Effects of Deposition of Heavy-Metal-Polluted Harbor Mud on Microbial Diversity and Metal Resistance in Sandy Marine Sediments

Abstract

Deposition of dredged harbor sediments in relatively undisturbed ecosystems is often considered a viable option for confinement of pollutants and possible natural attenuation. This study investigated the effects of deposition of heavy-metal-polluted sludge on the microbial diversity of sandy sediments during 12 months of mesocosm incubation. Geochemical analyses showed an initial increase in pore-water metal concentrations, which subsided after 3 months of incubation. No influence of the deposited sediment was observed in denaturing gradient gel electrophoresis (DGGE) profiles of bacterial 16S rRNA genes, whereas a minor, transient impact on the archaeal community was revealed. Phylogenetic analyses of bacterial 16S rRNA clone libraries showed an abundance of members of the Flavobacteriaceae, the a-and c-Proteobacteria, in both the muddy and the sandy sediments. Despite the finding that some groups of clones were shared between the metal-impacted sandy sediment and the harbor control, comparative analyses showed that the two sediments were significantly different in community composition. Consequences of redeposition of metalpolluted sediment were primarily underlined with cultivation-dependent techniques. Toxicity tests showed that the percentage of Cd-and Cu-tolerant aerobic heterotrophs was highest among isolates from the sandy sediment with metal-polluted mud on top.

Geographic distribution of cadmium and its interaction with the microbial community in the Longjiang River: risk evaluation after a shocking pollution accident

“…Metals (Fe, Ni and Zn) 29 and Cr 30 changed the bacterial community composition of river sediments. During 12 months of incubation in mesocosms with metal-polluted harbour mud, the percentage of Cd- and Cu-tolerant aerobic heterotrophs was the highest in sandy marine sediment 31 . The microbial communities of the Longjiang River might also have been affected and changed due to the Cd pollution accident in the Longjiang River.…”

Activation of Methanogenesis by Cadmium in the Marine Archaeon Methanosarcina acetivorans

“…Most studies of microbial communities in the ocean have focused on bacterial diversity in marine sediments and the long-term impact brought about by heavy metals exposure [6]. There are few works about the toxic effect of heavy metals on methanogens in sludge [7] and laboratory strains [8], [9].…”

Molecular analysis of bacterial diversity in mudflats along the salinity gradient of an acidified tropical Bornean estuary (South East Asia)

“…Most of these candidate divisions and ‘uncertain’ groups are currently identified in a wide and diverse variety of environments making a potential link to ecosystem functioning impossible until members of these groups are isolated and characterized or until full genomic information is available. Despite the large number of novel species, the Shannon diversity and Chao richness estimators are comparable to similar studies of mudflat microbial diversity in estuaries world-wide [39,40]. We have to keep in mind that the rarefaction curves show that with ~110 -135 clones the mudflats are under-sampled and that the actual richness and diversity are likely higher than estimated here especially since the Chao index is known to underestimate true richness at low sample sizes [41].…”