Multivariate community analysis
  1. The results of the cluster analyses, SIMPROF test and SIMPER analyses were used, together with the raw untransformed data, to assign epifaunal biotopes to each epibenthic trawl. In several instances, clusters that were identified as significantly different from each other in the SIMPROF tests were assigned the same biotope code. This was based on a review of the SIMPER results which indicated that the differences between the groups could be explained by differences in abundances of characterising species rather than the presence/absence of key species. Full results of the multivariate analysis are presented in Annex H: Benthic Trawls Epifaunal Data Multivariate Analysis Results.
  2. The results of the hierarchical clusters analysis of the fourth root transformed epifaunal dataset together with the SIMPROF test identified four faunal groups that were statistically dissimilar. The raw data was transformed using the fourth root due to the high abundance of C. crangon compared to other taxa. The 3D MDS plot is presented in Figure 3.23   Open ▸ and the low stress value (0.05) indicates that this was a good representation of the data. Faunal group A (SIMPROF a; BT15, BT16, BT17, BT18) showed clear clustering away from all the other faunal groups with a Bray-Curtis similarity of 64.83% ( Figure 3.22   Open ▸ ). Faunal group C and D showed greater similarity with each other than with any other faunal group with a Bray-Curtis dissimilarity of 56.40%.

Figure 3.22:
Dendrogram of Epifaunal Communities in the Epibenthic Trawl Samples

Figure 3.22:  Dendrogram of Epifaunal Communities in the Epibenthic Trawl Samples

 

  1. Figure 3.24   Open ▸ to Figure 3.27   Open ▸ show representative images of the epibenthic trawl samples associated with each of the Faunal groups. The abundance of F. foliacea varied across the trawls but, as discussed in paragraph 186, this species was recorded only as presence/absence and so the occurrence of this species may have been underrepresented in the statistical analysis. The images of the benthic trawl catch showed that BT02, BT03, BT05, BT07 and BT12 recorded very high abundance of F. foliacea. These benthic trawls are mostly in Faunal group B (BT02, BT03, BT05, BT07) with BT12 in Faunal group C. The occurrence of F. foliacea in these faunal groups has been considered when assigning preliminary epifaunal biotopes to the faunal groups.
  2. Faunal group A (BT15, BT16, BT17, BT18) included trawl locations within the Proposed Development export cable corridor and was associated with sand sediments (muddy sands, sands and slightly gravelly muddy sand). Characterising species included C. crangon (making up 29.26% of the similarity between trawls within Faunal group A), Pandalidae, the Atlantic bobtail Sepiola atlantica, Paguridae and A. rubens ( Figure 3.24   Open ▸ ). Crangon crangon was recorded in very high numbers (>830) in BT15, ST17 and ST18 while being recorded in lower numbers (61) in BT16. Atlantic bobtail Sepiola atlantica was only recorded in these four epibenthic trawls. Review of the individual epibenthic trawl data also highlighted that the bony fish Glyptocephalus cynoglossus and Enchelyopus cimbrius removed from the multivariate analysis were also only recorded in these four epibenthic trawls. Faunal group A was distinct from the other Faunal groups due to the presence and abundance of the characterising species as well as the absence of O. fragilis and E. esculentus, which distinguished it from Faunal group C. It also did not record M. modiolus which distinguished it from Faunal group D. Faunal group A showed the highest Bray-Curtis dissimilarly with Faunal group B (84.28%) due to the high abundance of C. crangon in Faunal group A but not B and due to the absence of hermit crab Pagurus prideaux and Ophiura in Faunal group A that were present in Faunal group B. Faunal group A was allocated a preliminary biotope based on the epibenthic trawls data of SS.SSa.CMuSa [C. crangon]: C. crangon aggregations on Circalittoral Muddy Sand ( Table 3.18   Open ▸ ).
  3. Faunal group B (BT02, BT03, BT05, BT07) included trawl locations across the eastern section of the Proposed Development array area and was associated with gravelly sand and slightly gravely sand sediments. Characterising species included P. prideaux, Ophiura, A. palliata and A. irregularis (
  4. Figure 3.25   Open ▸ ). P. prideaux was recorded in is highest abundance at BT03 (n=36). Faunal group B was distinct from the other Faunal groups due to the presence and abundance of the characterising species. It showed a low Bray-Curtis dissimilarity (56.12%) with Faunal group C and was distinct due to the differing of abundances of the characterising species, rather than the present/absence of key species. Faunal group B showed the highest Bray-Curtis dissimilarly with Faunal group A. As discussed above in paragraph 179, the abundance of F. foliacea in trawls within Faunal group B was also high. Faunal group B was allocated a preliminary biotope based of the benthic trawls epifaunal data of SS.SCS.CCS ( Table 3.14   Open ▸ ).
  5. Faunal group C (BT01, BT10, BT11, BT12, BT14) included trawl locations outside the western section of the Proposed Development array area and offshore section of the Proposed Development export cable corridor and was associated with mixed sediments (sandy gravel, gravelly sand and slightly gravelly sand sediments). Characterising species included: A. rubens, Munida, Liocarcinus, A. irregularis, P. maximus, E. esculentus and O. fragilis ( Figure 3.26   Open ▸ ). A. rubens, A. irregularis, O. fragilis and P. maximus were all recorded in their highest abundances in an epibenthic trawl within Faunal group C (BT10-outside the western section of the Proposed Development array area). Faunal group C was distinct from the other faunal groups due to the presence and abundance of the characterising species. Faunal group C showed the highest Bray-Curtis dissimilarly with Faunal group A (79.00%) due to the high abundance of O. fragilis and E. esculentus in Faunal group C but not A and due to the lack of C. crangon in Faunal group C that was present in Faunal group A. As discussed above in paragraph 179, the abundance of F. foliacea in trawls within Faunal group C was also high. Faunal group C was allocated a preliminary biotope based of the benthic trawls epifaunal data of SS.SCS.CCS: Circalittoral coarse sediment. BT11 and BT12 were allocated SS.SMx.CMx.FluHyd: Flustra foliacea and Hydrallmania falcata on tide-swept circalittoral mixed sediment based on the high density faunal turf and dense F. foliacea associated with these sites ( Table 3.14   Open ▸ ).
  6. Faunal group D (BT04, BT09) included trawl locations within the centre of the Proposed Development array area and was therefore associated with sandy gravel and slightly gravelly sand sediments. Characterising species included: Munida, M. modiolus and Liocarcinus ( Figure 3.27   Open ▸ ). M. modiolus was recorded in its highest abundance at BT09 (n=31) with other benthic trawls only recording a few individuals. Faunal group D was distinct from the other faunal groups due to the presence and abundance of the characterising species as well as the absence of Ophiura which distinguishes it from Faunal group C and P. prideaux which distinguishes it from Faunal group B. Faunal group D showed the highest Bray-Curtis dissimilarly with Faunal group A (78.04%), due to the high abundance M. modiolus in faunal group D but not A and due to the absence of Pandalidae, which was present in Faunal group A but not D. Faunal group D was allocated a preliminary biotope based of the benthic trawls epifaunal data of SS.SCS.CCS ( Table 3.11   Open ▸ ).

