An Overview of Potential Ecological Consequences of Habitat Modification from Offshore Energy Structures

In the future, offshore environments may host an increasing amount of energy infrastructure, including offshore wind and wave farms, ocean thermal conversion installations, and liquid natural gas terminals. Using studies compiled from offshore oil and gas facilities and other emplaced infrastructure around the world, we review the potential ecological consequences of prospective rigs-to-reefs programs. Offshore energy installations establish fixed, hard substrate in surface waters, where current flow is generally greater when compared to nearshore environments. Depending upon the biogeography, this can create productive habitat for filter-feeding sessile invertebrates and results in a thick biotic layer on the infrastructure. In some instances, non-indigenous species may prevail as the primary space-holders on the novel surface habitat. Through cleaning, storm activities, or simple sloughing, large amounts of organic material fall to the seabed, transforming soft sediments into extensive “shell mound” habitat. These novel surface and benthic habitats have been observed to act as nurseries for many fish species found offshore. If unconsolidated, soft sediments dominate the regional seafloor character, offshore energy installations may enhance the ecological connectivity of once isolated hard substrate habitats, and subsequently modify regional population dynamics of some marine species. Finally, we outline how the management of human activities such as fishing and shipping plays an important role in determining the magnitude and direction of potential ecological consequences, and suggest that coastal and marine spatial planning efforts will play an important role in the offshore environment.