8. Benthic Subtidal Ecology

8.1. Introduction

  1. This chapter of the Array Environmental Impact Assessment (EIA) Report presents the assessment of the likely significant effects (LSE1) (as per the “EIA Regulations”) on benthic subtidal ecology as a result of the Ossian Array, which is the subject of this application (hereafter referred to as “the Array”). Specifically, this chapter assesses the LSE1 of the Array on offshore benthic subtidal ecology during the construction, operation and maintenance, and decommissioning phases.
  2. Likely significant effect is a term used in both the EIA Regulations and the Habitat Regulations. Reference to LSE1 in this Array EIA Report refers to LSE1 as used by the EIA Regulations. This Array EIA Report is accompanied by a Report to Inform Appropriate Assessment (RIAA) (Ossian OWFL, 2024) which uses the term as defined by the Habitats Regulations (LSE2).
  3. This chapter also summarises information contained within volume 3, appendix 8.1.

8.2. Purpose of the Chapter

  1. The Array EIA Report provides the Scottish Ministers, statutory and non-statutory stakeholders with adequate information to determine the LSE1 of the Array on the receiving environment. This is further outlined in volume 1, chapter 1.
  2. The purpose of this benthic subtidal ecology Array EIA Report chapter is to:
  • present the existing environmental baseline established from desk studies, site-specific surveys, numerical modelling studies, and consultation with stakeholders;
  • identify any assumptions and limitations encountered in compiling the environmental information;
  • present the environmental impacts on benthic subtidal ecology arising from the Array and reach a conclusion on the LSE1 on benthic subtidal ecology, based on the information gathered and the analysis and assessments undertaken; and
  • highlight any necessary monitoring and/or mitigation measures which are recommended to prevent, minimise, reduce or offset the likely significant adverse environmental effects of the Array on benthic subtidal ecology.

8.3. Study Area

  1. Figure 8.1   Open ▸ illustrates the two benthic subtidal ecology study areas which have been defined for the purpose of this assessment:
  • the Array benthic subtidal ecology study area, which is defined as the area encompassed by the site boundary and one mean spring tidal excursion ( Figure 8.1   Open ▸ ). This area is therefore appropriate for assessing impacts associated with the Array, which are highly localised. The site-specific benthic subtidal ecology surveys were undertaken within the site boundary, the results of which were used to inform the baseline characterisation and identify benthic receptors which could potentially be impacted by the Array; and
  • the regional benthic subtidal ecology study area, which is defined as the area encompassing the wider North Sea ( Figure 8.1   Open ▸ ). The boundaries for this regional benthic subtidal ecology study area were adapted from the Sectoral Marine Plan (SMP) Assessment region: East Region. The regional benthic subtidal ecology study area boundary to the south of the site boundary was extended to take account of feedback received during the pre-Scoping workshop (14 November 2022) (see Table 8.5   Open ▸ ) suggesting that the regional benthic subtidal ecology study area was not large enough to account for both direct and indirect effects. Desktop data sources have been used to characterise the regional benthic subtidal ecology study area, to provide wider context to the site-specific data collected within the Array benthic subtidal ecology study area.


Figure 8.1:
Benthic Subtidal Ecology Study Areas

Figure 8.1: Benthic Subtidal Ecology Study Areas


8.4. Policy and Legislative Context

  1. Volume 1, chapter 2 of the Array EIA Report presents the policy and legislation of relevance to renewable energy infrastructure. Policy specifically in relation to benthic subtidal ecology is contained in the SMP for Offshore Wind Energy (Scottish Government, 2020a)[1], the Scottish National Marine Plan (NMP) (Scottish Government, 2015), and the United Kingdom (UK) Marine Policy Statement (MPS) (UK Government, 2011). Table 8.1   Open ▸ presents a summary of the legislative provisions relevant to benthic subtidal ecology, with relevant policy provisions set out in Table 8.2   Open ▸ to Table 8.4   Open ▸ .
  2. Further detail is presented in volume 1, chapter 2.

