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Algal Communities on Ice

Posted on: October 13, 2019

 

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AGW IMPLICATIONS OF CRYOCONITE & ALGAL COMMUNITIES ON THE GREENLAND ICE SHEET

  1. Cryoconite is a very fine powder-like dust consisting of fine rock particles, soot, and microbes. When deposited on snow or ice, it tends to accumulate and accelerate ice melt. The greater rate of ice melt is facilitated by the darker color of the affected areas as well as by the waste heat of the biological processes of the microbes and their growth in population. Of course, cryoconite does not seek out ice to settle on but they are easier to identify on ice surfaces and that creates a bias in their distribution in the data.
  2. Other organic matter blown on to icy surfaces include snow and ice”algal communities”. These are various varieties of ice algae that can also be blown on to ice surfaces where they grow and multiply to the extent that the affected ice is described as having been colonized. They can change the color of large areas of ice, ten or more square kilometers, to various hues of blue, brown, red, and purple so thick that the overall feature of the hue is one of blackness such that ice albedo of the affected area is greatly reduced and solar radiation absorbed can greatly accelerate the rate of ice melt.
  3. The effect is also described as an overall reduction in ice albedo in the climate system with the net effect of accelerated rate of global warming with the possibility of a runaway feedback effect that could cause rapid ice melt and instability of ice sheets such as the Greenland Ice Sheet (GRIS) that could in turn accelerate sea level rise.
  4. In fact, the GRIS is the focus of research in this area and most if not all of the cryoconite and algal community ice-melt events observed have been found on the GRIS. A bibliography of research in this area is included below. The importance of the year 2012 in this line of research is that it marks a year of significant GRIS melt that was at first attributed to the possibility of AGW stronger than previously thought but later amended to include the effect of the algal communities found on the affected ice areas.
  5. A related dynamic of the ice-algae connection is that algae are plants that carry our photosynthesis and remove CO2 from the atmosphere. This removal is not permanent of course but part of the life cycle and carbon cycle dynamics as in any other example of photosynthesis. Yet, the carbon capture feature of algae is an important part of their effect on ice in the AGW context.
  6. The use of algae affected ice melt can serve a purpose in the effort to push for climate action with the fear of the alternative along the lines of “worse than previously thought” because it is true that the melt rate of the GRIS is worse when the algae effect is included; and it is true that, if AGW theory is correct, fossil fuel emissions have increased the energy available to the algae affected areas of the ice.
  7. However, the algae ice-melt dynamic has a very different interpretation in terms of AGW. It shows that life on earth affects the climate system and the rate of ice sheet melt and sea level rise. It’s an organic and inclusive part of nature such that nature cannot be separated into isolated blocks in a way that the impact of humans on climate should be interpreted as an alarming, sinful, unnatural. and unholy relationship between humans and nature that will bring about the end of the planet.
  8. The Ecology and Climatology ideal that humans must live in a way such that there should be no measurable impact of human activity upon the ecosystem, upon the climate, and upon the rest of nature in general, is itself unnatural. Life forms on earth don’t live in isolation but in an interactive web and nature itself including the climate, atmosphere, the glaciers, the ice sheets, and the oceans are all part of this interactive web. It is neither possible nor desirable that humans should separate themselves from nature’s web. They are part of this web and not from outer space. [RELATED POST]   

 

 

