Drop Down Video

65. In addition to the 92 DDV deployments at each of the grab sample location, the subtidal survey included 15 additional DDV only transects within the Proposed Development array area, Proposed Development export cable corridor and just outside the Proposed Development export cable corridor ( Figure 3.4   Open ▸ ). These additional DDV locations were planned into the survey design to target 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 as well as included during the survey in areas where grab sampling was unsuccessful. Sample stations were numbered in the order in which they were sampled. The DDV only sample stations are interspersed among the combined sample stations therefore the combined sample stations numbers go up to ST112.
66. All DDV sampling was undertaken in line with the JNCC epibiota remote monitoring operational guidelines (Hitchin et al., 2015). A minimum of five images were taken from each DDV station along with approximately five minutes of video. Along the transects, images were taken every 10 – 20 m over heterogeneous habitat types, at the interface between different habitats and of any notable features along the transects. All video footage was reviewed in situ by the lead marine ecologist.
67. The camera system was deployed as follows:

• Vessel approached target location and alerted deck personnel to prepare camera and umbilical.
• Sea fastening on camera frame was released to allow deployment from the deck.
• Umbilical released overboard with sufficient length paid out to cover water depth.
• Camera raised and lowered into the water column to within 5 m of the seabed.
• Ecologist switched on video recording and the camera was lowered until gently landing on the seabed at which point a positional fix was taken.
• The ecologist then waited for any suspended sediments in the field of view to disperse before taking an image and confirming with the skipper to move on.
• The camera was then raised from the seabed and moved to obtain more images of the surrounding area or, when sampling transects, the camera was moved along the transect at approximately 1 - 2 knots; Where possible the seabed was maintained in view at all times.
• Following the capture of the final image, the camera was lifted, video recording was stopped, and the camera was retrieved to the surface.
• The winch operator then took tension on the winch cable and the ecologist ensured the camera umbilical was free for recovery.
• Once the camera was at the surface, the vessel was positioned to minimise pitch and roll (e.g. into wind/tide).
• The vessel skipper then confirmed sea conditions were suitable for retrieval and the camera system was recovered aboard.
• The camera frame was then lowered onto the vessel deck and the tension released.

Epibenthic trawls

68. The benthic subtidal survey included 15 epibenthic beam trawls distributed across representative sediment types to characterise epibenthic communities. Six of these sampling locations were within the FFBC MPA ( Figure 3.4   Open ▸ ). Beam trawl tows were undertaken in line with the guidelines set out by Cooper and Mason (2019) and Curtis and Coggan (2007). Tows were undertaken for a duration of 15 minutes on the seabed, at a speed of 1.5 – 2.0 knots. The approximate length of each tow was between 600 – 1,100 m. The direction of each tow was dependent on tide and wind conditions, where tow direction was always against the prevailing direction of the tide. Epibenthic beam trawls were undertaken using a 2 m scientific beam trawl with 0.5 mm mesh cod end insert.

Survey limitations

69. An adjustment to the boundary of the Proposed Development export cable corridor, following the completion of the site-specific benthic subtidal surveys, resulted in a small part of the mid-section of the Proposed Development export cable corridor not being sampled during the site-specific benthic surveys ( Figure 3.4   Open ▸ ; Figure 3.6   Open ▸ ). Desktop data was therefore used to extrapolate the biotope map to cover the whole Proposed Development export cable corridor.
70. Due to the presence of dense fishing gear (potting buoys) across some of the survey area, three mini Hamon grab stations (ST47, ST52 and ST84) and two DDV locations (ST52 and ST84) were relocated to minimise the risk of snagging. The orientation of one beam trawl (BT09) was also adjusted to avoid fishing gear whilst another (BT10) was relocated due to both fishing gear and its proximity to a wreck.
71. 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 export cable corridor). DDV was deployed prior to the deployment of the grab at every combined grab/DDV sample location to determine whether Annex I reef was present, so 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 export cable corridor and ST112 from the east of the Proposed Development array area).
72. One mini Hamon grab station (ST01), one Day grab station (ST01) and three beam trawls were left outstanding at the point that survey operations were stood down due to an unfavourable long-term weather forecast.
73. Overall, 92 combined DDVs and 0.1 m2 mini Hamon grab sampling locations, 12 additional DDV only transects and 15 epibenthic beam trawls were taken.

