Rise of pollutants in the cryosphere

Abstract/Description

Since their mass introduction for agricultural use during the last century, pesticides attracted an increasing amount of attention from the scientific community due to their unique nature of being released in the environment not by mistake, but by design. While some of these compounds are generally sprayed directly onto crops to reduce yield losses caused by pests, their environmental repercussions can hardly be circumscribed to the area of application. Driven by their differential chemical affinity towards environmental matrices, some classes of pesticides that are more prone to resuspension go through medium/long-range atmospheric transport and end up accumulating elsewhere. Glacial habitats are sometimes referred to as “cold condensers” precisely due to their tendency of acting as such accumulating compartments, exposing off-target (micro)biological communities to enhanced levels of toxicants. In this study, we determine the degradative adaptations and pesticide mineralization rates by spiking and incubating microbial communities sampled from cryoconite holes on the Forni Glacier (Central Alps, Italy) and the Greenland Ice Sheet. Cryoconite holes are unique glacial habitats: when wind-blown dark-colored sediment is deposited on the bare ice, in virtue of its lower albedo it melts through the surface while gradually filling up with melt water, resulting in a sheltered environment for microorganisms to thrive in. To simulate the native environment, we employ a custom-built incubation unit running on a 12-h light and 12-h dark regime and controlled temperature. The compounds of choice are 14C-labelled 2,4D, MCPA, Chlorpyrifos and glucose, respectively being two widely used herbicides, an insecticide and a positive control, inoculated at zero, 1 and 100ppm concentrations. A scintillation counter is used to quantify the mineralization along the 6 months microcosm experiment, while small aliquots of sediment are sampled from the bottles for the subsequent metagenomics and transcriptomics analyses. Preliminary results highlight significant differences in mineralization across all compounds between Alpine and Greenlandic communities, with the former consistently outperforming the latter in mineralized percentage. Further genomic insights will be crucial to characterize the microbial taxa responsible for the degradation processes and their adaptations, to better understand the underlying processes they are responsible for.