Figure 3.23:
3D MDS Plot for the Epibenthic Trawl Samples (with biotopes)

Figure 3.23:  3D MDS Plot for the Epibenthic Trawl Samples (with biotopes)

 

Figure 3.24:
Representative Image of Epibenthic Trawl Catch for Faunal Group A (BT15)

Figure 3.24: Representative Image of Epibenthic Trawl Catch for Faunal Group A (BT15)

Figure 3.25:
 Representative Image of Epibenthic Trawl Catch for Faunal Group B (BT07)

Figure 3.25:  Representative Image of Epibenthic Trawl Catch for Faunal Group B (BT07)

Figure 3.26:
Representative Image of Epibenthic Trawl Catch for Faunal Group C (BT11)

Figure 3.26: Representative Image of Epibenthic Trawl Catch for Faunal Group C (BT11)

Figure 3.27:
Representative Image of Epibenthic Trawl Catch for Faunal Group D (BT09)

Figure 3.27: Representative Image of Epibenthic Trawl Catch for Faunal Group D (BT09)

  1. The preliminary epifaunal biotopes from the DDV/grab data were not combined with the epibenthic trawls biotopes as the epibenthic trawls cover a wider area compared to the grab and DDV data and therefore are not suitable for combining. However, they provide a broad indication of species present across a wider area. The DDV/grab epibenthic data was used as the primary dataset with the trawls providing a broad overview. 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 export cable corridor were characterised as SS.SSa.CMuSa [C. crangon].
FFBC MPA
  1. Two epibenthic trawls (BT01 and BT02) overlapped with the FFBC MPA in the eastern section of the Proposed Development array area. Two epibenthic trawls (BT10 and BT12) overlapped with the FFBC MPA in the western section of the Proposed Development array area. Epibenthic trawls within the FFBC MPA contained high abundances of Crustacea (Liocarcinus, A. rotundatus) and Echinodermata (E. esculentus, A. rubens, A. irregularis and O. nigra). From the images of the epibenthic trawl catch BT02 and BT12 showed very high abundance of F. foliacea. They were all allocated the biotope SS.SMx.CMx.FluHyd ( Table 3.14   Open ▸ ).
Table 3.14:
Epifaunal Groups Identified from the Epibenthic Trawls