Figure 3.4: Completed Site Specific Sample Locations within the Proposed Development Benthic Subtidal and Intertidal Ecology Study Area

Sample analysis

Benthic infaunal analysis

74. Sediment samples for benthic infaunal analysis were processed through a 1 mm sieve and the retained material transferred to an appropriate container and preserved immediately in 4% buffered saline formalin solution. The samples were analysed at OEL’s benthic laboratory which participates in the North East Atlantic Marine Biological Analytical Quality Control Scheme (NMBAQC scheme) for identification (to species level), enumeration and biomass determination. Biomass of the infaunal component was recorded from the ash free dry mass, in grams (g). The retained infauna was separated into the following phyla: Polychaeta; Crustacea; Echinodermata; Mollusca; and Others.
75. The epifaunal component of each sample was analysed separately with identification to species level. Where possible each component was enumerated and presented as discrete counts or in the case of colonies, recorded as present and given a P (present) value.

Particle Size Analysis (PSA)

76. Sediment samples were analysed for particle size distribution at OEL’s benthic laboratory. Representative sub samples of each sediment sample were oven dried to a constant weight and sieved through a series of mesh apertures over the range 64 mm to 63 μm (0.063 mm) on the Wentworth scale. The weight of the sediment fraction retained on each mesh was measured and recorded. This method was in accordance with NMBAQC Best Practice Guidelines (Mason, 2016). Laser diffraction techniques were also used for samples where sediments of less than 63 μm accounted for more than 5% by weight of the sample.

Drop Down Video (DDV) analysis

77. All images were reviewed by OEL’s environmental scientists in situ to ensure a minimum of five representative images per station. Any stations that did not fit these criteria were revisited to obtain more imagery. Digital photographic stills and video footage were successfully obtained along all transects and subsequently analysed to aid in the identification and delineation of European Nature Information System (EUNIS) habitats and potential Annex I habitats. Seabed images were enhanced prior to analysis using the open-source image editing software GNU Image Manipulation Program (www.gimp.org). All seabed imagery analysis was undertaken using the Bio-Image Indexing and Graphical Labelling Environment (BIIGLE1) annotation platform (Langenkämper et al., 2017) and in line with JNCC epibiota remote monitoring interpretation guidelines (Turner et al., 2016).
78. Analysis of still images was undertaken in two stages. The first stage, “Tier 1”, consisted of labels that referred to the whole image being assigned, providing appropriate metadata for the image. The second stage, “Tier 2”, was used to assign percentage cover of habitat types by drawing polygons to inform the habitat assessment process. This analysis produced a list of discrete taxa identified and their abundance (number of individuals), or percentage cover for colonial organisms, within each image at each sample station. It also identified burrows, grouping them into size categories to give number and size of burrows per image at each sample station, this is discussed further in paragraph 97 and section 3.4.7.

Epibenthic trawls analysis

79. Epibenthic trawl samples were processed in line with the guidelines set out by Cooper and Mason (2019) and Curtis and Coggan (2007) as follows:

• A photograph of the entire catch, prior to sorting, with station details was taken.
• All fish and epibenthic fauna were sorted for identification and enumeration (presence/absence for colonial/encrusting species) in the field.
• Length measurements (to the nearest mm) were taken for all commercial fish and shellfish species and further photographs taken of cryptic specimens.
• Epibenthic invertebrate species were identified to the lowest taxonomic resolution possible and commercial shellfish were measured using the methods set out in EC Regulation 850/983 (i.e. carapace length for lobsters Homarus gammarus and carapace width for edible and velvet crabs Cancer pagurus and Necora puber respectively, mantle length for all cephalopods, shell height for whelk Buccinum undatum and shell width for king scallop Pecten maximus and queen scallop Aequipecten opercularis). Measurements and age estimations were also taken for ocean quahog A. islandica in situ with the specimens then returned to the sea.
• Where identification required clarification, individuals were transferred to a labelled sample container and fixed in 4-5% buffered formalin solution and identified on return to OEL’s laboratory.
• The entire sample was then returned to the water once all individuals were identified, enumerated, and measured (where required). No fish were retained following processing other than those required for subsequent laboratory identification.

Sediment chemistry

80. As part of the subtidal survey, sediment samples were taken for the purpose of sediment chemistry analysis ( Figure 3.5   Open ▸ ). Samples were transferred to an appropriate sample container, labelled and sent to a suitable qualified laboratory for analysis. The RPS laboratory has United Kingdom Accreditation Service (UKAS) accreditation to carry out tests for all the contaminants listed. Samples were analysed for the following contaminants:

• metals;
• polychlorinated biphenyl (PCB) congeners;
• total Hydrogen Content (THC) by fluorescence spectrometry;
• total organic Carbon (TOC);
• organotins;
• polycyclic aromatic hydrocarbons (PAH);
• physical parameters; and
• PSA.

