Argyll SMR

Location and physical characteristics

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

Coastline length (km) 2,918
Sea area (km2)    12,044
Deepest point (m)    320
Shallowest point (m)  coastline
Average depth (m)  66
Tides (m)    0.3 – 4.2
Sea surface salinity  34.30 – 34.74
Sea surface temperature (°C)      8.0 – 14.3

The Argyll SMR, located on the south-west coast of Scotland, has a complex and indented coastline with multiple sea lochs and islands. It includes Loch Linnhe and Loch Etive, two large sea lochs. This SMR extends out into the deeper regions of the Malin Shelf (150 – 200 m). Many of the sea lochs have one or multiple sills that restrict water exchange between the coastal area and surrounding sea. There are also areas with strong tidal currents such as the Great Race of the Gulf of Corryvreckan. Current speeds in this narrow strait can be greater than 4 m/s and set-up a whirlpool at certain times in the tide. Between Islay and the Mull of Kintrye there is an amphidromic point where the tidal range is at a minimum, but where strong tidal currents occur.

The Argyll SMR also experiences large freshwater inflow in places, with Loch Eil (which flows into Loch Linnhe) being one of the main contributors. Salinity changes are influenced by land runoff and small rivers. They display a large variability in space and time. Surface layer currents generally flow seaward in sea lochs and northwards in the more open sea.

The complex and indented coastline also means that wave exposure is variable with more exposed areas in the outer reaches and more sheltered in the inner reaches of the sea lochs, sounds and bays.

Seabed sediments in the Argyll SMR are highly variable in both geological characteristics and thickness. Thin gravels and sands predominate in the North Channel (between Scotland and Northern Ireland), where tidal currents are strongest. These gravels are locally shell-rich, and in places shell-gravel pavements may develop on bedrock. Sand is predominant near the coast, leading to a profusion of small, sandy beaches including Ganavan Sands (Oban) and Lossit Bay and Machir Bay (Islay). Within the glacially deepened sea lochs, tidal currents are weak and thick sequences of mud accumulate. Cemented calcareous dunes are found on Coll, the cementation locally picking out ‘fossilised’ hoof prints.

The major north-east/south-west faults, which divide the onshore geology into distinct sectors, formed before the Quaternary period (i.e. more than 2.6 million years ago) and continue across the offshore part of the Argyll SMR. The Great Glen Fault may be traced as a series of faults, along Loch Linnhe to the north-western part of Islay and further to Donegal in Ireland. These faults were most active during Precambrian (4.6 billion to 541 million years ago) and Paleozoic (541 to 252 million years ago) times, but later tensions in the Earth’s crust reactivated these faults. Thick basaltic lavas from igneous complexes in the Tertiary period (66 million to 2.6 million years ago) can be found on Mull, extending offshore to the west of the island and form the island of Staffa, including the world famous columnar jointing basalt at Fingal’s Cave.

Productive

The Productive Assessment for the Argyll SMR has been undertaken on a sectoral basis, with a focus on 2014 – 2018. The Argyll SMR provides important opportunities for fisheries, aquaculture and passenger transport. Figure 2 highlights the key economic statistics for the various productive sectors from SMA2020 for the period 2014 – 2018. Of the 11 SMRS, Argyll provides the median gross value added, at £34.7 million, for tourism in 2018.

Argyll and Clyde SMRs are especially important for aquaculture, especially oyster production. Argyll accounted for 41% of pacific oyster production in 2018. Military activity also provides an important source of employment in Argyll and Bute, with 4,840 MOD personnel based there, 36% of all MOD personnel in Scotland. In 2018, Argyll had the second busiest maritime passenger transport, accounting for 15% of all passenger numbers.

For a number of Sectors, including renewables, oil and gas, carbon capture and storage and aggregates, there was no activity within the Argyll SMR during the period 2014 – 2018. However, for many sectors, there were changes over the defined period (Figure 2).



