A review of benthic ecological surveying for marine renewable developments in Scottish waters
This study reviews different intertidal and seabed ecology survey methods, used to identify baselines for environmental assessments.
5 Benthic tools and technologies – comparative review of performance
5.1 Method used for assessing appropriate tools and technologies
A tabular evaluation framework for analysing and comparing seabed surveying tools and technologies has been produced (See Appendix 1: Evaluation Matrix, for details including instruction for use in the first tab). This matrix provides users with a comprehensive option evaluation toolkit for identifying the technical solution best suited for surveying benthic ecology features in the context of MREDs within Scottish waters.
The Evaluation Matrix is the product of a comprehensive review conducted on the various tools and technologies available. It comprises of an extensive list of traditional, novel, and newly emerging tools and technologies displayed in a format that easily identifies the most effective tools and methods for a wide range of survey purposes as well as in relation to a range of performance criteria.
The tools and technologies displayed within the matrix were selected based on a broad review of the current available guidance, research, and grey literature as well as expert knowledge and experience. The list was refined following further discussions with stakeholders on their applicability and likelihood/frequency of current use within the MRED sectors.
Within the Evaluation Matrix, the various options have been organised under three broad classifications: biological, physical and chemical; and main themes (Main Role): geophysical/geotechnical; visual imagery; specimen sampling; and sediment, rock, water, specimen sampling. Some of the approaches investigated perform multiple roles and functions, and therefore were assessed under more than one of the main categories in the matrix.
Within each row of the evaluation tab there are three sets of information presented:
- The first set provide factual information/specifications under generic categories about the approach which it is not relevant to scoring.
- The second is a set of performance metrics that are linked to the sampling process only. These tend to be associated with at sea and shoreline activities.
- The third set of parameters are again performance metrics, but they could apply to both sampling and sample analysis. These tend to be factors linked to land and lab-based activities.
Although the Evaluation Matrix is comprehensive, it is intended as an aid to decision making and option evaluation rather than it being a definitive standard to be followed. It is intended that the information within each output provides the user with the flexibility to select the tools and technologies they deem best suited to a particular development whilst also offering a comparison and alternatives.
Further details on the context for and the individual criteria in each of these sets are provided the following sub-sections as well as in the evaluation matrix itself in Appendix 1.
5.1.1 Generic Categories - Basic characterising features of candidate sampling tools and techniques
This first set of factors provide a simple description of a particular tool or technique without providing a judgement as to suitability. In a few cases some specific sub-definitions have been provided to help with consistency in classification.
Other characterising information and some of the background statement materials from the latter two sets of performance metric criteria in the master evaluation matrix can also be considered as background descriptors to be considered. The basic descriptors are set out in Table 5.1.
5.1.2 Performance metrics linked to sample acquisition.
These initial performance metrics focus upon the challenges and opportunities associated with gathering of samples whilst at sea or on the coast. Each tool/technology has been assessed for their suitability against the list of performance metrics presented in Table 5.2. There are three levels of classification for each criterion. These levels are backed up by clarifying definitions that allow users to understand and ascribe levels of suitability to any seabed or intertidal surveying activity consistently and reliably. In addition to the details provided in Table 5.2, further expressions of the reasons for a given classification are embedded as hidden but available cells in the Evaluation Matrix (Appendix 1), in the final Evaluation of Performance tab.
Where multiple suitability factors for characterising a tool are considered applicable in a given category, the lowest scoring suitability statement should be used as a reference. In this way the assessment presents a worst-case scenario where uncertainty, or lack of information, is relevant.