Table 3.14:  Epifaunal Groups Identified from the Epibenthic Trawls

Univariate analysis
  1. The following univariate statistics were calculated for each epibenthic trawl: number of species (S), abundance (N), ash free dry mass in grams (g), Margalef’s index of Richness (d), Pielou’s Evenness index (J’), Shannon-Wiener Diversity index (H’) and Simpson’s index of Dominance (λ). The mean of each of these indices was then calculated for each of the epifaunal biotopes and these are summarised in Table 3.15   Open ▸ with univariate statistics for individual sites presented in Annex I: Benthic Trawls Epifaunal Data Univariate Analysis Results.
  2. The univariate statistic showed that the biotope SS.SMx.CMx.FluHyd had the highest number of taxa (20 ± 1.41). This biotope did not have the highest number of individuals (262 ± 90.50) however, it was the next highest, with the highest occurring in the SS.SSa.CMuSa biotope (965 ± 447.60). This high number of individuals in the SS.SSa.CMuSa biotope was due to the very high abundance of C. crangon. The biotope SS.SCS.CCS had lowest number of taxa and individuals ( Table 3.15   Open ▸ ).
  3. The highest mean diversity score of all the identified communities was associated with the SS.SMx.CMx.FluHyd biotope (d = 3.42± 0.03 and H’ = 1.53 ± 0.10) which was expected as this biotope had the highest number of taxa due to the nature of the mixed sediments with a high density of faunal turf. The biotope SS.SCS.CCS had the next highest mean diversity score (d= 3.25 ± 0.34, H’ = 1.04 ± 0.27). The lowest diversity recorded was at the biotope SS.SSa.CMuSa. This is consistent with this biotope having the lowest numbers of taxa and individuals. The biotope was recorded within the Proposed Development export cable corridor which had finer sediments than the coarse sediments recorded in the western section of the Proposed Development array area. The coarse sediments create a more complex and diverse habitat than the finer sediments in the eastern section of the Proposed Development array area and Proposed Development export cable corridor, supporting a higher diversity and number of taxa and individuals.
  4. Pielou’s evenness scopes (J’) and the Simpson’s index of Dominance (λ) scores varied across the biotopes. J’ was highest and λ was lowest at SS.SCS.CCS indicating an even distribution of taxa and that these communities are not dominated by a small number of species. The biotope SS.SSa.CMuSa [C. crangon] had the lowest J’ and highest λ indicating that this biotope was dominated by a high number of individuals from a small number of taxa. From the raw data this is likely to be the effect of high numbers of C. crangon in the epibenthic trawls assigned to this biotope.

 

Table 3.15:
Mean (± Standard Deviation) Univariate Statistics for the Preliminary Epibenthic Biotopes Recorded from the Epibenthic Trawls

Table 3.15:  Mean (± Standard Deviation) Univariate Statistics for the Preliminary Epibenthic Biotopes Recorded from the Epibenthic Trawls

 

  1. Figure 3.28   Open ▸ and Figure 3.29   Open ▸ show the mean number of taxa and individuals within each of the major taxa group (Annelida, Crustacea, Mollusca, Echinodermata and Other) for each of the biotopes identified within the Proposed Development benthic subtidal and intertidal ecology study area from the epibenthic trawls. As previously discussed, the univariate analysis showed that SS.SSa.CMuSa contained the highest number of individuals, this is reflected in Figure 3.28   Open ▸ . Figure 3.29   Open ▸ shows that the dominance of Crustacea in the number of taxa in SS.SSa.CMuSa was not as great as the dominance of Crustacea in the number of individuals, further highlighting that the high number of individuals was due to a small number of taxa. This was also shown in the univariate analysis which highlighted SS.SSa.CMuSa as the biotope most dominated by a small number of taxa. This reflects the dominance of Crustacea in the biotopes recorded from the infaunal grab samples from the Proposed Development benthic subtidal and intertidal ecology study area. Annelida were generally poorly represented across all faunal groups, making up the smallest proportion of individuals in each faunal group. This may be due to the nature of epibenthic trawl sampling as annelids live within the seabed sediments and therefore may be underrepresented.
  2. As shown in Figure 3.29   Open ▸ , the proportions of the number of taxa in each major taxonomic group are similar across the biotopes, with Crustacea and Echinodermata dominating the taxa present in each biotopes. All major taxonomic groups were represented in all biotopes despite the section for Annelida being too small to see on the graph.

Figure 3.28:
Mean Abundance of Individuals per Taxonomic Group Identified for Each Biotope from the Epibenthic Trawls

Figure 3.28: Mean Abundance of Individuals per Taxonomic Group Identified for Each Biotope from the Epibenthic Trawls

Figure 3.29:
Mean Number of Taxa per Taxonomic Group Identified for Each Biotope from the Epibenthic Trawls

Figure 3.29: Mean Number of Taxa per Taxonomic Group Identified for Each Biotope from the Epibenthic Trawls

Figure 3.30:
Preliminary Epifaunal Benthic Trawl Biotopes Identified within the Proposed Development Benthic Subtidal and Intertidal Ecology Study Area

Figure 3.30: Preliminary Epifaunal Benthic Trawl Biotopes Identified within the Proposed Development Benthic Subtidal and Intertidal Ecology Study Area

