray Firth SMR to avoid disclosure.

Pressures from human activities

As part of SMA 2020, an assessment of the main pressures from human activities in each of the Scottish Marine Regions and Offshore Marine Regions was undertaken through a MASTS-led workshop. The process and outcomes are presented in detail in the Pressure from Activities section. Five main pressures identified for the North Coast SMR ordered as per the MASTS-led Pressure Assessment Workshop were:

Priority [1] Pressure (FeAST classification) [2] Main healthy and biologically diverse components affected [3] Main contributing FeAST activity /activities to pressure [4] Associated productive assessments [5]
1 Removal of target species (including lethal)
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Creeling and potting (FPO)
2 Removal of non-target species (including lethal)
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Creeling and potting (FPO)
3 Physical change (to another seabed type)
  • Extraction – Dredging (capital and maintenance)
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Creeling and potting (FPO)
4 Surface/Sub-surface abrasion/penetration
  • Extraction – Dredging (capital and maintenance)
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Creeling and potting (FPO)
5 Underwater noise
  • Extraction – Dredging (capital and maintenance)
  • Fishing – any gear
  • Infrastructure - Coastal (ports, marinas, leisure facilities)
  • Military activities – Sonar use
  • Shipping
  • Tourism & recreation

Clean and safe

The assessments cover eutrophication, hazardous substances, marine litter, noise and microbiology and algal toxins which have the potential to impact on habitats and species as well as being a consequence of human activity. Although sources of litter or contaminants may be local, there are cases when the source is some distance from the impacted area. The main findings for the North Coast SMR are:

Eutrophication

The North Coast showed no evidence of eutrophication as a consequence of nutrient enrichment. However, there was a statistically significant increasing trends in nutrient inputs although loads were an order of magnitude lower than most other SMRs. This increase was attributed to an increase in riverine inputs in the region. Winter nutrient concentrations and chlorophyll concentrations were below assessment criteria and relatively stable. There were no dissolved oxygen data for the North Coast.

Hazardous substances

Hazardous substances (polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and heavy metals (Hg, Cd and Pb)) assessments in sediment and biota (fish and shellfish) were undertaken at the scale of the five Scottish biogeographic regions: Atlantic North-West Approaches, Irish Sea (Clyde and Solway), Minches and Western Scotland, Scottish Continental Shelf and Northern North Sea. The North Coast SMR is in the Scottish Continental Shelf biogeographic region. There are limited biota and sediment sites in the Scottish Continental Shelf biogeographic region, and no sites in the North Coast SMR. Where contaminants were measured in the Scottish Continental Shelf, biogeographic region concentrations were generally above background but below concentrations where adverse effects could occur. In addition, there were no increasing trends, and for lead inputs there was a significant decreasing trend which is related to decreasing river inputs.

Of the biological effects measurements included in the assessment, there are no sites in the North Coast SMR and also limited data at the biogeographic region scale for the Scottish Continental Shelf. External fish disease, a general measure of fish health, was assessed at one site in the Scottish Continental Shelf biogeographic region and showed that the fish health status was satisfactory. However ,this site was not in the North Coast SMR.

Marine litter

Due to the lack of assessment criteria for marine litter, beach litter and microplastic, status assessments were not possible. However, litter and microplastics are present in all SMRs, including the North Coast. The North Coast SMR has a relatively low concentration of microplastics in surface water (< 5,000 microplastics per km2 of sea surface).

Seafloor litter was assessed at the scale of the biogeographic regions; The North Coast SMR is in the Scottish Continental Shelf biogeographic region. The evidence indicates that there are apparent decreases in sea-loor litter density over time between 2012 to 2018.

Beach litter data were not available for the North Coast SMR.

Noise

There are limited noise data for the North Coast; no continuous noise data were collected and there are very few impulsive noise data for this region. It is not possible to do a status assessment as there are no assessment criteria to say what levels of noise are harmful, and not enough years of data to carry out a trend assessment.

Microbiology and algal toxins

There were 2 bathing waters in the North Coast SMR that were assessed according to levels of Escherichia coli and intestinal enterococci, one was classified as Excellent and one Good in the latest classification (2018).