Category |
Definition |
|---|---|
Classification |
The type of feature being investigated – geotechnical, geophysical, biological, chemical or physical. |
Main Role |
The key role of the activity in terms of gathering existing or new data or collecting physical samples of species or materials. |
Function |
The data related purpose that the technology, tool or technique is applied for. |
Technology/Tool/Technique |
A high-level description of the equipment being used (e.g., grab sampler). |
Equipment |
The specific type of tool or technology (e.g., drop camera). |
Sub-category |
If required to provide further detail (e.g., freshwater lens). |
Depth Zone |
Refers to the water depth zone that the tool or technology can be applied within. This could be: Subtidal: >5 m water depth at Lowest Astronomical Tide (LAT) (chart datum). Shallow subtidal: 0.5 – 5 m water depth at Mean Low Water Springs (MLWS) (larger vessels may have restricted access and movement). Intertidal: shore area down to <0.5 m below LAT (including rockpools). |
Guidelines and approaches |
References are provided to any literature that outlines the published guidelines for using the tool/technology or other supporting information. |
Project development stage |
The stages of the development in which the tool/technology can be used. Benthic characterisation: This encompasses all pre-placement and pre-operational stages where baseline line data is required. (Pre)operational: surveys designed to establish a baseline for any future monitoring activities. Operational This encompasses the operational lifespan of the MRED (25-30 years). Decommissioning This encompasses the pre-decommissioning pre-removal and post-removal and any subsequent legacy monitoring. |
Tethered/Untethered |
Tethered: The tool or technology is attached in some way either to the vessel or the seabed. Untethered: The tool or technology is controlled remotely or is autonomous. |
Performance metrics |
Definitions |
|---|---|
Ease of Deployment |
This refers to the ease with which a tool or technology can be deployed from a vessel or on the shore. It includes practical considerations such as the nature of the lifting or winching needs if any, the size and weight of a given tool or technology and also the complexity and vulnerability in terms of the number and types of connections needed (lifting, communications, power etc). The definitions are: High (easy to deploy): hand-held, small scale (10s kg), minimum take-off and landing restrictions, Medium (some difficulties to deploy): mechanically aided, moderate scale (10s-100 kg), Low (hard to deploy): dedicated lifting technique, with multiple tethers, larger scale (100-1000 kg), restricted take-off and landing requirements |
Capacity for simultaneous operations on vessel |
This refers to the ability of the technique to be applied alongside or to dovetail into other work tasks. This may link to the degree of co-location and co-timing with engineering, design, inspection, maintenance and repair work/surveys. It also links to the way in which any deployment vessel or platform can carry out other tasks during surveying activity. For example, underwater noise monitoring will most likely require effective operational silence from other activities. High, multiple operations possible: good capacity for simultaneous activities Moderate, dual operations possible: moderate capacity for simultaneous activities Low, sole use only: no or limited capacity for simultaneous activities |
Skills and training |
This refers to the skills and competence levels required from personnel to successfully and safely deploy the tool, technology or technique. This may include instrumentation and system set-up skills, deployment and recovery skills, as well as sample acquisition and QC skills. High: low level skills needed. Moderate: some training and core competency needed. Low: specialist training and good experience needed. |
Survey Cost (Time/ Monetary) |
The relative costs associated with the survey including the capital in order to purchase or hire the equipment, and to mobilise or use it, the survey personnel and whether they need to be skilled/trained or novice/trainable, and the time associated with the data collection. Cost effective: Fast, easy to mobilise and collect data. Minimum skilled work. Requires a small survey vessel with a davit/small winch (£1000’s). Moderate cost: Takes a significant amount of time and effort to mobilise and collect data. Crew require additional skills or qualifications. Requires a work boat with crane/winch (£10,000’s). High cost: Expensive/time consuming to mobilise and collect data, highly skilled or specialist personnel required, requires a large vessel with Dynamic Positioning and A-frame (£100,000’s). |
Physical Operating Constraints Upon Deployment |
This refers to the number of sensitivities that the approach has with regards to local operating conditions such as weather, sea state, and communities present (e.g., kelp) regards possible propeller fouling or equipment entanglement. High suitability: No occasional operating constraints Moderate suitability: Some regular operating constraints Low suitability: Many consistent operating constraints or constraints unknown |
Spatial/ Temporal Restrictions |