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GREENLAND ICE SHEET ALGAL COMMUNITY BIBLIOGRAPHY

  1. Wharton Jr, Robert A., et al. “Cryoconite holes on glaciers.” BioScience (1985): 499-503.  Cryoconite holes are water-filled depressions on the surface of glaciers. They contain microbial communities and may contribute to glacial melt and biological colonization of ice-free areas. 
  2. Uetake, Jun, et al. “Communities of algae and cyanobacteria on glaciers in west Greenland.” Polar Science 4.1 (2010): 71-80.  Communities of algae and cyanobacteria on two glaciers in west Greenland (the Qaanaaq and Russel glaciers) were analyzed and compared with the aim of explaining why the Qaanaaq Glacier (in northwestern Greenland) has a dark-colored surface in satellite images whereas the Russel Glacier (in western central Greenland) has a light-colored surface. We found that algal and cyanobacterial communities differed between the glaciers and that the amount of biomass was higher on the colder glacier (Qaanaaq Glacier). The community on the Qaanaaq Glacier was composed mainly of green algae, whereas that on the Russel Glacier was dominated by cyanobacteria. Despite the shorter melting period (due to colder air temperature) for the Qaanaaq Glacier, the biovolume of algae and cyanobacteria was 2.35 times higher than that on the Russel Glacier at a similar altitude, suggesting greater primary production on the Qaanaaq Glacier. We discuss the possible effects of temperature, nutrient concentrations, and cryoconite holes (melt-holes in the glacier) on the community structure and productivity of algae and cyanobacteria on each glacier, and consider the influence of the identified differences in algal and cyanobacterial communities on the amount of surface melt.
  3. Wientjes, I. G. M., et al. “Dust from the dark region in the western ablation zone of the Greenland ice sheet.” The Cryosphere 5.3 (2011): 589-601.  A dark region tens of kilometres wide is located in the western ablation zone of the Greenland ice sheet. The dark appearance is caused by higher amounts of dust relative to the brighter surroundings. This dust has either been deposited recently or was brought to the surface by melting of outcropping ice. Because the resulting lower albedos may have a significant effect on melt rates, we analysed surface dust on the ice, also called cryoconite, from locations in the dark region as well as locations from the brighter surrounding reference ice with microscopic and geochemical techniques to unravel its composition and origin. We find that (part of) the material is derived from the outcropping ice, and that there is little difference between dust from the dark region and from the reference ice. The dust from the dark region seems enriched in trace and minor elements that are mainly present in the current atmosphere because of anthropogenic activity. This enrichment is probably caused by higher precipitation and lower melt rates in the dark region relative to the ice marginal zone. The rare earth elemental ratios of the investigated material are approximately the same for all sites and resemble Earth’s average crust composition. Therefore, the cryoconite probably does not contain volcanic material. The mineralogical composition of the dust excludes Asian deserts, which are often found as provenance for glacial dust in ice cores, as source regions. Consequently, the outcropping dust likely has a more local origin. Finally, we find cyanobacteria and algae in the cryoconite. Total Organic Carbon accounts for up to 5 weight per cent of the cryoconite from the dark region, whereas dust samples from the reference ice contain only 1% or less. This organic material is likely formed in situ. Because of their high light absorbency, cyanobacteria and the organic material they produce contribute significantly to the low albedo of the dark region. 
  4. Cook, J. M., et al. “An improved estimate of microbially mediated carbon fluxes from the Greenland ice sheet.” Journal of Glaciology 58.212 (2012): 1098-1108.  Microbially mediated carbon fluxes on the surface of the Greenland ice sheet (GrIS) were recently quantified by Hodson and others (2010) using measurements of the surface coverage of debris (cryoconite) and rates of biological production associated with debris near the ice-sheet margin. We present updated models that do not assume the same spatial uniformity in key parameters employed by Hodson and others (2010) because they make use of biomass distribution and biological production data from a 79 km transect of the GrIS. Further, the models presented here also include for the first time biomass associated with both cryoconite holes and surficial algae. The predicted annual carbon flux for a small (1600 km2) section of ice surrounding the field transect is about four times that estimated using spatially uniform biomass and production in this area. When surficial algae are included, the model predicts about 11 times more carbon fixation via photosynthesis per year than the cryoconite-only models. We therefore suggest that supraglacial carbon fluxes from the GrIS have previously been underestimated by more than an order of magnitude and that the hitherto overlooked surficial algal ecosystem can be the most crucial contributor. The GrIS is shown to be in a relatively stable state of net autotrophy according to our model and so a strong link between bare-ice area and total carbon fluxes is evident. The implication is a biomass feedback to surface albedo and enhanced ablation as a result. Climate predictions for the year 2100 show that greater carbon fixation could also result from climate warming.