3.4.7.    Results - Combined Infaunal and Epifaunal Subtidal Biotopes

  1. Figure 3.30   Open ▸ presents the combined infaunal and epifaunal biotopes identified across the Proposed Development benthic subtidal and intertidal ecology study area. The method of classifying combined, holistic biotope codes was informed by the preliminary infaunal and epifaunal biotopes, the characterising species for these biotopes (as highlighted by the SIMPER analysis) and environmental variables (e.g. sediment type and water depth) at each site. The quantitative benthic infaunal grab dataset was prioritised when combining the datasets, due to this being the most standardised dataset. The DDV footage, the results of the analysis of the epifaunal component of the grabs and the trawl data were then used to identify subtle differences in epifaunal communities.
  2. The infaunal and epifaunal biotopes have been combined to form one single biotope, due mainly to the typically sparse epifaunal communities characterising these areas. Where DDV data only was taken, these epifaunal biotopes have been taken as the final biotopes.
  3. The epifaunal data identified SS.SCS.CCS across the eastern section of the Proposed Development array area however the infaunal data identified sandy mud and fine sand habitat across the eastern section of the Proposed Development array area and sandy mud and mixed sediments in the western section of the Proposed Development array area. 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 epifaunal data analysis classified much of the central and inshore parts of the Proposed Development export cable corridor as SS.SMu.CFiMu.SpnMeg. This area was classified as SS.SMu.CSaMu.ThyNten from the infaunal data and was therefore described as a similar mud habitat. SS.SMu.CFiMu.SpnMeg was taken forward as the final biotope, as this biotope was allocated as a result of detailed analysis of the DDV which identified the characteristic burrows of this habitat which are not recorded in grab sampling. The DDV data also recorded CR.MCR.EcCr in the nearshore environment and this was taken forward as the final biotope as there was sufficient data in the DDV data to allocate a detailed biotope description. The trawls data recorded C. crangon dominated circalittoral muddy sand in this part of the Proposed Development export cable corridor, further supporting the presence of the SS.SMu.CFiMu.SpnMeg habitat.
  4. The final biotope map shown in Figure 3.31   Open ▸ confirms many of the patterns described previously for the subtidal communities present in the Proposed Development benthic subtidal and intertidal ecology study area. The eastern section of the Proposed Development array area is characterised by the SS.SMu.CSaMu.AfilMysAnit and SS.SSa.CFiSa.Epus.OborApri biotopes with the SS.SSa.OSa and SS.SSa.OSa [Echinocyamus pusillus] biotopes in the south and small area of SS.SMx.CMx.MysThyMx in the centre of the Proposed Development array area. The western section of the Proposed Development array area is characterised by the SS.SMx.OMx.PoVen, SS.SMu.CSaMu.AfilMysAnit, and SS.SSa.CFiSa.Epus.OborApri biotopes with two patches of non-reef forming SS.SBR.PoR.SspiMx biotope in the south. The Proposed Development export cable corridor is characterised by the SS.SSa.OSa and SS.SMu.CSaMu.AfilNten near the boundary of the Proposed Development array area and by the SS.SMu.CFiMu.SpnMeg biotope in the central section. The CR.MCR.EcCr biotope was recorded in the inshore areas adjacent to the landfall.
  5. The location of the sample sites where ocean quahog A. islandica and M. modiolus were recorded are also noted on Figure 3.31   Open ▸ . M. modiolus were recorded in several of the benthic trawls and therefore the full extent of the benthic trawls is presented in Figure 3.31   Open ▸ as the exact location of the M. modiolus is unknown.


Figure 3.31:
Combined Infaunal and Epifaunal Biotope Map of the Proposed Development Benthic Subtidal and Intertidal Ecology Study Area

Figure 3.31: Combined Infaunal and Epifaunal Biotope Map of the Proposed Development Benthic Subtidal and Intertidal Ecology Study Area

3.4.8.    Results- Habitat Assessment


Seapen and burrowing megafauna communities assessment

Figure 3.32:
Seapen Pennatula phosphorea at ST82

Figure 3.32: Seapen Pennatula phosphorea at ST82

 

  1. The seapen and burrowing megafauna communities assessment was conducted on the sample stations where DDV data identified the presence of the SS.SMu.CFiMu.SpnMeg biotope and indicated the habitat aligned with the OSPAR habitat (i.e. due to the presence of fine mud and burrows). The PSA data also confirmed the presence of sandy mud and slightly gravelly muddy sand at these stations, as typical for the ‘seapen and burrowing megafauna communities’ habitat. Other sample stations recorded seapens and burrows however there was no indication of megafauna being present as all the burrows in the images and burrows from these sample stations were small in size (<1 cm). Burrows were observed at 14 sample stations within the seabed stills and DDV footage. Seapens (Pennatulacea) were also observed at 11 of these sample stations ( Table 3.16   Open ▸ ; Figure 3.32   Open ▸ ); V. mirabilis and P. phosphorea were also both observed. The sediment type recorded at the sample stations listed in Table 3.16   Open ▸ , across the Proposed Development export cable corridor, were consistent with the mud and muddy sand sediments required for the ‘seapen and burrowing megafauna communities’ habitat as defined by OSPAR (2010). The densities of burrows and seapens at all stations where present, were analysed and their abundance categorised using the JNCC’s SACFOR classification, to assess if the station habitat should be classified as a ‘seapen and burrowing megafauna communities’ habitat. Table 3.16   Open ▸ presents the burrows and seapen abundance data and analysis for each sample station where burrows were recorded.
  2. The density of burrows was assessed to consider if this was a prominent feature of the sediment surface and indicative of a sub-surface complex burrow system. Stations with burrows with densities considered ‘frequent’ or more under the SACFOR scale were considered likely to constitute the ‘seapen and burrowing megafauna communities’ OSPAR habitat. However, as recommended in the JNCC report (2014b), interpretation of the density of burrows should be treated with a degree of caution as it can be difficult to identify species based on burrow alone. Burrow density was calculated for each station using the total area covered by the photographs as calculated from laser scale lines (average image swathe x camera transect length).
  3. The presence of seapens is not a prerequisite for the classification of this OSPAR habitat however seapens were also recorded in the grab samples, V. mirabilis at ST63 and ST44, and P. phosphorea at ST97. This somewhat correlated with the DDV seabed imagery which recorded P. phospohorea at ST97, however this species was also recorded within the Proposed Development export cable corridor at ST105, ST106, ST79, ST80, ST82 and ST98. V. mirabilis was recorded within the Proposed Development export cable corridor at ST106, ST109, ST85, ST87 and ST99.
  4. For most of the sample stations where burrows were present in the DDV footage, burrow density was classified as ‘common’ according to the SACFOR scale. In accordance with the JNCC (2014b) guidance they were, therefore, classified as a prominent feature of the site (frequent on the SACFOR scale is required for burrows to be classified as a prominent feature). Several sample stations (ST105, ST85, and ST87) recorded burrows present in frequent abundance and were therefore considered to be a prominent feature of the sample station. Only ST82 and ST99 DDV stations recorded N. norvegicus, which is one of the species known to be responsible for creating the characteristic burrows of the ‘seapen and burrowing megafauna communities’ habitat. The presence of seapens is not a prerequisite for the classification of this habitat however where they were recorded, they were classified as occasional or frequent. It was therefore concluded that the 14 stations within the mid-section of the Proposed Development export cable corridor which were identified as SS.SMu.CFiMu.SpnMeg from the epifaunal data, were representative of the ‘seapen and burrowing megafauna communities’ OSPAR habitat ( Table 3.16   Open ▸ ). Two other sample stations (ST104 and ST78) were classified as SS.SMu.CFiMu.SpnMeg from the epifaunal data however the data did not indicate the presence of the OSPAR habitat. They were located on the edge of the area of SS.SMu.CFiMu.SpnMeg habitat therefore were poorer examples of this habitat as it graded into another biotope.

