Appendix 7 Benthic Ecology – Baseline Environment
7.1 Desktop Study
- An initial desk based review of literature and data sources to support this Offshore EIA Scoping Report has identified a number of data sources which provide coverage of the Proposed Development, and which will provide context to the site-specific benthic ecology survey data collected (see section 7.2). These are summarised in Apx. Table 7. 1 Open ▸ .
Apx. Table 7. 1: Summary of Key Desktop Datasets and Reports
- An overview of the site-specific survey data available to support the Offshore EIAR is provided below:
- existing data: habitat data and maps generated by the benthic baseline characterisation surveys (grab, video and epibenthic trawl surveys) for Seagreen Alpha/Bravo in 2011 (Seagreen, 2012a);
- Benthic subtidal ecology validation survey undertaken for the Seagreen 1A ECC Marine Licence application;
- acoustic geophysical survey data covering the Proposed Development Array Area and proposed ECC. Data includes high resolution side scan sonar and multibeam bathymetry. These data were collected in July - August 2019 (Fugro, 2020a and Fugro 2020b);
- site-specific survey data: benthic subtidal survey data gathered across the Proposed Development benthic ecology study area in summer 2020; and
site-specific survey data: intertidal survey data from both landfall locations collected in summer 2020.
- Other reference sites will also support the development and assessment of benthic subtidal and intertidal ecology in the Offshore EIAR, such as:
- the Marine Life Information Network (MarLIN);
- Marine Environmental Data and Information Network (MEDIN);
- the National Biodiversity Network Gateway (NBN);
- Scottish Environment Protection Agency (SEPA) for sediment contaminant data; and
Benthic Subtidal Surveys
- A site-specific subtidal survey was undertaken across the Proposed Development benthic subtidal and intertidal ecology study area in 2020. The subtidal survey combined DDV and 0.1 m2 Hamon grab sampling with epibenthic trawls. The sampling strategy was designed to adequately sample the area to provide up to date data for baseline characterisation. The survey design was discussed and agreed with NatureScot and Marine Scotland in July 2020.
- The benthic subtidal survey was undertaken by Ocean Ecology Ltd. (OEL) in September 2020. All sampling was conducted aboard the 22 m Category 2 survey vessel ‘MV Marshall Art’. The survey comprised:
- Benthic Subtidal Surveys
- combined Drop-Down Video (DDV) and 0.1 m2 Hamon grab sampling at 92 sampling locations to ensure adequate data coverage for both infaunal and epifaunal communities at each location, with grab samples analysed for benthic infauna (abundance and biomass) and particle size analysis (PSA). Approximately a quarter of these sampling locations were located within the Firth of Forth Banks Complex MPA;
- 12 DDV transects within the proposed ECC which targeted areas of hard substrate where grab sampling was unlikely to be successful and where there was the potential for habitats of conservation importance to be present;
- Day grab samples for sediment chemistry at nine sampling locations, of which three sampling locations were located within the Firth of Forth Banks Complex MPA; and
epibenthic 2 m beam trawling at 15 sampling locations distributed across representative sediment types to characterise epifaunal communities. Four of these sampling locations within the Firth of Forth Banks Complex MPA.
- Six mini-Hamon grab stations were abandoned due to there being an insufficient quantity of sediment within the grab jaws after multiple attempts due to coarse or hard ground (ST25, ST39, ST66, ST67, ST75 and ST84 from with the east of the Proposed Development Array Area and the Proposed Development ECC). DDV was deployed prior to the deployment of the grab at every combined grab / DDV sample location in order to determine whether Annex I reef was present, such that grab sampling could be avoided in these areas. As a result, mini-Hamon grab stations were removed from the scope following an initial review of the seabed imagery from seven stations (ST02, ST04, ST20, ST38, ST56, ST69 and ST89). Additional grabs were added following the Annex I assessment as the DDV imagery showed soft sediments therefore grab sampling was possible (ST102, ST104, ST105, ST106, ST108, ST109 from with the Proposed Development ECC and ST112 from the east of the Proposed Development Proposed Development Array Area).
- The sampling locations are illustrated within Apx. Figure 7. 1 Open ▸ . A detailed analysis of these results will be appended to the EIA Report within a Benthic Subtidal and Intertidal Ecology Technical Report.
