Marine Protected Areas and Large-Scale Features. Position Paper

Marine Protected Areas and Large-Scale Features.

Position paper

Summary This document considers the role of large-scale features in developing the Marine Protected Area (MPA) network in Scotland’s seas. It describes each of the large-scale features, outlines the approach to their inclusion in the process, and considers the possible MPAs and MPA search locations which contain these features in relation to the evidence available. Five large-scale features are included on the list of MPA search features: seamounts; continental slope; shelf deeps; shelf banks and mounds; and fronts. These features have been included to represent areas of potential wider significance to the overall health and biodiversity of Scotland’s seas in the development of the MPA network. Specific examples of large-scale features have only been included in possible MPAs and MPA search locations where evidence is available to suggest that they contribute to ecosystem function, for instance in terms of playing a key supporting role within the site or more widely; or providing functional links within the site; or in supporting linkages within the network and wider seas. It is anticipated that MPAs may be able to provide direct protection for large-scale features through management of pressures that have implications for their extent, structure and distribution within the site and thereby their wider function. Draft conservation objectives are to ‘conserve’ the function of large scale features included as protected features. In total 13 areas (10 possible MPAs and 3 MPA search locations) have been identified for large-scale features, where evidence is available to suggest they play a role in supporting ecological function. Assuming that at least 11 sites (taking account of alternatives) are progressed as MPAs, the coverage of large-scale features within the network is considered adequate, based on assessment against stage 5 of the MPA Selection Guidelines. Descriptions of specific large-scale features are provided in the annex, along with information on the role they are thought to play in supporting ecological function within possible MPAs / MPA search locations and more widely.

Contents table Page no. SUMMARY ...... 1 DOCUMENT PURPOSE ...... 3 LARGE-SCALE FEATURES AND THEIR ROLE IN THE SELECTION PROCESS ...... 3 DESCRIPTION OF FEATURES AND THEIR FUNCTIONAL IMPORTANCE ...... 4 Continental slope ...... 4 Seamounts ...... 5 Shelf banks and mounds ...... 6 Shelf deeps ...... 7 Fronts...... 7 PRINCIPLES FOR CONSIDERATION OF LARGE-SCALE FEATURES ...... 8 HOW IT IS ENVISAGED AN MPA WOULD BE USED ...... 9 Continental slope ...... 9 Seamounts ...... 9 Shelf banks and mounds / Shelf deeps...... 9 Fronts...... 10 DRAFT CONSERVATION OBJECTIVES FOR LARGE-SCALE FEATURES ...... 10 COVERAGE IN POSSIBLE MPAS / MPA SEARCH LOCATIONS ...... 10 REFERENCES ...... 12 ANNEX ...... 14 Annex 1 The role of large-scale features in supporting ecological function...... 14 Annex 2 Descriptions of large-scale features in possible MPAs/ MPA search locations24 Annex 3 Summary of data used to inform the definition of fronts ...... 29 Annex references ...... 31

Document purpose 1. This document considers the role of large-scale features in developing the MPA network in Scotland’s seas. It describes each of the large-scale features, outlines the current approach to their inclusion in the process and considers the possible MPAs/ MPA search locations which contain these features in relation to the evidence available.

Large-scale features and their role in the selection process 2. Five large-scale features are included on the list of MPA search features: seamounts; continental slope; shelf deeps; shelf banks and mounds; and fronts. The known distribution of large-scale features in Scotland’s seas is provided in Figure 1. 3. Large-scale features have been included as MPA search features to represent areas of potential wider significance to the overall health and biodiversity of Scotland’s seas in the development of the MPA network. This may be through taking into account ecological and geomorphological processes of importance to MPA search features or the wider marine environment. Large-scale features may also help enable consideration of connectivity within the network where they play a role in providing key linkages between different features. Specific large-scale features may contribute to the network through supporting species at a range of trophic levels, for example from areas of high primary productivity through to aggregations of mobile top predators. 4. This type of approach is inherent in the Scottish MPA Selection Guidelines, most notably in: guideline 1c which looks at the inclusion of areas of functional significance to the overall health and biodiversity of Scotland’s seas; guideline 2a which looks at the inclusion of combinations of features which are functionally linked; guideline 3 which describes the requirement to ensure integrity for the features an area contains; and guideline 5 which looks at functional links across the network. 5. Specific large-scale features are only being progressed within possible MPAs and search locations where there is evidence of the role they play in supporting ecosystem function, e.g. through the existence of data to suggest overlap or linkages with areas of high primary productivity or relative abundance of mobile top predators. This evidence would not necessarily have to relate back to other MPA search features or threatened/declining features. For example, it may also relate more generally to provision of ecosystem services and/or supporting the wider biodiversity of Scotland’s seas.

Figure 1 Known distribution of large-scale features in Scotland’s seas

Description of features and their functional importance

Continental slope 6. The continental slope is a geological feature which divides the shelf sea and deep ocean ecosystem. 7. In Scotland, the continental slope comprises two distinct regions; that to the north of the Wyville-Thomson ridge (the Faroe-Shetland Channel slope) and that to the south of the Wyville-Thomson ridge (the Hebridean slope). 8. Dependent on depth, a wide range of sediment types may be present on the continental slope that provide habitat for a variety of benthic species. These range from cobbles and boulders in shallower areas of the slope to finer sands and muds in deeper areas (Bett, 2000). For example, the presence of iceberg ploughmark zones, derived during glacial melt on the Faroe-Shetland Channel slope, provide hard substrata for the settlement of a range of benthic species such as cold-water corals and deep sea sponges. 9. The interaction between hydrographic processes and the topography of the slope can also be significant. In the Faroe-Shetland Channel, for example, five different water masses converge in the relatively narrow channel. Of particular importance is the boundary between the relatively cooler and relatively warmer masses of water that occur between approximately 350 and 650 m, known as the intermediate water masses. Here the presence of strong vertical gradients in temperature permits internal wave formation leading to a zone of deep-water mixing and enhanced current speeds. This has a strong influence on primary and secondary productivity in the channel at these depths and the diversity of life found on the slope. Benthic fauna

for instance show a diversity and abundance maximum at the intermediate water masses (Bett, 2000, Narayanaswamy et al., 2005, 2010). The same is true for fish assemblages in the channel, with a diversity maximum at the transition zone between water masses (Bullough et al., 1998; Gordon, 2001). 10. The interaction between hydrographic processes and the continental slope may enhance feeding conditions through the aggregation of principle prey items (e.g. squid, herring, blue whiting and krill) for several species of cetacean, including sperm whale, minke whale, killer whale, fin whale, long-finned pilot whale and Atlantic white- sided dolphin (Macleod, 2004; Macleod et al., 2006, Stone, 1988; Swift et al., 2002; Weir et al., 2001). 11. Large et al. (2010) report that blue ling are known to aggregate for spawning on the Hebridean slope and at peak depths of between 730 and 1100 m. 12. To the north of Scotland, the topographic nature of the Faroe-Shetland Channel slope and wider channel is thought to be of significance as a migratory pathway/corridor for several cetacean species. Of these, fin and sperm whales are the most regular users of the route based on the data available. These cetacean species seem to use the channel as a passage way to move through into colder, temperate waters to the north to feed in the early summer months whilst some remain in the channel (e.g. Macleod et al. 2006) before travelling further south to lower latitudes to overwintering and breeding grounds in the autumn and winter.

