Benthic microbial diversity trends in response to heavy metals in an oxygen-deficient eutrophic bay of the Humboldt current system offshore the Atacama Desert

• Published in: Environmental pollution (1987) Vol. 286; p. 117281
• Main Authors: Zárate, Ana, Dorador, Cristina, Valdés, Jorge, Molina, Verónica, Icaza, Gonzalo, Pacheco, Aldo S., Castillo, Alexis
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-10-2021
• Subjects: Heavy metals; Marine sediment; Microbial network assemblages; Semi-enclosed bay; Microbial network assemblages; Semi-enclosed bay; Marine sediment; Heavy metals
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2021.117281

Mejillones Bay is a coastal ecosystem situated in an oxygen-deficient upwelling area impacted by mining activities in the coastal desert region of northern Chile, where conspicuous microbial life develops in the sediments. Herein, heavy metal (loid)s (HMs) such as Cu, Pb, As, Zn, Al, Fe, Cd, Mo, Ni and V as well as benthic microbial communities were studied using spectrometry and iTag-16 S rRNA sequencing. Samples were taken from two contrasting sedimentary localities in the Bay named Punta Rieles (PR) and Punta Chacaya (PC) within 10–50 m water-depth gradient. PR sediments were organic matter rich (21.1% of TOM at 50 m) and overlaid with low-oxygen waters (<0.06 ml O2/L bottom layer) compared with PC. In general, HMs like Al, Ni, Cd, As and Pb tended to increase in concentration with depth in PR, while the opposite pattern was observed in PC. In addition, PR presented a higher number of unique families (72) compared to PC (35). Among the top ten microbial families, Desulfobulbaceae (4.6% vs. 3.2%), Flavobacteriaceae (2.8% vs. 2.3%) and Anaerolineaceae (3.3% vs. 2.3%) dominated in PR, meanwhile Actinomarinales_Unclassified (8.1% vs. 4.2%) and Sandaracinaceae (4.4% vs. 2.0%) were more abundant in PC. Multivariate analyses confirmed that water depth-related variation was a good proxy for oxygen conditions and metal concentrations, explaining the structure of benthic microbial assemblages. Cd, Ni, As and Pb showed uniformly positive associations with communities that represented the keystone taxa in the co-occurrence network, including Anaerolineaceae, Thiotrichaceae, Desulfobulbaceae, Desulfarculaceae and Bacteroidales_unclassified communities. Collectively, these findings provide new insights for establishing the ecological interconnections of benthic microorganisms in response to metal contamination in a coastal upwelling environment.
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•Benthic microbial assemblage significantly differed along the water-depth gradient.•Exhibit significant correlation between benthic microbial assemblage and heavy metals.•Network patterns were modulated by the ecological preferences linked to environmental heterogeneity.
The benthic microbial assemblages was driven by the metal concentrations distribution at spatial scale within the bay.