Effect of physical sediments reworking on hydrocarbon degradation and bacterial community structure in marine coastal sediments

Abstract

The present study aimed to examine whether the physical reworking of sediments by harrowing would be suitable for favouring the hydrocarbon degradation in coastal marine sediments. Mudflat sediments were maintained in mesocosms under conditions as closer as possible to those prevailing in natural environments with tidal cycles. Sediments were contaminated with Ural blend crude oil, and in half of them, harrowing treatment was applied in order to mimic physical reworking of surface sediments. Hydrocarbon distribution within the sediment and its removal was followed during 286 days. The harrowing treatment allowed hydrocarbon compounds to penetrate the first 6 cm of the sediments, and biodegradation indexes (such as n-C18/phytane) indicated that biodegradation started 90 days before that observed in untreated control mesocosms. However, the harrowing treatment had a severe impact on benthic organisms reducing drastically the macrofaunal abundance and diversity. In the harrowing-treated mesocosms, the bacterial abundance, determined by 16S rRNA gene Q-PCR, was slightly increased; and terminal restriction fragment length polymorphism (T-RFLP) analyses of 16S rRNA genes showed distinct and specific bacterial community structure. Co-occurrence network and canonical correspondence analyses (CCA) based on T-RFLP data indicated the main correlations between bacterial operational taxonomic units (OTUs) as well as the associations between OTUs and hydrocarbon compound contents further supported by clustered correlation (ClusCor) analysis. The analyses highlighted the OTUs constituting the network structural bases involved in hydrocarbon degradation. Negative correlations indicated the possible shifts in bacterial communities that occurred during the ecological succession.

Role of environmental factors and microorganisms in determining the fate of polycyclic aromatic hydrocarbons in the marine environment

“…The effect of such fluctuations on the dynamics of microbial communities and PAH degradation capacities has been demonstrated in several microcosm (Duran et al. 2015b; Militon et al. 2015) and bioreactor studies (Cravo-Laureau et al.…”

Fate of petroleum hydrocarbons in bioturbated pristine sediments from Caleta Valdés (Patagonia Argentina): An ex situ bioassay

“…Low energy environments, where macrobenthos activity plays an important role in the fate of sedimentary organic matter, are usually more damaged by oil spills than high energy environments and their recovery is slower. Actions to mitigate ecological impacts, such as shorelines cleaning methods, are difficult to implement in highly productive ecosystems characterized by fine sediments (Duran et al, 2015), and the natural attenuation of petroleum often constitutes the best option. The activity of macro invertebrates significantly influences microbial activities and biogeochemical processes in sediments by modifying water and sediment fluxes at the water-sediment interface (Mermillod-Blondin and Rosenberg, 2006) and mixing physically sediments introducing oxygen by burrow ventilation, which affect nutrient cycles, fate of contaminants, and microbial metabolisms (Cuny et al, 2011;Duran et al, 2015).…”

“…Actions to mitigate ecological impacts, such as shorelines cleaning methods, are difficult to implement in highly productive ecosystems characterized by fine sediments (Duran et al, 2015), and the natural attenuation of petroleum often constitutes the best option. The activity of macro invertebrates significantly influences microbial activities and biogeochemical processes in sediments by modifying water and sediment fluxes at the water-sediment interface (Mermillod-Blondin and Rosenberg, 2006) and mixing physically sediments introducing oxygen by burrow ventilation, which affect nutrient cycles, fate of contaminants, and microbial metabolisms (Cuny et al, 2011;Duran et al, 2015). These processes stimulate the oxygenation of sediments (Timmermann et al, 2011) and favour the aerobic biodegradation of hydrocarbons (Duran et al, 2015).…”

“…The activity of macro invertebrates significantly influences microbial activities and biogeochemical processes in sediments by modifying water and sediment fluxes at the water-sediment interface (Mermillod-Blondin and Rosenberg, 2006) and mixing physically sediments introducing oxygen by burrow ventilation, which affect nutrient cycles, fate of contaminants, and microbial metabolisms (Cuny et al, 2011;Duran et al, 2015). These processes stimulate the oxygenation of sediments (Timmermann et al, 2011) and favour the aerobic biodegradation of hydrocarbons (Duran et al, 2015). Bioturbation plays an important role in the burial and degradation of aliphatic hydrocarbons and PAHs (Christensen et al, 2002;Duran et al, 2015;Timmermann et al, 2011), whereas bacteria are considered to be the predominant hydrocarbon-branched isoprenoids of diatom origin) (unpublished data).…”

Microbial ecology of hydrocarbon-polluted coastal sediments

“…The study also reveals the importance of Oleibacter, Alcanivorax, Cycloclasticus, and Thalassolituus related species in hydrocarbon degradation. The organization of a hydrocarbon-degrading microbial assemblage is strongly influenced by environmental conditions as illustrated in this issue by mechanical reworking of sediments (Duran et al 2015b) and oxygenation regimes , studies that demonstrated the complexity of bacterial interactions and revealed potential new hydrocarbondegrading candidates. The study focusing on sulfatereducing microorganisms (SRM) by Stauffert et al (2014a) confirms the influence of environmental parameters, particularly the bioturbation activity of burrowing macrofauna such as Hediste diversicolor.…”