Seamounts 13. Seamounts are undersea geological structures at least 100 m high that do not reach the sea surface. They are generally conical, elliptical or elongated in shape, and usually of volcanic origin and/ or associated with geological faults and magma production hotspots. 14. There are three seamounts in Scottish waters, all of which fall within the Rockall Trough to the far west of Scotland. These are Rosemary Bank, Anton Dohrn and the Hebrides Terrace. 15. Internal tides and seamount-trapped waves may be created by the interaction between oceanic currents and the topography of seamounts (Stashchuk and Vlasenko, 2005). This can generate downwelling and advection processes at seamounts that supply particulate organic matter to filter feeders such as cold-water corals (Davies et al., 2009). As a result of this and the availability of hard substrata, seamounts in Scottish waters can often host diverse benthic communities which include cold-water corals, deep sea sponges and coral gardens. The three- dimensional structure of these communities serve to increase species richness on seamounts, including crustaceans, cephalopods, echinoderms, and anemones (FRS, 2008; Howell et al., 2010; ICES, 2011). 16. The hydrographic processes occurring on and around seamounts can also promote upwelling of deeper, nutrient-rich waters that increase surface primary production (White et al., 2007). They can also serve to retain prey items and key species around seamounts. For example, down-welling eddies associated with Taylor Cones (cone shaped jets) can promote the retention of larval fish (Dower and Perry, 2001). These larvae may be important sources of food for other fish, marine mammals, cephalopods and birds. 17. The biodiversity on seamounts attract rich fish communities that may use the seamount for foraging, breeding and spawning. Rosemary Bank for example has been identified as an important spawning ground for blue ling (Large et al., 2010), with over 40% of the population engaged in spawning there (Large et al., 2004), and hosts important aggregations of blue whiting (Neat et al., 2008).

18. The positive relationship between the steep slopes of the seamounts and enhanced vertical mixing supports higher fish and cephalopod prey densities. This in turn supports cetacean populations. The aggregations of blue whiting at the Rosemary Bank seamount for example may be linked to the occurrence of large schools of marine mammals (Weir et al., 2001), where they may topographically ‘focus’ prey across small areas thereby minimising energy expenditure (Bailey and Thompson, 2010). 19. Many marine mammals are long-ranging species, travelling hundreds to thousands of kilometres along traditional migration routes. For the cetaceans found in the vicinity of Scottish seamounts, the migration route through the Rockall Trough to their overwintering grounds in the Faroe-Shetland Channel is one of the most important to their life histories (Evans, 1997; Swift et al., 2002; Macleod et al., 2003). 20. The hydrography of Scottish seamounts could affect larval dispersion and species connectivity over wide spatial scales. Eddie formation near Rosemary Bank for example may serve to advect particles further downstream. This could include nutrients, organic matter, phytoplankton, zooplankton and even fish.

Shelf banks and mounds 21. Shelf banks and mounds are formed by the action of strong currents on mobile sediments (usually coarse sands and gravels) and rise with a slope greater than 2% from the seafloor. 22. Shelf banks and mounds occur off all Scottish coasts e.g. the Shiant East Bank in the Minch; Nun, Whiten Head and Stormy Banks off the north coast; Dutch and Forty Mile Banks to the east of Shetland; the Smith Bank in the outer Moray Firth; and the Marr, Montrose, Berwick, and Scalp Banks, together with the Wee Bankie, in the outer Firth of Forth. 23. The structure and substrate of shelf banks and mounds can enable a range of benthic habitats and species to colonise (e.g. northern sea fan and sponge communities on Shiant East Bank), which may in turn provide increased shelter for other species, thereby supporting a localised increase in biodiversity. 24. The passing of tidal currents across the surface of banks and mounds can create turbulence leading to the formation of internal waves. This allows relatively cooler, nutrient-rich deeper waters to mix with relatively warmer, nutrient-depleted waters serving to increase primary and secondary production. This has been shown for example over the Firth of Forth Banks (Scott et al., 2010). 25. Increased productivity can in turn lead to prey aggregations, for example of sandeels, which are also able to settle in the coarse sediments characteristic of some shelf banks and mounds. The shallower nature of some shelf banks and mounds may make prey more available for predators such as seabirds, which are therefore likely to be attracted to these features. Other predators, such as seals and cetaceans, may also be attracted to prey concentrations. 26. Bank and mound features have been shown to be important habitat areas for sandeels and other fish species. Turbot Bank, and other such banks and mounds in deeper areas of Scotland’s seas, may be important as sandeel larval sources (Heath et al., 2012). Similarly Berwick Bank, for example, is thought to be an important spawning ground for plaice (Pleuronectes platessa), and may be important as a larval source for repopulating exploited stocks along the east coast of England (Lockwood and Lucassen, 1984).

Shelf deeps 27. Shelf deeps are enclosed topographic depressions on the seabed, in most cases created by glacial erosion during periods of lower sea level. Several types of deeps have been recognised in Scottish waters, including channels, troughs, valleys and canyons. 28. Shelf deeps are recorded from the north Irish Sea (e.g. Beauforts Dyke and the Mull of Galloway Canyons), around the west coast (e.g. Stanton and Malin Deeps, Gulf of Corryvreckan, Inner Sound of Raasay), to Shetland, and south through the Fladen Deeps in the northern North Sea to the Southern Trench in the Moray Firth, the Buchan Deep off Aberdeenshire and the Devil’s Hole, about 200km east of Dundee. 29. There have been few studies on the hydrographic characteristics of Scottish shelf deeps. In general, it is expected that deeps will exhibit weaker tidal and residual currents and therefore may be relatively low-energy areas, with reduced levels of mixing near the seabed and increased seasonal stratification. However, in some deep areas, energy may be enhanced through internal mixing as a result of sloping bathymetry, or through generation of density driven currents. The Muck Deep, for example, has been shown to have variable, but intensified near-bottom currents, generated as a result of internal tide (SAMS, unpub.). The residual flow has been described as westward towards land (SAMS, unpub.) and may contribute to density driven cross-shelf circulation (e.g. Ellett & Edwards, 1983). 30. Benthic community composition is highly likely to depend on the substrate type e.g. the base of the troughs where sediments accumulate is likely to support deep sediment (mud, sand or gravel) communities including seapens, burrowing sea anemones, sea cucumbers, starfish, brittlestars, and polychaetes. Hard substrates on the walls or steeper slopes of the deep might support assemblages of faunal communities, including cup and soft corals, sponges, encrusting sea mats, and feather stars. 31. Studies related to the foraging behaviour of minke whales suggest there may be associations with the southern extent of the Muck Deep (Anderwald et al., 2011) and with deep areas in the Moray Firth (Robinson et al., 2009). However it is not clear whether the deeps specifically are providing enhanced feeding opportunities for cetaceans. A concentration of minke whale records also exist from an area of the central northern North Sea which encompasses the Devil’s Hole deeps (Reid et al., 2003), but again a direct correlation between bathymetry and whale distribution is not clear. 32. There is some evidence linking shelf deeps to seabird foraging in the North Sea, where, for example, approximately 19% of foraging trips by gannets at the Bass Rock colony were in the vicinity of the Buchan Deep. The distribution of key foraging areas has been linked to sites of enhanced productivity, such as fronts (Camphuysen & Webb, 1999), which may be related to bathymetric features such as deeps.

