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. 1 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 2 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. 3 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 4 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,