Escherichia coli is monitored in shellfish as a proxy of the microbiological quality of the water from shellfish production areas. Classifications are awarded according to the Food Standards Scotland (FSS) Protocol for Classification and Management of Escherichia coli. A site can be designated A, B, C, A/B or B/C, with Class A products able to go direct for human consumption. Three sites were monitored in the North Coast SMR, with no site having prohibited levels of Escherichia coli.

A number of marine algal species produce biotoxins which, by accumulation in bivalve molluscs such as mussels and oysters, can cause human illness when these shellfish are eaten. Both biotoxins and phytoplankton are routinely monitored in classified shellfish production areas under Regulation (EU) 2017/625. Such monitoring takes place at three sites within the North Coast SMR. Concentrations of diarrhetic shellfish toxins (DSTs) exceeded regulatory limits (RL) in 2015 and 2018, and paralytic shellfish toxins were reported above RL in 2017. No samples exceeded RL for amnesic shellfish toxins.

 

Healthy and biologically diverse

This section summarises the information from the Marine Protected Areas (MPAs) and intertidal and continental shelf habitats assessments from SMA2020. It also provides information from the relevant case studies relating to Priority Marine Features (PMFs), with a focus on habitats.  Further work is required to enable assessment at a regional scale for most species; this will be included in Scotland’s next marine assessment.

At a regional scale for MPAs the focus is on the number of new MPAs, MPAs with new spatial management measures, and MPAs in which spatial management measures are in discussion, as well as recognising monitoring that has been undertaken between 2012-2018.  For the marine habitats, the focus is on interpreting the relevant intertidal and continental shelf habitat assessments – biogenic habitats, predicted extent of physical disturbance to the seafloor (BH3) and intertidal seagrass beds.  For PMFs, a summary is provided of the changes in our understanding of the habitats of most relevance to the SMR, including changes in distribution and extent.

Marine Protected Areas

Progress in developing the Scottish MPA network

There are three MPAs in the North Coast SMR that contribute to the Scottish MPA network (see Table 1).  Some of these MPAs overlap completely or partially in terms of their spatial coverage and/or the features (habitats, species, etc.) they were set up to help conserve.  They are counted as separate MPAs because they have been established under different legislation which influences the way in which they are managed.  Also note that there are MPAs that straddle the boundaries between different SMRs.  Where this is the case, these MPAs have been counted as contributing to the MPA network in all of the SMRs/OMRs in which they are present.  This means that the total number of MPAs in Scotland cannot be calculated through combining the regional totals.  Please see the Marine Protected Area assessment which contains statistics for the Scottish MPA network as a whole.  

Table 1. Numbers of types of MPAs in the North Coast SMR that contribute to the Scottish MPA network, including the number of new MPAs introduced since 2012.

Type of MPA

Abbr.

Total no. of MPAs

No. of new MPAs 2012-2018

Special Area of Conservation

SAC

1

0

Special Protection Area

SPA

2

0

The MPAs are focused on the protection of breeding seabirds, otters and offshore reefs.

The North Caithness Cliffs SPA and Cape Wrath SPA, situated at the north-easternmost and north-westernmost respectively extremities of mainland Scotland, support internationally important numbers of breeding seabirds, especially gulls and auks.  During the breeding season, these seabirds forage over large areas of sea returning frequently with food to feed their chicks.  Durness SAC is designated for the population of otters that frequent the coast.

Progress in managing MPAs

The progress in implementing management for MPAs in the North Coast SMR is summarised in Table 2.  This includes information on where spatial management measures are in place and where they are under discussion.  It also includes information on the number of MPAs that have been monitored, whether by statutory bodies or through citizen science.

Table 2. Summary of progress in managing Marine Protected Areas in the North Coast SMR

Note that the spatial measures listed in the table are in addition to the protection provided as a result of consideration of activities/developments through licensing and consenting processes.

Type of MPA

Spatial measures in place pre-2012

New spatial measures in place 2012-2018

Spatial  measures in discussion 2012-2018

No. of MPAs monitored by statutory bodies 2012-2018

No. of MPAs monitored via citizen science 2012-2018

Special Area of Conservation

0

0

0

Habitats

1

Habitats

0

Special Protection Area

0

0

0

2

0

               

There are currently no spatial measures in place or under discussion for any of the MPAs in this SMR.  All of the MPAs have been monitored at least once during the assessment period with the main focus on breeding seabirds.