Fronts 33. Fronts form at the boundary between two different water bodies, for example where tidally mixed coastal waters meet thermally stratified offshore waters, or where fully saline oceanic waters meet lower salinity inshore waters that have freshwater influence. The interaction between oceanic currents and topographic features such as islands, seamounts, banks, mounds, deeps and channels can also lead to the formation of localised fronts and other hydrographic processes such as eddies and internal waves. 34. Persistent fronts are known to occur on the west coast of Scotland, particularly from the Clyde (Clyde Sea sill) out to the west of Islay (the Islay front), south-west of Tiree and south of the outer Hebrides (Barra mixing zone). Fronts also occur around the

Northern Isles (Orkney-Shetland front) and in the North Sea (e.g. the Aberdeen- Buchan front). 35. Frequently occurring fronts (e.g. spatially and/or seasonally) are widely recognised as supporting enhanced biological activity. Mixing at the boundary between two water bodies can lead to elevated primary and secondary production and as a result can serve to aggregate prey species. For example, the early life stages of fish have been linked to the presence of fronts in the North Sea and settled sandeels often feed on plankton concentrated in nearby frontal features at the edge of sand banks. 36. Predators such as seabirds, marine mammals and predatory fish are attracted to prey aggregations. Other species such as basking shark, have been associated with fronts where zooplankton prey is concentrated. Speedie et al. (2009) identified basking shark hotspots to the south-west of Canna and around Tiree, which may relate to the presence of small-scale fronts associated with complex topography and tidal currents. 37. Sharp gradients in temperature and salinity at fronts may also result in these areas being used as migration corridors or potentially delineate boundaries for some species if they are near the edge of their range. 38. Fronts and other hydrographic processes also play an important role in the circulation and ecology of Scotland’s seas and more widely. Specifically, they may have a role to play in terms of connectivity, through enabling the circulation and transport of nutrients, larvae, oxygen from primary production and heat within Scotland’s seas and the wider North-East Atlantic. Fronts and other hydrographic processes may also lead to separation and/ or influence local recruitment, for example where forcing mechanisms result in areas of retention (e.g Hill et al., 2008).

Principles for consideration of large-scale features 39. Large-scale features are only being included in possible MPAs/ MPA search locations where evidence is available to suggest they meet one or more of the principles set out for their inclusion in the network. The principles for inclusion of large-scale features have been developed based on the MPA Selection Guidelines and are outlined below: a. Does the large-scale feature play a key supporting role, either for other MPA search features within the search location or for the wider health and biodiversity of Scotland’s seas, for example in terms of supporting areas of enhanced primary and secondary productivity or significant prey aggregations that might result in important feeding, nursery or spawning grounds (Guideline 1c); b. Does the large-scale feature provide an important functional link between MPA search features or other protected features within the MPA search location, for example where the large-scale feature provides the conditions which allow presence of the other protected features, such as a shelf deep providing the substrate and other environmental conditions necessary for colonisation by benthic protected features (Guideline 2a); c. Does the large-scale feature provide a mechanism by which the scale of the search location could be sensibly adapted to ensure it is suitable for maintaining the integrity of the features for which the area is being considered (Guideline 3); d. Does the large-scale feature support linkages within the network or more widely e.g. representing important sources or sinks of larvae, or areas important for key life stages for mobile species such as cetaceans (Guideline 5).

How it is envisaged an MPA would be used 40. In general it is anticipated that MPAs may be able to provide direct protection for large-scale features through management of pressures that have implications for their extent, structure and distribution within the site and thereby their function, both within the site and more widely. In some sites it may also be relevant to provide protection for species and habitats which are linked to the presence of the large- scale feature within an MPA. These habitats and species may also be recognised as protected features in some sites. Further detail on how an MPA might be used for each type of large-scale feature is provided below. 41. Work has been undertaken to assess the sensitivities of important geodiversity features in Scotland’s seas and this has implications for the management of geological large-scale features (Brooks, 2013). This will be reflected in the relevant site Management Options Papers.

Continental slope 42. Inclusion of areas of the continental slope in the MPA network presents the opportunity to capture the ecological range and geographic variation associated with offshore subtidal sands and gravels and offshore deep sea muds in Scotland’s seas. The Faroe-Shetland Channel slope for example represents the only area in UK waters influenced by Arctic waters. 43. MPAs with representative areas of the continental slope included as proposed protected features will be managed for the sensitivity of benthic communities associated with this feature. Significant geodiversity features, e.g. iceberg ploughmark zones, will also be taken into account where there is evidence to suggest management may be required. The continental slope itself is not considered to be threatened (Brooks, 2013).

Seamounts 44. The inclusion of seamounts in the MPA network presents the opportunity to afford protection to a range of fragile habitat-forming benthic communities including cold- water corals and deep sea sponges and the biodiversity they harbour. 45. It is likely that MPAs designated for seamounts will be managed in accordance with the sensitivity and known condition of the benthic communities they support. However, where persistent aggregations of mobile species are present, it may also be appropriate to consider them. 46. The physical presence of seamounts and the way they interact with oceanic currents plays an important role with respect to patterns in hydrography and subsequently primary and secondary production. As such, it may become important to safeguard the physical presence of seamounts against potential future pressures such as removal of substrate.

