Benthic Prokaryotic Community Response to Polycyclic Aromatic Hydrocarbon Chronic Exposure: Importance of Emission Sources in Mediterranean Ports

Abstract

The present study aimed to evaluate the impact of polycyclic aromatic hydrocarbons (PAHs) produced by multiple emission sources on prokaryotic communities in sediments chronically affected by anthropogenic pressures. In this context, surface sediments were investigated in three Mediterranean touristic ports over three sampling periods and in different port sectors. The levels of 16 priority PAHs varied over three orders of magnitude (25-49,000 ng g −1) covering the range of concentrations previously reported for Mediterranean harbors. Pyrogenic processes were found to be the dominant emission source of PAHs, with considerable differences among ports. The prokaryotic communities were identified by using the terminal restriction fragment length polymorphism, targeting the 16S rRNA gene for Bacteria and Archaea as well as the dsrAB gene for sulphate-reducing bacteria (SRB). The structure of the three benthic prokaryotic communities varied consistently among the ports. The structure of Bacteria and Archaea exhibited strong spatiotemporal variations that did not allow us to specifically link the observed differences in community structures with PAH sources. On the contrary, our study provided, for the first time, evidence that the PAH emission sources play a role in structuring benthic communities of SRB. Our findings indicate that the SRB community can be used as a valuable candidate biotic descriptor for bioremediation monitoring in heavily impacted port sediments.

Impacts of Anthropogenic Pollutants on Benthic Prokaryotic Communities in Mediterranean Touristic Ports

“…Concentrations of 31 individual aliphatic hydrocarbons (AHs) in the range C10-C40, Unresolved Complex Mixture (UCM), and 16 US EPA priority PAHs in superficial sediments were previously evaluated by gas chromatography-mass spectrometry in Chatzinikolaou et al (2018) and Vitali et al (2019). Abbreviations for the 16-EPA priority PAHs are as follows: 2-ring PAH -naphthalene (Naph); 3-ring PAHs -acenaphthylene (Aceph), acenaphthene (Ace), fluorene (Fl), phenanthrene (Phen), anthracene (Ant); 4-ring PAHs -fluoranthene (Flu), pyrene (Pyr), benzo[a]anthracene (BaA), chrysene (Chr); 5-ring PAHs -benzo [b] [a,h]anthracene (DBA).…”

“…Abbreviations for the 16-EPA priority PAHs are as follows: 2-ring PAH -naphthalene (Naph); 3-ring PAHs -acenaphthylene (Aceph), acenaphthene (Ace), fluorene (Fl), phenanthrene (Phen), anthracene (Ant); 4-ring PAHs -fluoranthene (Flu), pyrene (Pyr), benzo[a]anthracene (BaA), chrysene (Chr); 5-ring PAHs -benzo [b] [a,h]anthracene (DBA). The following hydrocarbon pollution descriptors were used: (i) the total level of AHs, calculated as the sum of individual compounds in the range C10-C40, (ii) the sum of four low-molecular-weight PAHs (Phen, Ant, Flu, Pyr, LPAHs) and the sum of eight high-molecular-weight (BaA, Chr, BbF, BkF, BaP, Inp, BgP, DBA, HPAHs) as descriptors of PAH pollution levels; (iii) the molar ratios of selected PAHs ( LPAH/ HPAH, Ant/Ant + Phen, Flu/Flu + Pyr, BaA/BaA + Chr, Inp/Inp + BgP), as descriptors of PAH sources (Vitali et al, 2019).…”

“…Sample collection and DNA extraction were performed as previously described by Vitali et al (2019). Briefly, three samples of surface sediments (0-1 cm) were collected using small plastic corers from each station (Chatzinikolaou et al, 2018).…”

“…Long-range aeolian PAH transport of fine combustion particles appears to dominate the oceanic PAH flux (Gustafsson et al, 1997). In ports and marinas, the predominance of pyrogenic emission sources has extensively been reported with marked differences in pollutant compositions among different sites and the coexistence of petroleum and pyrogenic PAHs in multi-sectoral harbors (McCready et al, 2000;De Luca et al, 2004;Sprovieri et al, 2007;Merhaby et al, 2015;Schintu et al, 2015;Vitali et al, 2019). Lastly, metals and PAHs entering the marine environments accumulate in sediments, which act as a long-term contaminant sink (Christophoridis et al, 2009).…”

“…In the framework of the ENPI CBCMED project MAPMED, sediments were collected from three touristic ports located along the Mediterranean Sea. The pollution status of the three harbors has been recently determined by Chatzinikolaou et al (2018) and Vitali et al (2019). Moreover, their environmental properties have been defined based on the combined assessment of physical parameters, chemical variables (i.e., nutrients, pigments), and macrobenthic diversity (Chatzinikolaou et al, 2018).…”