Information on MPA boundaries can be viewed in Marine Scotland’s NMPi. To find out more about specific MPAs, please visit NatureScot’s SiteLINK

Intertidal and continental shelf habitats

SMA2020 contains three relevant habitat assessments: intertidal seagrass beds, subtidal biogenic habitats, and predicted extent of physical disturbance to seafloor.  Assessment of the status of subtidal biogenic habitats is based on temporal reductions in extent of six habitat types: seagrass beds, serpulid aggregations, flame shell beds, maerl beds and horse and blue mussel beds.  Although blue mussel beds, horse mussel beds, maerl beds and seagrass beds have been recorded within the SMR, no data are available on temporal changes in extent of these habitats and hence no status assessments could be made;  the other biogenic habitats i.e. serpulid aggregations, flame shell beds and intertidal seagrass beds have not been recorded in this SMR.  Modelling work was carried out as part of the assessment to predict the extent of physical disturbance to the seafloor more generally.

Predicted physical disturbance to the seafloor

To assess physical disturbance to seafloor habitats SMA2020 employed a modelling approach which generates a map of predicted relative disturbance levels from demersal fishing activity on a scale of 0 (zero) to 9 (severe).  The map was produced by the combination of information on the distribution of habitats, the sensitivity of the habitats (and species present to varying degrees) and the fishing pressure from demersal trawling, dredging and seine netting.  Fishing pressure information was derived from Vessel Monitoring System (VMS) data from 2012 - 2016 and was categorised as either surface abrasion (disturbance of surface and upper layers of sediment) or sub-surface abrasion (disturbance to a depth of >3 cm).  The final predicted disturbance index utilises the greater of these two pressure values and for descriptive purposes has been categorised as no disturbance (0), low disturbance (1-4) and high disturbance (5-9).

It should be emphasised that this method does not measure disturbance to seabed habitats, but predicts relative levels of disturbance. These relative levels are dependent upon the accuracy of habitat data and sensitivity assessments.  Many of the habitat data are derived from modelling and there is a low level of confidence in its accuracy.  Geographical variation in the accuracy of the sensitivity information employed is likely to be great, being dependent upon the level and quality of information used locally.  A significant limitation of the method is that during the assessment period pressure data were only available for vessels >12 m, which has probably resulted in an underestimation of disturbance.

Predicted habitat disturbance by mobile demersal fishing for the North Coast SMR is close to the average for SMRs in terms of the proportion of the seabed with 49% high disturbance compared to the average of 50% for all SMRs (Figure X).  Only 5% of the seabed is predicted to experience no disturbance (average of 12% for all SMRs).  Disturbance levels closely mirror the degree of surface abrasion and are relatively heavy in the central part of the SMR where the substrate is predominantly sand, and lighter towards the eastern and particularly western side where coarse sediments predominate. 

Figure 3.  Predicted physical disturbance to the seafloor in the North Coast SMR and prohibition areas for all mobile demersal fishing. 

Priority Marine Features and birds (non-PMF)

Overview of recorded PMFs and birds

The North Coast SMR supports a range of PMFs and breeding seabirds as well as wintering waterbirds (i.e. waders, estuarine waterfowl, seaduck and coastal water feeding birds) as detailed in Table 3. 

Table 3: Details of PMFs, seabirds, and wintering waterbirds found in the North Coast SMR

Priority Marine Features (PMFs; grouped habitats and species) and birds

No. of species/

habitats recorded

Intertidal and continental shelf habitats

10

Fish[1]

21

Mammals (regularly occurring)

9

Shellfish & other invertebrates

3

Seabirds[2] (non-PMF) – breeding

20

Wintering waterbirds[3] (non-PMF) – non-breeding

13

There are 43 PMFs and 33 marine birds recorded in this region.  The North Coast SMR supports a number of benthic PMFs at the limit of their recorded distribution, which are more commonly found on the west coast.  Loch Eriboll supports a number of PMFs, such as seagrass beds and maerl beds, which are not found elsewhere in the SMR. Six cetacean species occur regularly in the Pentland Firth, namely harbour porpoise, minke whale, white-beaked dolphin, Risso’s dolphin, killer whale, and bottlenose dolphin with a further four species that normally inhabit more offshore waters as casual visitors: short-beaked common dolphin, Atlantic white-sided dolphin, long-finned pilot whale and sperm whale. Together with otters and harbour and grey seals the Pentland Firth supports one of the highest numbers of PMF mammal species, making it one of richest areas in the UK.