Figure 3.5: Locations of the Sediment Chemistry Samples

Data analysis

Sediment characteristics analysis

81. The PSA data were categorised using the Folk classification which groups particles into mud, sand and gravel (mud <63 μm = mud; sand <2 mm; gravel >2 mm) and the relative proportion of each used to ascribe the sediment to one of 15 classes (e.g. slightly gravelly sand, muddy sand etc.) (Folk, 1954; Long, 2006). These classifications were then used to describe the data in the analysis. Proportions of mud, sand and gravel, as well as the Folk and Ward sorting coefficient, were also used to describe the sediment data. The Folk and Ward sorting coefficient describes the extent of deviation from lognormality of the particle size distribution (i.e. the variation in particle size with a sample).

Sediment chemistry analysis

82. The results of the sediment chemistry analysis have been compared to the Marine Scotland chemical guideline Action Levels (ALs), administered by MS-LOT (Marine Scotland, 2017). Action Level 1 (AL1) and Action Level 2 (AL2) give an indication of how suitable the sediments are for disposal at sea. Contaminant levels which are below AL1 are of no concern and are unlikely to influence the marine licensing decision while those above AL2 are considered unsuitable for disposal at sea. Those between AL1 and AL2 would require further consideration before a licensing decision can be made. Sediment chemistry data were also compared to the Canadian Sediment Quality Guidelines (CSQG; CCME, 2001), which give an indication on the degree of contamination and the likely impact on marine ecology. For each contaminant, the guidelines provide threshold effects levels (TEL), which is the minimal effect range at which adverse effects rarely occur and a probable effect levels (PEL), which is the probable effect range within which adverse effects frequently occur.

Macrofaunal analysis

Data Rationalisation

83. The benthic infaunal dataset was initially square root transformed to down-weight the species with the highest abundances for multivariate community analysis. The analysis of the infaunal community was made using the enumerated taxa only dataset to avoid skewing the results with the encrusting/colonial taxa recorded as ‘present’; these taxa were combined with the DDV data and analysed separately. Juvenile data were included in the data analysed however the multivariate analysis was also run on the infaunal data which excluded the juvenile data to check for any differences in patterns or groupings. Within all dataset, all fish species were removed prior to analysis and discussed separately and within volume 3, chapter 9.1.
84. Colonial/encrusting taxa within the grab samples, which were recorded only as present, were combined with the DDV data and given an abundance of 1 or 0 respectively to enable them to be included in a separate multivariate analysis. Within the DDV data, taxa recorded as percentage cover were also transformed into presence/absence data for analysis. The combined DDV and grab epifaunal dataset was square root transformed.
85. Multivariate analyses were also run separately on the DDV percentage cover data alone to ensure that the proportions of the taxa present were captured and considered in the biotope allocations. Percentage cover estimates was allocated using the BIIGLE1 software. For taxa where percentage cover could not be estimated by the BIIGLE1 software, the marine ecologist identified areas of taxa coverage during the review of the DDV images. The software calculated the proportion of the image which was covered by the taxa area identified. Where an area of taxa coverage could not be allocated, percentage cover was identified directly by the marine ecologist to the nearest 10%.
86. The epibenthic trawl dataset was initially standardised by total abundance per sample across all variables (species) to account for the slightly varied lengths of the trawls, and therefore sampling effort. The epibenthic trawl data was also fourth root transformed to down-weight the species with the highest abundances for multivariate community analysis. A fourth root transformation was used in comparison to the square root transformation used for the other analysis due to the very high abundances of the brown shrimp Crangon crangon in three of the epibenthic trawls.

Univariate analysis

87. The untransformed benthic infaunal data, epibenthic trawl data and combined DDV and grab epifaunal data were summarised to highlight the number of individuals and number of taxa recorded. Analysis was also undertaken to identify the percentage composition of the major taxonomic groups within each sample station, the percentage contribution of each taxonomic group to the total number of taxa and to the total number of individuals.
88. A number of univariate indices were calculated to further describe the untransformed infaunal and epifaunal data, including: S = number of species; N = abundance; B = Biomass (ash free dry mass); d = Margalef’s index of Richness; J’ = Pielou’s Evenness index; H’ = Shannon-Wiener Diversity index;  = Simpson’s Dominance index for each identified biotope.

Multivariate community analysis

89. The benthic infaunal grab data, epibenthic trawl data and combined DDV and grab epifaunal data were analysed using the PRIMER v6 software (Clarke and Gorley, 2006).
90. To determine the relative similarities between stations, the benthic infaunal and epifaunal community structure were investigated using CLUSTER analysis (hierarchical agglomerative clustering). Separate multivariate analyses were undertaken on the infaunal, epifaunal and epibenthic trawls dataset however the same methodology was used. This used the Bray Curtis similarity coefficient to assess the similarity of sites based on the faunal components. The procedure produces a dendrogram indicating the relationships between sites based on the similarity matrix and uses a Similarity Profile (SIMPROF) test (at a 5% significance level) to test whether the differences between the clusters are significant.
91. Similarity Percentages (SIMPER) analyses were subsequently undertaken on the infaunal and two epifaunal datasets to identify which species best explained the similarity within groups and the dissimilarity between groups identified in the cluster analysis. The similarity matrix was also used to produce a multi-dimensional scaling (MDS) ordination plot to show, on a two or three-dimensional representation, the relatedness of the communities (at each site) to one another. Full methods for the application of both the hierarchical clustering and the MDS analysis are given in Clarke and Warwick (2001).