This refers to methods of sampling that may be sensitive to the specific location sampled or to the timing of samples. For example, if a sample is too spatially restricted and the feature being sampled is very variable at that scale, many samples would be needed to gather a representative sample (e.g., sampling Arctica islandica molluscs with a small grab sampler). Likewise a factor that has strong seasonal trends may need to be sampled at the same time of year to be representative (e.g., large populations of juveniles that do not survive to adulthood), similarly a feature which is known to vary strongly year by year (e.g., species prone to population explosions) may need a longer time series of samples to get a true picture of what is happening than for something more stable. Low risk of spatial/temporal restrictions: sampling strategy/method deals well with scale, and timeliness (large scale and easy/cheap to mobilise/replicate). Moderate risk of spatial/temporal restrictions: sampling scale moderately appropriate, and timeliness moderately achievable. High risk of spatial/temporal restrictions: sampling strategy may be too restricted in terms of scale and timeliness (too small and difficult/costly to mobilise/replicate). |
Potential impact to other marine users |
The level of consideration required regarding the potential impact of other marine users includes stakeholder engagement, environmental valuation, cost-benefit analysis, licensing, notice to mariners, and further research requirements to identify socio-economic impacts of using a particular tool/technology. The score for this metric is a combination of the considerations required on the factors above and the risk to other marine users. The risk to co-located marine activities (buffer zones/exclusion zones): Low potential impact: The use/misuse of tool/technology is not likely to negatively impact other marine users, or it may impact users but over a short time frame with no lasting impact. Medium potential impact: The use/misuse of tool/technology is more likely to negatively impact other marine users in the short but not the long-term. High potential impact: The use/misuse of tool/ technology will likely negatively impact other marine users in the longer term. |
Environmental Sensitivity Considerations |
The capacity of a tool/technology to be used on habitats and biotopes found throughout Scottish waters, including those of conservation importance and those sensitive to disturbance. This includes the risk of a net negative impact and disturbance arising from the use of a tool/technology (e.g., pollution (light/noise), release of materials, excavation). Includes whether more environmentally friendly alternatives are available. Risk of a net-negative impact from use of the tool/technology: Low: Impact to the environment is low or short-lived and covers a small area over a short period of time, habitat type goes back to normal function fast (weeks to months). Medium: Impact to the environment is low to moderate over a short to moderate time frame across a larger area and longer period of time, habitat type may take longer to recover (months to years). High: Impact to environment is moderate to high over a large area over a long or prolonged period of time, habitat type takes a long time to recover (years to decades). |
5.1.3 Performance metrics linked to sample gathering and analysis.
Having considered the factors only associated with the various approaches to sample gathering, a second set of performance factors includes those linked to sample analysis as well as sample gathering and is presented below (Table 5.3). A similar definition and classification system as used previously has been applied.
Performance Metric |
Definitions |
|---|---|
Strengths of the Method |
Strengths are described as traits of the sampling tool or technique that make it widely applicable in terms of habitats and species that can be sampled, without losing definition or detail, where it is reliability and robustness in sample acquisition. Such traits which are applicable to each tool/technique option are listed in the body of the evaluation matrix. High suitability: Many inherent strengths. Moderate suitability: Some inherent strengths. Low suitability: No, or very few inherent strengths. |
Limitations of the Method |
Limitations are described as traits of the sampling tool or technique that make it only narrowly applicable in terms of habitats and species that can be sampled. There being inherent issues over accuracy, detail, reliability and/or robustness. Such traits which are applicable to each tool/technique option are listed in the body of the evaluation matrix. High suitability: No inherent limitations. Moderate suitability: Some inherent limitations. Low suitability: Many inherent limitations. |
Secondary Use |
A tool or technology may be suitable for collecting additional samples/data that are not its original intended purpose. For example, it may serve as a platform for additional sensor deployment, or the primary data may be analysed for additional purposes other than its original intent. High suitability: Many secondary applications and uses. Moderate suitability: Some secondary applications and uses. Low suitability: No secondary applications and uses. |
Frequency of current use in MREDs |
The number of times that the approach is used across the sector as a proportion of the total opportunities. High suitability: Widely used throughout the sector on the majority of developments within the majority of marine areas globally. Moderate suitability: Moderately used throughout the sector on some developments mostly UK but also used outside UK waters. Low suitability: Limited use throughout the sector – single or sporadic use within the sector at a local/national scale. |
Operational Experience |
The timespan over which the approach has been utilised High - widely adopted; Used extensively throughout industry for a minimum of 5 years. Moderate - some industry use; 3–5 years of industry use. Low - little industry use (novel); 0–3 years, R&D stage with little experience in an industry setting. |
Spatial Scale of Application |
