Perturbation of seafloor bacterial community structure by drilling waste discharge

Abstract

Offshore drilling operations result in the generation of drill cuttings and localized smothering of the benthic habitats. This study explores bacterial community changes in the in the upper layers of the seafloor resulting from an exploratory drilling operation at 1400m water depth on the Barents Sea continental slope. Significant restructurings of the sediment microbiota were restricted to the sampling sites notably affected by the drilling waste discharge, i.e. at 30m and 50m distances from the drilling location, and to the upper 2cm of the seafloor. Three bacterial groups, the orders Clostridiales and Desulfuromonadales and the class Mollicutes, were almost exclusively confined to the upper two centimeters at 30m distance, thereby corroborating an observed increase in anaerobicity inflicted by the drilling waste deposition. The potential of these phylogenetic groups as microbial bioindicators of the spatial extent and persistence of drilling waste discharge should be further explored.

Desulfovibrio and Pseudomonas Dominated Enriched Produced Water Reinforcing their Importance in Oilfields and Production Processes

“…Sun et al 48 isolated 61 phylogenetic groups that belong to 32 genera in the phyla Actinobacteria, Firmicutes, and Proteobacteria in oil-production water from the Karamay Oil eld, Xinjiang, China. The Enterobacteriales and Alteromonadales orders that were detected in this study are in agreement with other reports in the literature that relate these orders to oil environments 49,50 . Liu and Liu 51 analyzed the bacterial community of oil collected from the sea surface of the northern Gulf of Mexico, as a result they found high proportions of Alteromonas, Marinobacter, Thalassospira, Bartonella, Rhodovulum and Stappia.…”

Global Trends of Benthic Bacterial Diversity and Community Composition Along Organic Enrichment Gradients of Salmon Farms

“…Since its first isolation in Chile in 1989, the bacterium has been reported in Norway, Scotland, Greece, Canada, and the United States, among others ( Marshall et al, 2014 ). While Desulfuromonadaceae (iron-reducing bacteria and SRBs) were more abundant in unperturbed sediments in studies of Dowle et al (2015) and Aylagas et al (2017) , the same family was indicating perturbed coastal sediment conditions ( Lanzen et al, 2020 ), pollution from oil drilling in offshore sediments ( Nguyen et al, 2018 ), and organically enriched sediments ( Julies Elsabé et al, 2012 ; Aranda et al, 2015 ). Likewise, Syntrophobacteraceae were found in undisturbed sediments as well as at sites with high organic enrichment ( Choi et al, 2018 ).…”

Measuring the biological impact of drilling waste on the deep seafloor: An experimental challenge

“…For example, in Norway, since 2001 OBM and subsequent drill cuttings are no longer permitted to be released at sea. If the concentration of hydrocarbons (HC) in sand, mud and cuttings exceed 10 g.kg -1 , they are systematically recovered and shipped to shore for land disposal (Nguyen et al, 2018). This kind of approach is mainly based on the "precautionary principle" and the "polluter pays principle" that were initiated with Helcom (Helsinki Commission) in the 1980s for the Baltic Sea (despite its low available hydrocarbon reserves) as well as with the OSPAR (Oslo-Paris) convention in the early 1990s for the North-Eastern Atlantic (Ekins et al, 2007).…”

“…Reported studies point out a seafloor bacterial community shift in cases of drilling waste deposition (Main et al, 2015;Nguyen et al, 2018). This shift is accompanied by biogeochemical perturbation affecting the S and N-cycle (King et al, 2015) and a rapid decrease of dissolved oxygen (36h, Main et al, 2015) leading to localized anaerobic spots (Nguyen et al, 2018) and a potentially strong redoxcline (Schaanning et al, 1997;Trannum et al, 2011). Microbial community restructuration is also marked by a functional shift toward an enrichment of the hydrocarbon anaerobic metabolism repertoire (King et al, 2015).…”