Action: Repurpose obsolete offshore structures to act as artificial reefs
Key messagesRead our guidance on Key messages before continuing
- One study examined the effects of repurposing obsolete offshore structures on subtidal benthic invertebrates. The study was of a sunken oil rig in the Mediterranean Sea (Italy).
COMMUNITY RESPONSE (1 STUDY)
- Overall species richness/diversity (1 study): One study in the Mediterranean Sea recorded at least 53 invertebrate species having colonised a sunken oil rig after 30 years. Species included 14 species of molluscs, 14 species of worms, and 11 species of crustaceans.
POPULATION RESPONSE (0 STUDIES)
Offshore structures (such as oil rigs and windfarm turbine bases), have been shown to support diverse invertebrate assemblages, and act as artificial reefs (Coates et al. 2014; Krone et al. 2017; Langhamer & Wilhelmsson 2009). For instance, wind turbine foundations in a windfarm in the German Bight, North Sea, were found to host over 5,000 edible crabs Cancer pagurus per foundation (Krone et al. 2017).
Following decommissioning, entire or parts of obsolete offshore structures can potentially be repurposed to act as artificial reefs instead of being removed from the marine environment (Frumkes 2002). By repurposing obsolete offshore structures within the marine environment and leaving them in place or placing them in strategic locations, they can potentially provide additional hard surface for subtidal benthic invertebrates to colonise and seek shelter, and thereby enhance local invertebrate biodiversity (Frumkes 2002; Ponti et al. 2002). This can also benefit subtidal benthic invertebrates by avoiding or reducing the disturbance associated with the removal of these structures from the marine environment.
Evidence for interventions relating to the decommissioning of offshore structures is summarised under “Threat: Energy production and mining – Leave pipelines and infrastructure in place following decommissioning” and “Threat: Transportation and service corridors – Leave utility and service lines in place after decommissioning”. Evidence related to artificial reefs is summarised under “Habitat restoration and creation – Habitat enhancement” and “Habitat restoration and creation – Artificial habitat creation”.
Coates D.A., Deschutter Y., Vincx M. & Vanaverbeke J. (2014) Enrichment and shifts in macrobenthic assemblages in an offshore wind farm area in the Belgian part of the North Sea. Marine Environmental Research, 95, 1–12.
Frumkes D.R. (2002) The status of the California Rigs-to-Reefs Programme and the need to limit consumptive fishing activities. ICES Journal of Marine Science, 59, 272–276.
Krone R., Dederer G., Kanstinger P., Krämer P., Schneider C. & Schmalenbach I. (2017) Mobile demersal megafauna at common offshore wind turbine foundations in the German Bight (North Sea) two years after deployment-increased production rate of Cancer pagurus. Marine Environmental Research, 123, 53–61.
Langhamer O. & Wilhelmsson D. (2009) Colonisation of fish and crabs of wave energy foundations and the effects of manufactured holes–a field experiment. Marine Environmental Research, 68, 151–157.
Ponti M., Abbiati M. & Ceccherelli V.U. (2002) Drilling platforms as artificial reefs: distribution of macrobenthic assemblages of the ‘‘Paguro’’ wreck (northern Adriatic Sea). ICES Journal of Marine Science, 59, 316–323.
Supporting evidence from individual studies
A study in 1994 in the northern Mediterranean Sea, Italy (Ponti et al. 2002) found that a drilling platform that had been left in place to act as an artificial reef after sinking was colonised by at least 53 invertebrate species. Species included 14 species of molluscs, 14 species of worms, and 11 species of crustaceans. Most recorded species were associated with the hard habitat created by mussels and oysters. The drilling platform sank in 1965 due to a fire. The area surrounding it was then declared a marine protected area prohibiting all fishing. Samples were collected in summer 1994 between 10 and 34 m depths using two methods. Divers manually scraped off three 20 x 20 cm areas from each of four sites (two orientations within two water depths). Invertebrates (>0.5 mm) were identified and counted. Divers also took photographs along five vertical transects. Percentage cover of organisms were estimated from the photographs.