Factors influencing bacterial dynamics along a transect from supraglacial runoff to proglacial lakes of a high Arctic glacier [corrected

Bacterial production in glacial runoff and aquatic habitats along a c. 500 m transect from the ablation area of a Svalbard glacier (Midre Lovénbreen, 79 degrees N, 12 degrees E) down to a series of proglacial lakes in its forefield were assessed. In addition, a series of in situ experiments were conducted to test how different nutrient sources (glacial flour and dissolved organic matter derived from goose faeces) and temperature affect bacterial abundance and production in these ecosystems. Bacterial abundance and production increased significantly along this transect and reached a maximum in the proglacial lakes. Bacterial diversity profiles as assessed by denaturing gradient gel electrophoresis indicated that communities in glacial runoff were different from those in proglacial lakes. Heterotrophic bacterial production was mainly controlled by temperature and phosphorus limitation. Addition of both glacial flour and dissolved organic matter derived from goose faeces stimulated bacterial production in those lakes. The results suggest that glacial runoff sustains an active bacterial community which is further stimulated in proglacial lakes by higher temperatures and nutrient inputs from bird faeces. Thus, as in maritime temperate and Antarctic settings, bacterial communities developing in the recently deglaciated terrain of Svalbard receive important inputs of nutrients via faunal transfers from adjacent ecosystems.     

Cryosphere: ice on Niwot Ridge and in the Green Lakes Valley,Colorado Front Range

Background: Subsurface ice preserved as ice lenses and within rock glaciers as well as glacial and lake ice provides sensitive indicators of climate change and serve as a late-season source of meltwater.

Aims: We synthesise the results of geomorphological, geophysical and geochemical studies during the period of 1995–2014, building on a long history of earlier work focused on ice and permafrost studies on Niwot Ridge and the adjacent Green Lakes Valley (GLV), which is part of the Niwot Ridge Long Term Ecological Research Site.

Methods: These studies are discussed in the context of how bodies of ice and rock glaciers reflect changing local climate. We review recent results from geophysical investigations (resistivity, seismic refraction and ground-penetrating radar) of the shallow subsurface, ongoing monitoring of the Arikaree Glacier, three rock glaciers and lake ice in the GLV, and interpretations of how subsurface ice melt regulates the flow and chemistry of alpine surface water after seasonal snowfields melt.

Results and conclusions: Permafrost conditions reported from Niwot Ridge in the 1970s are generally absent today, but ice lenses form and melt seasonally. Ice is present permanently within the Green Lakes 5 rock glacier and at nearby favourable sites. The Arikaree Glacier has shown a marked decline in cumulative mass balance during the past 12 years after a 30-year period when net mass balance was ca. 0. Duration of seasonal lake ice increases with elevation in GLV, but duration has decreased at all seven lakes that have been monitored during the last three decades. This decrease has been most marked at the lowest elevation where it amounted to a reduction of about 1 d year^?1 and least at Green Lake 5 where the loss has been at a rate of 0.5 d year^?1. Surface temperature measurements from rock glaciers have not shown strong trends during the past 15 years. It has been suggested that almost all of the 2.5-mm year^?1 increase in stream discharge from the upper GLV in September and October has been derived from melting of subsurface ice.     

Particulate organic matter inputs to a glacial stream ecosystem in the Swiss Alps

1. Traps for litterfall and for lateral transport of organic matter were sampled over a 1-year period along longitudinal and lateral transects in a glacial stream system (Val Roseg, Swiss Alps), which is characterized by single-thread reaches and a large subalpine floodplain.
2. Allochthonous inputs to the glacier stream were low close to the glacier terminus but increased as woody riparian vegetation and forests develop. Annual inputs varied from 0.4 g ash free dry matter (AFDM) m^–2 year^–1 (direct input) and 0.7 g AFDM m^–2 year^–1 (lateral input) in the proglacial area to 23.0 g AFDM m^–2 year^–1 (direct input) and 10.7 g AFDM m^–2 year^–1 (lateral input) in the lowest reach with adjacent subalpine forests.
3. Direct inputs of organic matter decreased exponentially from forests at the floodplain edge to the floodplain centre, while lateral inputs of organic matter correlated linearly with distance to trees. Direct litterfall dominated litter input close to the forest, while lateral transport was the major pathway for channels more than 20 m away from the forest.
4. A conceptual framework is developed illustrating the influence of terrestrial vegetation and fluvial morphology on organic matter input along the continuum of glacial streams.     