Shelf banks and mounds / Shelf deeps 47. For shelf banks and mounds and shelf deeps, MPAs may be able to provide direct protection through management of pressures which have implications for the structural integrity of these large-scale features. There is considerable overlap with these large-scale features and areas considered to be of geodiversity importance in Scotland’s seas (see Brooks et al., 2011) and so information on the sensitivity of these geodiversity features will be used (Brooks, 2013). 48. Shelf banks and mounds and shelf deeps may also need to be managed in accordance with the sensitivities of the benthic communities they support. For example, sandeels and sand and gravel habitats are often associated with shelf banks, while burrowed mud communities may be associated with fine muds and silty

sands that accumulate in shelf deeps. It may also be appropriate to consider persistent aggregations of mobile species if they are associated with shelf banks and mounds, or shelf deeps, including indirectly, for example due to the influence of local topography on hydrographic conditions and productivity.

Fronts 49. For fronts, MPAs may be able to provide direct protection through management of pressures, such as the removal or diversion of energy, which could have implications for the structure or distribution of the feature, and therefore secondary effects on its functional role. It may also be important to consider the species and habitats (or geological features) which occur consistently in association with the front, due to the favourable conditions (e.g. elevated productivity) it provides.

Draft Conservation Objectives for large-scale features 50. Conservation objectives have been developed for protected features to reflect the purpose of Nature Conservation MPAs, as defined in the Marine (Scotland) Act 2010 and the Marine and Coastal Access Act 2009. The Acts describe Nature Conservation MPAs as being for the conservation of marine flora or fauna, or for the conservation of marine habitats or geological/ geomorphological features. Two broad categories of conservation objectives will be set; either to ‘conserve’ or ‘recover’ the protected feature. ‘Conserve’ conservation objectives have been recommended for all large-scale features within possible MPAs and MPA search locations.

Coverage in possible MPAs / MPA search locations 51. Thirty-three possible MPAs were included in the 2013 MPA consultation. An additional four MPA search locations are pending further review before assessment and consultation. Of these total 37 possible MPAs / MPA search locations, 13 have been identified for large-scale features. Table 1 and Figure 2 illustrate the coverage of large-scale features in possible MPAs/ MPA search locations. 52. The adequacy of coverage of large-scale features within the network has been considered in accordance with the MPA Selection Guidelines. 53. In the first instance, specific examples of large-scale features were only included in possible MPAs / MPA search locations where evidence was available to suggest they play a role in supporting ecological function, as outlined under principles for consideration of large-scale features. A summary of the evidence available for each possible MPA / MPA search location is presented in Annex 1. Detailed assessments against the MPA Selection Guidelines are also available for each possible MPA, and can be accessed via the SNH and JNCC MPA web pages. Equivalent assessments will be completed for the remaining MPA search locations in due course. 54. Coverage was then considered in terms of the stage 5 guidelines, which look at whether areas contribute to the overall coherence of the network through representation and replication of features, provision of key linkages, as well as reflection of the range, geographic variation and resilience of features. Assuming that at least 11 (taking account of alternatives) of the 13 sites in table 1 are progressed as MPAs, the coverage of large-scale features within the network is considered adequate. 55. The characteristics of specific large-scale features present within each possible MPA / MPA search location are described in Annex 2. An assessment for each type of large-scale feature against stage 5 of the MPA Selection Guidelines has also been undertaken.

Table 1 Coverage of large-scale features in possible MPAs / MPA search locations*. (Areas marked with an asterisk are currently search locations) Name of possible MPA / MPA Code Large-scale features present search location* Faroe-Shetland sponge belt FSB Continental slope

Firth of Forth Banks Complex FOF Shelf banks and mounds

Geikie Slide and Hebridean Slope GSH Continental slope North-east Faroe-Shetland NEF Continental slope Channel Rosemary Bank Seamount RBS Seamounts Small Isles SMI Shelf deeps South-west Sula Sgeir Slide and SSH Continental slope Hebridean Slope The Barra Fan and Hebrides BHT Continental slope Terrace Seamount Seamounts Clyde Sea Sill CSS Fronts

Shiant East Bank* SEB Shelf banks and mounds Skye to Mull* STM Fronts Southern Trench* STS Shelf deeps Fronts Turbot Bank TBB Shelf banks and mounds

Figure 2 Coverage of large-scale features in possible MPAs / MPA search locations

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Large, P.A., Diez, G., Drewery, J., Laurans, M., Pilling, G.M., Reid, D.G., Reinert, J., South, A.B., and Vinnichenko, V.I. 2010. Spatial and temporal distribution of spawning aggregations of blue ling (Molva dypterygia) west and northwest of the British Isles. ICES Journal of Marine Science, 67. 494-501. Lockwood, S.L, and Lucassen, W. (1984). The recruitment of juvenile plaice (Plueronectes platessa) to their parent spawning stock. J. Cons. Int. Explor. Mer 41: 268-275. Macleod, K., Simmonds, M.P., and Murray, E. 2003. Summer distributions and relative abundance of cetacean populations off north-west Scotland. Journal of the Marine Biological Association of the UK, 83. 1187-1192. Macleod, K. 2004. Abundance of Atlantic white-sided dolphin (Lagenorhynchus acutus) during summer off northwest Scotland. Journal of cetacean research and management 6 (1) 33-40 Macleod, K., Simmonds, M., Murray, L. 2006. Abundance of fin (Balaenoptera physalus) and sei whales (B. Borealis) amid oil exploration and development off northwest Scotland. Journal of cetacean research and management 8 (3) 247-254. Narayanaswamy, B.E., Bett, B.J., Gage, J.D. 2005. Ecology of bathyal polychaete fauna at an Arctic–Atlantic boundary (Faroe-Shetland Channel, North-east Atlantic). Marine Biological Research 1, 20-32. Narayanaswamy, B.E., Bett, B.J., Hughes, D.J. 2010. Deep-water macrofaunal diversity in the Faroe-Shetland region (NE Atlantic): a margin subject to an unusual thermal regime. Marine Ecology 31, 237-246. Neat, F., Burns, F., and Drewery, J. 2008. The deepwater ecosystem of the continental shelf slope and seamounts of the Rockall Trough: a report on the ecology and biodiversity based on FRS scientific surveys. Fisheries Research Services Internal Report, No.02/08. Reid, J.B., Evans, P.G.H., and Northridge, S.P. (2003). Atlas of Cetacean distribution in north-west European waters. Joint Nature Conservation Committee. Peterborough, UK. Robinson K.P., Tetley M.J. & Mitchelson-Jacob E.G. (2009). The distribution and habitat preference of coastally occurring minke whales (Balaenoptera acutorostrata) in north-east Scotland. Journal of Coastal Conservation 13(1): 39-48 Scott, B.E., Sharples, J., Ross, O.N., Wang, J., Pierce, G.J., Camphuysen, C.J. 2010. Sub- surface hotspots in shallow seas: fine-scale limited locations of top predator foraging habitat indicated by tidal mixing and sub-surface chlorophyll. Marine Ecology Progress Series 408: 207-226. Speedie, C.D., Johnson, L.A., and Will, M.J. (2009). Basking shark hotspots on the West Coast of Scotland: Key sites, threats and implications for conservation of the species. SNH Commissioned Report No.339. Stashchuk, N., and Vlasenko, V. 2005. Topographic generation of internal waves by nonlinear superposition of tidal harmonics. Deep-Sea Research I, 52. 605-620. Stone, C.J. 1998. Cetacean observations during seismic surveys in 1997. JNCC Report 278. 57pp. [Available from the Joint Nature Conservation Committee, Aberdeen] Swift, R.J., Hastie, G.D., Barton, T.R., Clark, C.W., Tasker, M.L., and Thompson, P.M. 2002. Studying the distribution and behaviour of cetaceans in the northeast Atlantic using passive acoustic techniques. Report for the Atlantic Frontier Environmental Network. Weir, C.R., Pollock, C., Cronin, C. and Taylor, S. 2001. Cetaceans of the Atlantic Frontier, north and west of Scotland. Continental Shelf Research, 21: 1047-1071. White, M., Bashmachnikov, I., Arístegui, J., and Martins, A. 2007. Physical processes and seamount productivity. In: Seamounts: Ecology, Fisheries and Conservation. Pitcher, T.J., Morato, T., Hart, P.J.B., Clark, M.R., Haggan, N., and Santos, R.S. (Eds). Blackwell Publishing, Oxford. 65-84.