 

Table 8.1:
Summary of Habitat Regulations (Conservation of Offshore Marine Habitats and Species Regulations 2017and Conservation of Habitats and Species Regulations 2017) of Relevance to Benthic Subtidal Ecology

Table 8.1: Summary of Habitat Regulations (Conservation of Offshore Marine Habitats and Species Regulations 2017and Conservation of Habitats and Species Regulations 2017) of Relevance to Benthic Subtidal Ecology

 

Table 8.2:
Summary of the SMP for Offshore Wind Energy Relevant to Benthic Subtidal Ecology (Scottish Government, 2020a)

Table 8.2: Summary of the SMP for Offshore Wind Energy Relevant to Benthic Subtidal Ecology (Scottish Government, 2020a)


Table 8.3:
Summary of the Scottish NMP Relevant to Benthic Subtidal Ecology (Scottish Government, 2015)

Table 8.3: Summary of the Scottish NMP Relevant to Benthic Subtidal Ecology (Scottish Government, 2015)


Table 8.4:
Summary of the UK MPS Relevant to Benthic Subtidal Ecology (UK Government, 2011)

Table 8.4: Summary of the UK MPS Relevant to Benthic Subtidal Ecology (UK Government, 2011)

 

8.5. Consultation

  1. Table 8.5   Open ▸ presents a summary of the key issues raised during consultation activities undertaken to date specific to benthic subtidal ecology for the Array, including advice received in the  Ossian Array Scoping Opinion (Marine Directorate – Licensing Operations Team (MD-LOT), 2023), along with how these have these have been considered in the development of this benthic subtidal ecology Array EIA Report chapter. Further detail is presented within volume 1, chapter 5.
Table 8.5:
Summary of Issues Raised During Consultation and Scoping Opinion Representations Relevant to Benthic Subtidal Ecology

Table 8.5: Summary of Issues Raised During Consultation and Scoping Opinion Representations Relevant to Benthic Subtidal Ecology

 

8.6. Methodology to Inform Baseline

  1. Topic specific information has been reviewed and analysed to inform this benthic subtidal ecology baseline. In addition, consultation with stakeholders and Statutory Nature Conservation Bodies (SNCBs) has been carried out to aid the collection of baseline information.

8.6.1. Desktop Study

  1. Information on benthic subtidal ecology within the regional benthic subtidal ecology study area was collected through a detailed desktop review of existing studies and datasets which are summarised in Table 8.6   Open ▸ .
  2. Both the literature review of the reports and numerical modelling using the datasets were used to characterise the baseline. The benthic subtidal ecology technical report (volume 3, appendix 8.1) includes full details of the analysis undertaken to develop the benthic subtidal ecology baseline.

 

Table 8.6:
Summary of Key Desktop Reports

Table 8.6: Summary of Key Desktop Reports

 

8.6.2. Identification of Designated Sites

  1. A three-step process was used to identify all designated sites within the regional benthic subtidal ecology study area and qualifying interest features that could be affected by the construction, operation and maintenance, and decommissioning phases of the Array. This process is described below:
  • Step 1: All designated sites of international, national, and local importance within the regional benthic subtidal ecology study area were identified using a number of sources. These sources included JNCC (2023) and NMPi (2023).
  • Step 2: Information was compiled on the relevant benthic subtidal ecological features for each of these sites as follows: Firth of Forth Banks Complex MPA, Berwickshire and North Northumberland Coast SAC, Firth of Tay and Eden Estuary SAC, and Isle of May SAC.
  • Step 3: Using the above information and expert judgement, sites were included for further consideration if:

–           a designated site directly overlaps with the Array and therefore has the potential to be directly affected by the Array; or

–           sites and associated features were located within the benthic subtidal ecology Zone of Influence (ZoI) for impacts associated with the Array. The ZoI varies for the different impacts scoped in for assessment and refers to the area in which benthic subtidal ecology could be impacted as a result. For all direct impacts, the ZoI is represented by the Array benthic subtidal ecology study area, and for indirect impacts associated with SSCs, the ZoI is represented by one tidal excursion. As dominant current direction of north/south is evident, a mean spring tidal excursion of 8 km has been determined for these directions, reducing to 4 km for the east/west tidal regime, thus representing the ZoI for this impact.

8.6.3. Site-Specific Surveys

  1. Site-specific surveys were undertaken, as agreed following consultation with MD-LOT and NatureScot, to inform the benthic subtidal ecology Array EIA Report chapter (see Table 8.5   Open ▸ for further details). A summary of the surveys undertaken used to inform the benthic subtidal ecology assessment of effects is outlined in Table 8.7   Open ▸ .

 

Table 8.7:
Summary of Site-Specific Survey Data Collected

Table 8.7: Summary of Site-Specific Survey Data Collected