Abstract
Fossil fuel drilling operations create sediment plumes and release waste materials into the ocean. These operations sometimes occur close to sensitive marine ecosystems, such as cold-water corals. While there have been several studies on the effects of energy industry activities on adult corals, there is very little information on potential impacts to their early life history stages. Larval stages of many marine organisms, including cold-water corals use cilia as a means of feeding and swimming, and if these structures become clogged with suspended particulates, the larvae may sink and be lost to the system.The objective of this study was to understand the response of Lophelia pertusa larvae to a different drilling waste components, and assess post-exposure recovery. Larvae of two ages (eight and 21 days) were exposed to a range of concentrations of bentonite, barite and drill cuttings. Larval sensitivity was assessed using the concentration at which 50% of the larvae showed behavioral effects (EC50) or lethal effects (LC50). Larvae showed greatest sensitivity to bentonite, followed by barite and drill cuttings, and also showed age-related responses that differed among the test materials. Post exposure recovery was variable across materials, with larvae exposed to bentonite having the lowest recovery rates. Understanding the vulnerability of early life history stages to human activities can help inform management strategies to preserve reproductive capacity of important marine ecosystems.
Highlights
Renewable energy sources and natural gas are the fastest-growing sectors of the energy industry, but petroleum and other liquid fossil fuels still represent the largest source of energy globally, and are ex pected to remain the dominant fuel sources (>30%) until 2040 and probably beyond (US Energy Information Administration, 2017)
The calibration curves show that each material has a different concentration-turbidity relationship, with barite having the highest turbidity value for a given concentration, followed by drill cuttings and bentonite
Under experimental con ditions, the test concentration of barite declined quicker than the other two materials, which can be explained by its higher density; the bentonite concentration declined slightly more quickly than drill cuttings, which was unexpected as the drill cuttings were coarser than the bentonite and were expected to settle out of the suspension more quickly
Summary
Renewable energy sources and natural gas are the fastest-growing sectors of the energy industry, but petroleum and other liquid fossil fuels still represent the largest source of energy globally, and are ex pected to remain the dominant fuel sources (>30%) until 2040 and probably beyond (US Energy Information Administration, 2017). Development of commercial oil extraction involves several stages, which include exploration, ground-truthing geological and acoustic data, production, and possible expansion of a field (Boesch and Rabelais, 1987; Hyne, 2001; Gausland, 2003; Sanzone et al, 2016). This process requires the drilling of multiple wells, and installation of infrastructure that ranges from large platforms constructed on the seafloor, to floating production units. Water-based DM consists of water, a weighting agent (often barite), drilling fluid chemicals and various inorganic salts and organic additives (Caenn et al, 2011)
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