Figure 2: Changes that gave taken place in the Argyll 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 and mussel production for Argyll SMR has been merged with Clyde 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 Argyll 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)
  • Fishing - Dive fisheries (not including hydraulic dredging) (HF, MIS)
  • Fishing - Recreational Fishing
  • Fishing - Scallop dredging (DRB)
2 Removal of non-target species (including lethal)
  • Aquaculture - Finfish
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Creeling and potting (FPO)
  • Fishing - Recreational Fishing
  • Fishing - Scallop dredging (DRB)
3 Surface abrasion
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Creeling and potting (FPO)
  • Fishing - Scallop dredging (DRB)
4 Synthetic compound contamination (inc. pesticides, antifoulants, pharmaceuticals). Includes those priority substances listed in Annex II of Directive 2008/105/EC.
  • Aquaculture - Finfish
  • Shipping
5 Underwater noise
  • Aquaculture - Finfish
  • Military activities – Sea surface activity
  • 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 Argyll SMR are:

Eutrophication

There is no evidence of eutrophication as a consequence of nutrient enrichment with nutrient inputs, winter nutrient concentrations and chlorophyll concentrations relatively stable. In addition, dissolved oxygen concentrations are above levels required to maintain healthy marine ecosystems.

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 Argyll SMR is in the Minches and Western Scotland biogeographic region.

Contaminant concentrations in the Minches and Western Scotland biogeographic region were generally above background but below concentrations where adverse effects could occur. In addition, concentrations in sediment and biota were generally stable or declining for all hazardous substances measured. There are few biota and sediment sites in Argyll SMR, and contaminant concentrations at these sites are typical of the Minches and Western Scotland biogeographic region. Of greatest concern was the most toxic PCB compound (CB118) in sediment and biota, with the concentrations at some sites in Argyll SMR being unacceptable > Environmental Assessment Criteria and furthermore, there is an increasing trend in CB118 at one site in Argyll SMR.

A number of biological effects were also measured and assessments undertaken at the scale of the five Scottish biogeographic regions. The contaminant specific biological effects (PAH bile metabolites and 7- ethoxyresorufin O-deethylase (EROD) activity) were measured at one site in Argyll SMR, EROD activity did not indicate that the fish had been exposed to contaminants. The external fish disease assessment, which is a general measure of fish health showed that the fish health status at the one site in Argyll SMR was satisfactory.

Marine litter

Due to the lack of assessment criteria for marine litter, beach litter and microplastic, status assessments were not possible. Microplastics are present in all SMRs, including Argyll. Microplastic concentrations in surface water were elevated in this SMR.. Coastal currents are generally north-eastwards and may be transporting microplastics into this area. 

Seafloor litter was assessed at the scale of the biogeographic regions; Argyll SMR is included in the Minches and Western Scotland biogeographic region. The evidence indicates that there is no consistent trend in seafloor litter density between 2012 to 2018.

Beach litter data were not available for Argyll SMR.

Noise

There are limited noise data for Argyll SMR; no continuous noise data were collected and very few impulsive noise data for this SMR. 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

Two of the four bathing waters in the Argyll SMR were assessed according to levels of Escherichia coli and intestinal enterococci, both were classified as Excellent 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. Argyll SMR contains Class C areas (2/11 production areas), Argyll SMR also had the highest proportion of B/C classifications and least Class A.

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 several sites within the Argyll SMR. Concentrations of diarrhetic shellfish toxins (DSTs) exceeded regulatory limits (RL) in every year between 2010 and 2018. Amnesic shellfish toxins in mussels were above regulatory limits in August 2012, whilst paralytic shellfish toxins (PSTs) resulted in closures in 2013, 2014, 2015 and 2017.

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 SMR/OMR 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 23 MPAs in the Argyll 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 / OMRs.  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 SMR/OMR 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 Argyll SMR that contribute to the Scottish MPA network, including number of new MPAs introduced since 2012.

Type of MPA

Abbr.

Total no. of MPAs

No. of new MPAs 2012-2018

Historic MPA

HMPA

1

1

Nature Conservation MPA

MPA

3

3

Ramsar

-

1

0

Site of Special Scientific Interest

SSSI

6

0

Special Area of Conservation

SAC

10

1

Special Protection Area

SPA

2

0

Note that in December 2020 there were another three MPAs designated in this region in addition to those in the table above, comprising two SPAs (Coll and Tiree and Sound of Gigha) and one Nature Conservation MPA (Sea of the Hebrides).

