Cumulative and in-combination effects of offshore infrastructure on ecological resources

Project Description:

The urgent need for renewable energy development requires significant investment in offshore wind energy. The R4 offshore windfarm leasing round has been confirmed by the Crown State, securing more areas and subsequently the need for targeted ecological assessments. The proposed scale of offshore development poses a significant threat to the marine environment in the form of physical disturbance. This alters the structure and function of seabed (benthic) communities which, in turn, influences wider ecosystem processes (Birchenough & Degraer, 2020). This is of major concern since biodiversity in coastal and shelf seas is high and the benthic communities in these regions contribute disproportionately to ecosystem function through their high productivity, role in nutrient cycling and carbon sequestration their influence on sedimentary processes.

The long-term impacts of offshore wind energy development on benthic habitats and communities are poorly understood, as highlighted by Dannheim et al. (2020). They highlighted the need for hypothesis-driven experimental and survey work to improve our understanding of cumulative and potentially cascading effects. The scale and speed of offshore development necessitates a better understanding of these impacts in order to inform the offshore wind energy sector, the regulatory bodies and the scientific community.

The novelty of this study lies in the spatial (North Sea-wide) and temporal scale of tracking change in benthic resources (species presence, formation of a new habitat type and repercussions for ecological structure and function) as offshore wind energy development has progressed. We aim to better understand the long-term and cumulative impacts of offshore infrastructure via:

• Large-scale spatial and temporal analysis of existing video, sedimentological and ecological  data to establish how habitats and benthic communities have been modified over time, in relation to offshore wind energy development
• Ground-truthing surveys to support gap filling exercises around infrastructure.
• Establish recommendations and guidelines to inform the offshore wind energy sector and the Regulatory bodies on optimal survey, data collection and analysis techniques to reliably inform cumulative impact assessment as part of the Environmental Impact Assessment (EIA) process.

Methodology
Video and acoustic data obtained by Cefas from the Oil and Gas Industry (e.g. INSITE phase II), the offshore wind industry and their consultants (Crown Estate archives) collected under a BACI design – Before-After-Control-Impact) will be collated and assessed for spatial distribution, temporal distribution, size of the data set (spatial extent, transect length, number of transects), habitats covered and infrastructure type. A targeted data set will be compiled to ensure good replication, spatially and temporally in a variety of substratum and infrastructure types. The data set covers offshore wind and oil and gas infrastructure, providing an opportunity to study the in-combination impacts of offshore activities (including decommissioning). We will make use of existing benthic data available via Benthos UK, Marine Data Exchange (Crown Estate) and Big Data (Cefas).
These data will be supplemented by benthic grab sampling and (where possible) Sediment Profile Imaging (an optical technique to visualise biological activity within the sediment). Key indicators of community structure (species, abundance, diversity and biomass (from direct sample collection) will be derived. Species will be assigned to functional traits to assess spatial and temporal modification of ecological functioning of marine benthic communities during and post installation of offshore infrastructure. Spatial analysis will be via GIS; multivariate and univariate