Epibenthic fauna from DDV and still photography

  1. Analysis of the DDV and photography showed that the habitats were generally dominated by sand and muddy sand with occasional shell debris, cobbles and pebbles. Generally, the faunal presence in the imagery was sparse, and mainly comprised of L. conchilega, Paguridae, the bryozoan F. foliacea, Tubularia sp., and scattered colonies of Epizoanthus sp. Cnidarians and annelids were conspicuous, mostly associated with areas of sandy substrate. There were three sites with no fauna recorded (S012, S026, and S064), and consisted of sand or muddy sand with occasional shell debris present. The average number of species per site was four, and the highest number of taxa (n=17) was recorded at S066 ( Table 3.15   Open ▸ ). The ten sites with the highest number of taxa recorded are presented in .


Table 3.15:
Top Ten DDV and Photography Sampling Sites with the Greatest Diversity of Taxa

Table 3.15: Top Ten DDV and Photography Sampling Sites with the Greatest Diversity of Taxa

Figure 3.19:
Photograph from Sampling Site S066, showing Circalittoral Fine Sand with Caridae, Paguridae, Gastropoda, Urticina sp., Idotea sp. and Scalpellum sp.

Figure 3.19: Photograph from Sampling Site S066, showing Circalittoral Fine Sand with Caridae, Paguridae, Gastropoda, Urticina sp., Idotea sp. and Scalpellum sp.

 

                        Non-colonial epifauna from seabed photographs
  1. The most abundant phylum in the photographs was Annelida, which represented 39% of all individuals recorded, with the majority of recordings represented by L. conchilega (38%) and the remaining 1% comprised of Aphrodita aculeata, Spirobranchus triqueter, Serpulidae and Polychaeta. L. conchilega was the most abundant and common species overall, with a total of over 1,234 individuals per m2 in the photographs. They were recorded in 30% of images, with the largest number observed at site S029 and an average of 67 individuals per m2 per photograph. Cnidaria were the second most abundant phyla, representing 28% of all individuals recorded; Epizoanthus sp., was the most abundant cnidarian. Arthropoda represented 14% of all individuals recorded, comprising mainly of different Paguridae species. Other phyla, such as Chordata, Echinodermata, and Mollusca, were also recorded. The total relative abundance of all the non-colonial fauna recorded in the photographs is presented in Figure 3.20   Open ▸ .

Figure 3.20:
Total Relative Abundance of Non-Colonial Fauna in the Seabed Photographs

Figure 3.20: Total Relative Abundance of Non-Colonial Fauna in the Seabed Photographs

 

                        Sessile colonial fauna from seabed photographs
  1. Three sessile colonial phyla were recorded in the still photographs: Bryozoa, Cnidaria and Porifera. Cnidaria covered the largest surface area, with a total contribution of 48%. Bryozoa, Bryozoa/Cnidaria and Porifera contributed 47%, 5%, and 0.2%, respectively Figure 3.21   Open ▸ ). Cnidarians were present at 44 out of 80 sampling sites, mostly visible as a range of indistinguishable hydrozoans. Bryozoans were recorded at 38 out of the 80 sites, with F. foliacea being the most common species observed in the imagery.

Figure 3.21:
Total Coverage of Sessile Colonial Fauna in the Seabed Photographs

Figure 3.21: Total Coverage of Sessile Colonial Fauna in the Seabed Photographs

 

                        Epibenthic beam trawl analysis

                        Total biomass
  1. The total biomass of non-colonial and sessile colonial epifauna was dominated by Chordata (67%). Echinodermata was the second largest group (15%), followed by Bryozoa (7%). The total biomass varied from 0.00 g in sample BT010 (which recovered no sample), to 1,860.82 g in BT001, with an average biomass of 436.26 g per sample (SD=550.61). Various fish species were observed in the trawl samples, which are discussed in volume 3, appendix 9.1.
                        Non-colonial epifauna
  1. Arthropoda had the highest abundance and diversity of the non-colonial fauna identified in the beam trawl samples, followed by Chordata and Mollusca, as illustrated in Table 3.16   Open ▸ .

