Meltwater export of prokaryotic cells from the Greenland ice sheet

Abstract

Microorganisms are flushed from the Greenland Ice Sheet (GrIS) where they may contribute towards the nutrient cycling and community compositions of downstream ecosystems. We investigate meltwater microbial assemblages as they exit the GrIS from a large outlet glacier, and as they enter a downstream river delta during the record melt year of 2012. Prokaryotic abundance, flux and community composition was studied, and factors affecting community structures were statistically considered. The mean concentration of cells exiting the ice sheet was 8.30 × 10 cells mL and we estimate that ∼1.02 × 10 cells were transported to the downstream fjord in 2012, equivalent to 30.95 Mg of carbon. Prokaryotic microbial assemblages were dominated by Proteobacteria, Bacteroidetes, and Actinobacteria. Cell concentrations and community compositions were stable throughout the sample period, and were statistically similar at both sample sites. Based on our observations, we argue that the subglacial environment is the primary source of the river-transported microbiota, and that cell export from the GrIS is dependent on discharge. We hypothesise that the release of subglacial microbiota to downstream ecosystems will increase as freshwater flux from the GrIS rises in a warming world.

Mapping Ice Algal Blooms in Southwest Greenland From Space

“…Figure shows the temporal development of algal abundance over four dark ice sites. We use the dates of maximum dark ice presence, 21 July 2016 and 27 July 2017, as the beginning time of algal population growth, considering the impacts of snow burial and hydrological flushing events on algal distribution (Cameron et al, ; Stibal et al, ). According to the MAR time series (Figures f and g), the selected periods plotted in Figure were less affected by snowfall or rainfall events.…”

Glacier Outflow Dissolved Organic Matter as a Window Into Seasonally Changing Carbon Sources: Leverett Glacier, Greenland

“…The second potential source of C 416 is subglacially derived DOM either reworked or produced in situ by microbial communities. Microbial production and transformation of DOM can be through aerobic and anaerobic microbial processes (Cameron et al, ; Lamarche‐Gagnon et al, ; Stibal et al, ). Although the LG subglacial outflow is supersaturated in oxygen, it is also supersaturated in methane (Lamarche‐Gagnon et al, ); thus, the spatial extent of GrIS subglacial anaerobic environments is potentially vast.…”

“…Overridden soils and vegetation are a potentially important source of DOM along the southwestern margin of the GrIS, where the margin of the ice sheet retreated back from its current position during the Holocene Thermal Maximum (Lecavalier et al, ; Levy et al, ). Alternative subglacial sources to overridden soils and vegetation might include lithogenic DOM (Petsch et al, ; Petsch et al, ), chemolithoautotrophic production of DOM (Birdwell & Engel, ; Chen et al, ; Harrold et al, ), and the reworking of existing DOM by subglacial microbial communities (Cameron et al, ; Lamarche‐Gagnon et al, ; Stibal et al, ).…”

Snapshot of micro-animals and associated biotic and abiotic environmental variables on the edge of the south-west Greenland ice sheet

“…For each group, we computed models consisting of all the possible combinations of explanatory variables, and evaluated them with quasi-AIC (QAIC). We followed an information-theoretic approach to identify the most parsimonious models (Burnham and Anderson 2002). The model with the lowest QAIC within the set was considered the best, given the data (Burnham and Anderson 2002), but we discarded models with uninformative parameters that were more complex versions of a competitive model with fewer parameters whose QAIC\ 2 (Arnold 2010).…”