Appraisal of Network Connectivity between North Sea subsea oil and gas platforms – ANChor

Installations of oil and gas platforms across the North Sea have introduced substantial amounts of hard substrate to the seafloor. These structures promote dense growth of hard-bottom marine organisms: algae, mussels, tube-building worms, hydroids, anemones and reef-building corals all colonise these platforms from the top of the platform jacket down to the footings resting at the depths of the seafloor. Platforms have been thought to function as “artificial reefs” in the North Sea for decades. However, the magnitude of effects these man-made structures have had in creating a larger inter-connected hard substrate reef system is not known, but current tests of this concept suggest connectivity varies across North Sea regions.

As the North Sea enters the decommissioning era, we also do not understand how platform removal will affect the overall structure and functioning of North Sea ecosystems. The ANChor project, “Appraisal of Network Connectivity between North Sea subsea oil and gas platforms”, adopts an innovative approach to appraise connectivity of today’s mature North Sea platform network and its sensitivity to re-configuration. For INSITE’s Foundation Phase, we will use industry marine growth surveys and cutting-edge computer simulations of high-resolution coastal ocean conditions and dynamics to estimate dispersal potential of common rig species between “donor” and all potential “recipient” platforms. Species’ depth on the platform and propagule properties (mode, timing of release, and duration) will be key input for these simulations.

Using a graph theoretic approach allows visualising and mapping the North Sea network, with the “graph” formed by platform “nodes” connected to each other by “edges” that vary in strength according to the number of connections each platform potentially makes either as a donor or recipient of propagules. Effects of decommissioning on network connectivity will be simulated by removing the strongest donor platform nodes to assess changes in overall network connectivity and thus determine how strongly the integrity of North Sea ecosystem connectivity depends on these man-made structures.