Geographical Variability of Bacterial Communities of Cryoconite Holes of Andean Glaciers

Cryoconite holes, ponds full of melting water with a sediment on the bottom, are hotspots of biodiversity on glacier surface and host dynamic micro-ecosystems on these extreme environments. They have been extensively investigated in different areas of the world (e.g., Arctic, Antarctic, Alps, and Himalaya), but no study so far has described the bacterial communities of the glaciers in the Andes, the world longest mountain range. In this study, we start filling this gap of knowledge and describe the bacterial communities of Southern Andes in three small (< 2 km2) high elevation (< 4200 m a.s.l.) glaciers of Central Andes (Iver, East Iver and Morado glaciers) and two large (> 85 km2) glaciers in Patagonian Andes (Exploradores and Perito Moreno glaciers) whose ablation tongues reach low altitude (< 300 m a.s.l). Results show that the bacterial communities were generally similar to those observed in the cryoconite holes of other continents. Indeed, the most abundant orders were Burkholderiales, Cytophagales, Sphingobacteriales, Actinomycetales, Pseudomonadales, Rhodospiarillales, Rhizobiales, Sphingomonadales and Bacteroidales. However, the bacterial communities differed between glaciers and both water pH and O2 concentration influenced the bacterial community composition.

Assessment of lignocellulosic residues from Northern Patagonian Andes (Argentina) for cultivation of Pleurotus ostreatus

This work evaluated mycelial growth rate (Kr) and fruiting of two Pleurotus ostreatus commercial strains (A01, 129) on formulations composed of lignocellulosic residues from farming and agroindustry of Northern Patagonian Andes, and of woody materials from invasive plants. Rosehip fluffs (RF), rosehip woodchips (RWC), southern beech wood shavings (SBWS), wheat straw (WS), and willow woodchips (WWC) were used as base substrates, and brewing bagasse (BB) as an alternative supplement to wheat bran (WB). Kr was higher in WS-WB and WS-BB for both strains. Experiments in fruiting chambers showed biological efficiencies (BEs) above 40% in WS-BB (both strains) and WS-WB (strain 129). Formulations using RWC or WWC gave BEs under 40%, while those composed of SBWS or RF showed lower Kr and contamination by moulds. Medium-scale fruiting experiments using strain A01 showed the highest BEs in WS-BB and RWC-WB. These results suggest that WS is the best substrate for Pleurotus ostreatus culture, although scarce in Northern Patagonian Andes. Nevertheless, WWC and RWC are suggested as alternative substrates, while BB is cheap and abundant, suitable as an alternative supplement to WB.

Evolution of Surface Characteristics of Three Debris-Covered Glaciers in the Patagonian Andes From 1958 to 2020

A number of glaciological observations on debris-covered glaciers around the globe have shown a delayed length and mass adjustment in relation to climate variability, a behavior normally attributed to the ice insulation effect of thick debris layers. Dynamic interactions between debris cover, geometry and surface topography of debris-covered glaciers can nevertheless govern glacier velocities and mass changes over time, with many glaciers exhibiting high thinning rates in spite of thick debris cover. Such interactions are progressively being incorporated into glacier evolution research. In this paper we reconstruct changes in debris-covered area, surface velocities and surface features of three glaciers in the Patagonian Andes over the 1958–2020 period, based on satellite and aerial imagery and Digital Elevation Models. Our results show that debris cover has increased from 40 ± 0.6 to 50 ± 6.7% of the total glacier area since 1958, whilst glacier slope has slightly decreased. The gently sloping tongues have allowed surface flow velocities to remain relatively low (&lt;60 m a−1) for the last two decades, preventing evacuation of surface debris, and contributing to the formation and rise of the ice cliff zone upper boundary. In addition, mapping of end of summer snowline altitudes for the last two decades suggests an increase in the Equilibrium Line Altitudes, which promotes earlier melt out of englacial debris and further increases debris-covered ice area. The strongly negative mass budget of the three investigated glaciers throughout the study period, together with the increases in debris cover extent and ice cliff zones up-glacier, and the low velocities, shows a strong linkage between debris cover, mass balance evolution, surface velocities and topography. Interestingly, the presence of thicker debris layers on the lowermost portions of the glaciers has not lowered thinning rates in these ice areas, indicating that the mass budget is mainly driven by climate variability and calving processes, to which the influence of enhanced thinning at ice cliff location can be added.