- A phase 1 intertidal survey was undertaken at each of the selected landfall locations, Skateraw Landfall and Thorntonloch Landfall. The survey was undertaken on a spring tide cycle in August 2020 and focussed on intertidal biotopes from MHWS to approximately MLWS. The survey was undertaken with reference to standard intertidal survey methodologies as outlined in the JNCC Marine Monitoring Handbook (Davies et al., 2001) within Procedural Guidance No 3-1 In situ intertidal biotope recording (Wyn and Brazier, 2001 and Wyn et al., 2000) and The Handbook for Marine Intertidal Phase 1 Biotope Mapping Survey (Wyn et al., 2006). The survey was carried out by two suitably qualified ecologists experienced in habitat mapping in intertidal, coastal and terrestrial environments.
- The intertidal survey comprised both a general walkover, noting changes in ecological and physical characteristics, and on-site dig-over macrofauna sampling and analysis in soft sediments, to help characterise the habitats. During the walkover survey, notes were made on the shore type, wave exposure, sediments / substrates present and descriptions of species / biotopes present. The spatial relationships between these features were observed and waypoints were recorded by a hand-held global positioning system (GPS) device, in conjunction with hand-written descriptions and photographs. All biotopes present were identified, and their extents mapped, with the aid of aerial photography and a GPS recorder. Other features within the intertidal zone were also noted including rock pools, man-made structures and any habitats / species of conservation importance. Where present, these features were target noted in the intertidal biotope maps.
- On-site dig-over sampling stations were undertaken in different biotopes, where possible, the locations of which were determined in the field. This involved the collection of four spade-loads (approximately 0.02 m2) of sediment dug to a depth of 20-25 cm, which were then sieved through a series of stacked sieves, the finest of which was 0.5 mm mesh. All macrofauna species present were identified and enumerated on site, where possible. Field notes were also taken on the physical characteristics, including sediment type and presence of anoxic layers in the sediment.
- A detailed analysis of these results will be appended to the EIA Report within a Benthic Subtidal and Intertidal Ecology Technical Report.
Apx. Figure 7. 1: Location of Benthic Subtidal Completed Samples within the Proposed Development Array Area and Proposed ECC Collected during the Site-specific Benthic Subtidal Survey
7.3.1 Subtidal Sediments
- The subtidal benthic sediments recorded across the Proposed Development benthic subtidal and intertidal ecology study area during the site-specific survey were classified into sediment types according to the Folk classification. Sediments ranged from sandy gravel to muddy sand with a third of the samples classified as slightly gravelly sand. The sediments within the east of the Proposed Development Array Area were dominated by slightly gravelly sand with areas of gravelly sand in the north and south. The sediments within the west of the Proposed Development Array Area were typically slightly coarser and characterised by sandy gravel sediments in addition to slightly gravelly sand and gravelly sand. The sediments within the Proposed Development ECC were mainly muddy sands.
- The EUSeaMap data illustrates the regions of higher topography and those associated with the Banks complexes within the Proposed Development Array Area are dominated by deep circalittoral coarse sediments whereas those in deeper water and flanks of the banks are dominated by deep circalittoral sands (Apx. Figure 7. 2 Open ▸ ). These two broad habitat types are also predicted across the majority of the proposed ECC, with discrete areas of faunal communities on deep low energy circalittoral rock. As the proposed ECCs moves into shallower waters towards landfall, sandy sediments grade into deep circalittoral muds, deep circalittoral mixed sediments and deep circalittoral coarse sediments (Apx. Figure 7. 2 Open ▸ ).
- The Proposed Development Array Area overlaps with the Firth of Forth Banks Complex ncMPA, designated for offshore subtidal sands and gravels, shelf banks and mounds, and moraines representative of the Wee Bankie Key Geodiversity Area (JNCC, 2020a). The ncMPA is comprised of the large-scale morphological bank features Berwick, Scalp and Montrose Banks and the Wee Bankie. The area is described as strongly influenced by water currents with a mosaic of different types of sand and gravels present which create a unique range of habitats (JNCC, 2020a). Although these sediments are relatively common around Scotland, the dynamic currents in the Firth of Forth Banks area influence the distribution of the sands and gravels (JNCC, 2014a). A large proportion of the Wee Bankie moraine formation is located within the Wee Bankie (including Scalp Bank) part of the ncMPA and is considered to be a key geodiversity area in Scotland’s seas. This formation is a series of prominent (20 m high) submarine glacial ridges, composed of poorly sorted sediments (boulders, gravels, sands and clays) (JNCC, 2020a).
- The surveys conducted in 2011 to support the EIA benthic baseline characterisation for Seagreen Alpha/Bravo (located immediately to the north of the Proposed Development Proposed Development Array Area) also provide an overview of the sedimentary habitats present within the immediate vicinity of the Proposed Development. The sediments present across the Seagreen Project Alpha Proposed Development Array Area ranged from cobbles with sand and gravelly sand in the west, to sandy gravel in the east. There was a greater predominance of fine sediments recorded across the Seagreen Project Bravo array compared with Seagreen Project Alpha Proposed Development Array Area, with sediments ranging from slightly gravelly sand in the west, sandy gravel in the central section and gravelly sand in the east of the Seagreen Bravo offshore wind farm (Seagreen, 2012a).
