A review of benthic ecological surveying for marine renewable developments in Scottish waters

Executive Summary

The pace of development in the offshore wind, wave, and tidal sectors in Scotland, referred to here as Marine Renewable Energy (MRE), has increased significantly recently. This is especially the case in the offshore wind sector with the ScotWind and Innovation and Targeted Oil and Gas (INTOG) leasing rounds now completed. Development in this sector is likely to continue to progress to meet Scottish and wider UK decarbonisation targets.

A variety of environmental assessments are needed as part of the MRE development process. Characterising the intertidal and seabed features within development areas is key to establish a baseline and can be useful during and post-construction to monitor any potential changes arising from development activity.

Scotland has a rich marine geodiversity and biodiversity that are intrinsically linked to the unique physical characteristics and processes that occur within the marine environment. These features and patterns have some similarities to the other parts of the UK but can also be distinctly different. The equipment and methods employed elsewhere for intertidal and seabed ecology surveys are therefore not necessarily suitable for the inshore and offshore waters around Scotland.

The Scottish Government aims to ensure that planning and consenting decisions are informed by sound evidence and makes reasonable efforts to address any gaps in knowledge in line with the National Marine Plan (Scottish Government, 2015). This report, commissioned by the Scottish Marine Energy Research (ScotMER) programme, provides a detailed appraisal of possible intertidal and seabed ecology surveying options. It also provides recommendations on planning and executing seabed ecology surveys for the characterisation and monitoring of Marine Renewable Energy Developments (MREDs) at each stage of activity.

At the heart of the project outputs is a tabular “tool, technology and technique evaluation matrix”, which is presented as an Appendix to the main report. This Evaluation Matrix and supporting commentary in the report provides users with a comprehensive option evaluation toolkit. The toolkit can be used to identify the technical solutions best suited for surveying benthic ecology features in the context of specific MRED project needs within Scottish waters.

The report evaluates the key issues and decisions linked to applying these tool, technology and technique options within an overall seabed survey planning and delivery framework.

The report highlights that:

• Topography, bathymetry, geophysical and geotechnical techniques can give initial insights about the type and extent of habitats likely to be present.
• Visual tools of skilled eye appraisal, video and photographs can provide confirmatory evidence of the key macro indicator species that are present and of the status of colonising communities. Repeated visual monitoring can give cost-effective information on community types, their distribution, abundance and dynamic trends.
• Physical samples recovered from the seabed provide tangible evidence of some of the smaller, cryptic and buried species present and more details regarding abundance, size, age structure, reproductive state. Such samples can also be used to characterise detailed physical and chemical conditions, as well as obtaining genetic material from environmental DNA (eDNA), for example.
• Increased intensity of sampling in terms of sample replication or more regular undertaking of surveys over time often gives a more comprehensive insight into the details of seabed ecosystem characteristics and dynamics.

Some of the underpinning principles applied to this evaluation of options for surveying tools, technologies and techniques, as well as survey strategy and design, were:

• Consideration of surveying approaches and strategies that are best aligned with the project type and purpose.
• The right survey method and level of sampling effort needs to be found to deal with the prevailing local conditions, and to help resolve key topics of concern and uncertainty.
• Anticipated sensitivity potential and likely project complexity can be determined from existing information. An appropriate level of survey intensity for a intertidal/seabed survey design can then be based upon these factors.
• The importance of taking into account any cumulative influences that may arise from nearby or co-located activities.
• The need to understand existing pressures on ecosystems, levels of natural change and the merits of suitable control stations to be incorporated into monitoring strategies.

Taking all these factors into account, an overall intertidal and seabed survey framework is presented based upon the level at which community details need to be described. The framework recognises and describes three levels of survey intensity: standard; enhanced; and comprehensive. The appropriate level of intensity is designed to be applied to each project element based upon location-specific sensitivity and complexity. This means that different intensities of surveying may be appropriate for different parts of a project’s layout.

The approach and methods required to deliver such levels of survey intensity also vary. For ‘standard’ intensity surveys, for example, there is a greater reliance upon descriptions of physical habitats and key indicator species which can be easily seen in video footage; for ‘enhanced’ intensity surveys there is a greater emphasis placed upon the gathering of still photographs and physical samples from seabed grab devices; and for ‘comprehensive’ intensity surveys, there is even greater emphasis upon physical sampling and likely increased sample replication.

A key aim of this study has been to establish a staged process to help guide project developers, survey practitioners, regulators and advisors towards a consensual understanding of what might be an appropriate intertidal and seabed ecology survey strategy for a given set of circumstances. Consequently, a table of key actions to be followed when planning and executing any seabed survey has been prepared and is included (see Table 8.1). Within this table and other supporting materials there has been a strong focus upon generating the level of information required to undertake assessments involved in licensing and consenting applications at each project development stage. There is then an option to expand and extend that work scope as appropriate for added value.

This guidance is intended to be used to make recommendations for best practice only.