Highlights from the various MPAs include:

The MPAs in the Argyll SMR protect a wide variety of features including benthic and intertidal habitats, fish, marine mammals, and birds.  Loch Sween MPA is home to a number of features including maerl beds, sublittoral mud and mixed sediment communities, and burrowed mud habitats. The surface of the latter habitats is dotted with the dome-shaped mounds of the volcano worm along with the burrow openings other animals including Norway lobsters and burrowing gobies.  Loch Sunart to the Sound of Jura MPA supports a resident population of flapper skate.  Skates are an ancient group of fish that first appeared in fossil records about 150 million years ago and the flapper skate is the largest extant skate in the world and can reach a length of 2.5 m and weigh over 100 kg.  Loch Creran SAC, situated at the northern end of the Firth of Lorn, is a typical fjordic sea loch. The site is particularly notable for biogenic reefs of the calcareous tube-worm Serpula vermicularis, which occur in shallow water around the periphery of the loch. This species has a world-wide distribution but the development of reef structures is extremely rare; Loch Creran is the only known site in the UK to contain living S. vermicularis reefs. The skerries, islands and rugged coastline of the South-east Islay Skerries SAC support a nationally important population of harbour seals. Gruinart Flats Ramsar site supports internationally important numbers of non-breeding light-bellied brent geese and Greenland barnacle geese. 

Progress in managing MPAs

The progress in implementing management for MPAs in the Argyll 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 Argyll 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. Also, the monitoring of birds, mammals and habitats within SSSIs and SACs has been split out to reflect the different programmes of work.  These figures cannot be added together to provide a total number of SSSIs or SACs in which monitoring took place because of overlaps in coverage.  

Type of MPA

No. of MPAs with spatial measures in place pre-2012

No of MPAs with new spatial measures in place 2012-2018

No. of spatial  measures in discussion 2012-2018

No. of MPAs monitored by statutory bodies 2012-2018

No. of MPAs monitored via citizen science 2012-2018

Historic MPA

N/A

0

0

1

0

Nature Conservation MPA

N/A

3

0

3

3

Ramsar

0

0

0

1

0

Site of Special Scientific Interest

0

0

0

Birds

1

Birds

0

Mammals

2

Mammals

0

Habitats

1

Habitats

0

Special Area of Conservation

2

3

1

Mammals

7

Mammals

1

Habitats

1

Habitats

2

Special Protection Area

0

0

0

2

0

Note that the Marine Conservation Order (MCO) for Loch Sunart to the Sound of Jura MPA provides benefits for the Duart Point Historic MPA.

The management measures for fishing activities in place for Loch Creran and Firth of Lorn SACs were replaced in 2015. A new Fisheries Order covers Loch Creran SAC and MPA, Loch Sween MPA and the Treshnish Isles SAC, whilst the Firth of Lorn SAC is now included under the Loch Sunart to the Sound of Jura Marine Conservation Order, which also covers the MPA of the same name. The management measures for fishing activities in the MPAs across Argyll SMR mainly focus on restrictions to demersal mobile gear but there are measures for static gear within Loch Creran because of the fragility of the serpulid reefs. A further measure for Moine Mhor SAC is under discussion.

During this assessment period the majority of the MPAs have been monitored at least once by the statutory bodies, and some have had multiple visits.  Monitoring has covered birds, fish, mammals and seabed habitats.  A partnership project – the Movement Ecology of Flapper Skate - between St Andrews University, Marine Scotland Science, and NatureScot has significantly improved the understanding of the flapper skate in the Loch Sunart to the Sound of Jura MPA.  This compliments the records collected by recreational anglers (see below).  Monitoring of seals continues to be undertaken via a collaboration between the Sea Mammal Research Unit and NatureScot.