Annex

Annex 1 The role of large-scale features in supporting ecological function within possible MPAs / MPA search locations and more widely. Possible MPA / Name of large- Plays a key supporting role for health and Provides an important Provides a Supports linkages within the MPA search scale feature(s) biodiversity of Scotland’s seas? functional link within mechanism for network or more widely? location possible MPA / MPA scaling possible search location? MPA / search location to ensure integrity of protected features? Firth of Forth Shelf banks and Shelf bank and mound features support sand Interaction between The majority of the Connectivity modelling has Banks Complex mounds (Wee and gravel habitats suitable for the oceanic currents and banks and mounds identified a number of discreet Bankie, Marr, colonisation of sandeels (Wright et al., 2000). bank features creating in the area are areas of importance for Berwick, Scalp complex flow rates thought to play a sandeels on the Scottish and Montrose The shallow nature of the bank and mound and patterns resulting key supporting role continental shelf. The sandeels Banks) features makes sandeels more available to in a wide range of for health and in the Firth of Forth are thought foraging seabirds. The area is important for offshore subtidal sand biodiversity of to be relatively isolated to other seabird foraging from colonies on the Isle of and gravel sediment Scotland’s seas populations due to the May and as far afield as Berwick and types and and so have been hydrography in the area. As Northumberland (Camphuysen et al., 2011). subsequently diverse used as an such, the numbers present on benthic communities. important driver in the Firth of Forth Banks are Grey seal (Halichoerus grypus) are thought to determining the likely to be largely self- use the bank areas, particularly the Wee size of the area. recruiting. Bankie and Berwick Bank, as foraging areas for sandeel and demersal fish which are prey of grey seal (Prime and Hammond, 1990; McConnell et al., 1999).

Plaice spawning ground on Berwick bank (Lockwood and Lucassen, 1984).

Turbot Bank Shelf banks and The depth of the bank may limit seabird Significant Turbot Bank has Sandeels present on Turbot mounds (Turbot foraging for sandeels. Unknown for seals and aggregations of been a key driver in Bank may be an important Bank) cetaceans. sandeel are determining the larval source to wider UK supported on Turbot scale of the MPA populations Bank search location

The Minch is known to be an important area for seabirds (e.g. guillemot, razorbill, kittiwake, common tern and puffin) at various times throughout the year (Pollack et al., 2000), as well as cetaceans (e.g. minke whale and white beaked dolphin, Weir et al., in press).

Southern Trench Shelf deeps Frontal areas within the search location may The Southern Trench Both fronts and Minke whales are most (Southern Trench) provide enhanced foraging opportunities for a provides suitable shelf deeps may commonly observed during the Fronts range of species. Important areas for sandeel conditions for provide a useful summer feeding season for this (Aberdeenshire and herring are found within the Moray Firth burrowed mud, which mechanism for species. This is an important front) and off the Aberdeenshire coast (Coull et al., is located within the scaling the search lifecycle stage, where animals 1998; Ellis et al., 2012) and the location of deep. location. are believed to be building up these may partly be influenced by the energy reserves before presence of fronts (Munk et al., 2002). The Aberdeenshire The Southern migrating to winter breeding

Possible MPA / Name of large- Plays a key supporting role for health and Provides an important Provides a Supports linkages within the MPA search scale feature(s) biodiversity of Scotland’s seas? functional link within mechanism for network or more widely? location possible MPA / MPA scaling possible search location? MPA / search location to ensure integrity of protected features? front, and other Trench provides a areas. Minke whales are frequently observed in the hydrographic useful boundary for outer Moray Firth during summer (Robinson processes in the outer protection of an White beaked dolphins are also et al. 2007) when minke distribution is highly Moray Firth, may area of deep recorded most frequently in dependent on prey. Minke abundance in the influence prey burrowed mud. summer. It is thought the region outer Moray Firth has been positively availability in the area may provide habitat for correlated with both sandeel habitat and and thereby be linked Fronts have also important calving, nursing and hydrographic processes (Tetley et al. 2008). to the distribution of been used to guide breeding stages (Weir et al., Sandeel, followed by herring and sprat, were predators such as the boundary of the 2007; Canning et al., 2008) found to be the most important prey items for minke whale. search location and minke whales across Scottish waters, based are considered to While there are important on analyses of stranded animals (Pierce et provide a useful spawning areas for sandeel in al., 2004). mechanism for the Moray Firth, larvae are also scaling protection thought to be transported from White-beaked dolphins are recorded along for cetacean search the north-west of Orkney area the east Aberdeenshire coast, most features. (Proctor et al., 1998) commonly in summer. Coastal waters in the search location are also important for other Tagging data shows that cetaceans, including bottlenose dolphins seabirds are travelling large (Weir et al., 2008; Cheney et al., 2012), distances from northern harbour porpoise (Weir et al., 2007; Evans & colonies (e.g. Fair Isle and Wang, 2008) and, in recent summers, Orkney) in both egg laying and common dolphins (Robinson et al., in press). chick rearing lifecycle stages in In addition, modelling suggests that grey order to feed in this area (E. seals frequently use areas along the east Owen, pers. comm.) Aberdeenshire coast and off Rattray Head. The distribution of predators (including cetaceans and seals) is influenced in part by that of their prey, which may aggregate in more productive frontal areas.