 

Figure 3.33:
Example of Burrows at ST80


Figure 3.33: Example of Burrows at ST80

Table 3.16:
Analysis of Sample Stations where Burrows and Seapens were Recorded within the Seabed Imagery

Table 3.16:  Analysis of Sample Stations where Burrows and Seapens were Recorded within the Seabed Imagery

Annex I reef assessment

  1. An Annex I habitat assessment was undertaken on any sampling locations where potential biogenic and/or geogenic reef habitats were identified within the Proposed Development benthic subtidal and intertidal ecology study area. These habitats were identified from the DDV and seabed imagery. A S. spinulosa reef assessment was required at three sites (ST20, ST04 and ST56) and a cobble/stony reef assessment was performed at 11 sites (ST02, ST04, ST107, ST20, ST38, ST61, ST69, ST89, ST101, ST110, ST111). The reef assessments at these sites were undertaken with reference to the relevant guidance with details of the assessment criteria outlined in paragraphs 93 to 95.
Sabellaria spinulosa reef assessment
  1. S. spinulosa aggregations at ST20 (in the centre of the eastern section of the Proposed Development array area) were recorded in small mounds generally 5-10 cm in height with a high level of patchiness (maximum percentage cover recorded at ST20 was 21.17%). The images assessed at ST20 recorded reef elevation ranging from high to low, reef extent from low to not a reef and reef patchiness medium to not a reef. The reefiness score for images at ST20 ranged from low to not a reef with a low reefiness score given to five of the six images assessed at ST20. Therefore, ST20 overall was given a reefiness score of low potential reef ( Figure 3.34   Open ▸ ).
  2. Only one image was assessed for S. spinulosa reef at each of ST04 and ST56 (located south-east outside of the Proposed Development array area and north of the western section of the Proposed Development array area respectively). Elevation was 5-10 cm at both sample stations, and consequently the reef structure at both sample stations were determined as ‘not a reef’. Therefore, these sample stations could only achieve a ‘not a reef’ reefiness score and these could not be considered Annex I S. spinulosa reef habitat.
Geogenic reef assessment
  1. Annex I reef assessment for cobble/stony reef was also conducted at one to three images from ST02, ST04, ST20, ST61, ST83, ST84 and ST101. All sample stations were classified as ‘not a reef’ or low reef as they all had an extent of <25 m2 and/or composition of <25%. Therefore, these areas were not considered to be Annex I cobble/stony reef habitat.
  2. At ST38 (in the centre of the eastern section of the Proposed Development array area) reef composition was given a score of low, ranging from 6.35 to 15.81%, elevation of 64 mm-5 m was medium, and extent was >25 m2. Therefore, ST38 was given an overall reefiness score of low potential reef and it is unlikely that this would be considered Annex I cobble/stony reef habitat.
  3. At ST69 (at the north-west outside of the Proposed Development array area) cobble/stony reef elevation was recorded as low (< 64 mm) with an extent of < 25 m2, and therefore classified as ‘not a reef’.
  4. At ST107 (nearshore section outside the Proposed Development benthic subtidal and intertidal ecology study area) cobble elevation was recorded as 64 mm-5 m at each image assessed, and extent was >25 m2. Composition ranged from 9.56 to 66.09% therefore ranging from medium to ‘not a reef’. In many images where the reef composition was allocated a score of medium, the percentage cover was towards the lower end of the medium criteria. Therefore, ST107 overall was given a reefiness score of low potential reef and it is unlikely that this would be considered Annex I cobble/stony reef.
  5. At ST110 (nearshore section of the Proposed Development export cable corridor) elevation was also recorded as 64 mm-5 m in each image assessed (with the exception of one which recorded <64 mm) with extent recorded as >25 m2. Composition ranged from 10.79 to 62.21% therefore ranging from medium to low reefiness score. Only three images out of 11 assessed at ST110 were given a medium reefiness score, therefore overall ST110 was given a reefiness score of low potential reef, and it is unlikely that this would be considered Annex I cobble/stony reef habitat.
  6. At ST89 (at the nearshore section of the Proposed Development export cable corridor) medium elevation of 64 mm-5 m and medium extent >25 m2 was recorded. Potential reef composition ranged from 2.45 to 95.25% with most images recorded as medium composition. ST89 was therefore given an overall reefiness score of medium potential reef. Due to the medium potential reef, a larger number of images were taken at this station to identify its wider extent. Images were taken until the marine ecologist reviewing the images in situ deemed the images to show no potential for reef, this was confirmed through subsequent analysis of the images, extent is shown through the reefiness assessment of images taken at ST89 on Figure 3.34   Open ▸ .
  7. At ST111 (nearshore section of the Proposed Development export cable corridor) an Annex I reef assessment for rocky reef was undertaken. Medium extent >25 m2 and high 99.54% to low 35.82% composition was recorded. For rocky reef, the reef is not defined by elevation, only that it must arise from the sea floor. ST111 was therefore given an overall reefiness score of medium potential reef. Therefore, there is medium potential for Annex I rocky reef at the nearshore section of the Proposed Development export cable corridor.
  8. The results of the Annex I reef assessment are aligned with the JNCC Annex I cobble/stony reef data ( Figure 3.34   Open ▸ ). The Annex I reef assessment recorded medium and low potential Annex I cobble reef in the nearshore sample stations which overlap with the JNCC Annex I reef data. Sample stations in the nearshore section of the Proposed Development export cable corridor and nearshore section of the Proposed Development benthic subtidal and intertidal ecology study area, which were included in the assessment but determined to be not a reef (ST72, ST73, ST74, ST75, ST78, ST79, ST80, ST81, ST82, ST83, ST85, ST86, ST87, ST88, ST96, ST100, ST101, ST102, ST103, ST104, ST105, ST106, ST108, ST109), are located in patches in the JNCC Annex I reef data where reef is not predicted. Sample stations from the Proposed Development array area included in the assessment were almost all classified as ‘not a reef’ (with the exception of ST20 and ST38 which were classified as low potential reef), the JNCC Annex I reef data shows no Annex I reef recorded in the Proposed Development array area.
  9. The results of the Annex I reef assessments alongside the JNCC data of Annex I reef locations is presented in Figure 3.34   Open ▸ . The full results (including assessment criteria used) of the reefiness assessments are presented in Annex B: Annex I Reef Assessments.