Biotope allocation

92. The results of the cluster analyses and associated SIMPER were reviewed alongside the raw, untransformed data to assign preliminary biotopes (Connor et al., 2004). Using the clusters identified, several sites within a cluster and, where appropriate several clusters, were assigned to a single biotope, where possible, based on relatedness and presence/absence of key indicator species for a particular biotope. The infaunal and epifaunal biotopes were plotted out over the results of the geophysical survey for the Proposed Development subtidal and intertidal ecology study area to map the area and extent of each habitat across sediment types/features and presented in the biotope map. The infaunal and epifaunal biotope allocations were combined to provide a combined biotope map.

Annex I reef assessment

93. As discussed in paragraph 65, DDV was deployed prior to the deployment of the grab at every combined grab/DDV sample location to determine whether Annex I reef was present, such that grab sampling could be avoided in these areas. Seven mini Hamon grab stations were removed from the scope following an initial review of the seabed imagery (ST02, ST04, ST20, ST38, ST56, ST69 and ST89). Potential Annex I reef was observed during the DDV sampling at ST02, ST04, ST20, ST38, ST56, ST69 and ST89 sample locations, therefore a full Annex I reef assessment has been undertaken for these locations (Annex B: Annex I Reef Assessments).
94. Where Sabellaria spinulosa aggregations were observed in the DDV footage of the Proposed Development benthic subtidal and intertidal ecology study area, a reefiness assessment with reference to relevant guidance documents (i.e. Jenkins et al., 2015; Gubbay, 2007; Limpenny et al., 2010), was undertaken to determine whether or not a potential S. spinulosa reef was present. To ensure that the assessment was transparent, it comprised a measure of elevation and patchiness, as outlined in Table 3.3   Open ▸ . The scoring system proposed by Gubbay (2007) and the ‘reefiness’ matrix described in Jenkins et al., 2015 was used to draw together all the information to interpret the ‘reefiness’ of S. spinulosa aggregations ( Table 3.4   Open ▸ ).

Table 3.3:  Summary of the Analysis and Scoring of S. Spinulosa Reef Characteristics (based on Gubbay, 2007)

Table 3.4:  Sabellaria spinulosa Reef Assessment Matrix (based on Gubbay, 2007 and Jenkins et al., 2015)

95. Where coarse/stony and/or rocky substrate was observed in the DDV footage of the Proposed Development benthic subtidal and intertidal ecology study area, a stony reef assessment according to the appropriate guidance (Irving, 2009; Golding et al., 2020) was undertaken to determine if a potential stony reef was present. The assessment comprised of a measure of elevation and patchiness, and extent where possible, as outlined in Table 3.5   Open ▸ . The scoring system proposed by Irving (2009) and the ‘reefiness’ matrix described in Jenkins et al. (2015) was used to draw together all the information to interpret the ‘reefiness’ of stony features ( Table 3.5   Open ▸ ). The conclusion of the Irving (2009) guidance was that a reef should be elevated above flat sea floor, have an area of at least 25 m2 and have a composition of no less than 10% coverage of the seabed (Irving, 2009). Irving (2009) also recommended that, when determining whether an area of the seabed should be considered as Annex I stony reef, if a ‘low’ is scored in any of the four characteristics (composition, elevation, extent or biota), then a strong justification would be required for this area to be considered as contributing to the Marine European Sites with qualifying reef features. Golding et al. (2020) provides further guidance on the interpretation of the guidance set out in Irving (2009) and has therefore been reviewed alongside Irving (2009).
96. Where bedrock was observed in the DDV footage, a rocky reef assessment was undertaken. Unlike biogenic and stony reef, there is little guidance of classifying bedrock reef. The elevation assessment criteria do not apply to bedrock reef; bedrock reef was therefore assessed based on cover and extent alone, using the same thresholds as for stony reef, listed in Table 3.5   Open ▸ .