Northern sea fan communities and dense aggregations of northern feather star are present on the slope leading into the shelf deep. Skye to Mull Fronts A surface thermal front arises to the south It is likely that the It is considered that Unknown. It may be useful to (Skerryvore front) west of Tiree during spring and summer, and skerryvore front and the skerryvore front consider potential links based an example 8-day composite satellite image other smaller scale may provide a on pathway of Scottish Coastal from spring 2011 suggests enhanced surface tidal fronts within the useful mechanism Current. phytoplankton levels on the nearshore side of search location help for scaling the the front. to provide favourable search location to feeding conditions for ensure integrity of Aggregations of basking shark are recorded both basking shark protection for to the south-west of Tiree, corresponding with and minke whale. mobile species. the location of tidal fronts. Basking sharks are known to associate with fronts where copepod prey is typically concentrated in areas of higher phytoplankton abundance (e.g. Sims and Quayle 1998).

Hydrographic processes are also likely to influence minke whale prey distribution and availability. Anderwald et al. (2012) found that chlorophyll concentration influenced minke whale distribution in the region during autumn, which may be due to aggregation of sprat prey in areas of higher productivity.

The Clyde Front likely provides important foraging habitat for seabirds, given the proximity to colonies on Sanda and Sheep Islands.

Basking sharks in the Clyde Sea were found to occupy stratified and frontal water masses in summer, which are associated with higher productivity (Sims et al., 2003)

North-east Continental slope Internal waves support heightened primary Enhanced current - Some cetaceans, most notably Faroe-Shetland (Faroe-Shetland and secondary productivity with evidence to speeds and food fin and sperm whales, use the Channel Channel slope) suggest a diversity maximum at the boundary availability associated passage through the Faroe- between water masses for the benthic with the boundary Shetland Channel as a passage

Dependent on depth, a wide range of sediment types may be present on the continental slope that provide habitat for a range of benthic species.

South-west Sula Continental slope Cold water cascades produced as a result of Large et al. (2010) - No evidence available Sgeir and (Hebridean slope) the topograpy of the Hebridean slope may report that blue ling Hebridean slope serve to increase water column mixing and are known to levels of primary productivity in some areas aggregate for Geikie Slide and spawning on the Hebridean slope The effects of hydrographic processes such Hebridean slope and as the North Atlantic Current and Slope at peak depths of The Barra Fan Current impinging on the Hebridean slope between 730 and and Hebrides serve to concentrate zooplankton, squid and 1,100 m.

There are no direct studies of the relationship between marine mammals and the Hebridean slope, but positive relationships between teutophagic species and continental shelf edges/slopes are recorded from elsewhere

Seabirds such as gannets, fulmars, great skua, Manx shearwaters, storm petrels and various gulls are known to congregate around the shelf break of the continental slope. The exact reason behind this is unknown, but may be associated with hydrographic processes taking place at the shelf break.

Rosemary Bank Seamounts The three-dimensional structure of fragile Seamounts in Seamounts provide The hydrography of Scottish Seamount (Rosemary Bank, benthic communities on seamounts serve to Scotland’s seas can a useful functional seamounts could affect larval Hebrides Terrace) increase species richness on seamounts, support a biologically unit for scaling dispersion and species The Barra Fan including crustaceans, cephalopods, diverse assemblage these areas in connectivity over wide spatial and Hebrides echinoderms, and anemones. of cold-water coral relation to the scales. The presence of eddies Terrace reefs, coral gardens features they near Rosemary Bank for

Possible MPA / Name of large- Plays a key supporting role for health and Provides an important Provides a Supports linkages within the MPA search scale feature(s) biodiversity of Scotland’s seas? functional link within mechanism for network or more widely? location possible MPA / MPA scaling possible search location? MPA / search location to ensure integrity of protected features? Seamount The biodiversity on seamounts attract rich fish and deep sea sponge contain example brings Norwegian Sea communities that may use the seamount for communities (Neat et Deep Water (Ellett et al., 1983) foraging, breeding and spawning. Blue Ling al., 2008; Howell et that could collide with has been identified as hosting important al., 2010), which seamounts and advect particles aggregations of blue whiting (Neat et al., suggests that local further downstream. 2008). Diverse fish assemblages found in productivity and/or Indeed, seamount productivity association with seamounts make them production are or production is more frequently important foraging areas for marine mammal coupled with derived from upstream sources species. important retention of nutrients, organic matter, The positive relationship between the steep mechanisms to phytoplankton, zooplankton, support these slopes of the seamounts and enhanced larvae and even fish that get communities. vertical mixing supports higher fish and advected to the seamount cephalopod prey densities. This in turn Rosemary Bank has (Genin and Dower, 2007). This supports cetacean populations. The been identified as an suggests seamount protection aggregations of blue whiting at the Rosemary important spawning could play an important role in Bank seamount for example may be linked to ground for blue ling the wider conservation of the occurrence of large schools of marine (Large et al., 2010), Scotland’s seas and further mammals at Rosemary Bank (Weir et al., with over 40% of the afield. 2001), where they may topographically ‘focus’ population engaged in Many marine mammals are prey across small areas thereby minimising spawning there long-ranging species, travelling energy expenditure (Bailey and Thompson, (Large et al., 2004), hundreds to thousands of 2010). hosts important kilometres along traditional

migration routes. Along the way, cetaceans are known to frequent seamounts as part of their life histories. For the cetaceans found in the vicinity of Scottish seamounts, the migration route through the Rockall Trough to their overwintering grounds in the Faroe-

Annex 2 Descriptions of large-scale features in possible MPAs / MPA search locations OSPAR Possible MPA/ Description of large-scale feature Datasets Characterisitics Region MPA search location Shelf banks and mounds The Firth of Forth Banks Complex is a series of UK Hydrographic Office Admiralty Charts. submarine glacial ridges, composed of poorly sorted East coa st, shallow open sediments (boulders, gravels, sands and clays) located Multibeam, backscatter and particle size coast examples. Firth of Forth in the outer Firth of Forth. Survey work has been analysis interpreted habitat maps (under II Banks Complex undertaken on the bank features in the area and on consideration). Largest complex of bank and

interpretation this will better develop our understanding mound features recorded in of the benthic communities with which they are 2011 ground-truthed data (drop down video Scotland’s seas. associated. and stills, grab samples.

Turbot Bank is a relatively small sandy bank feature UK Hydrographic Office Admiralty Charts. located north-east of the outer Firth of Forth. It East coast, deep open coast II Turbot Bank comprises circalittoral coarse sediments. 2013 ground-truthed data (drop down video example. and stills, grab samples, multibeam data.

