Abstract
Benthic microorganisms are key players in the recycling of organic matter and recalcitrant compounds such as polyaromatic hydrocarbons (PAHs) in coastal sediments. Despite their ecological importance, the response of microbial communities to chronic PAH pollution, one of the major threats to coastal ecosystems, has received very little attention. In one of the largest surveys performed so far on coastal sediments, the diversity and composition of microbial communities inhabiting both chronically contaminated and non-contaminated coastal sediments were investigated using high-throughput sequencing on the 18S and 16S rRNA genes. Prokaryotic alpha-diversity showed significant association with salinity, temperature, and organic carbon content. The effect of particle size distribution was strong on eukaryotic diversity. Similarly to alpha-diversity, beta-diversity patterns were strongly influenced by the environmental filter, while PAHs had no influence on the prokaryotic community structure and a weak impact on the eukaryotic community structure at the continental scale. However, at the regional scale, PAHs became the main driver shaping the structure of bacterial and eukaryotic communities. These patterns were not found for PICRUSt predicted prokaryotic functions, thus indicating some degree of functional redundancy. Eukaryotes presented a greater potential for their use as PAH contamination biomarkers, owing to their stronger response at both regional and continental scales.
Highlights
Coastal ecosystems ecologically support numerous human activities, which exert considerable anthropogenic pressure, potentially leading to the erosion of ecosystem health (Halpern et al, 2008; Borja et al, 2011)
A HCA performed on the polyaromatic hydrocarbons (PAHs) concentrations showed that Mediterranean, and to a lesser extent Atlantic, sites were well separated according to our a priori contamination criterion (Supplementary Figure 2)
sediment quality guidelines (SQGs) were available for 9 PAHs among the concentrations of 11 PAHs measured for the whole sample set
Summary
Coastal ecosystems ecologically support numerous human activities (e.g., fishing, aquaculture, tourism, urban development, transport and refining of oil, industrial activities, etc.), which exert considerable anthropogenic pressure, potentially leading to the erosion of ecosystem health (Halpern et al, 2008; Borja et al, 2011). Estimates of oil contamination show that oil spills are quantitatively less important than chronic pollution. They represent less than 30% of total input into the Mediterranean Sea (European Environment Agency, 2006). Coastal ecosystems receive significant and continuous inputs of pyrogenic hydrocarbons generated by combustion of fossil fuels (coal and oil) and other organic material such as wood (Page et al, 1999; Ravindra et al, 2008)
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