Table 3.5:  Stony Reef Assessment Matrix (based on Irving, 2009 and Jenkins et al., 2015)

Seapen and burrowing megafauna community assessment

97. The seapens and burrowing megafauna habitat is described by OSPAR as ‘Plains of fine mud, at water depths ranging from 15‐200 m or more, which are heavily bioturbated by burrowing megafauna with burrows and mounds typically forming a prominent feature of the sediment surface. The habitat may include conspicuous populations of seapens, typically Virgularia mirabilis and Pennatula phosphorea’. At stations where burrows were sufficiently large enough to indicate the presence of burrowing megafauna, an assessment was undertaken to determine whether the OSPAR Seapens and Burrowing Megafauna communities habitat was present. As detailed in the JNCC (2014b) clarification document for defining this habitat, the following data was required for this assessment:

• video and still imagery to confirm burrows and/or mounds and, where present, seapens;
• infaunal grab samples to confirm relevant fauna; and
• PSA data to confirm a fine mud habitat.
  98. The PSA data from the grab samples were initially analysed to determine if fine mud sediments were present. The DDV data were then analysed to determine which images showed burrows and/or mounds and their locations. The number of burrows within each image were counted, along with the size of the burrows, to produce a matrix of burrow density. The abundance of burrows was then categorised using the SACFOR[1] scale in order to determine whether their density was a ‘prominent’ feature of the sediment surface and potentially indicative of a sub-surface complex gallery burrow system; burrows are required to be classified as at least frequent on the SACFOR scale for this habitat to be assigned (JNCC, 2014b; Hiscock, 1996). The number of seapens were also counted within each image to produce a matrix of seapen density at each location where burrows where identified. This was used to classify the abundance of seapens using the SACFOR scale. It should be noted, however, that the presence of seapens is not a prerequisite for the classification of this habitat (JNCC, 2014b). Based on the results of the analysis imagery data and PSA data for the presence of seapens, burrows and fine mud habitat, a conclusion was made as to the presence of the Seapens and Burrowing Megafauna communities habitat for each sample station. Based on this, and the overall epifaunal data, the sample stations were assigned a preliminary biotope classification.

3.4.2.    Results - Seabed Sediments

99. In 2019 and 2021, site-specific geophysical survey campaigns were conducted across the Proposed Development (Fugro, 2020a; Fugro 2020b; XOCEAN, 2021). The side scan sonar (SSS) data indicated 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 in the flanks of the banks ( Figure 3.6   Open ▸ ), this correlated with the EUSeaMap data ( Figure 3.1   Open ▸ ). There were also extensive boulder fields present across the broad topographic highs and the banks. Hard and coarse substrates, and rock were present in the nearshore area of the Proposed Development export cable corridor, with sand sediments in the central section grading into more gravelly sands and areas of hard substrate. This geophysical data also showed that the majority of the seabed is ‘featureless’, however the southern and north-western extent of the Proposed Development array area was dominated by megaripples, sandwaves, ribbons and bars ( Figure 3.6   Open ▸ ). Boulders were also prevalent across the area and were either represented as isolated boulders or as clusters.

Figure 3.6: Interpreted Geophysical Data from the Site Specific Survey within the Proposed Development Benthic Subtidal and Intertidal Ecology Study Area

3.4.3.    Results - Physical Sediment Characteristics

100. The subtidal benthic sediments across the Proposed Development benthic subtidal and intertidal ecology study area were classified into sediment types according to the Folk classification ( Figure 3.5   Open ▸ and Annex A: Seabed Sediments). Sediments ranged from sandy gravel to muddy sand with 36% of the samples classified as slightly gravelly sand ( Figure 3.7   Open ▸ ). The only sample station classified as sand was ST108 which was located to the southeast of the nearshore section of the Proposed Development export cable corridor ( Figure 3.5   Open ▸ ). All sediment samples classified as muddy sands were also from the Proposed Development export cable corridor. 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 offshore section of the Proposed Development export cable corridor were characterised by the same sediment types as the Proposed Development array area. The slightly gravelly sand/gravelly sand sediments graded into muddy sand with patches of slightly gravelly muddy sand in the inshore and central sections of the Proposed Development export cable corridor ( Figure 3.7   Open ▸ ). According to the simplified Folk Classification (Long, 2006), most stations were classified as coarse sediments with areas of mud and sandy mud and mixed sediments.

Figure 3.7: Representative Image of Slightly Gravelly Sand (ST06)

101. The percentage sediment composition (i.e. mud ≤0.63 mm; sand <2 mm; gravel ≥2 mm) at each grab sample station is presented in Figure 3.8   Open ▸ and Annex A: Seabed Sediments. Across all sample stations, the average percentage sediment composition was 9.78% gravel, 82.76% sand and 7.47% mud. Generally, sand made up the highest proportion of the sediment composition, with the exception of a few sites within the western section of the Proposed Development array area which were dominated by gravel, some of which overlap with the Berwick Bank features. As expected, the sediment composition also showed a higher percentage of gravels within the western section of the Proposed Development array area in comparison to the eastern section of the Proposed Development array area. The sample stations with the highest percentage composition of mud were generally found along the inshore section of the Proposed Development export cable corridor ( Figure 3.9   Open ▸ ).
102. Sediments across the Proposed Development benthic subtidal and intertidal ecology study area were typically poorly sorted or moderately sorted. One sample station (ST83) was extremely poorly sorted, this station was classified as muddy sandy gravel with 32.2% gravel, 40.4% sand and 27.4% mud ( Figure 3.9   Open ▸ and Annex A: Seabed Sediments).