Shiant East Bank is a series of bedrock, cobble and sand/mud sediment banks located in the Minch to the east of Harris and north of the Shiant Isles.

Scottish MPA project - Minches Survey. Based on 2011 survey data, the tops of the banks (at

about 30 m) are mainly scoured bedrock, with large 2011 data (towed video, grab samples) as coralline encrusted boulders and dense cobbles described in Moore, C.G. (2012), Moore and recorded below this at around 30-40 m. On the bank Atkinson (2012) and Axelsson, M. (2012). slopes, encrusted cobbles, boulders and pebbles on West coast, semi-exposed, III Shiant East Bank gravely sand are present to ~60 metres, with finer strong tidal currents. 2013 data (towed video) as described in sediments (silty fine sands with scattered gravel and Moore, C.G. (In press) sandy muds) present on slopes between ~60-100 m.

Fine burrowed mud typically present at the base of Geological data as described in Bradwell and banks (~75 – 150 m). Stoker (In press)

The underlying geology has been influenced by repeated glaciations over at least the last 500,000 years. Key geological features of interest include

bedrock and soft sediment drumlins, glacial lineations and iceberg scours (Bradwell & Stoker, In press) and the area is considered to be of international geological importance (Bradwell pers. comm.). Shelf deeps The Southern Trench is located along the south coast of the Moray Firth. It is an enclosed seabed basin 58 km long and up to 250 m deep, formed predominantly as a result of glacial processes. The morphology of the Scottish MPA project - East coast Survey 2011 East coast, open coast trench is irregular and forms the most topographically data (drop camera, grab samples). feature, glacial, largest of complex and deepest region of the Moray Firth. II Southern Trench ~150 similar (but smaller) BGS acoustic survey 2011. enclosed channels located off Based on 2011 survey data, soft sediments are east coast of Scotland. recorded throughout the central strip of the Southern DTI acoustic data 2003. Trench and predominantly in deeper areas, while harder substrates were recorded on plateaus near steep slopes. The Sound of Canna is a steep-sided channel, formed by glacial erosion and reaching a maximum depth of MSS survey 2009. 275 m. It has steep sublittoral rock walls along the

south and east coasts of Sanday which drop to a Scottish MPA project – Canna surveys 2010/ West coast, glacial troughs/ III Small Isles sediment floor at over 60 m, where there is an area of 2011 (drop down video, grabs). channels. glacial moraine. Small rock walls and boulder piles are

also scattered throughout the deep channel. Extensive BGS acoustic survey 2011. areas of burrowed mud and mixed shelly mud are present in the deep. Fronts (and other hydrographic processes) The Clyde front forms in the area of the Clyde Sea sill, where the tidally mixed North Channel of the Irish Sea MB0102 – surface fronts based on 1km SST West coast, continental shelf meets the calmer less saline Clyde Sea. Beyond the data 2000-2009. feature. sill, the North Channel is well mixed year round, while

weak tidal currents in the Clyde Sea allow thermal Surface fronts based on 300m and 1km ocean Surface to bottom fronts III Clyde Sea Sill stratification, particularly in summer when the weather colour data 2009-2011. present year round, although is warmer and typically more stable. In winter, frequent thermal fronts are increased freshwater input from the Clyde and other Clyde sea- Malin shelf transect (e.g. Tett, evident during summer rivers helps to preserve a density driven stratification. 1997). Not yet incorporated. particularly. Thermal and density stratification result in a relatively persistent year-round front, although the balance of

factors influencing front formation varies seasonally.

The location of the front is evident from satellite-derived frequent fronts data, based on sea surface temperature, which indicate that thermal fronts are present throughout the year. A less frequent front based on satellite derived colour (chl-A) is also evident. A data snapshot from autumn 2010 indicates slightly elevated concentrations of phytoplankton in the area of the Clyde Sea sill.

Frequent thermal fronts are present to the south west of Tiree within the Skye to Mull MPA search location. These are tidally/ topographically driven and present to some extent year round, although particularly evident in spring and summer. The fronts in this location form at the boundary between the tidally-mixed zone on the West coast, continental shelf relatively shallow inner shelf of Skerryvore and more feature. stratified waters further away from the shelf. As such, the location of the front closely reflects the bathymetry MB0102 – surface fronts based on 1km SST Frequent thermal fronts in the region. A slightly increased front frequency is data 2000-2009. arising particularly in spring- observed in the same location based on ocean colour summer, although present to III Skye to Mull data also, although this is less clear. An enhanced Surface fronts based on 300m and 1km ocean some extent throughout the colour snapshot during spring (April) 2011 indicates a colour data 2009-2011. year. Slight increased clear front between nutrient rich coastal water and frequency in fronts based on clearer offshore water during the spring bloom. chlorophyll signature – Simplified tidal mixing maps based on h/U3 similarly seasonality difficult to highlight regions of strong mixing (no stratification) interpret. around headlands and areas with complex topography, such as over the skerryvore shelf to the south-west of Tiree. Layering is predicted to be stronger away from these mixed zones, with fronts forming at the mixed/layered boundary. Frequent thermal fronts are present along the east MB0102 – surface thermal fronts at 1km North Sea, continental shelf Aberdeenshire coast and further offshore in the region resolution. feature. of Rattray Head. These are thought to be tidally/ II Southern Trench topographically driven, as a result of mixing in shallow Surface fronts based on 300m and 1km ocean Thermal fronts are evident all coastal waters as tidal currents pass over a narrow colour. year round, but particularly in shelf along the east coast. spring and summer, where the

Data described in Tetley (2008). fronts extend further offshore A frequent colour front is also observed along the east (and likely relate to spring coast in all seasons. Off Rattray Head two distinct Data described in Hill et al. (2008). bloom). During autumn and fronts appear to be present, with an enhanced colour winter thermal fronts are snapshot from spring (March) 2011 suggesting the present in a narrow coastal more coastal front is primarily related to sediment band. (which appears to be retained in a narrow band) while the offshore front relates to a phytoplankton bloom. Colour fronts are present in all seasons, although near The hydrography in the southern outer Moray Firth is coastal fronts are particularly thought to be influenced by the mixing of and/or obvious in autumn winter, transition between a warm water plume extending out while front frequency offshore from the inner Firth and a coldwater extension of the is increased during spring/ Fair Isle current which circulates colder water into the summer. Moray Firth.