- A site-specific geophysical survey campaign was conducted across the Proposed Development in 2019 (Fugro, 2020a and Fugro 2020b). The SSS data collected has been correlated to the European University Information Systems (EUNIS) Classification data available from EMODnet (Apx. Figure 7. 3 Open ▸ ). The data indicates a heterogenous sediment across the Proposed Development Array Area with coarse and cobbly sediments on topographic highs, and sand to gravelly sand in the topographic lows and flanks of the banks. There are also extensive boulder fields present across the broad topographic highs and the banks. Hard substrates are present in the nearshore area of the proposed ECC for the Thortonloch landfall, with sand sediments in the central section grading into more gravelly sands and areas of hard substrate.
- This geophysical data also show that the majority of the seabed is ‘featureless’, however the southern and north-western extent of the Proposed Development Array Area are dominated by megaripples, sandwaves, ribbons and bars. Boulders are also prevalent across the area and are either represented as isolated boulders or as clusters (Apx. Figure 7. 4 Open ▸ ).
- An additional geophysical survey has been undertaken in 2021 to collate additional data to support the baseline characterisation for the Offshore EIAR.
Apx. Figure 7. 2: Predicted EUNIS Habitats from the EUSeaMap for the Proposed Development Array Area and Proposed ECC (Source: EMODnet, 2014)
Apx. Figure 7. 3: Sediment Interpretation from Side Scan Sonar for the Proposed Development Array Area and Proposed ECC (Source: Fugro, 2020a and Fugro 2020b)
Apx. Figure 7. 4: Seabed Features Data for Proposed Development Array Area and Proposed ECC (Source: Fugro, 2020a and Fugro 2020b)
7.3.2 Subtidal Benthic Communities
- The site-specific surveys across the Proposed Development benthic subtidal and intertidal ecology study area recorded 15 infaunal biotopes. The west of the Proposed Development Array Area was dominated by mixed sediment, fine sand and sandy mud biotopes (SS.SMu.CSaMu.AfilMysAnit in the south, SS.SSa.CFiSa.EpusOborApri in the north and SS.SMx.OMx.PoVen and SS.SSa.CFiSa.ApriBatPo). The east of the Proposed Development Array Area was dominated by sandy mud and find sand biotopes (SS.SMu.CSaMu.AfilMysAnit and SS.SSa.CFiSa.EpusOborApri). The Proposed Development ECC was dominated by mixed sediment and sandy mud biotopes (SS.SMu.CSsMu.ThyNten, S.SMx.OMx and SS.SMuCSaMuAfilNten).
- The site-specific surveys across the Proposed Development benthic subtidal and intertidal ecology study area recorded five epifaunal biotopes based on the DDV survey and the epifaunal components of the grab samples. The biotope SS.SCS.CCS was recorded across the eastern section of the Proposed Development Array Area with a small area of SS.SSa.IFiSa in the north of the eastern section of the Proposed Development Array Area and a small area of SS.SSa.CMuSa in the centre of the eastern section of the Proposed Development Proposed Development Array Area. The Proposed Development ECC was also dominated by SS.SCS.CCS with areas of CR.MCR.ECcR and SS.SSa.IFiSa in the nearshore subtidal area.
- The site-specific surveys across the Proposed Development benthic subtidal and intertidal ecology study area recorded three epifaunal biotopes based on the epibenthic trawls. The epibenthic trawls within the eastern section of the Proposed Development Array Area were classified as SS.SCS.CCS with two trawls within the western section of the Proposed Development Array Area classified as SS.SMx.CMx.FluHyd. The epibenthic trawls in the central section of the Proposed Development ECC were characterised as SS.SSa.CMuSa [C. crangon].
- The infaunal biotopes were taken forward to the combined biotope map as they were derived from more detailed data with the epifaunal data providing further context. The seapen and burrowing megafauna assessment classified much of the central and inshore parts of the Proposed Development ECC as the SS.SMu.CFiMu.SpnMeg habitat. The S. spinulosa Annex I reef assessment assigned all sample stations analysed ‘Not a Reef’. The nearshore area of the Proposed Development ECC recorded medium and low potential Annex I cobble reef. The Proposed Development Array Area recorded areas classified as ‘Not a Reef’ and two sample stations which were low potential reef. One sample station in the nearshore area of the Proposed Development ECC was classified as medium potential rock reef.