Marine reefs, flame shell beds and burrowed mud are some of the protected features which are monitored through Seasearch surveys in the Firth of Lorn SAC, Loch Creran SAC, Loch Creran MPA and Loch Sween MPA. Recreational sea anglers play an important role in monitoring the flapper skate in the Loch Sunart to the Sound of Jura MPA through photograph submissions to SkateSpotter. Sightings data of harbour porpoise in the Inner Hebrides and the Minches SAC are recorded by the Hebridian Whale and Dolphin Trust (HWDT) and the Whale and Dolphin Conservation Shorewatch Sightings programme. Sightings data of minke whales and basking sharks in the Sea of the Hebrides MPA are collected through the HWDT, Basking Shark Scotland and the Marine Conservation Society’s Basking Shark Watch.

Information on MPA boundaries can be viewed in Marine Scotland’s NMPi. To find out more about specific MPAs, please visit NatureScot’s SiteLINK.  Detailed reports on habitat monitoring are referenced in Further reading – seabed habitat monitoring reports.

Intertidal and continental shelf habitats

SMA2020 contains three relevant habitat assessments: intertidal seagrass beds, subtidal biogenic habitats, and the predicted extent of physical disturbance to the seafloor.  The biogenic habitats assessment considered the status and trend of four marine habitats within Argyll SMR: horse mussel beds, flame shell beds, subtidal seagrass beds and serpulid aggregations. The assessment aimed to include maerl beds and blue mussel beds as well, but although these are present in the SMR, there were insufficient data for their inclusion.  Modelling work was also carried out to predict the extent of physical disturbance to the seafloor more generally.  Assessment of the status of intertidal seagrass beds could not be carried out in this SMR due to lack of relevant information.

Biogenic habitats

For the biogenic habitats as a whole, the status category assigned for SMA2020 was ‘Some concerns’ on the basis of recorded reductions in extent of flame shell, horse mussel and seagrass beds, as well as serpulid aggregations.

A loss in flame shell bed extent was recorded as the result of the disappearance of a bed at Port Appin with coverage of 40 ha during the years 2001 - 2006. Subsequent surveys in 2011 (Moore, Harries, & Trigg, 2012), 2015 (Cook, 2016) and from 2018 to 2019 (Heriot-Watt University, unpublished) have revealed shrinkage of the bed and eventually virtual extinction.  In Loch Creran known flame shell bed extent has increased from 18.5 ha in 2012 (Moore et al., 2013) to 35 ha in 2018 (Moore et al., 2020); however, the increase is likely to be due to the increase in spatial spread of survey sites rather than expansion of the habitat.

Declines in horse mussel density have been recorded on three beds in Loch Creran (with extent reduction also recorded at one of them) between 2005 (Moore et al., 2006) and 2018 (Moore et al., 2020). The scale of bed loss is unknown, although the previous extent of the bed is likely to have been small (based on the limited sampling intensity in 2005, Moore et al., 2006).  The total known habitat extent in Loch Creran has increased between 2005 and 2018, although this is due to wider sampling, as in the case of flame shell beds.  Surveys in 2019 by SNH and Marine Scotland (Williams, 2019; Moore, 2020) have revealed new beds off Gigha and in the Sound of Mull.

Complete subtidal seagrass bed loss is known to have taken place within the last 20 years in Loch Creran. There are no measures of bed extent for the habitat, but there are several records of its presence from 1883 - 2002.  A 2019 survey of the sea loch (Moore, unpublished) confirmed its absence.  Recent citizen science surveys have extended our knowledge of the distribution of the habitat elsewhere in the SMR, with new beds identified in 2019 in Loch Craignish by Seasearch and in 2020 in Loch Shuna by Narwhal Expeditions.

Within the Argyll SMR serpulid aggregations are only known to occur in Loch Creran, where they have formed bushy, well-developed reefs up to 75 cm in height and 1-2 m in diameter.  In 2005 the extent of the serpulid reef habitat was assessed at 108 ha (Moore et al., 2006). Most of the habitat appeared in good condition, albeit there was localised damage from demersal fishing, finfish and mussel farming, vessel moorings and organic pollution, although cessation of a major organic discharge had led to some recovery of the habitat (Moore et al., 2006). Condition monitoring in 2017 to 2019 revealed a marked deterioration in the status of the habitat, with widespread fragmentation of the reefs, loss of most of the larger structures and a loss of habitat extent of the order of 38 ha (Moore et al., 2020).    The cause of habitat deterioration is uncertain; however, it is considered most likely that it is part of a long-term natural cycle of degradation without compensatory replenishment (see Moore et al. (2020) for further details).

