Abstract
Offshore marine renewable energy installations (MREI) introduce structure into the marine environment and can locally exclude destructive, bottom trawl fishing. These effects have the potential to aid restoration of degraded seabed habitats but may be constrained by timescales of ecological succession following MREI construction, and the removal of infrastructure during decommissioning. To inform managers about appropriate decommissioning strategies, a 25 km cable and associated rock armouring (Wave Hub, UK), installed on rocky reef, was monitored up to 5 years post-deployment. The epibenthic Assemblage composition, and Number of taxa remained significantly different from surrounding controls, while Abundance was similar in all survey years between the cable and controls. Six morphotaxa showed four patterns of colonization on cable plots compared to the controls: (i) Early colonization, which remained in greater abundances (Porifera), (ii) early colonization, converging (Turf), (iii) slow colonization, converging Anthozoa and Vertebrata), and (iv) slow colonization, remaining lower in abundance (Tunicata and Echinodermata). The environmental relevance of this MREI is considered relatively benign as it covers 0.01% of the surrounding bioregion, appears to be supporting similar assemblages to the surrounding habitat, and exhibited minimal evidence of invasive species (three records of two non-native species). Longer monitoring timescales are required to provide comprehensive, site-specific decommissioning advice.