- The marine ecology surveys conducted for Seagreen Alpha/Bravo found that the benthic habitats were characterised by patchy communities of polychaete worms and shellfish (Seagreen, 2012a). The benthic communities identified for each site are described in Apx. Table 7. 2 Open ▸ .
- The distribution of the epifauna from these surveys was related to the sediment type with the sandy gravels and gravelly sands supporting a rich epifauna, while the slightly gravelly sands were generally low in epifauna. The majority of species recorded were opportunistic species, with bryozoans / hydroid turfs, tube worm Hydroides norvegica, pea urchin Echinocyamus pusillus and sea squirt Ascidiella scabra. High species richness was recorded in association with areas of the Sabellaria habitat, although no evidence from the DDV surveys suggests extensive or well-developed aggregations of Sabellaria in the Seagreen Alpha/Bravo Proposed Development Array Area. The benthic communities present were considered typical of the outer Firth of Forth and northwest North Sea (Seagreen, 2012a).
Apx. Table 7. 2: Benthic Ecology Community Overview from Seagreen Project Alpha and Seagreen Project Bravo Survey Data (Seagreen, 2012a)
- As discussed in the previous sub-section ‘Section 5.3.1 Subtidal Sediments’, the Proposed Development Array Area overlaps with the Firth of Forth Banks Complex ncMPA. The ncMPA is described as strongly influenced by water currents with a mosaic of different types of sand and gravels present which create a unique range of habitats and species such as the common brittlestar Ophiothrix fragilis, soft coral Dead man's fingers Alcyonium digitatum, hornwrack (colonial bryozoan) Flustra foliacea and ocean quahog Arctica islandica (JNCC, 2020a).
- Still image survey data collected to support the designation of the ncMPA around Berwick Bank indicate the presence of the SS.SMx.CMx.FluHyd (Flustra foliacea and Hydrallmania falcata on tide-swept circalittoral mixed sediment) biotope to the east and north of the area, with areas of circalittoral mixed sediments and circalittoral muddy sand (JNCC, 2014b). However, the infaunal communities recorded from grab samples in the Berwick Bank area of the ncMPA did not fit within the standard Marine Habitat Classification of Britain & Ireland and were allocated new biotope proposals (Pearce et al., 2014):
SS.SSa.OSa.[Sbom] - Spiophanes bombyx aggregations in offshore sands. This proposed biotope falls under the EUNIS Level 4 habitats offshore coarse (JNCC, 2014b).
- The biotopes identified around the Wee Bankie area (including Scalp Bank) and Montrose Bank also indicated the presence of SS.SMx.CMx.FluHyd (Flustra foliacea and Hydrallmania falcata on tide-swept circalittoral mixed sediment). The infaunal communities sampled at these two areas of the ncMPA also did not fit within the standard Marine Habitat Classification of Britain and Ireland and were allocated new biotope proposals (Pearce et al., 2014):
- Wee Bankie:
- SS.SSa.OSa.[Sbom] - Spiophanes bombyx aggregations in offshore sands; and
SS.SMx.OMx.[PoGintBy] - Polychaete-rich Galathea community with encrusting bryozoans and other epifauna on offshore circalittoral mixed sediment.
- Montrose Bank:
- SS.SCS.OCS.[PoGintBy] - Polychaete-rich Galathea community with encrusting bryozoans and other epifauna on offshore coarse sediment;
- SS.SCS.OCS.[Sbom] - Spiophanes bombyx aggregations in offshore coarse sands;
- SS.SSa.OSa.[Sbom] - Spiophanes bombyx aggregations in offshore sands; and
SS.SMx.OMx.[PoGintBy] - Polychaete-rich Galathea community with encrusting bryozoans and other epifauna on offshore circalittoral mixed sediment.
- As part of the Regional Seabed Monitoring Programme (RSMP), Cooper and Barry (2017) describe the results of a baseline assessment of the UK’s macrobenthic infauna. Although the aggregates industry was the focus of the study, a “big data” approach was taken which collated data from across UK waters, including in proximity to the Proposed Development (see Apx. Figure 7. 6 Open ▸ ), from various industries including offshore wind farms, oil and gas, nuclear and port and harbour sectors.