Confidence in the SMA2020 subtidal biogenic habitat assessment is low.  Apart from serpulid aggregations, the extent of the habitats in the SMR is poorly understood.  Also, the relative importance of natural versus anthropogenic drivers of temporal change is inadequately known, although it does appear that anthropogenic factors are considered unlikely to be significant drivers in serpulid reef habitat loss.

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 for the SMRs.

Twenty per cent of the seafloor of the Argyll SMR is predicted to experience no mobile fishery disturbance, which is the second highest figure for all SMRs (average 12%) (Figure 3).  The model predicts 44% of the seabed to suffer high disturbance, which is slightly below the average value of 50% for the SMRs.  Areas of high disturbance are concentrated to the west of Kintyre, between Jura and Mull, off the north and west of Mull and north west of Coll and Tiree.  This corresponds largely to the distribution of mud, with some areas of sand and, to the north of Mull, coarse sediment and also reflects very closely the distribution of subsurface abrasion levels.  With the exception of the Firth of Lorn Fisheries Order, which was enacted in 2007, the demersal fisheries prohibitions within the relevant MPAs commenced in 2016 and so will have had little effect on the assessment, which covered the period 2012-2016.

 

Figure 3.  Predicted physical disturbance to the seafloor in the Argyll SMR and prohibition areas for all mobile demersal fishing.  (Note that the prediction of physical disturbance covered the period 2012-2016 and so the fisheries prohibition relating to the relevant MPAs will have had little effect on this assessment.  The exception is the prohibition that has been in place for the Firth of Lorn since 2007.

Priority Marine Features and birds (non-PMF)

Overview of recorded PMFs and birds

The Argyll 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 Argyll SMR

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

No. of species/

habitats recorded

Intertidal and continental shelf habitats

17

Fish[1]

21

Mammals (regularly occurring)

11

Shellfish & other invertebrates

7

Seabirds[2] (non-PMF) – breeding

20

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

14

The Argyll SMR has a total of 56 PMF habitats and species, and 34 marine bird species.  There is a number of records of native oysters, including native oyster beds of which there are very few remaining in Scotland.  Pink sea fingers have a restricted distribution and there are only a few records from the whole west coast including the Firth of Lorn and the Sound of Mull. Basking sharks migrate to this SMR during the summer and can be seen feeding at the surface between June and October each year. They gather in large numbers, sometimes hundreds, and may remain within the SMR until late October before many head south for the winter or into deeper water.

Progress in understanding intertidal and continental shelf habitats listed as PMFs

Over the last 10 years there has been a change in emphasis of survey work in the region, with much of the earlier work by government agencies focused on obtaining an understanding of the distribution and conservation importance of habitats and species through detailed examinations of the sea lochs.  Over the 2012 - 2018 assessment period the focus has turned to improving understanding of PMF distribution and to the identification and subsequent monitoring of MPAs, as well as building up a broad understanding of habitat distribution to guide MPA boundary setting and checking that implemented management measures are effective.

The temporal sequence of records of all PMF habitats in Argyll SMR is provided in Table 4 and illustrated in Figures 4 and 5 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.  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.

Table 4.  Temporal frequency of PMF habitat records within the Argyll 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.  *3579 records derived from the analysis of single video frames of serpulid aggregations are excluded.

PMF

<2012

2012-2018

>2018

 

All

CS

All

CS

All

CS

Blue mussel beds (intertidal)

12

0

1

0

0

0

Blue mussel beds (subtidal)

4

0

5

4

0

0

Burrowed mud

266

9

165

19

31

6

Flame shell beds

18

3

184

2

0

0

Horse mussel beds

31

1

140

25

16

4

Inshore deep mud with burrowing heart urchins

14

0

0

0

0

0

Intertidal mudflats

48

0

0

0

0

0

Kelp and seaweed communities on sublittoral sediment

168

30

38

34

47

7

Kelp beds

312

40

63

56

8

0

Low or variable salinity habitats

56

0

30

30

12

12

Maerl beds

66

6

108

21

30

0

Maerl or coarse shell gravel with burrowing sea cucumbers

7

2

2

2

3

0

Native oysters

2

0

10

2

0

0

Northern sea fan and sponge communities

73

19

43

26

32

2

Seagrass beds (intertidal)