 

Figure 3.34:
Results of the Annex I Reef Assessment within the Proposed Development Benthic Subtidal and Intertidal Ecology Study Area

Figure 3.34: Results of the Annex I Reef Assessment within the Proposed Development Benthic Subtidal and Intertidal Ecology Study Area

Species of conservation importance

Ocean Quahog
  1. As described in the infaunal data analysis above, S. spinulosa and ocean quahog A. islandica were recorded in the benthic infaunal grab survey. Sabellaria spinulosa individuals were recorded across the Proposed Development benthic subtidal and intertidal ecology study area, at ST23, ST27, ST32, ST36, ST45, ST54, ST57, ST63, ST65, ST70, ST83, ST92 and ST102. The highest abundances were recorded at ST36 (n=83) and ST83 (n=336), with all other sample stations recording less than 10 individuals. While S. spinulosa themselves are not a species of conservation importance, they can build biogenic reefs through forming tubes in the sand. Within the UK, these biogenic reefs are afforded protection under Annex I of the Habitats Directive. The benthic characterisation for Seagreen (Alpha) and Seagreen (Bravo) offshore find farms and sampling for the FFBC MPA also recorded Sabellaria, but no biogenic reefs in the region. The FFBC MPA is not designated for biogenic reefs. A S. spinulosa reef assessment was required at three sites (ST20, ST04 and ST56), but no Annex I reef was recorded (section 3.4.7 and section 6).
  2. The FFBC MPA is also designated for ocean quahog A. islandica aggregations. Ocean quahog A. islandica is listed on the OSPAR list of threatened and/or declining species and habitats (OSPAR, 2008). In addition, ocean quahog A. islandica is a species listed as a Scottish PMF (Tyler-Walters et al., 2016). Ocean quahog A. islandica was recorded from eight grab samples across the Proposed Development array area and the Proposed Development export cable corridor ( Table 3.17   Open ▸ ). A summary of the ocean quahog A. islandica recorded across the Proposed Development benthic subtidal and intertidal ecology study area is provided in Table 3.17   Open ▸ . Age estimates were calculated by counting the growth rings on the Ocean quahog A. islandica shell. Counting growth bands in the shell is a common method used in the literature for ageing Ocean quahogs (e.g. Strahl et al., 2007; Abele et al., 2008). Most individuals recorded were juveniles (<1year old) however two were mature specimens. These two ocean quahog A. islandica were both recorded from the north of the eastern section of the Proposed Development array area. One juvenile (at ST55) was recorded with the FFBC MPA.

 

Table 3.17:
Ocean Quahog A. islandica Recorded in the Infaunal Grab Survey

Table 3.17:  Ocean Quahog A. islandica Recorded in the Infaunal Grab Survey

 

  1. Consistent with the infaunal data, ocean quahog A. islandica were recorded in two epibenthic trawls (BT07 and BT12, within the east of the Proposed Development array area, Figure 3.31   Open ▸ .
  2. A summary of the ocean quahog A. islandica recorded in the epibenthic trawls is provided in Table 3.18   Open ▸ .