FFBC MPA

103. Sediments from within the FFBC MPA were generally representative of the sediments recorded across the Proposed Development benthic subtidal and intertidal ecology study area. Sediments within the eastern section of the FFBC MPA overlapping with the Proposed Development array area were classified as slightly gravelly sand and gravelly sand. Sediments within the western section of the FFBC MPA were slightly coarser and characterised by sandy gravel and slightly gravelly sand (see Figure 3.8   Open ▸ ).

Figure 3.8: Folk Sediment Classifications for Each Benthic Grab Sample

Figure 3.9: Sediment Composition (from PSA) at Each Benthic Grab Sample Location

3.4.4.    Results - Sediment Contamination

104. Table 3.6   Open ▸ to Table 3.8   Open ▸ in the following subsections present the levels of contaminants that were recorded in the sediment samples. Where contaminants exceeded the Marine Scotland chemical guideline ALs their cells have been highlighted with the corresponding colour. Where contaminant levels exceed the Canadian TEL the contaminant level has been marked with an asterisk. No contaminants were found to exceed AL1/AL2 or the Canadian PEL with only arsenic at five sample stations exceeding Canadian TEL ( Table 3.6   Open ▸ ).

Metals

105. Heavy metals are readily adsorbed by sediments, this can lead to metals accumulating to concentrations far higher than the surrounding environment. These sediments can become re-suspended through bioturbation or through physical processes/disturbances. Metals will tend to accumulate in these fine-grained sediments and can become bioavailable to marine organisms through ingestion. The uptake of heavy metals by marine organisms can lead to bioaccumulation through trophic levels leading to apex organisms accumulating metals to adverse and toxic levels. This could result in significant adverse effects including mortality, impaired reproduction, reduced growth, alterations in metabolism as a result of oxidative stress and disruption to the food chain.
106. The sediment chemistry results, presented in Table 3.6   Open ▸ , concluded that all the metal contaminants did not exceed the AL1. The majority of the metal contaminants also did not exceed the Canadian TEL, with the exception of Arsenic at five sample stations (ST92, ST93, ST94, ST95, ST96). Metal concentrations within the sediment across the Proposed Development benthic subtidal and intertidal ecology study area were well below the Canadian PEL and AL2.

Table 3.6:  Concentrations of Metals Recorded in Sediments within the Proposed Development Benthic Subtidal and Intertidal Ecology Study Area

Organotins

107. Organotin compounds are based on tin with hydrocarbon substitutes, these include the historically used biocides dibutyltin (DBT) and tributyltin (TBT). Primarily used as antifungal and antifouling agents to improve the efficiency, performance and longevity of marine structures and vessels, concerns over toxicity of these compounds to biological organisms led to the International Maritime Organisation (IMO) introducing a worldwide ban. Adverse biological effects are comparable to hydrogen cyanide, whereby the compound halts cellular respiration within the mitochondria leading to cell and organism death. Legacy trace TBT and DBT can still be present within sediments in harbours and low energy environments. Total organic carbon (TOC) is the amount of carbon found in a sediment sample and is often used as a non-specific indicator of water quality. TOC is important when detecting contaminants in drinking water and manufacturing cooling water, including monitoring run off water into the marine environment. Levels of TOC were low (<1%) across all samples except ST94, however the TOC at ST94 was still <5%. Total hydrocarbon content (THC) is used to describe the quantity of the measured hydrocarbon impurities present. This can be used as an indicator of anthropogenic pollution. Levels of TOH were generally in the region of 1,000-6,000 mg/kg with the exception of ST99 and ST89 which had higher levels of TOH. These sample stations were closest to shore and therefore are likely to have experienced higher levels of vessel traffic and/or contaminated effluent from coastal/onshore works.
108. Levels of DBT and TBT for all samples were found to be below the Marine Scotland ALs (
     Annex J: Sediment Contamination Results).

Table 3.7:  Concentrations of Organotins Recorded in Sediment within the Proposed Development Benthic Subtidal and Intertidal Ecology Study Area

Polychlorinated biphenyls (PCBs)

109. PCBs are toxic to fish and other aquatic organisms. Reproductive and developmental problems have been observed in fish at low PCB concentrations, with the early life stages being most susceptible. There is growing evidence linking PCBs and similar compounds with reproductive and immuno-toxic effects in wildlife, including effects on seals and other marine mammals. Due to their persistence and lipophilic nature, PCBs have the potential to bioaccumulate, particularly in lipid rich tissue such as fish liver. Bioaccumulation of PCBs is recorded in fish, birds and marine mammals with known sublethal toxicological effects. Accumulation of PCBs in sediments poses a potential hazard to sediment-dwelling organisms.
110. Levels of PCBs, for all samples, were found to be under the respective Marine Scotland ALs and were below the limit of detection for each PCB at each sample station (
     Annex J: Sediment Contamination Results).

