A spatial investigation of the environmental controls over cryoconite aggregation on Longyearbreen glacier, Svalbard

Abstract

Abstract.A cryoconite granule is a near-spherical aggregation of biota and abiotic particles found upon glacier surfaces. Recently, microstructural studies have revealed that photosynthetic microorganisms and extracellular polymeric substances (EPS) are omnipresent within cryoconite granules and have suggested their importance as biological "forming factors". To assess these forming factors, and their biological control over aggregate size and stability, across a typical Arctic valley glacier surface, a suite of rapid, spectrophotometric, microplate methods were utilised. Subsequent spatial mapping of these data revealed distinct patterns. Labile carbohydrates were found to increase up-glacier, suggestive of EPS production for cryoprotection and nutrient assimilation. Conversely, pigment concentrations were found to increase towards the glacier terminus and valley sides, suggestive of allochthonous input, a general reduction in physical disturbance and of the build-up of photosynthetic pigments and less labile cyanobacterial sheath material. Aggregate size was found to increase towards the glacier edges, linked to the input of particulate matter from the valley sides, and to broadly increase down-glacier, in the same way as pigment concentrations. Statistical analyses of transect data revealed that the photoautotrophic count and carbohydratechlorophyll ratio of the cryoconite sampled could explain 83 % of the measured variation in aggregate size and stability. Considering solely aggregate size, the number and length of photoautotrophic filaments could explain 92 % of the variation in this parameter. These findings demonstrate the twodimensional distribution of key biological controls upon cryoconite aggregation for the first time, and highlight the importance of filamentous cyanobacteria and EPS production to the development of stable cryoconite granules.

Supraglacial weathering crust dynamics inferred from cryoconite hole hydrology

“…Langford et al . () further found cryoconite aggregates in the interior of Longyearbreen (Svalbard) to be smaller than at the sides due to enhanced hydraulic erosion by concentrated flow in a central tract. Our data therefore add to a growing literature supporting the importance of weathering crust dynamics for supraglacial ecology, both as a medium for hydrologic transfer of cells and as a substrate for cryoconite hole formation.…”

“…Cryoconite holes therefore represent sites of enhanced microbial activity, storage and nutrient transformation within the weathering crust. Prolonged residence times are associated with stability and extended periods of net carbon fixation on Arctic ice surfaces (Hodson et al, 2007;Anesio et al 2009;Cook et al, 2012) resulting in larger, more robust cryoconite aggregates (Langford et al, 2014). This suggests cell fluxes into cryoconite holes may be important for determining surface albedo and supraglacial carbon cycling.…”

“…In Arctic settings, the lack of isolation by ice lids has been linked to different biotic communities compared with those in the Antarctic, due to frequent mixing and flushing with meltwater (Mueller and Pollard, 2004) and greater inputs of allochthonous biota (Paultier et al, 2013). Furthermore, an active supraglacial hydrological system may cause disaggregation (Takeuchi et al, 2000) and redistribution (Hodson et al, 2007;Irvine-Fynn et al, 2011) of cryoconite, influencing microbial activity (Stibal et al, 2012), cyanobacterial filament lengths and therefore cryoconite grain stability (Langford et al, 2014). However, these observations are not independent from the weathering crust, where a reduction in interstitial void spaces in increasingly dense ice establishes a gradient of decreasing hydrologic transmission of labile microbes with depth (Irvine-Fynn and .…”

Extreme weather event results in the removal of invertebrates from cryoconite holes on an Arctic valley glacier (Longyearbreen, Svalbard)

“…The northeast‐facing Longyear Glacier has an area of ~2.5 km 2 and extends from ~250 m to over 1000 m above sea level, with a mean width of approximately 500 m (Figures and S1). Additional detailed information on the glacier and cryoconite is provided in Hodson et al () and Langford, Irvine‐Fynn, Edwards, Banwart, and Hodson ().…”

In-field metagenome and 16S rRNA gene amplicon nanopore sequencing robustly characterize glacier microbiota

“…A preponderance of Alphaproteobacteria over Betaproteobacteria is consistent with trends observed in 16S rRNA gene amplicon pyrosequencing for Arctic cryoconite versus alpine cryoconite(Cook et al 2015, Edwards et al 2014b).Cryoconite is characterized as a microbe-mineral aggregate formed by the action of phototrophic bacteria, typically filamentous cyanobacteria(Cook et al 2015). Hitherto, within studies of Arctic cryoconite(Chrismas et al 2016, Cook et al 2016, Hodson et al 2010, Langford et al 2014 the impact of Oscillatoriophycidae as microbial ecosystem engineers is noted, and in particular the prevalence of Phormidesmis pristleyi in cryoconite.Therefore, while the abundance of Cyanobacteria within the WIMP profile of CryoFox is consistent with other work, the prevalence of Nostocaceae, and in particular reads matching Nostoc punctiforme PCC73102 is an unexpected result, especially considering the prevalence of Oscillatoriophycidae (specifically Phormidesmis) over Nostocaceae in a recent study of Foxfonna cryoconite. BLASTn searches of a randomly selected subset of 50 reads from the 237 reads matching Nostoc punctiforme PCC73102 verifies the legitimacy of WIMP annotation.…”