 

Table 3.18:
Ocean Quahog A. islandica Recorded in the Epibenthic Trawls

Table 3.18: Ocean Quahog A. islandica Recorded in the Epibenthic Trawls

 

Modiolus modiolus
  1. As described in paragraph 204, M. modiolus were recorded in five of the epibenthic trawls (BT01, BT04, BT05, BT09, BT11). They were recorded in low numbers (<4 individuals) in the trawls with the exception of BT09 which recorded 31 individuals. Epibenthic trawl BT09 is from the centre of the Proposed Development benthic subtidal and intertidal ecology study area and was associated with coarse sediments (sandy gravel and gravelly sand).
  2. A high volume of boulders and cobbles as well as large M. modiolus were observed at BT09 during the survey. M. modiolus beds in Scotland are concentrated around Orkney and on the west coast however they have been recorded in the Firth of Forth (paragraph 22). Beds are formed from clumps of M. modiolus and shells covering more than 30% of the seabed over an area of at least 5 m x 5 m. M. modiolus beds are generally recorded on open coast circalittoral mixed sediments or with hydroids and red seaweeds on tide swept circalittoral mixed substrata. They support a rich diversity of organisms, especially polychaete worms, bivalves and brittlestars. M. modiolus beds are a Scottish priority marine feature, an OSPAR threatened and/or declining habitat (OSPAR, 2009) and are recognised as biogenic reefs under the EU Habitats Directive (European Commission, 2013). No M. modiolus beds were recorded during the DDV survey and no M. modiolus was recorded in the infaunal grab survey.

3.5. Site Specific Intertidal Survey

3.5.1.    Methodology

  1. A benthic phase 1 intertidal survey was undertaken at the selected landfall location. 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.
  2. 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 handwritten descriptions and photographs. All biotopes present were identified, and their extents mapped with the aid of aerial photography and a hand-held 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.
  3. 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.

3.5.2.    Results

Overview

  1. The Skateraw Landfall rock platform was 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. Boulders were distributed throughout the rocky vertical shore profile and generally ranged from 10-75% cover in fucoid dominated habitats where bedrock was not extensively outcropping. Boulders accounted for approximately 75% or more of the upper substrate layer in lower shore kelp beds, except where kelp was directly attached to bedrock. Cobbles dominated mixed sediments in the upper fucoid zone with typical percentage coverage of around 75%.
  2. Pebbles and cobbles were present throughout the rocky areas of the landfall and were abundant where they formed an extensive shingle bank at the beach head in the northern section of the landfall. Coarser sand was occasionally present at the head of the beach in small patches at the foot of the shingle bank. Freshwater flowed into the intertidal zone from the Dry Burn at National Grid Reference (NGR) NT 73461 75928.
  3. The biotopes present at the proposed landfall are mapped in Figure 3.44   Open ▸ and are described with their full JNCC classifications presented in Annex K: Intertidal Biotopes.

Upper shore

  1. Areas of barren bedrock which were not inhabited by species are mapped as LR: Littoral rock. These habitats mainly occurred at MHWS though extended down the shore into other biotopes particularly where the bedrock occurred at a higher elevation than surrounding habitats. These are therefore mapped as mosaics and their percentage contribution is denoted in Figure 3.44   Open ▸ .
  2. A medium grained sand occurred at the head of Skateraw Beach with patches of shingle and rocks at the edges of the sand. These habitats were inhabited by talitrid amphipods which occurred super abundantly under the decomposing seaweeds of the drift line though were fairly sparse where the seaweed was absent. These areas were characteristic of the biotope LS.Lsa.St.Tal (Talitrids on the upper shore and strand-line ( Figure 3.35   Open ▸ ) which also occurred fairly extensively on shingle (mobile cobbles and pebbles) and occasionally under larger rocks in other upper shore areas of the site ( Figure 3.36   Open ▸ ).
  3. The biotope LR.FLR.Lic.YG (Yellow and grey lichens on supralittoral rock occurred sparsely and was dominated by Xanthoria parietina). This habitat occurred in a scattered fringe and is not mapped.
  4. LR.FLR.Lic.Ver (Verrucaria maura on littoral rock fringe occurred on upper shore bedrock, boulders and cobbles). The black lichen V. maura was dominant though a significant amount of rock was uncolonized and remained bare. Enteromorpha intestinalis occurred frequently and Littorina saxatilis was occasionally present. This habitat occurred in a scattered fringe and is not mapped.
  5. The ephemeral green algae E. intestinalis was the dominant species in the biotope LR.FLR.Eph.Ent (Enteromorpha spp. on freshwater influenced and or unstable upper eulittoral rock (
  6. Figure 3.37   Open ▸ )). This habitat occurred on the upper shore on unstable rock and where fresh water from the dry burn flowed into the intertidal zone. Few other species occurred other than sparse patches of Ulva lactuca and occasional individuals of L. saxatilis. LR.FLR.Rkp.G (Green seaweeds (Enteromorpha spp. and Cladophora spp.) in shallow upper shore rockpools) occurred within this biotope and had a similar species assemblage.
  7. The biotopes LR.LLR.F.Fspi.B (Fucus spiralis on exposed to moderately exposed upper eulittoral rock) and LR.LLR.F.Fspi.X (Fucus spiralis on full salinity upper eulittoral mixed substrata) were both dominated by the brown alga F. spiralis with abundant black lichen V. maura. E. intestinalis, Semibalanus balanoides, Patella vulgata, L. saxatilis and Littorina littorea occurred occasionally. The brown alga Pelvetia canaliculata occurred in occasional patches within this biotope and on its landward fringe occasionally became dominant, forming a thin band of the habitat LR.LLR.FVS.PelVS (Pelvetia canaliculata on sheltered variable salinity littoral fringe rock). This biotope contained the same associated species as Fspi.X and was impractical to map.
  8.  

