Influence of crude oil on changes of bacterial communities in Arctic sea-ice

Abstract

The danger of a petroleum hydrocarbon spillage in the polar, ice-covered regions is increasing due to oil exploration in Arctic offshore areas and a growing interest in using the Northern Sea Route (NSR) as an alternative transportation route for Arctic oil and gas. However, little is known about the potential impact of accidental oil spills on this environment. We investigated the impact of crude oil on microbial community composition in six different Arctic sea-ice samples incubated with crude oil at 1 degrees C in microcosms for one year. Alterations in the composition of bacterial communities were analyzed with the culture-independent molecular methods DGGE (denaturing gradient gel electrophoresis) and FISH (fluorescence in situ hybridization). DGGE, FISH and cultivation methods revealed a strong shift in community composition toward the gamma-proteobacteria in sea-ice and melt pool samples incubated with crude oil. Marinobacter spp., Shewanella spp. and Pseudomonas spp. were the predominant phylotypes in the oil-treated microcosms. The ability of indigenous sea-ice bacteria to degrade hydrocarbons at low temperature (1 degrees C) was tested using four representative strains cultivated from sea-ice enriched with crude oil. [14C]Hexadecane was degraded by the sea-ice isolates at 20-50% capacity of the mesophilic type strain Marinobacter hydrocarbonoclasticus, a known hydrocarbon degrader, incubated at 22 degrees C.

Obligate oil-degrading marine bacteria

“…In contrast to the cosmopolitan OHCBs discussed above, distribution of the psychrophilic OHCB Oleispira antarctica (55 sequences until now) is thus far limited to the colder waters found at high latitudes [38,39]: the least cold sites at which O. antarctica has been found are Cape Cod (MA, USA, GenBank Acc.Nr.AM117931) 42°04′26″N, 70°12′19″W and South Tasmania [40].…”

“…in such a study, in addition to a number of species of gamma-Proteobacteria (e.g., Psychromonas spp.) and Bacteroidetes, and Gerdes et al [39] emphasized the importance Pseudomonas spp., Shewanella spp. and Marinobacter spp.…”

Hydrocarbon biodegradation by Arctic sea-ice and sub-ice microbial communities during microcosm experiments, Northwest Passage (Nunavut, Canada)

“…5B). Alkanes are major components of crude oil, and are typically utilized as carbon and energy sources by bacteria (Rojo 20 2009), including Arctic populations growing at 4°C (Deppe et al 2005) down to 1°C (Gerdes et al 2005), and as low as -1°C (McFarlin et al 2014). Interestingly, the methylated forms of PAHs were degraded almost as much as the alkanes by the sub-ice seawater bacteria (Fig.…”

“…7). Gammaproteobacteria 23 were confirmed to be the main players of oil biodegradation in cold marine environments (Yakimov et al 2004;Gerdes et al 2005;Brakstad & Bonaunet 2006;Brakstad et al 2008). Bacterial diversity also changed in the presence of hydrocarbons (Figs.…”

“…Sea ice is another distinctive Arctic ecosystem, characterized by very cold temperature and high brine content, and yet it harbors abundant and diverse microbial assemblages thriving in several distinct microhabitats (Bowman et al 2012). Some studies have addressed the hydrocarbon degradation potential of ice-associated microbes (Atlas et al 1978;Gerdes et al 2005;Deppe et al 2005;Brakstad et al 2008), but overall this area of research is rather unexplored, especially regarding first-year sea ice. The identification of key oil-degrading microorganisms that live in and below the sea ice is essential for the development of bioremediation strategies suitable for the ice-covered Arctic Ocean.…”