- Data points coinciding with the Proposed Development Array Area were predominantly characterised by slightly muddy sands with a small gravel component, and associated benthic infaunal communities of polychaetes (Spionidae, Nephtyidae, Lumbrineridae, Oweniidae, Cirratulidae, Capitellidae and Ampharetidae), echinoderms (Amphiuridae) and nemerteans (Cooper and Barry, 2017). There were also records of gravelly sands with a small mud fraction characterised by communities of polychaetes (Spionidae, Glyceridae, Terebellidae, Capitellidae and Phyllodocidae) and nemerteans. The only samples coinciding with the proposed ECC are located in the inshore part of Skateraw Landfall and correlate with slightly gravelly slightly muddy sand and species rich communities of polychaetes (Spionidae, Nephtyidae, Capitellidae, Cirratulidae, Oweniidae and Pholoidae), bivalve molluscs (Montacutidae, Semelidae and Nuculidae) and nemerteans (Cooper and Barry, 2017).
- The baseline benthic communities within the Proposed Development benthic subtidal and intertidal ecology study area will be described in depth following the completion of analysis of site-specific survey data, and the results of these surveys and analyses will be presented within the Benthic Subtidal and Intertidal Ecology Technical Report.
- The proposed landfall locations are located at Thortonloch and Skateraw near to Torness, on the East Lothian coast. The following biotopes, recorded at both the Skateraw Landfall and Thortonloch Landfall, are part of the Annex I Habitats Directive habitat – 1140 Mudflats and sandflats not covered by seawater at low tide:
- LS.Lsa.St.Tal Talitrids on the upper shore and strand-line;
- LS.LSa.MoSa, Barren or amphipod dominated mobile sand shores (recorded at Thorntonloch landfall only);
- LS.LSa.MuSa.MacAre, Macoma balthica and Arenicola marina in littoral muddy sand;
- LS.LSa.MuSa.Lan, Lanice conchilega in littoral sand (recorded at Skateraw Landfall only); and
LS.LSa.MuSa.MacAre, Macoma balthica and Arenicola marina in littoral muddy sand. This biotope is also part of the Intertidal Mudflats habitat listed on the Scottish Biodiversity List and is a UK Priority Biodiversity Action Plan (see Apx. Figure 7. 5
- The following sections presents a summary of the site-specific survey data collected during intertidal surveys of each landfall.
- Thortonloch Landfall
The Thorntonloch Landfall rock platform is predominantly covered by sediments. A sandy bay is present at Thorntonloch beach which was mainly composed of fine and medium grained sand which becomes muddier at the lower shore. A small proportion of gravel was also present within the lower shore sands. Occasional strips of shingle (cobbles and pebbles) were present at the beach head. High cliffs occurred to the south of Thorntonloch beach abutting a sedimentary rock platform with overlying large mobile sediments (pebbles, cobbles and boulders). Large areas of the bedrock remained exposed and contained a mosaic of deep pools cut into the rock platform by wave action. Rockpools also occurred frequently in other rocky areas between and under seaweeds and stones.
220.127.116.11 Skateraw Landfall
- The Skateraw Landfall rock platform is predominantly covered by sediments. A sandy bay is present at Skateraw beach which was mainly composed of fine and medium grained sand which becomes muddier at the lower shore. A small proportion of gravel was also present within the lower shore sands. Larger mobile sediments (pebbles, cobbles and boulders) covered the rest of the rock platform with exposed areas of bedrock occurring in places. Rockpools frequently occurred in the rocky zone.
Apx. Figure 7. 5: LS.LSa.MuSa.MacAre at Thorntonloch Landfall
7.3.4 Designated sites
- A number of sites of nature conservation importance, which are designated for benthic subtidal and/or intertidal features, have been identified as overlapping with, or occurring in close proximity to, the Proposed Development (Apx. Table 7. 3 Open ▸ ).
- A full screening of European designated sites with qualifying benthic interest features will be undertaken in the LSE Screening Report for the Proposed Development. Relevant Annex I habitats of Natura 2000 sites screened into the benthic subtidal and intertidal ecology assessment will be fully considered and assessed in the benthic subtidal and intertidal ecology Offshore EIAR section, with the assessment on the Natura 2000 site itself deferred to the Report to Inform Appropriate Assessment (RIAA).
- The screening to be undertaken in the benthic subtidal and intertidal ecology Offshore EIAR section will also include national designations (i.e. SSSIs, MPAs and Marine Conservation Zones (MCZs)). Nationally designated sites and the relevant qualifying benthic features screened into the assessment will also be fully considered and assessed in the benthic subtidal and intertidal ecology Offshore EIAR section.
Apx. Table 7. 3: Summary of Designated Sites with Relevant Benthic Ecology Features in Proximity to the Proposed Development
Apx. Figure 7. 6: Location of Faunal Samples from Cooper and Barry (2017) within the Proposed Development Array Area and Proposed ECC