Microbial Degradation of 2,4-Dichlorophenoxyacetic Acid on the Greenland Ice Sheet

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>The Greenland ice sheet (GrIS) receives organic carbon (OC) of anthropogenic origin, including pesticides, from the atmosphere and/or local sources, and the fate of these compounds in the ice is currently unknown. The ability of supraglacial heterotrophic microbes to mineralize different types of OC is likely a significant factor determining the fate of anthropogenic OC on the ice sheet. Here we determine the potential of the microbial community from the surface of the GrIS to mineralize the widely used herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Surface ice cores were collected and incubated for up to 529 days in microcosms simulating<jats:italic>in situ</jats:italic>conditions. Mineralization of side chain- and ring-labeled [<jats:sup>14</jats:sup>C]2,4-D was measured in the samples, and quantitative PCR targeting the<jats:italic>tfdA</jats:italic>genes in total DNA extracted from the ice after the experiment was performed. We show that the supraglacial microbial community on the GrIS contains microbes that are capable of degrading 2,4-D and that they are likely present in very low numbers. They can mineralize 2,4-D at a rate of up to 1 nmol per m<jats:sup>2</jats:sup>per day, equivalent to ∼26 ng C m<jats:sup>−2</jats:sup>day<jats:sup>−1</jats:sup>. Thus, the GrIS should not be considered a mere reservoir of all atmospheric contaminants, as it is likely that some deposited compounds will be removed from the system via biodegradation processes before their potential release due to the accelerated melting of the ice sheet.</jats:p>

Metabolome‐mediated biocryomorphic evolution promotes carbon fixation in Greenlandic cryoconite holes

“…In contrast, previous studies imply that respiration in cryoconite might resist environmental disturbances in the interior zones of the Greenland Ice Sheet. There, the dominant heterotrophs are metabolically flexible (White et al, 1996;Stibal et al, 2015) and unlikely to be limited by contemporary autochthonous OC production (Stibal et al, 2010;2012b;Telling et al, 2012). Our data cannot be used to determine rates of photosynthesis and respiration individually because the artificial manipulation of light regime in our experiments weakens the assumption of parity between respiration in light and dark incubations (e.g.…”

Snow and ice ecosystems: not so extreme

“…Numerous genes detected in glacier ice core metagenomes related to xenobiotics, biopolymers and other carbon sources suggest that glacial ice microorganisms have the potential to degrade a wide range of substrates [17]. Microbial degradation of xenobiotic compounds from distant allochtonous sources has been observed on the Greenland ice sheet [91]. Microbial preferences for different carbon classes were also studied in Antarctic snow and results showed a higher rate of carbon uptake when snow microcosms were amended with a combination of simple and complex carbon sources [92].…”

Understanding the dynamics of black carbon and associated contaminants in glacial systems

“…It is now known that about half of the world's freshwater bacterial biomass is present within the world's glaciers and ice sheets, and that these environments represent active ecosystems in their own right . However, while the role of microbes in the bioremediation of contaminants in polluted soils and sediments is well known, it has been almost completely overlooked in the case of glacial ecosystems . The role of biofilms in glacial contaminant dynamics therefore requires quantitative treatment for the first time.…”

“…42 However, while the role of microbes in the bioremediation of contaminants in polluted soils and sediments is well known, it has been almost completely overlooked in the case of glacial ecosystems. 43 The role of biofilms in glacial contaminant dynamics therefore requires quantitative treatment for the first time. Recent research has demonstrated how biofilm-type microbial ecosystems thrive upon glaciers when they melt, producing aggregates of mineral and anthropogenic particulates encapsulated by extracellular polymeric substances (EPS) that are exuded by very active cyanobacteria and other microorganisms 36,44 (Figure 1).…”