Progress in understanding intertidal and continental shelf habitats listed as PMFs

There are relatively few records of PMF habitats in the North Coast SMR, either before or during the assessment period of between 2012-2018.  These records are focused in Loch Eriboll and the Kyle of Tongue.

The temporal sequence of records of all PMF habitats is provided in Table 4, based on inclusion in the Marine Recorder (2021) and GeMS (2021) databases, as well as identified additional sources.  Associated commentary, however, is restricted to PMFs for which the information has the potential to inform regional marine planning (see Figure 4 for their distribution).  For example, some PMFs are excluded on the basis that they are very widely distributed and for which the records represent a small proportion of their likely distribution, such as several of the kelp habitats.

The contribution of citizen science records has fallen slightly from the pre-2012 level of 23% to 16% in later years (Table 4).  Overall, there has been little identification of PMF habitats in the SMR since 2012, with the notable exception of records from an unpublished report resulting from a 2019 diving survey of Loch Eriboll and the Kyle of Tongue (Thouless, to be published).

PMF records in the SMR are largely restricted to Loch Eriboll and its approaches.  There are no post-2012 records and only sparse pre-2012 records of the biogenic habitats, blue mussel beds and seagrass beds.  Burrowed mud is widely distributed in the sheltered conditions of Loch Eriboll, with all records derived from Marine Scotland and SNH surveys in 2011 and 2012 (Moore, 2012; Moore & Atkinson, 2012) and the 2019 diving survey (Thouless, to be published)).  The latter also recorded previously unknown locations for a maerl bed and patches of 'maerl or coarse shell gravel with burrowing sea cucumbers' in Loch Eriboll, and a sparse horse mussel bed and tide-swept algal communities within and around the Kyle of Tongue.

Table 4.  Temporal frequency of PMF habitat records within the North Coast SMR obtained from GeMS (2021), Marine Recorder (2021) and other sources.  The numbers of All records are given, as well as those from Citizen Science (CS) surveys alone.

PMF

<2012

2012-2018

>2018

 

All

CS

All

CS

All

CS

Blue mussel beds intertidal)

1

0

0

0

0

0

Burrowed mud

12

0

6

0

7

0

Horse mussel beds

1

1

0

0

1

0

Intertidal mudflats

1

0

0

0

0

0

Kelp and seaweed communities on sublittoral sediment

10

1

1

1

7

0

Kelp beds

34

11

13

13

30

0

Low or variable salinity habitats

2

0

0

0

0

0

Maerl beds

2

2

0

0

11

0

Maerl or coarse shell gravel with burrowing sea cucumbers

1

0

0

0

5

0

Seagrass beds

1

0

0

0

0

0

Tide-swept algal communities

1

0

0

0

7

0

Figure 4.  Temporal pattern of records of selected PMF habitats for the North Coast SMR, with inset showing location of main map and additional PMF records outside Loch Eriboll.

Status and trend in grey and harbour seals

The North Coast SMR is included in the Orkney and North Coast seal management area and as such there are not specific assessments of the status and trends in grey and harbour seals in this SMR.  Within the combined Orkney Islands and North Coast SMRs the number of grey seals is stable and their status is assessed as ‘few or no concerns’.  Harbour seal numbers were high and stable until the early 2000s but from 2005 onwards their numbers have been steadily declining and their status is assessed as ‘many concerns’.

 

[1] Records from International Bottom Trawl Surveys from MSS.

[2] Records of seabirds during breeding season only, from BTO Bird Atlas.

[3] Records of birds during the non-breeding season, from the BTO Bird Atlas

Climate change

There is good evidence that climate change is driving changes in the physical, chemical and biological conditions of the marine environment but the current evidence base limits the ability to draw conclusions at the scale of the individual marine regions, including North Coast SMR. This is a combination of the lack of comprehensive spatial coverage of key monitoring programmes, the relatively short time series, and the complex linkages of climate change impacts in the marine environment.

Increasing concentrations of atmospheric greenhouse gases have caused more energy to be trapped within the Earth’s atmosphere, land and ocean. Approximately 90% of this excess energy has been absorbed by the ocean, resulting in warming ocean temperatures (see Temperature assessment and Climate change Sea temperature assessment).

