Henry L-A. - University of Edinburgh
Eight international energy companies (BP, Centrica, CNR International, ExxonMobil, Marathon Oil, Shell, Talisman–Sinopec and Total) are funding scientific research projects as part of the INSITE North Sea programme. One of these, the ANChor project (Appraisal of Network Connectivity between North Sea subsea oil and gas platforms), has adopted an innovative approach studying how today’s mature network of oil and gas subsea structures in the North Sea might assist regional ecological health and connectivity of dispersed biological populations. The results will allow us to understand the sensitivity of North Sea biological communities to the partial or complete decommissioning of subsea structures.
A wide variety of offshore man-made structures promote the dense growth of marine organisms such as algae, mussels, tube-building worms, hydroids, anemones and even reef-building corals. Have these man-made structures created new hard substrate reef systems? Do they play a wider role in the health of the North Sea, such as supporting more productive fisheries? How will the whole or partial removal of subsea structures during decommissioning affect the overall structure and functioning of North Sea ecosystems?
Figure 1. Original photograph courtesy of Lundin Britain Ltd. Reproduced from Roberts J.M., Wheeler A., Freiwald A., Cairns S. (2009) Cold-water corals: the biology and geology of deep- sea coral habitats. Cambridge University Press.
ANChor is a 2-year project (2016-2018) that combines surveys from 57 North Sea platforms with numerical models linking particle tracking simulations (such as the dispersal trajectories of eggs and larvae released by adults) with a high horizontal resolution (1.8 km) ocean circulation model of the Northwest European Shelf called NEMO. Inspired by graph theory, ANChor visualises platforms as “nodes” connected to each other by “edges” that vary in strength according to the number of connections each platform makes. The connections may be either as a donor or as a recipient of larvae of a wide variety of organisms, as estimated by the combined NEMO and larval biophysical model.
ANChor results show that there are strongly interconnected regional networks in the North Sea for most species which settle on subsea structures (such as the soft coral Alcyonium digitatum, the mussel Mytilus edulis, the barnacle Chirona hameri, and the anemone Metridium senile). CITES-protected reef framework-forming corals (Lophelia pertusa) which occur on platforms were highly connected in the northern North Sea, with several platforms acting as important donors to other structures and to coral reefs in Scandinavian waters.
The potential effects of decommissioning today’s network of oil and gas structures on ecological connectivity are now being simulated in the model by removing the strongest donor platforms. These simulations will be used as part of the European Horizon 2020 project ATLAS (Understanding Deep Atlantic Ecosystems) to assess whether leaving subsea structures wholly or partly in place could be a viable method for industry to contribute to biodiversity offsetting and restoration measures in the North Sea.