Bacterial community succession in a high‐altitude subarctic glacier foreland is a three‐stage process

Alpine glaciers are retreating rapidly, exposing foreland minerals, which develop into soils. Bacterial communities in glacier forelands exhibit high rates of turnover and undergo dramatic shifts in composition within the first 50 years after deglaciation, followed by relative stabilization and convergence. This period of microbial development occurs simultaneously with plant colonization in most systems; thus, it remains unclear whether the changes in the bacterial communities occur primarily as the result of edaphic, climatic or biotic factors. We examined bacterial community structure along two replicate chronosequences within the glacial foreland of Duke River Glacier, Yukon, Canada. This foreland is estimated to include >200 years of bare soils before an appreciable grassline, likely due to the high latitude and altitude of the glacier. This enabled us to examine bacterial community development prior to plant colonization over a longer period than previous studies. We observed three successional groups in the chronosequence: (i) an ‘early’ group in soils of less than approximately 50 years since deglaciation; (ii) an ‘intermediate’ group within bare soils, after the early period but before the grassline, containing communities with a relatively high degree of variability in composition; and (iii) a ‘grassline’ group in soils collected after plant colonization with higher diversity but lower age‐group variability in community composition. These findings suggest rapid replacement and addition of species better adapted to glacier foreland conditions followed by slower community shifts over the next 150 years and, finally, indications of a possible response to plant colonization.     

Trophic status of Tilitso,a high altitude Himalayan lake

The trophic status and water quality of Lake Tilitso (4920 m above sea level) in a high altitude region in central Nepal were surveyed in September, 1984. The lake is rather large with a maximum depth of 95 m and a surface area of 10.2 km². The lake water was turbid due to glacier silt and the euphotic layer was only 5 m deep. The nutrient concentration was very low with total phosphorus concentration 1–6 μg l⁻¹, and DTN concentration 0.10–0.22 mg l⁻¹. The phytoplankton biomass and chlorophyll-a concentration were also low. Primary production was estimated to be about 12 mg C m⁻² d⁻¹. The concentrations of particulate matter and most cations and bacterial number were higher in the epilimnion than in the hypolimnion. The trophic status of this lake was estimated as ultraoligotrophic.     

The stone age iceman from the Alps: The find and the current status of investigation

On September 19, 1991, a body protruding from glacial ice was discovered in the Alps between Austria and Italy. Considered a forensic case, and having been found on Austrian soil according to initial information, it was transported to the Department of Forensic Medicine in Innsbruck. Rumors about the body not being recent were readily confirmed, and news about the body and accompanying equipment immediately spread all over the world. The body itself was shown to be a natural mummy, as opposed to a corpse that has been embedded in glacial ice for some time, where soft tissue generally changes into grave wax (adipocere). The mummy was male and was remarkably well preserved. The preserved condition of his equipment and some organic material was astonishingly good. Isotope dating of the body by means of the ¹⁴C method has given an age of about 3,300 BC, or Late Stone Age. A survey of the border, however, revealed that the body was found just on the Italian side (within the autonomous province South Tyrol), and not as first assumed, in Austria (the province Tyrol). But according to an agreement between South Tyrol and the University of Innsbruck, the body will be kept at the Department of Anatomy in Innsbruck for a period of at least three years for research purposes. The research is to be carried out on an international basis, and the first symposium about the find was held in Innsbruck, June 3–5, 1992.     