13

0

1

1

0

0

Seagrass beds (subtidal)

44

3

15

5

3

3

Sea loch egg wrack beds

7

0

1

0

9

9

Serpulid aggregations

54*

2

48

21

2

0

Tide-swept algal communities

102

1

22

20

20

3

Table 4 illustrates the increasing importance of citizen science records in raising our understanding of PMF distribution.  The proportion of such records has increased from 9% before 2012 to 29% in more recent years.

There has been modest progress in the improvement of knowledge of blue mussel bed distribution in the region (Figure 4).  Seasearch surveys from 2016 - 2018 have expanded the known distribution of a subtidal bed on rock in West Loch Tarbert and new subtidal and intertidal beds were recorded in 2012 in Loch Sween (ASML, 2014).

There has been a large increase in the number of burrowed mud records since 2011, although this has largely served to better define habitat extent within areas of existing, but often sparse, records (Figures 4 and 5).  Knowledge of the probable distribution of the habitat is also available from annual Nephrops burrow density surveys carried out by Marine Scotland from 2007 - 2016.  While Nephrops is also associated with several other habitat types, these data indicate that burrowed mud is likely to cover extensive areas of the seabed to the west of Kintyre, west of Mull and north of Coll and Tiree.  Recent surveys in Loch Linnhe (SEPA, unpublished) and Loch Sween (Moore et al., 2013) emphasize the importance of Loch Linnhe in supporting the PMF component biotope SS.SMu.CFiMu.SpnMeg.Fun, characterised by the tall seapen Funiculina quadrangularis, and the importance of Loch Sween in supporting the most extensive UK example of the component biotope SS.SMu.CFiMu.MegMax, characterised by the large mounds of the spoon worm, Maxmuelleria lankesteri.

Surveys over the period 2012 - 2019 have recorded losses in extent of seagrass and horse mussel beds and serpulid aggregations in Loch Creran, and the loss of a flame shell bed at nearby Port Appin (see the biogenic habitat assessment) ). Elsewhere, knowledge of the distribution of subtidal seagrass beds has been much improved, particularly in Loch Sween (Moore et al., 2013; Seasearch, unpublished).

There have been considerable recent gains in knowledge of the distribution of low or variable salinity habitats and tide-swept algal communities in the SMR, principally as a result of 2017 - 2019 Seasearch surveys of Lochs Creran, Etive, Linnhe and Sween and a 2019 Marine Scotland survey off Jura and Islay (Shucksmith, Shelmerdine, & Shucksmith, 2021).

Maerl is not particularly well-developed in the Argyll SMR, but post-2011 survey work by SNH and Marine Scotland have confirmed and mapped in detail dense maerl beds in Loch Sween (Moore et al., 2013) and identified new beds in the Sound of Islay (Shucksmith et al., 2021) and off Gigha (Williams, 2019), whilst a 2016 Seasearch survey recorded a rich bed off Ulva, west of Mull.  The few existing records of the related ‘maerl or coarse shell gravel with burrowing sea cucumbers’ PMF have also been supplemented by recent observations around Islay (Shucksmith et al., 2021) and Mull (Seasearch, unpublished).

Since 2011 information relating to the native oyster in the Argyll SMR has been expanded through a Marine Scotland/SNH distributional survey of oyster beds in Loch Sween (Moore et al., 2013) and 2018 Seasearch records of the species in West Loch Tarbert.

There is now a more detailed understanding of the distribution of ‘northern sea fan and sponge communities’ following recent Seasearch observations, particularly in the Firth of Lorn, and surveys by Marine Scotland and SNH around Jura (Shucksmith et al., 2021) and in the Sound of Mull (Moore, 2019).

The number of known sea loch egg wrack beds in the SMR has more than doubled since 2018, largely as a result of 2020 surveys by Narwhal Expeditions in Loch Sween and in the vicinity of Loch Shuna.



Figure 4.  Temporal pattern of records of selected PMF habitats for the Argyll SMR.