Polycyclic Aromatic Hydrocarbons (PAHs)

111. PAHs enter the environment through a number of sources, these include road run-off, sewage, atmospheric circulation and from historical industrial discharge. Once in the environment, PAHs exert a strong affinity for organic carbon and as such organic sediment in rivers can act as a substantial sink. Due to the high affinity for organic carbon, once ingested by fauna the PAHs cause oxidative stress and lead to adverse effects in the organism. Most species have a limited ability to metabolise PAHs and as a result can bioaccumulate to toxic levels.
112. Across all PAHs, levels were higher in sample stations ST98 and ST99 with some registering over ten times the levels at other stations but still below AL1 (
     Annex J: Sediment Contamination Results). These sample stations were closest to shore and therefore are likely to have experienced higher levels of vessel traffic and/or contaminated effluent from coastal/onshore works. In addition, seabed habitats closer to the coast had higher proportions of fine sand and mud (paragraph 101) which contaminants such as metals and hydrocarbons are typically bound to. Moreover, seabed habitats closer to the coast represent a lower energy environment which will reduce the likelihood of dilution and dispersal of any contaminants. However, PAH levels were consistently very low (mostly below the limit of detection) and levels for all samples were found to be under AL1 and the CSQGs (
     Annex J: Sediment Contamination Results).

3.4.5.    Results - Infaunal Analysis

Summary statistics

113. A total of 518 taxa were recorded from the 92 infaunal grab samples collected across the Proposed Development benthic subtidal and intertidal ecology study area. Of these, 57 taxa were colonial or taxa whose abundance could not be enumerated, and therefore were recorded as present (P). These taxa were removed from the infaunal numerical and statistical analysis but were included in the epifaunal numerical analysis (section 3.4.6). A total of 9,093 individuals representing 461 enumerated taxa were recorded across the Proposed Development benthic subtidal and intertidal ecology study area. Of these, juveniles accounted for 1,386 individuals from 49 taxa representing 15% of the total number of individuals and 10% of the total number of taxa recorded. Two of the recorded taxa were bony fish species (turbot Scophthalmus maximus and lesser sandeel Ammodytes tobianus) and represented 23 individuals. As they are highly mobile species, they were removed from the statistical analysis but are discussed in paragraph 116.
114. Of the 461 total taxa enumerated throughout the Proposed Development benthic subtidal and intertidal ecology study area, none were observed at all stations. A total of 114 taxa (25%) were recorded as single individuals; these rarely recorded taxa were distributed across the Proposed Development benthic subtidal and intertidal ecology study area. A total of 312 taxa (68%) were represented by <10 individuals. It is generally accepted that ecological communities which are frequently subjected to local disturbance or contamination events will be dominated by a limited number of tolerant taxa, which will be represented in high individual abundances (Clarke and Warwick, 2006). The relatively high numbers of single and low abundance species recorded in this survey could suggest a reasonably diverse community that has been subjected to relatively limited disturbance or contamination.
115. Juveniles were recorded from stations across the Proposed Development benthic subtidal and intertidal ecology study area from taxa including Mollusca, Crustacea, Echinodermata, Annelida, Sipunculidea and Tunicata. The five most abundant juvenile taxa were within the Echinodermata (Amphiuridae juveniles and Ophiuridae juveniles) and Mollusca (Abra juveniles, Mytilidae juveniles and Thracioidea juveniles). These five juvenile taxa made up 62% of the total number of juvenile individuals. ST32 (in the north-east of the Proposed Development array area; Figure 3.4   Open ▸ ) was the only sample station that recorded all five of the highest abundance juvenile taxa. ST50 recorded the highest numbers of juvenile individuals (114; mainly Amphiuridae, Leptochiton, Mytilidae and Ophiuridae) with ST71 recording the highest number of juvenile taxa (16). In addition to juvenile taxa, Decapoda megalopa and zoea were recorded; these larval stages were recorded at ST11, ST54, ST55, ST58, ST60, ST71 and ST104.
116. As previously mentioned, 56 taxa were recorded only as present; these taxa were dominated by Bryozoa and Hydrozoa. Epifaunal/colonial/encrusting taxa across the Proposed Development benthic subtidal and intertidal ecology study area included: Folliculinidae, Enteroprocta, Phoronidaea and Porifera. Of these taxa, Folliculinidae were present across the greatest number of sample stations ST50, ST54, ST71 (within the west of the Proposed Development array area) and ST36, ST70 (outside the Proposed Development array area to the southwest and north respectively). ST83 (outside the Proposed Development export cable corridor, nearshore to the south-east) recorded the highest number of epifauna/colonial/encrusting taxa. One individual turbot was recorded at ST83 and multiple individuals of the lesser sand eel were recorded at stations across the Proposed Development benthic subtidal and intertidal ecology study area.
117. Initially the dataset was divided into the five major taxonomic groups: Annelida (Polychaeta), Crustacea, Mollusca, Echinodermata and 'Others'. The 'Other' group comprised of:

• Eight taxa of Sipunculidea (Aspidosiphon (Aspidosiphon) muelleri, Golfingia (Golfingia) elongata, Golfingia (Golfingia) vulgaris, Nephasoma (Nephasoma) minutum, Onchnesoma squamatum, Phascolion (Phascolion) strombus, Sipuncula, Thysanocardia procera).
• Five taxa of Anthrozoa (Cerianthidae, Cerianthus lloydii, Edwardsiidae, Pennatula phosphorea and Virgularia mirabilis).
• Four taxa of Tunicata (Ascidiacea, Ciona intestinalis, Corella parallelogramma, and Dendrodoa grossularia).
• Two taxa of Pycnogonida (Anoplodactylus petiolatus and Nymphon brevirostre).
• One taxa of the following taxa groups: Chaetognatha, Enteropneusta, Molgulidae, Nematoda, Nemertea, Owenia, Plyatyhelminthes, Phoronis Brachiostomatidae (Branchiostoma lanceolatum) and Foraminifera (Astrorhiza).

118. The absolute and proportional contributions of these five taxonomic groups to the overall community structure is summarised in Table 3.8   Open ▸ whilst biomass values by gross taxonomic groups are presented in Annex E: Benthic Infaunal Contribution of Biomass to Gross Taxonomic Groups.

Table 3.8:  Contribution of Gross Taxonomic Groups Recorded in the Infaunal Grab Samples

119. Across the Proposed Development benthic subtidal and intertidal ecology study area, the faunal communities were generally dominated by Annelida (n=3,392) and Mollusca (n=1,850) which contributed 37% and 20% of the total number of individuals respectively ( Figure 3.10   Open ▸ ). Number of taxa were also dominated by Annelida; however, Crustacea provided a higher proportion of taxa than Mollusca, suggesting that the dominance of Mollusca individuals is provided by a small number of taxa. At individual sample stations, gross taxonomic group proportions reflected these results, however Annelida had a higher proportion, with Annelida making up the highest proportion of the taxa in 60% of sample stations and Mollusca making up the highest proportion of the taxa in 17% of sample stations. Annelida made up the highest proportion of individuals at 55 sample stations with proportion ranging from 27-73% of the total individuals. Mollusca made up the highest proportion of individuals at 16 sample stations with proportion ranging from 28-58% of the total individuals. Echinodermata made up the highest proportion of individuals at 15 sample stations with proportion ranging from 30-49% of the total individuals. Crustacea made up the highest proportion of individuals at seven sample stations with proportion ranging from 25-44% of the total individuals.
120. The biomass data did not reflect the dominance of Annelida with respect to the number of individuals and number of taxa, with Annelida providing the highest proportion of the biomass at only 18% of sample stations. Mollusca contributed the highest proportion of biomass at the greatest number of sample stations (n=41, 45%) with Echinodermata making up the highest proportion of biomass at the next highest number of sample stations (n=26, 28%). Mollusca contributed the highest proportion of the biomass at the sample stations with the highest total biomass. This may a result of Mollusca and Echinodermata being able to grow to a larger body size than most Annelida therefore are likely to have a higher weight per individual. Several stations where Echinodermata made up the highest proportion of the biomass, sea urchins (e.g. Echinocardium cordatum and Echinocyamus pusillus) were recorded.
121. The most abundant individuals generally belonged to Mollusca and Annelida although the tunicate D. grossularia was overall the most abundant species with a total of 523 individuals recorded. However, all 523 individuals were recorded from a single station (ST83 outside the nearshore section of the Proposed Development benthic subtidal and intertidal ecology study area, Figure 3.4   Open ▸ ). The species with the second highest abundance was S. spinulosa with 456 individuals; 336 of those individuals were also recorded at ST83. ST83 also had a much higher abundance of the polychaete Lumbrineris cingulata compared with the rest of the sample stations. ST83 recorded the highest total number of individuals (1,296) across only 77 taxa. ST54 recorded the highest number of taxa (95) with the next highest being ST50 (92 taxa) and ST71 (85 taxa).