This considered the degree of geographical territory over which a particular approach has been used. This helps to define the applicability across different conditions and the potential for national and international standardisation. High: Global; A tool/technology or technique that is widely used by multiple users in MRE developments worldwide. Medium: Regional; A tool/technology or technique that does not have global application but has been used extensively by a specific user in a global or multi-regional context. Low: Local; A bespoke tool/technology or technique used on an MRE development by a specific user within a specific area. |
QC (Availability of Robust and Reliable Procedures) |
The availability and level of methodological standardisation upon which a robust and repeatable approach can be based. High: Available and strong standards; suitable published guidance is available, current, and widely applied across the MRE sector or is an applicable and widely used and accepted method with strict samplings standards and procedures in place. History of inclusion in QC schemes. Moderate: Limited availability and some inconsistencies with standards; standards may not be published but are widely used and accepted, sampling standards and procedure have been produced, but the method is new and not widely used or not used across a breadth survey activities or sectors. Some inclusion in QC schemes. Low: No recognised standards; New or novel approach with little application to MRE or industry in general. Methodology is created in house and not widely shared or deviates with each application. Little to no inclusion in QC schemes. |
QC (Ability to Replicate) |
The likelihood that the method associated with the tool/technology delivers repeatable and accurate results. High: The method is well used, strong and reliable. The data obtained using the tool/technology is suitable to answer the required questions. No significant data gaps or uncertainties exist. Moderate: The data obtained using the tool/technology is mostly suitable for answering the required questions. A few knowledge gaps may be present, but the balance of understanding is strong. Low: The method has not been applied widely enough to identify its reliability spatially and/or on a temporal scale. There are still knowledge gaps which reduce confidence in results. More robust methods may be easily available in the marketplace. |
Analytical Cost (Time/Monetary) |
The relative costs associated with processing and analysing data. This includes the capital, time and skill level required. Cost effective: Fast, easy to process and analyse data. Minimum skilled work (£100s). Moderate cost: Takes a significant amount of time and effort to process and analyse data. Data analysts require additional skills or qualifications (£1,000s). High cost: Expensive/time consuming to process and analyse data, highly skilled or specialist personnel required (£10,000s). |
Added Value |
The potential for the approach to generate opportunities for added value contributions of data and associated metadata for purposes such as data bases, timeseries, models and inclusion in data repositories such as Marine Environmental Data and Information Network (MEDIN). Also, approaches that promote regional/national global data sharing. High suitability: good potential for added value data to be created. Moderate suitability: some potential for added value data to be created. Low suitability: little or no potential for added value data to be created. |
5.2 Results and discussion arising from the evaluation matrix
For each tool and technique option, a collation of the various performance metrics has been provided to show the overall number of high suitability, moderate suitability and low suitability categorisations ascribed. This spectrum of performance can be used to help identify the better and worse performing approaches given a particular purpose.
To help present an overview of these collated performance spectrums they have been presented in Appendix 1 Evaluation Matrix within the ‘Overall performance rankings’ Tab. The combined total was determined by the following calculation:
(2 x number of green) + (1 x number of amber) - (1 x number of red).
The wider Evaluation Matrix also represents a summary of current knowledge and understanding about the various techniques, technologies and tools that are available with appropriate references where available. Over time this matrix will benefit from updating due to advances in innovative technology and research, and progression of the MRE sector itself and the as accumulated experience of benthic surveying activity grows.
As technology and research advances some of the traditional tools and technologies may become less favourable, whilst some of those that are currently novel or innovative may become more favourable as their merits and benefits become more fully developed and understood. However, certain well proven approaches are likely to remain suitable for the foreseeable future and certain novel approaches may prove to be less useful.
The Evaluation Matrix can further be used to identify possible gaps and areas of weakness in present provisions as well as areas of performance uncertainty, which could be addressed through further specific studies and investigations as resources allow.
The Evaluation Matrix can also act as a selection guide to users, that forms part of the decision-making process. However, the matrix should not be considered as directly deterministic. Ultimately the final decision on what are the most appropriate tools and technologies to be used, in a particular situation, will depend on a combination of factors, including the nature and size of the site, costs and funds available, timescales needed, alongside advice from the statutory bodies which uphold legislative and leasing requirements and other consulted stakeholders.
Contact
Email: ScotMER@gov.scot
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