Efficacy of voluntary mitigation in reducing harbor seal disturbance

Marine and coastal tourism has rapidly expanded worldwide in the past 2 decades, often occurring in once secluded habitats. In Alaska, tourism near tidewater glaciers has attracted millions of visitors and increased the presence of ships, tour vessels, and coastal development. Although sustainable tourism, resulting from balanced effects on wildlife and client satisfaction, is a goal of most tourism operators, it is not always achieved. Voluntary compliance with viewing guidelines and codes of conduct have been encouraged, but few assessments have the longitudinal scope to evaluate long-term changes in impacts on wildlife and the ability of vessel operators and kayak guides to sustain lower impact operating practices over time. This study assessed vessel and kayak visitation and resulting impacts on harbor seals in the Kenai Fjords National Park, southcentral Alaska. We obtained observations from 2002 to 2011, using remotely controlled video cameras located near Aialik and Pedersen Glaciers in the Kenai Fjords National Park. Overall, disturbance was associated with 5.1% of vessel sightings, 28% of vessel interactions (vessel observed within approx. 300 m of seals), 11.5% of kayak sightings, and 61% of kayak interactions. Results demonstrated that voluntary changes in operations significantly reduced vessel and kayak disturbance of seals by 60–80%. Even with prior establishment of operating guidelines, tour vessel captains were able to further reduce their effect on wildlife with more careful operations. Rapid growth of guided kayak excursions that occurred during this study caused greater disturbance to seals than motorized vessels but guide trainings helped reduce disturbances. Diminished impacts of motor vessels and kayakers persisted across years although effects of kayaks were less consistent than motor vessels, which reflected greater variability in inter-annual spatial use patterns by kayakers. Long-term monitoring, including assessments of wildlife responses to vessel and kayak operations, combined with 2-way communication with vessel operators and guides, enhanced the effectiveness of mitigation and facilitated adaptive adjustments to mitigation protocols over time. © 2013 The Wildlife Society.     

Pursuing glacier retreat: genetic structure of a rapidly expanding Larix decidua population

One of the greatest threats to the long-term viability of migrating plant species is the loss of genetic diversity due to founder effects. Populations can expand as a response to climate change, but it is uncertain if long-lived plant species can maintain sufficient genetic diversity at the leading edge of migrating populations. This study uses an expanding Larix decidua population investigated along a chronosequence at landscape (350 ha) and local (0.8 ha) scales to test whether accelerated migration as a result of climate warming has the potential to intensify genetic erosion. Nine SSR markers revealed similar genetic diversity among eight sub-populations along the chronosequence (overall H(e) = 0.73; SE=0.04). Sub-populations were not genetically differentiated and all sampled individuals (N=730) formed one major genetic cluster indicating homogenizing gene flow despite spatial genetic structure (SGS) up to 80 m. At the local scale, individuals at the leading edge [early successional sub-population (ESSP), N =140] and a sub-population at equilibrium [late successional sub-population (LSSP), N = 290] revealed high genetic diversity in largest-sized cohorts. SGS among juveniles occurred up to 30 m in LSSP but there was no structure in ESSP. Accordingly, a maximum likelihood paternity assignment revealed local gene dispersal in LSSP (2-48 m) and intermediate-to-long distance dispersal into ESSP (115-3132 m). The findings indicate intensive mixing of the genes in this expanding population instead of founder effects and support the view that genetic diversity can be maintained in a long-lived species during rapid population expansion driven by climate warming.     

Long-term glacier monitoring at the LTER test sites Hintereisferner,Kesselwandferner and Jamtalferner and other glaciers in Tyrol: a source of ancillary information for biological succession studies

Background: Some 3% of the area of Tyrol is covered by glaciers. Since the end of the Little Ice Age, these glaciers have shrunk by about 50%, providing open ground for succession of biota. As the exposed bare ground becomes available for colonisation, pedogenesis, and primary succession, glaciological data provide important information for the analysis of chronosequences of biological succession.

Aims: This paper summarises long-term surveillance studies and provides information on annual glacier changes with a focus on the three Tyrolean LTER sites Hintereisferner, Kesselwandferner and Jamtalferner, together with two additional glaciers.

Methods: Annual changes in the length of 54 glaciers were recorded, with the first measurements made in 1891. In addition, the long-term mass balance data of five glaciers are presented. Two of these glaciers have been surveyed since 1953.

Results: Between 1901 and 2008, the temperature during the ablation season (May to September) increased by 1.7 °C (measured at one site in Vent). In the same period, winter (October to April) accumulation showed no significant trends. Measurements of length changes showed a general glacier retreat, with limited advances in the 1920s and 1980s. The mass balance measurements indicated mass losses since the 1980s at increasing rates, especially after 2000. The reaction of glaciers to the climate signal differed in timing and magnitude according to their topographic properties.

Conclusions: Although the Tyrolean glaciers have generally retreated since the end of the Little Ice Age, the magnitude and pace of advance or recession differs from glacier to glacier. This is important to consider in studies on succession of biological communities in glacier forelands