Figure 3.35:
Foreshore LS.Lsa.St.Tal; Mid shore LS.LSa.FiSa.Po at Skateraw Landfall

Figure 3.35: Foreshore LS.Lsa.St.Tal; Mid shore LS.LSa.FiSa.Po at Skateraw Landfall

Figure 3.36:
Foreground LR.FLR.Eph.Ent; Background LS.Lsa.St.Tal at Skateraw Landfall

Figure 3.36: Foreground LR.FLR.Eph.Ent; Background LS.Lsa.St.Tal at Skateraw Landfall

Mid shore

  1. The biotope LR.HLR.MusB.Sem.Sem (Semibalanus balanoides, Patella vulgata and Littorina spp. on exposed to moderately exposed or sheltered vertical eulittoral rock) occurred on bedrock and boulders and was dominated by the super abundant barnacle S. balanoides. limpet P. vulgata, winkle L. littorea, L. obtusata and whelk Nucella lapillus occurred occasionally throughout the zone. Black lichen V. maura occurred occasionally while the brown algae Fucus vesiculosus, red algae Porphyra purpurea and E. intestinalis were sparse.
  2. The biotope LR.MLR.BF.FvesB (Fucus vesiculosus and barnacle mosaics on moderately exposed mid eulittoral rock) occurred predominantly on mixed rocky sediments dominated by boulders and also on bedrock (
  3. Figure 3.37   Open ▸ ). The biotope was dominated by a scattered canopy of F. vesiculosus. The brown seaweed Ascophyllum nodosum was occasionally present with the epiphytic red seaweed Vertebrata lanosa attached. The red seaweeds Mastocarpus stellatus and Corallina officinalis were also occasionally present. The invertebrate fauna was dominated by super abundant S. balanoides with P. vulgata, L. littorea, L. obtusata, common shore crab Carcinus maenas and the anemone Actinia equina occasionally present. Juvenile mussel Mytilus edulis were rarely observed.
  4. A similar suite of species and substrates occurred in the biotope LR.LLR.F.Fves (Fucus vesiculosus on moderately exposed to sheltered mid eulittoral rock) however the canopy of F. vesiculosus was more continuous and S. balanoides were less abundant, occurring only sparsely, and species such as brown crab Cancer pagurus and C. maenas were occasionally present under rocks. This community was differentiated into two variants which largely had the same species assemblages. LR.LLR.F.Fves.X (Fucus vesiculosus on mid eulittoral mixed substrata) which contained a higher proportion of cobbles and pebbles and LR.LLR.F.Fves.FS (Fucus vesiculosus on full salinity moderately exposed to sheltered mid eulittoral rock) which occurred on boulders and bedrock. Patchworks of these closely related biotopes occurred together across the shore and are mapped as mosaics.
  5. The biotope LR.HLR.FR.Coff.Coff (Corallina officinalis and Mastocarpus stellatus on exposed to moderately exposed lower eulittoral rock) was dominated by C. officinalis and coralline crusts with abundant V. fucoides. The green algae Cladophora rupestris and F. vesiculosus occurred commonly while the brown algae Leathesia difformis and the red seaweed M. stellatus occurred occasionally. L. littorea occurred in variable densities from sparse on bedrock to super abundant under flat stones overlying shallow water on bedrock. This biotope contained numerous shallow coralline rock pools with flat rocks under which a diverse assemblage of species occurred.
  6. Numerous examples of the biotope LR.FLR.Rkp.Cor.Cor (Corallina officinalis and coralline crusts in shallow eulittoral rockpools) occurred from the middle of the shore up to the F. spiralis zone ( Figure 3.38   Open ▸ ). Corallina officinalis and coralline crusts dominated with frequent green seaweed C. rupestris and brown seaweed Halidrys siliquosa. The red seaweeds M. stellatus, Chondrus crispus, Ceramium sp. and the green seaweed U. lactuca occurred occasionally with a scattering of F. vesiculosus and P. vulgata. A diverse range of invertebrate animals occurred including occasional L. littorea, C. pagurus, Gibbula cineraria, tubeworm Spirorbis spirorbis, hermit crabs Pagurus bernhardus and C. maenas with the anemone Urticina felina, bryozoans Schizoporella unicornis, sponges Leuconia nivea, sea squirt Dendrodoa grossularia and sea slug Doris pseudoargus scarce. The intertidal fishes, the two-spotted goby Gobiusculus flavescens and worm pipefish Nerophis lumbriciformis, were also present. Myriads of these pools occurred within the rocky areas of this landfall and only the largest could be mapped in a timeous fashion.

Figure 3.37:
 LR.MLR.BF.FvesB at the Skateraw Landfall

Figure 3.37:  LR.MLR.BF.FvesB at the Skateraw Landfall

Figure 3.38:
LR.FLR.Rkp.Cor.Cor at Skateraw Landfall

Figure 3.38: LR.FLR.Rkp.Cor.Cor at Skateraw Landfall