Figure 5.  Temporal pattern of records of burrowed mud PMF component biotopes for the Argyll SMR.

Trends and status of grey and harbour seals

Grey seal pup production at the major breeding sites such as the Treshnish Isles SAC is monitored biennially and has shown an increasing trend in numbers and their status is assessed as ‘few or no concerns’.  Harbour seal numbers are monitored on a rolling 4/5year cycle and have shown little or no change over the assessment period and their status is assessed as ‘few or no 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 Argyll 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 Argyll SMR has increased since 1870 by 0.04 °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 +0.14 °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 Argyll SMR, as estimated from a historical climate model run (UKCP18), was 4 cm (likely range between 2 and 7 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 rise in the Argyll SMR is anticipated to be approximately 36 cm for a medium emissions scenario (UKCP18 RCP4.5; see also and Climate change Sea level assessment).

Detecting and understanding long-term change in biological time series is complex, and resolving that which is due to climate change remains a challenge. Data from the Lorn Pelagic Observatory in Loch Creran (1970-1981 and 2000-2015; see also see Plankton Assessment) show a decrease in abundance of diatom life forms and no trend for dinoflagellates. There are no data available for other pelagic lifeform groups. These changes were not correlated to sea surface temperature changes, used as a proxy for climate change. This may be due to a variety of factors, including the large gap in data (1982-1999) and other factors driving variability.

Summary

The Argyll SMR has seen a 6% decrease in freight tonnage over the five years from 2014-2018 and a 9% increase in passenger numbers over the same period whilst the GVA for marine tourism decreased by 26% in the four years from 2014-2017.  Over the five year period 2014-2018 in the Argyll and Clyde SMRs Atlantic salmon production increased by 41% and mussel production decreased by 48% and in the Argyll SMR Pacific oyster production increased by 14%. Rod and line salmon and sea trout catch weight decreased by 19% over the five years between 2014-2018.  An estimated 9 wet tonnes of seaweed were harvested annually.  Other active sectors include military activities, water abstraction and subsea cables.

The five main pressures affecting the SMR are Removal of target species, Removal of non-target species, Surface abrasion, Synthetic compound contamination and Underwater noise.  Other pressures identified are Deoxygenation, Death or injury by collision below water, Genetic modification and translocation of indigenous species, Hydrocarbon and PAH contamination, Introduction of microbial pathogens, Introduction and spread of non-indigenous species, Nitrogen and phosphorous enrichment, Organic enrichment, Physical change, Physical loss, Sub-surface abrasion/penetration and Visual disturbance.

There is no evidence of eutrophication as a consequence of nutrient enrichment 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 and concentrations in sediment and biota were stable or declining although concentrations of the PCB compound CB118 at some sites were unacceptable and at one site there was an increasing trend.  Litter and microplastics are present but microplastic occur at relatively low concentrations in the surface waters of the SMR and no beach litter data were available.  There are few noise data, and it was not possible to do an assessment.  Two of the four bathing waters in the SMR were assessed and were classified as excellent.  Concentrations of diarrhetic shellfish toxins exceeded regulatory levels in every year between 2010 and 2018, paralytic shellfish toxins concentrations resulted in site closures in 2013, 2014, 2015 and 2017.  Amnesic shellfish toxins in mussels were above regulatory limits in 2012.

Five new MPAs were designated between 2012-2018, and six new spatial management measures were put in place.  Spatial management was under discussion for a further one.  (Note that in December 2020, a further three MPAs were established.)  Subtidal biogenic habitats were assessed as ‘some concerns’ with recorded reductions in extent of flame shell, horse mussel and seagrass beds, and serpulid agregations.  44% of the seafloor is predicted to have been subject to high physical disturbance and 20% subject to none. 

There have been significant improvements in the knowledge of several seabed habitats including burrowed mud, flame shell beds, horse mussel beds, kelp beds and maerl beds, as well as northern sea fan and sponge communities, and serpulid aggregations. Citizen science records are making an increasingly important contribution to our understanding on habitats in this SMR. 

In the last 30 years sea temperature has risen by 0.14 °C per decade.  Sea level in 2018 is estimated 4 cm higher than the 1981-2000 average.