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

7 Benthic surveying – recommendations

7.1 Introduction

Building upon the previous materials presented, this section outlines the recommendations for how to establish the right intensity of benthic ecological survey for MRE activities. In any particular project scenario, the site, technology and purpose of the development will vary. This will lead to distinctive needs, as well as pressures and opportunities that may need to be considered. Consequently, there is no “one size fits all” solution to apply to benthic surveys for MREDs. These recommendations set out the general principles to be applied. Examples and mechanisms for how this might be best achieved have been provided.

Follow on work by a project developer and/or regulator can take these recommendations forward to create more fixed action plans for project-specific outcomes and sets of site conditions. Flexibility in the specifics of what is done and used, adaptability in terms of what is achievable and a high degree of data literacy to handle available data will all be essential.

The basic approach involves:

• Recognising that the right survey solution needs to be found for the prevailing local conditions – any existing knowledge about conditions will influence that need, with greater uncertainty likely leading to greater survey intensity and higher levels of existing knowledge reducing the intensity or providing more focus of work needed.
• Establishing anticipated sensitivity potential and likely project complexity based upon existing information.
• Determining appropriate sampling intensity level for survey design.
• Considering surveying techniques and strategies that are best aligned with the project type, likely habitat types, local sensitivities, and prevailing local conditions.

7.2 Determining sensitivity potential and likely project complexity in a prospective development area

It is clear from the previous sections of this report that objectives and strategies for surveying will vary from place to place based upon the habitats and species present, the logistical challenges of the area, the number of samples needed to characterise a habitat type, the level of environmental sensitivity of the development area and linked routes, as well as the complexity of the proposed project. The combination of these features in any development scenario may lead to different survey intensities being most appropriate.

For relatively small scale and simple projects taking place across low sensitivity habitat areas with a sufficient level of data available, a less intense surveying strategy may be appropriate. However, larger and more complex projects taking place across more sensitive areas will require a higher level of survey intensity to be applied.

This section therefore applies this principle by recommending a level of survey intensity that might be most appropriate taking into account the two core drivers: the potential for environmentally sensitive communities of species to be present (ecological sensitivity); and the likely complexity of a development project in terms of seabed impacts (development complexity). To achieve this, a scheme has been devised to differentiate and define each of the levels of ecological sensitivity (Table 7.1) and development complexity (see Table 7.2).

The ecological sensitivity is based upon three “topic areas”: the likelihood that conservation features will be present; the uniformity of conditions across the area (heterogeneity); and the availability of existing data. The development complexity is also linked to three separate topic areas: the size or scale of activities; the range and types of impact that might arise; and the levels of any existing pressures from other sea user activity (see Table 7.2). Once the level of ecological sensitivity and development complexity have been scored (low, medium or high/complex), these scores can feed into the Survey Intensity Matrix (Table 7.3) to determine the recommended survey approach (Standard, Enhanced or Comprehensive).

Within each of the topic areas in Table 7.1 and Table 7.2, examples have been established to describe different sensitivity and complexity levels. The definitions provided should be seen as examples or guiding principles rather than as prescriptive standards.

These classifications of sensitivity potential should not be conflated with assessments and actual community sensitivity as defined under the Marine Life Information Network (MarLIN), FeAST and Marine Evidence based Sensitivity Assessment (MarESA) schemes. Those schemes deal with the character and sensitivity of a habitat, community or species once detected rather than seeking to identify potential for such types of habitats, community or species to be found in an area.

7.2.1 Classifying environmental sensitivity

To appropriately classify a certain level of sensitivity for a given area, route (or section thereof), existing data, knowledge and understanding should be used to consider which levels the particular site or route correlates to (with reference to Table 7.1).

If the levels of sensitivity score differently for each topic area for a given place (site or route) then the highest, most sensitive ranking is used. However, where the level of sensitivity varies between places within a development site, or along a development corridor, then the level of most appropriate sensitivity should be applied on an area by area, section by section basis. The scale at which such sensitivity classification may be most appropriate is at a hectare (ha) by hectare or 100 m by 100 m level in most instances. The resultant level(s) of sensitivity indicated for the whole development or for individual parts of the development will then be used to cross reference to the right level of survey intensity in the different parts of the overall development area, as described in Section 7.3.

7.2.2 Classifying development complexity

To classify levels of project complexity, this scheme takes account of impact intensity, scale of facilities and the degree of co-development. These factors are determined by taking into account existing project design, operational plans and information about other activities in the area of interest. These sources would be used to inform the classification of the project in terms of impact intensity, scale and the presence of other nearby or co-located activities as set out in Table 7.2. As with sensitivity, a project may be most appropriately classified as a mix of complexity- the core array and the export cables being classified differently or where a project utilises different technology or operational solutions in different parts of the development. Again, when assigning complexity at a site or to a place, the topic area with the highest level of complexity ascribed is deemed to be dominant.

The resultant level of complexity indicated for the whole project or for individual parts of the projects will then be used to cross reference to the right level of survey intensity as described in Section 7.3.

This scheme provides an indicative framework for ascribing sensitivity and complexity levels. On a site/project-specific basis there may also be additional features or issues that suggest it might be appropriate to alter the classification up or down accordingly. Diversion from this generalised framework can be discussed with the relevant regulators and stakeholders.

