Biodegradation of dispersed oil in natural seawaters from Western Greenland and a Norwegian fjord

Abstract

With increasing oil exploration, production and transportation in the Arctic, predictions of the fate of spilled oil become important, including oil compound biodegradation. The use of chemical dispersants may result in increased biodegradation due to the generation of dispersions consisting of small oil droplets, but only few studies have focused on biodegradation of chemically dispersed oil in Arctic seawater. In this study we compared oil biotransformation in Arctic and temperate seawaters collected from Western Greenland (Disko Bay, surface and from 80 m depth) and a Norwegian fjord (Trondheimsfjord, surface). A naphthenic oil, premixed with a dispersant, was dispersed in the seawaters from the different sources, and the dispersions incubated in low concentrations in a carousel system at 4-5 °C for up to 64 days. Targeted oil compounds (n-alkanes, BTEX, naphthalenes and PAHs) were biotransformed in both Arctic and temperate seawaters, although the degradation was faster in the temperate seawater. In the Arctic seawater, transformation was faster in the surface than in the subsurface seawater. Calculations of biotransformation rates and half-lives of oil compound groups representing 70-80% of fresh oils also showed significantly faster depletion in the temperate than the Arctic seawater. Microbial analyses revealed differences between the bacterial communities in the seawater sources during oil biodegradation. The results emphasized, that oil compounds are biodegraded in Arctic seawater, but degradation potential and rates may vary between seawaters from different sources.

In situ biodegradation, photooxidation and dissolution of petroleum compounds in Arctic seawater and sea ice

“…2), we estimated first-order half-life times of 5.5e11.3 (on average 7.2) days. The substantial in situ n-alkane degradation observed in this study confirms results from previous microcosm-based studies of n-alkane degradation in seawaters from Greenland and Norway (Brakstad et al, 2018(Brakstad et al, , 2015Brakstad and Bonaunet, 2006;Kristensen et al, 2015;Scheibye et al, 2017). Similar n-alkane biodegradation rates, with half-life times in the order of 1e10 days, were measured in the permanently (4e5 C) cold deep sea but also in warmer (24 C) surface waters of the Gulf of Mexico (Hazen et al, 2010;Liu et al, 2017).…”

“…However, in natural sea ice contaminated with oil on Svalbard, biodegradation was only detectable for n-alkanes in the bottom section of the sea ice (Brakstad et al, 2008). Microcosm studies by Kristensen et al (2015), Scheibye et al (2017) and Brakstad et al (2018) with seawater from Disko Bay, W Greenland at 2e5 C demonstrated fast biodegradation for n-alkanes, alkyltoluenes and the most labile naphthalenes, but contradicting results were obtained for 2 to 4ring PACs. There continues thus to be considerable uncertainty about the potential of natural Arctic microbial communities exposed to low temperature or sea ice to degrade oil compounds, in particular PACs which are among the most toxic oil compounds (Incardona et al, 2013).…”

“…2). The other genera Dokdonia, Polaribacter, Pseudofulvibacter and Ulvibacter of cluster 10 have also been associated to oil pollution, but their function remain unclear (Alonso-Guti errez et al, 2008;Brakstad et al, 2018;Gerdes et al, 2005;Krolicka et al, 2017;Prabagaran et al, 2007). Clusters 5e7, 9 and 11 consisted of members of the genera Flavobacterium, Neptunomonas and Pseudomonas, which are known for their capabilities to degrade various 2 to 4-ring PACs (Hedlund et al, 1999;Trzesicka-Mlynarz and Ward, 1995;Wang et al, 2008), Sphingorhabdus, possessing aliphatic and aromatic hydrocarbon-catalysing genes (Jeong et al, 2016), and Hoeflea, able to grow on diesel (Rahul et al, 2015).…”

“…Considering that the fraction of biodegradation taking place at the oil-water interface increases for more oleophilic PACs (Brakstad and Bonaunet, 2006), an overall low PAC biodegradation potential can be concluded for the investigated seawaters. However, further research is required to better understand the parameters controlling PAC biodegradation in the Arctic, as a study by Brakstad et al (2018) with seawater from Disko Bay, SW Greenland, and several other studies from the Norwegian and Canadian Arctic (Garneau et al, 2016;McFarlin et al, 2014;Ribicic et al, 2018) have shown a potential for biodegradation of 2 to 4-ring PACs.…”

Putative degraders of low‐density polyethylene‐derived compounds are ubiquitous members of plastic‐associated bacterial communities in the marine environment

“…(OTU 95) and Roseobacter sp. (OTU 159), also enriched in the long‐term incubations with LDPE as the only carbon source, have also been associated with hydrocarbon degradation (Bacosa et al ., 2018; Brakstad et al ., 2018). Even though they were present in lower relative abundance than OTU 15, they were still present on plastics collected at all the different oceanic regions (Fig.…”