 

Table 3.16:
Phyletic Composition of Non-Colonial Epifauna from the Epibenthic Beam Trawls

Table 3.16: Phyletic Composition of Non-Colonial Epifauna from the Epibenthic Beam Trawls

 

                        Sessile colonial epifauna
  1. There were 20 different sessile colonial epifaunal taxa identified from the beam trawls. A total of three major phyla were identified: Cnidaria, Bryozoa and Porifera, comprising of 55%, 30% and 15% of the total number of taxa sampled, respectively. Of the 20 different taxa identified, Cnidaria comprised 33 colonies, followed by Bryozoan and Porifera, with a total of 21 and 8 colonies, respectively. Table 3.17   Open ▸ presents a summary of the sessile colonial epifauna identified in each trawl samples, using the (Super-Abundant, Abundant, Common, Frequent, Occasional, Rare) SACFOR Scale (JNCC, 2023b).

 

Table 3.17:
SACFOR Abundance Scale for Sessile Colonial Epifauna from the Epibenthic Beam Trawl (A = Abundant, C = Common, O = Occasional, R = Rare)

Table 3.17: SACFOR Abundance Scale for Sessile Colonial Epifauna from the Epibenthic Beam Trawl (A = Abundant, C = Common, O = Occasional, R = Rare)

                        Notable taxa

  1. There were no non-native species identified during the environmental survey. However, there were two species considered relatively infrequent in UK waters identified from the macrofaunal grab samples. These species were polychaete worms Cirratulus caudatus and Paradoneis ilvana.
  2. A total of 290 records of C. caudatus within UK waters are included within the NBN Atlas database (NBN Atlas, 2023a), and this database lists this species as native. The World Register of Marine Species (WoRMS) and Ocean Biodiversity Information System (OBIS) also report up to 628 records of this species between the years 1993 and 2020, with records concentrated within the North Sea, and extending into the Norwegian Sea, English Channel and Celtic Sea and North Atlantic (OBIS, 2023a; WoRMS, 2023). This polychaete is included within the European Register of Marine Species (Bellan, 2001).
  3. The NBN Atlas database includes 122 records of P. ilvana from UK waters and lists this species as native (NBN Atlas, 2023b). OBIS reports a total of 344 records globally from the years 1970 to 2021, with those in UK waters concentrated off the west coast, within the Celtic Sea, Irish Sea and Outer Hebrides and no documented records in the North Sea (OBIS, 2023b). This polychaete is included within the European Register of Marine Species (Bellan, 2001).
  4. C. caudatus was recorded in grab samples S044 and S061, with an abundance of one individual per 0.1 m2 in each sample. P. ilvana was recorded in three samples (S010, S023, and S070) at an abundance of one individual per 0.1 m2 in S010 and S023 and two individuals per 0.1 m2 in S070.

                        Potential areas and species of conservation importance

  1. Using the methodology outlined in paragraphs 56 to 58 and in Table 3.7   Open ▸ and Table 3.8   Open ▸ , there were no Annex I features identified. This includes Annex I (1170) stony reefs and biogenic reefs, as described in the Habitats Directive (European Commission, 2013).
  2. A range of different habitats or species of conservation importance were identified, summarised in Table 3.18   Open ▸ and Figure 3.22   Open ▸ . These include PMFs, SBL habitats and species, UK Biodiversity Action Plan (BAP) habitats, and OSPAR-listed threatened and/or declining habitats and species. Eight PMF, SBL and OSPAR fish species were also recorded, further detailed in volume 3, appendix 9.1.