In addition to surface frontal features, Hill et al. (2008) describe a seasonal near-surface frontal jet, running southwards through the MPA search location along the east Aberdeenshire coast, driven by the presence of a bottom front. These narrow, fast-flowing jets form above sharp horizontal gradients in bottom temperatures and/or salinities; in the region of the search location, this feature is likely formed due to a cold pool of water trapped below the summer thermocline in the North Sea (Hill et al., 2008). Continental slope South-west Sula The Hebridean slope to the west of Scotland extends V Sgeir and from the Wyville-Thomson ridge in the north Hebridean slope (approximately 60°N) in a southerly direction to the Geikie Slide and Porcupine Bank (approximately 54°N). The Hebridean V Faunally and hydrographically Hebridean slope shelf slope runs approximately NNE-SSW, falling away UK Hydrographic Office Admiralty Charts. distinct to the Faroe-Shetland sharply from the Hebridean Sea into the Rockall Channel slope to the north of The Barra Fan Trough. Relief is very sharply defined at the top of the Scotland. and Hebrides V shelf slope where the seabed gradient suddenly Terrace increases from on average 0.1 degrees to between 2 Seamount and 14 degrees between 140 and 200 m.

Large volumes of sediments have been deposited and in some places form distinct muddy sedimentary fans. The Hebridean slope represents the largest uninterrupted area of muddy sediments in the UK but in places is interspersed with boulders and cobbles. North-east Faroe The Faroe-Shetland Channel is a rift basin situated I,II Shetland between the Scottish continental shelf and the Faroe Channel Plateau at 60 ° W and 60 – 63 ° N and ranges in depth from 100 m on the continental shelf to approximately 1600 m at its deepest. The channel narrows from 175km wide in the North (62°N) to 90 km in the south (60°N) and depth also changes across the same distance from 1600 to 1000 m. The range in temperature is much greater than the Hebridean slope and varies from -1.5 – 14 °C. Faunally and hydrographically The channel is connected to the Norwegian Sea in the UK Hydrographic Office Admiralty Charts. distinct to the Hebridean slope northeast and to the Atlantic via the Wyville-Thomson Faroe-Shetland to the west of Scotland. II Ridge and Faroe Bank Channel in the southwest and is sponge belt an important exchange of water between the Atlantic and Norwegian Basins. The Wyville-Thomson Ridge has a sill depth of around 600 m (Sherwin, 1991) and acts to prevent deeper cold water flowing from the Faroe Shetland Channel into the Rockall Trough. A range of sediment types are present on the Faroe- Shetland Channel slope, ranging from cobbles and boulders in shallower areas to fine muds in deeper areas. Seamounts Rosemary Bank is circular in shape and about 65 km in UK Hydrographic Office Admiralty Charts. Rosemary Bank diameter. It is surrounded by moat and ridge features One of three seamounts V Multibeam and backscatter data. Seamount and gently slopes into a domed peak at about 550 m recorded from UK waters. depth. 2011 ground-truthed data (drop down video The Barra Fan Hebrides Terrace Seamount is an elongated seamount and stills, grab samples – under consideration). and Hebrides reaching to depths of 1000 m and has what appear to One of three seamounts V Terrace be extensive gully features. recorded from UK waters. Seamount

Annex 3 Summary of data used to inform the definition of fronts

The data which have been used to inform the definition of fronts in Scotland’s seas at a national level are described in table A3. These data are included in GeMS1.

Table A3 Indicating the main data that have been used to inform the definition of fronts and other hydrographic processes in Scotland’s seas Data source Description Seasonal surface thermal front  AVHRR 1km SST data 2000-2009. frequency, derived from sea surface temperature Front detection applied to sea surface temperature data (~1mm depth) can provide information on tidal mixing fronts and fronts Source: Miller et al. (2009) associated with large geomorphic features. There may be some overlap here as geomorphic features can cause tidal mixing fronts. Some shelf and oceanic fronts may also be detected, although where these are temporally and spatially consistent, its likely there is also a geomorphic reason for their presence.

Seasonal surface front  MERIS 300m chlorophyll data 2009-2011 frequency derived from ocean colour  MODIS 1km chlorophyll data 2009-2011 Source: Miller et al. (2014) Front detection applied to colour data (~10 metre depth) should provide information on shelf break fronts, estuarine and plume fronts, possibly on sea loch fronts. 300 m data provides increased resolution for fronts associated with geomorphic features and close to the coast, while 1km data provides better overall data coverage.

The existing national datalayers for fronts are considered to provide good representation of surface fronts in Scotland’s seas. However, it is recognised that the data sources listed in table A3 do not provide a national overview of sub-surface processes and also that additional data are available which could provide further information on fronts and other hydrographic processes. Many of these additional datasets are not able to provide a national overview for Scotland’s seas or would require considerable analysis in order to create such a layer.

Therefore MPA search locations for fronts have been identified primarily on the known distribution of surface fronts. Features present in the identified MPA search locations are recognised as surface to bottom fronts.

Where possible it is proposed that the following additional data will be used to provide further context or inform our understanding of particular areas of interest:

 Cefas model2 which defines various hydrodynamic regions in the North Sea, including permanently stratified, permanently mixed, seasonally stratified and

1 GeMS (Geodatabase of Marine Features in Scotland) is a collation of marine biodiversity data to inform work on the Scottish MPA project. It contains records of known Priority Marine Features (marine habitats and species of prioritised conservation importance) and MPA search features in Scottish waters. 2 Modelled results from a 50-year hindcast simulation (covering 1958-2008, using the GETM-ERSEM model) used to define different hydrodynamic regions in the North Sea.

ROFI areas. Areas which fall outwith any of these states within the model represent areas where there is regular exchange between the states of stratification and mixing and are considered to be of functional importance in context of the North Sea/ east coast region (P. Tett, pers. comm.).  Tidal mixing models for the west coast based on h/U3 (e.g. Pingree and Griffiths, 1978; more recent modelling of specific sub-areas). In relation to this, further consideration is needed on the types of area which may be of particular functional importance on the west coast e.g. it is considered possible that on the west coast, mixed areas rather than areas which fluctuate between mixing and stratification are of importance.  Mapped sub-surface fronts and near surface jets (Hill et al., 2008) can provide an indication of the location of important sub-surface features in Scotland’s seas, such as bottom fronts and near surface frontal jets.

It is acknowledged that more detailed investigation of existing datasets (e.g. drifter data, ICES temperature/ salinity data, Berx and Hughes (2009) data product and POLCOMS) could help to better define sub-surface features in Scotland’s seas, including bottom fronts and near surface frontal jets. However it is uncertain whether the necessary data to detect these features at suitable resolution exist in available data, or whether they would be well enough represented to provide detail on their location, duration, persistence and variability. Given the scale of the required analysis and uncertainty in the potential outputs, this work has not been progressed at a national level. However, it is anticipated that it may be relevant to undertake more detailed analyses of some of these datasets to inform our understanding within particular areas of interest in Scotland’s seas e.g. Faroe-Shetland channel.

It will also be important to take account of knowledge and information in published literature and, where available, through more detailed, area-specific studies.

Annex references

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