The increasing concentration of carbon dioxide, one of these greenhouse gases, has the additional consequence of driving a reduction in the pH of the ocean, a process known as ocean acidification (see Ocean acidification assessment and Climate change Ocean acidification assessment).

Mean sea level is rising due to increased contributions of freshwater from melting of land-based ice (glaciers and the polar ice sheets) and due to thermal expansion of water (see Sea level and tides assessment and Climate change Sea level assessment).

The warming temperatures also result in lower oxygen concentrations due to fact that warm water holds less oxygen and changes in stratification further influence oxygen concentrations (see Dissolved oxygen assessment and Climate change Dissolved oxygen assessment). Together with increased metabolic rates in organisms resulting in increased respiration, oxygen depletion has a severe impact on marine organisms due to the impact on metabolic processes.

These changes in the physical environment are also having an impact on marine life, such as changes to their metabolism, changes in seasonality and the timing of events in natural cycles, and changes in their distribution. These changes have consequences for the growth, survival and abundance of species, including those of commercial importance or critical to conservation objectives.

At present, most of these impacts are assessed at scales greater than marine regions. The Community Temperature Index combines species temperature affinity and their abundances. This index has the potential to inform how communities change due to climate change. An example of changes in the Community Temperature Index from bottom-living fishes can be found in the Fish section within Biological Impacts of Climate Change, where more information on other impacts in marine food webs can be found (such as seabirds and marine mammals) on large regional scales in Scottish waters.

Sea surface temperature in the North Coast region has increased since 1870 by 0.05 °C per decade on average.  The rate of increase has not been constant, and in the last 30 years (1988-2017), the rate of change in temperature was +0.22 °C per decade.

Tide gauge records from around Scotland’s coast show a high degree of year-to-year change in coastal water levels (typically several centimetres). The long-term average mean sea-level change in the North Coast SMR, as estimated from a historical climate model run (UKCP18), was 6 cm (likely range between 4 and 10 cm) higher in 2018 than the 1981-2000 average. For reference, the Scottish average is estimated to be 5 cm (likely range between 3 and 8 cm). By 2100, mean sea level in the North Coast SMR is anticipated to be approximately 44 cm for a medium emissions scenario (UKCP18 RCP4.5; see also and Climate change Sea level assessment).

Offshore renewable energy is an important component in respect of reducing emissions of greenhouse gases.  In 2018 the total installed wave and tidal capacity in the North Coast SMR was 6 MW.

Summary

The North Coast SMR contains the major ferry port of Scrabster which has seen an 27% increase in passengers in the five years between 2014-2018 and handled 20,665 tonnes of fish landings in 2018. The entire SMR has seen a 16% increase in the value of fish landings between 2014-2018. Salmon and sea trout rod and line catch decreased by 33% over the same period.  Other active sectors include renewables, subsea cables, aquaculture and seaweed harvesting and cultivation.

The five main pressures affecting the SMR are Removal of target species, Removal of non-target species, Physical change, Surface / Sub-surface abrasion / penetration, and Underwater noise.  Other pressures identified are Introduction of non-indigenous species and Litter.

Nutrient inputs to the North Coast SMR are an order of magnitude lower than most other SMRs although there was an increasing trend but there is no evidence of eutrophication in this SMR. Contaminant (i.e. PAHs, PCBs, PBDEs and heavy metals) concentrations are generally above background but below levels that might cause adverse biological effects.  There were no increasing trends and for lead there was a significant decreasing trend.  There are no data on levels or trends in litter and microplastics There are limited noise data, and no assessment was possible.  Two bathing waters were assessed, one classified as Excellent and the other Good. Algal biotoxins on occasions exceeded Regulatory Limits-diarrhetic shellfish toxins in 2015 and 2018 and paralytic shellfish toxins in 2017.  There were no samples that exceeded Regulatory Limits for amnesic shellfish toxins.

Forty-nine per cent of the seafloor is predicted to have been subject to high physical disturbance and 5% subject to none.  There are few records of benthic habitats in this SMR, beyond kelp beds.  

In the last 30 years sea temperature has risen by 0.22 °C per decade.  Sea level in 2018 is estimated 6cm higher than the 1981-2000 average.