 

Table 3.18:
Benthic Habitats and Species of Conservation Importance Identified during the Environmental Survey

Table 3.18: Benthic Habitats and Species of Conservation Importance Identified during the Environmental Survey

Figure 3.22:
Locations of Notable Species Recorded during the Environmental Survey

Figure 3.22: Locations of Notable Species Recorded during the Environmental Survey


                        Summary of habitats identified

  1. Overall, based on the data collected in the geophysical and environmental surveys, four habitats were interpreted as characterising the Array benthic subtidal ecology study area ( Table 3.19   Open ▸ ; Figure 3.23   Open ▸ ):
  • MC421 – Faunal communities of Atlantic circalittoral mixed sediment;
  • MC521 – Communities of Atlantic circalittoral sand;
  • MC5211 – E. pusillus, O. borealis, and A. prismatica in circalittoral fine sand; and
  • MC5212 – A. prismatica, B. elegans, and polychaetes in circalittoral fine sand.
  1. As the Array benthic subtidal ecology study area was mostly homogeneous a full delineation of the habitat boundaries shows minor variation in sediment composition and overlapping species compositions across sampling sites. Thus, the overall habitat classifications were delineated at the two lower levels: MC421 and MC521, and the higher-level classifications (MC5211 and MC5212) were overlaid ( Figure 3.23   Open ▸ ).
  2. As per Table 3.19   Open ▸ , one PMF habitat (offshore subtidal sands and gravels) and one SBL habitat (subtidal sands and gravels) were interpreted as being present. These habitats are considered to be very common around the British Isles and throughout the North Sea (Brig, 2008 (updated December 2011)).

 

Table 3.19:
Description of the Four Habitats Identified within the Array Benthic Subtidal Ecology Study Area

Table 3.19: Description of the Four Habitats Identified within the Array Benthic Subtidal Ecology Study Area

Figure 3.23:
Habitat Classifications Recorded during the Environmental Survey

Figure 3.23: Habitat Classifications Recorded during the Environmental Survey


3.3.3. Important Ecological Features

  1. In accordance with best practice guidelines developed by the Chartered Institute of Ecology and Environmental Management (CIEMM, 2022), Important Ecological Features (IEFs) have been identified for the purposes of the Array EIA Report. All potential impacts upon the IEFs due to the Array will be assessed to determine significance. According to the guidelines, importance may be determined by the quality or extent of habitats, rarity of habitats or species, and their conservation status (CIEEM, 2022). Species and habitats are considered to be IEFs if they are recognised through international or national conservation legislation or under regional or local conservation plans (e.g. Annex I and Annex II, OSPAR, National Biodiversity Plan, SBL, PMFs, etc.). The criteria used to evaluate the IEF level are presented in Table 3.20   Open ▸ .
  2. The IEFs identified within the Array benthic subtidal ecology study area are presented in Table 3.21   Open ▸ , and will be taken forward for assessment within the benthic subtidal ecology EIA Chapter (volume 2, chapter 8). Within the Array EIA Report, impacts upon IEFs associated with the construction, operation and maintenance, and decommissioning of the Array will be assessed. As outlined in paragraph 96 to 100 there were several benthic subtidal habitats and species of conservation importance identified during the environmental survey of the Array benthic subtidal ecology study area. As per Table 3.19   Open ▸ , individual horse mussel were identified across the survey, however no horse mussel beds were recorded. Therefore, as only the horse mussel beds themselves are of conservation importance (PMF, SBL and OSPAR habitats), this species will not be caried forward in the IEF evaluation. Similarly, P. phosphorea (SBL) was identified in multiple sampling sites, however the closely associated sea-pen and burrowing megafauna (OSPAR) and burrowed mud (PMF) habitats were not identified. Thus, only the SBL designation for the P. phosphorea itself will be taken forward in the IEF evaluation.

 

Table 3.20:
Criteria used to Evaluate IEFs within the Array Benthic Subtidal Ecology Study Area

Table 3.20: Criteria used to Evaluate IEFs within the Array Benthic Subtidal Ecology Study Area

 

Table 3.21:
IEFs within the Array Benthic Subtidal Ecology Study Area

Table 3.21: IEFs within the Array Benthic Subtidal Ecology Study Area