Microbial Communities in Long-Term Heavy Metal Contaminated Ombrotrophic Peats

Abstract

High concentrations of heavy metals are known to be toxic to many soil organisms. The effects of long-term exposure to lower levels of metals on the soil microbial community are, however, less well understood. The southern Pennines of the U.K. are characterised by expanses of ombrotrophic peat soils that have experienced deposition of high levels of heavy metals since the mid to late 1800s. Concentrations of metals in the peat remain high but the effect of the contamination on the in-situ microbial communities is unknown. Geochemical and molecular polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and sequencing techniques were used to derive new information on the metal chemistry and microbial populations in peat soils from six locations in the southern Pennines. All sites were highly acidic (pH 3.00?3.14) with high concentrations of potentially toxic heavy metals, particularly porewater Zn and particulate-associated Pb. The results also reveal a split in site characteristics between the most polluted sites with the highest levels of bioavailable metals (Bleaklow, FeatherBed Moss and White Hill) and those with much lower bioavailable metals (Cowms Moor, Holme Moss and Round Hill). There was no difference in the number of dominant bacterial species between the sites but there were significant differences in the species composition. At the three sites with the highest levels of bioavailable metals, bacterial species with a high similarity to acidophilic sulphur- and iron-oxidizing bacteria and those from high metal environments were detected. The transformations carried out by these metal mobilising and acid producing bacteria may make heavy metals more bioavailable and therefore more toxic to higher organisms. Bacteria with similarity to those typically found in forest and grassland soils were documented at the three sites with the lowest levels of bioavailable metals. The data highlight the need for further studies to elucidate the species diversity and functionality of bacteria in heavy metal contaminated peats in order to assess implications for moorland restoration

High concentrations of bioavailable heavy metals impact freshwater sediment microbial communities

“…Further, the research conducted here supports previous studies (Li et al 2006;Linton et al 2007;Sullivan et al 2013b;Yang et al 2013) that have shown that metal availability is important when considering the impacts of heavy metals on microbial community structure. While broad α-diversity metrics appear to be somewhat unaffected, β-diversity was significant between USA and PRC locations, and individual taxonomic groups correlate strongly with the presence of available heavy metals.…”

“…Generally, sites had low levels of available metals, other than available Zn. Several studies have previously found strong correlations between microbial communities and bioavailable metal concentrations (Li et al 2006;Linton et al 2007;Sullivan et al 2013b). Thus, total metal concentration could be viewed as potential impact to biological communities (should the metals become re-available), while bioavailable metal concentration directly influences the biota at that given time.…”

Effects of Metal and Metalloid Contamination on Microbial Diversity and Activity in Agricultural Soils

“…Ellis et al (2003), however, did not see any difference in bacterial communities between metal contaminated and pristine soils using this molecular technique despite finding significantly different community profiles using culture dependent techniques. Linton et al (2007) likewise reported no significant difference in the number of dominant species identified, although marked different in species composition was seen.…”

Mineral components in a peat deposit: looking for signs of early mining and smelting activities in Silesia–Cracow region (Southern Poland)

“…To a lesser extent the same phenomenon is observed for the bottom layers where an increase in Zn concentration can also be seen. Zn is rather weakly bound to organic matter (Linton et al 2007) thus its mobility in peat is expected to be higher than that of Pb. The visibly higher Zn content was observed down to 40-50 cm while higher Pb concentration reached the 30-40 cm layer.…”