Forecasting the legacy of offshore oil and gas platforms on fish community structure and productivity

Abstract

There are currently thousands of offshore platforms in place for oil and gas extraction worldwide, and decommissioning efforts over the next three decades are estimated to cost more than US$200 billion. As platforms reach the end of their useful lifetime, operators and regulatory agencies will assess the environmental impact of potential decommissioning strategies. Among the many factors that will be weighed in preparation for these major economic and engineering challenges is the fate of the fish and invertebrate communities that inhabit the structures underwater. Offshore platforms act as inadvertent artificial reefs, and some are recognized among the most productive fish habitats in the global oceans. We present a model for forecasting changes to fish communities surrounding offshore installations following a series of decommissioning alternatives. Using 24 platforms off southern California, we estimate fish biomass and somatic production under three possible decommissioning scenarios: leave in place, partial removal at 26-m depth, and complete removal of the platform and underlying shell mound. We used fish density and size data from scuba and submersible surveys of the platforms from 1995-2013 to estimate biomass and annual somatic production. Bottom trawl surveys were used to characterize future fish assemblages at platform sites under the complete-removal decommissioning scenario. Based on a conservatively modeled extrapolation of the survey data, we found that complete removal of a platform resulted in 95% or more reduction in the average fish biomass and annual somatic production at the site, while partial removal resulted in far smaller losses, averaging 10% or less. In the event that all surveyed platforms are completely removed, we estimated a total loss of more than 28,000 kg of fish biomass in the Southern California Bight. Platform habitats, which attract reef-dwelling fish species, had minimal overlap in community composition with the surrounding soft-bottom habitat. To best serve the wide range of stakeholder interests, the site-specific biomass, productivity and species composition information provided in this study should be incorporated into strategic decommissioning planning. This approach could be used as a model for informing "rigs to reefs" discussions occurring worldwide.

A Scientific Synthesis of Marine Protected Areas in the United States: Status and Recommendations

“…Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico is in an area with high oil and gas activity, including within its borders, with associated threats to biodiversity conservation (US Department of Commerce, National Oceanic and Atmospheric Administration, and Office of National Marine Sanctuaries, 2012). Decommissioning oil and gas platforms should be done strategically to minimize ecosystem impacts-"rigs-to-reefs" programs, for example in the Gulf of Mexico and California, can convert some portions of platforms into artificial reefs provided there is careful attention to weighing benefits (e.g., habitat preservation, fish biomass) vs. potential costs (e.g., pollutant leakage from capped wells) (Meyer-Gutbrod et al, 2020).…”

Ecotoxicological effects of decommissioning offshore petroleum infrastructure: A systematic review

“…Half of the US coastal states' guidelines and criteria are based on guidance from the National Artificial Reef Plan (amended in 2007), yet there is no federal coordination or oversight regulating the Rigs-to-Reef (RtR) program in US waters (Paxton et al, 2020). However, in 2010 California passed a bill to mandate the conditional partial removal of offshore platforms; California Marine Resources Legacy Act, with the inactivation of the RtR legalization (Meyer-Gutbrod et al, 2020). The application of the RtR program in Australia is mentioned, yet it is still not an option due to the absence of reliable research and evaluation.…”

Decommissioning Research Needs for Offshore Oil and Gas Infrastructure in Australia

“…Partial removal would likely result in the loss of fish biomass and production for species typically occupying the shallow portions of the platform structure. In California, it has been estimated that complete removal of a platform would result in 95% or more reduction in the average fish biomass and production, while losses due to partial removal would average 10% or less (Meyer-Gutbrod et al, 2020). We are unaware of similar studies having been conducted in Australia.…”