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Offshore platforms, subsea pipelines, wells and related fixed structures supporting the oil and gas (O&G) industry are prevalent in oceans across the globe, with many approaching the end of their operational life and requiring decommissioning. Although structures can possess high ecological diversity and productivity, information on how they interact with broader ecological processes remains unclear. Here, we review the current state of knowledge on the role of O&G infrastructure in maintaining, altering or enhancing ecological connectivity with natural marine habitats. There is a paucity of studies on the subject with only 33 papers specifically targeting connectivity and O&G structures, although other studies provide important related information.Evidence for O&G structures facilitating vertical and horizontal seascape connectivity exists for larvae and mobile adult invertebrates, fish and megafauna; including threatened and commercially important species. The degree to which these structures represent a beneficial or detrimental net impact remains unclear, is complex and ultimately needs more research to determine the extent to which natural connectivity networks are conserved, enhanced or disrupted. We discuss the potential impacts of different decommissioning approaches on seascape connectivity and identify, through expert elicitation, critical knowledge gaps that, if addressed, may further inform decision making for the life cycle of O&G infrastructure, with relevance for other industries (e.g. renewables). The most highly ranked critical knowledge gap was a need to understand how O&G structures modify and influence the movement patterns of mobile species and dispersal stages of sessile marine species. Understanding how different decommissioning options affect species survival and movement was also highly ranked, as was understanding the extent to which O&G structures contribute to extending species distributions by providing rest stops, foraging habitat, and stepping stones. These

Oil and gas platforms are common in the northern Gulf of Mexico. Platforms provide substrate for sessile organisms such as barnacles and oysters that enhance habitat for stone crabs Menippe spp. and other foulingassociated organisms. In recent years, Louisiana's small nearshore platforms (<15 m) have been subjected to a high rate of removal, but little is known about their relative value as artificial reefs. During 2014, we compared stone crab populations at platforms on and off Ship Shoal in order to evaluate habitat conditions in the two areas. We hypothesized that platforms on the shoal would provide higher quality habitat than those in the surrounding area because the shoal supports higher diversity and abundances of benthic organisms. Stone crab populations were characterized by means of visual counts and by removing subsamples for species identification, sexing, and carapace measurements. Of the 378 stone crabs collected, 368 were Gulf stone crabs M. adina and 10 were Cuban stone crabs M. nodifrons. Stone crabs colonized every platform studied, but densities were higher (mean values: 4.0 crabs/m 2 on the shoal versus 1.8 crabs/m 2 off the shoal), and carapace width at 50% maturity (CW50) was 27.1 mm larger for crabs on than off the shoal. Mean carapace width, size-class distribution, and sex ratio of crabs on and off the shoal were not significantly different. Platforms provided substrate for barnacles, which enhanced the structural complexity of platforms and were observed to be prey for stone crabs. Nevertheless, higher stone crab density and CW50 on the shoal suggested that shoal platforms are better habitat types for stone crabs. The Mississippi River watershed drains 41% of the contiguous United States (Milliman and Meade 1983; Turner and Rabalais 1991) and discharges into the northern Gulf of Mexico (nGOM) where it forms vast coastal wetlands, and

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