ORJIP BenCH: Benthic habitat changes postconstruction of offshore wind (Final report)

Abstract

The project evaluated five key research questions developed by the ORJIP steering group:

  • RQ1: Are there suitable metrics to detect changes in benthic habitats for offshore wind assessments?
  • RQ2: Is there measurable change in biodiversity and/or species composition?
  • RQ3: Are there localised and regional ecological effects around infrastructure?
  • RQ4: Is there change in ecological function as a result of biological changes?
  • RQ5: Can recovery and/or enhancement be demonstrated and in what timeframe?

The project was delivered across five work packages: a literature review; collation of benthic monitoring datasets; an interim workshop with the steering group to identify which research questions should be investigated further through benthic data analysis and which analytical approaches should be prioritised; analyses using AMBI (AZTI Marine Biotic Index) and biological traits analysis; and final reporting.

The literature review found that existing metrics (e.g. diversity indices) are suitable for detecting changes (RQ1), though other approaches such as AMBI and biological traits analysis could offer additional ecological insight that compliments traditional approaches. Evidence of biodiversity and species changes (RQ2) was noted in OWF monitoring reports but attributed mainly to natural variability, contrary to scientific literature which attributed benthic habitat changes to the construction and presence of offshore wind farms. Localised effects near turbines were documented (RQ3), but regional-scale impacts remain poorly understood. Functional ecological changes (RQ4) are rarely assessed and poorly understood, and recovery timelines and enhancement (RQ5) vary by habitat, with more long-term monitoring required.

Further analysis using AMBI and biological traits analysis found no significant spatial differences between array areas and reference stations, supporting conclusions that natural variability was the primary driver of benthic habitat change at the analysed sites. Limitations of these analyses were highlighted however, it was considered that these metrics offer potential to characterise ecological responses and ecosystem functioning, complementing traditional analyses.

The project's findings informed several policy considerations, including improving environmental impact assessment processes, supporting licensing standards, informing compensation strategies, and contributing to marine net gain approaches. Key recommendations included further research; development of monitoring approaches incorporating functional ecology, longer-term studies, standardised monitoring protocols with adequate statistical power, and consideration of cumulative regional effects across multiple offshore wind farms. 

Contents

Executive Summary

Final Report

  1. Introduction
  2. Project Team
  3. Project Outcomes
  4. Contribution to the Research Questions
  5. Informing Policy Positions
  6. Recommendations
  7. References

Appendix 1: Literature review (RQ 1 – 5)

  1. Introduction
  2. Project Team
  3. Methodology
  4. RQ1: Are there suitable metrics to detect changes in benthic habitats that could be applied to offshore wind assessments?
  5. RQ2: Is there a measurable change (increase/decrease) in biodiversity and/or species composition?
  6. RQ3: Are there localised and regional ecological effects around the infrastructure?
  7. RQ4: Is there change in ecological function (e.g. functional groups) as a result of biological changes?
  8. RQ5: Can recovery and/or enhancement be demonstrated and in what timeframe?
  9. Refrences

Appendix 2: Data Mapping Summary Report

  1. Introduction
  2. Data collation methodology
  3. Summary of data collated
  4. Potential for future data analysis
  5. Project Stage Gate Decision
  6. References

Appendix 3: AMBI Analysis Report

  1. Introduction
  2. Methodology
  3. Results
  4. Conclusions
  5. References

Appendix 4: Biological Traits Analysis Report 

  1. Introduction
  2. Anonymisation of OWF sites
  3. Methodology
  4. Results
  5. Discussion
  6. Conclusions
  7. Limitations
  8. References