7.3 Establishing appropriate surveying intensity levels

Having established a mechanism for classifying the level of sensitivity potential and development complexity for a prospective MRED, the next step is to integrate these two factors to indicate an appropriate level of survey intensity to apply to such an area. The approach is to use a simple interaction framework as shown below (Table 7.3.). This framework indicates the given level of survey intensity that is appropriate for each combination of sensitivity potential and project complexity. Three levels of intensity are used: Standard; Enhanced; and Comprehensive.

Table 7.3 Survey Intensity Framework illustrating the relationships between complexity and sensitivity and how they should be applied to determine a survey intensity approach (escalating environmental sensitivity factors derived from Table 7.1 and development complexity levels (derived from Table 7.2).

Further explanation of the likely survey strategies associated with each intensity level is provided in the following paragraphs.

• Standard – The minimum sampling required to collect at a site, including metadata and QC standards. Aimed at confirming presence/absence of indicator species in different identified habitat types implied from topographical/bathymetry data and existing/established knowledge and understanding.
• Enhanced – It may be necessary to collect additional data beyond the standard approach. For example, if more sensitive or vulnerable species or habitats are expected or detected. Additional benthic data can also be collected that enhances the value of the data at a local level that is compatible with a secondary purpose such as legacy creation, incorporation into regional or national models, data sharing with nearby projects and/or supporting research initiatives. This level of activity may also demonstrate enhanced corporate responsibility.
• Comprehensive – It may be beneficial to undertake a broad suite of benthic surveying techniques where key issues and concerns are shown to be active and dynamic, either due to ongoing nearby activities or where known pressures exist or where particularly vulnerable species and/or communities exist. Additional benthic data can be collected that greatly enhances the value of the data spatially and temporally, at a regional/national level that is widely compatible with secondary purposes (legacy/data sharing). Demonstrating a high level of corporate responsibility including marine net gain/nature positive approaches.

The classification of such survey intensity levels can provide two kinds of direction to any survey plan. Firstly, it can help ensure that the appropriate level of survey is undertaken for the conditions and circumstances that prevail. Secondly, the potential to increase survey intensity strategies can create an opportunity for wider social, science, or reputational benefits.

Whilst it might be easiest to apply this scheme where the development area is characterised by one level of sensitivity potential and one level of project complexity, the reality of MREDs around Scotland may not be that simple. There will be cases where the energy generation area, the cable/pipeline export route and the landfall for a project all have different levels of sensitivity potential and complexity. There may also be variation in such parameters along a cable/pipeline route or in different parts of generation device deployment area. A project itself may therefore have a mosaic of intensity levels that are appropriate.

This may lead to a surveying approach that has different sample numbers and indeed sample types gathered within each area of different sensitivity/complexity. The resultant targeting of effort to where it is most needed and best applied will help maintain survey effectiveness and efficiency at the same time and gives overall coherency and understanding for consenting and monitoring purposes.

To achieve this outcome, the exact configuration of survey effort in any particular place, at any time and for any particular purpose, will need to be agreed between the regulator, key stakeholders, the developer and wherever possible, the survey and consenting contractors, or similarly experienced advisors.

7.4 Applying specific surveying tools and techniques within the suggested survey intensity scheme

Building on from the Survey Intensity Framework, it is possible to align specific surveying tools to each level of seabed community investigation based on the required outputs for assigning samples or areas to the MHC and EUNIS classification systems. These classifications of seafloor habitats are organised in a hierarchy whereby each level introduces more detail. For example, the MHC starts at Level 1 “Marine” and in the EUNIS hierarchy, the first three levels describe the habitats (i.e. the abiotic part) while the last three describe the biotopes (i.e. habitats and benthic communities that occupy them). The first major division in the benthic marine part of the EUNIS classification is based on major biological zones (related to depth) and substrate type. As the hierarchical levels progress in resolution, more information is included in the descriptions. At level 4 the MHC describes a “Biotope Complex”, and at a high-resolution, records include typical prominent species (level 5: Biotopes). In some cases, these biotopes can be split into sub-biotopes where distinct sub-habitats can be described, and these generally describe a wider range of macrofaunal species.

These classification hierarchies are also aligned with a progression of data types and acquisition tools needed to provide the data used for community characterisation with increasing precision at the higher MHC/EUNIS levels. At the broad habitat level, remote sensing geophysical techniques are often used, at the next level visual video confirmation is often employed. At the third level, still photos can be very helpful and for the fourth and fifth levels increasing numbers of samples, or applying multiple techniques to get a fuller picture of the habitat may be used (e.g., grab and video). This scheme can be augmented by additional chemical and geotechnical analysis of samples where required as well as by other more detailed ecological studies.

An indication of the survey approaches and examples of tools used to obtain the required outputs at each level of the habitat classification hierarchies has been provided in Table 7.4. The EUNIS hierarchy and associated survey approaches can be applied to different stages of MRE developments. Table 7.5, 7.6 and 7.7 outline the surveying strategies that might be most appropriate for development projects of different types, with different intensity needs (based upon sensitivity and complexity) and at the various stages of the development cycle. Table 7.5 presents the anticipated surveying strategies expressed by the levels of habitat description likely to be required for Standard survey intensity, Table 7.6 for Enhanced survey intensity and Table 7.7 for Comprehensive survey intensity.

Table 7.5 Overview of applicable surveying types for different development stages of a project across different technologies for standard survey intensity. Numbers are based on the EUNIS classification system displayed in Table 7.4.