  5. Kamenos, Nicholas A., et al. “Reconstructing Greenland ice sheet runoff using coralline algae.” Geology 40.12 (2012): 1095-1098.  The Greenland ice sheet (GrIS) contains the largest store of fresh water in the Northern Hemisphere, equivalent to ∼7.4 m of eustatic sea-level rise, but its impacts on current, past, and future sea level, ocean circulation, and European climate are poorly understood. Previous estimates of GrIS melt, from 26 yr of satellite observations and temperature-driven melt models over 48 yr, show increasing melt trends. There are, however, no runoff data of comparable duration with which to validate the relationship between the spatial extent of melting and runoff or temperature-based runoff models. Further, longer runoff records are needed to extend the melt pattern of Greenland to centennial timescales, enabling recent observations and trends to be put into a better historical context. We have developed a new GrIS runoff proxy by extracting information on relative salinity changes from annual growth bands of red coralline algae. We observed significant negative relationships between historic runoff, relative salinity, and marine summer temperature in Søndre Strømfjord, Greenland. We produce the first reconstruction of runoff from a section of the GrIS that discharges into Søndre Strømfjord over several decades (1939–2002) and record a trend of increasing reconstructed runoff since the mid 1980s. In situ summer marine temperatures followed an equivalent trend. We suggest that since A.D. 1939, atmospheric temperatures have been important in forcing runoff. These results show that our technique has significant potential to enhance understanding of runoff from large ice sheets as it will enable melt reconstruction over centennial to millennial timescales.
  6. Anesio, Alexandre M., and Johanna Laybourn-Parry. “Glaciers and ice sheets as a biome.” Trends in ecology & evolution 27.4 (2012): 219-225.  The tundra is the coldest biome described in typical geography and biology textbooks. Within the cryosphere, there are large expanses of ice in the Antarctic, Arctic and alpine regions that are not regarded as being part of any biome. During the summer, there is significant melt on the surface of glaciers, ice caps and ice shelves, at which point microbial communities become active and play an important role in the cycling of carbon and other elements within the cryosphere. In this review, we suggest that it is time to recognise the cryosphere as one of the biomes of Earth. The cryospheric biome encompasses extreme environments and is typified by truncated food webs dominated by viruses, bacteria, protozoa and algae with distinct biogeographical structures.
  7. Yallop, Marian L., et al. “Photophysiology and albedo-changing potential of the ice algal community on the surface of the Greenland ice sheet.” The ISME journal 6.12 (2012): 2302.  Darkening of parts of the Greenland ice sheet surface during the summer months leads to reduced albedo and increased melting. Here we show that heavily pigmented, actively photosynthesising microalgae and cyanobacteria are present on the bare ice. We demonstrate the widespread abundance of green algae in the Zygnematophyceae on the ice sheet surface in Southwest Greenland. Photophysiological measurements (variable chlorophyll fluorescence) indicate that the ice algae likely use screening mechanisms to downregulate photosynthesis when exposed to high intensities of visible and ultraviolet radiation, rather than non-photochemical quenching or cell movement. Using imaging microspectrophotometry, we demonstrate that intact cells and filaments absorb light with characteristic spectral profiles across ultraviolet and visible wavelengths, whereas inorganic dust particles typical for these areas display little absorption. Our results indicate that the phototrophic community growing directly on the bare ice, through their photophysiology, most likely have an important role in changing albedo, and subsequently may impact melt rates on the ice sheet.
  8. Stibal, Marek, Marie Šabacká, and Jakub Žárský. “Biological processes on glacier and ice sheet surfaces.” Nature Geoscience 5.11 (2012): 771.  Glaciers and ice sheets are melting in response to climate warming. Whereas the physical behaviour of glaciers has been studied intensively, the biological processes associated with glaciers and ice sheets have received less attention. Nevertheless, field observations and laboratory experiments suggest that biological processes that occur on the surface of glaciers and ice sheets — collectively termed supraglacial environments — can affect the physical behaviour of glaciers by changing surface reflectivity. Furthermore, supraglacial cyanobacteria and algae capture carbon dioxide from the atmosphere and convert it into organic matter. Supraglacial microbes break down this material, together with organic matter transported from further afield, and generate carbon dioxide that is released back into the atmosphere. The balance between these two processes will determine whether a glacier is a net sink or source of carbon dioxide. In general, ice sheet interiors seem to function as sinks, whereas ice sheet edges and small glaciers act as a source. Meltwaters flush microbially modified organic matter and pollutants out of the glacier, with potential consequences for downstream ecosystems. We conclude that microbes living on glaciers and ice sheets are an integral part of both the glacial environment and the Earth’s ecosystem.
  9. Lutz, Stefanie, et al. “Variations of algal communities cause darkening of a Greenland glacier.” FEMS Microbiology Ecology 89.2 (2014): 402-414.  We have assessed the microbial ecology on the surface of Mittivakkat glacier in SE-Greenland during the exceptional high melting season in July 2012 when the so far most extreme melting rate for the Greenland Ice Sheet has been recorded. By employing a complementary and multi-disciplinary field sampling and analytical approach, we quantified the dramatic changes in the different microbial surface habitats (green snow, red snow, biofilms, grey ice, cryoconite holes). The observed clear change in dominant algal community and their rapidly changing cryo-organic adaptation inventory was linked to the high melting rate. The changes in carbon and nutrient fluxes between different microbial pools (from snow to ice, cryoconite holes and glacial forefronts) revealed that snow and ice algae dominate the net primary production at the onset of melting, and that they have the potential to support the cryoconite hole communities as carbon and nutrient sources. A large proportion of algal cells is retained on the glacial surface and temporal and spatial changes in pigmentation contribute to the darkening of the snow and ice surfaces. This implies that the fast, melt-induced algal growth has a high albedo reduction potential, and this may lead to a positive feedback speeding up melting processes.
  10. Takeuchi, Nozomu, et al. “Spatial variations in impurities (cryoconite) on glaciers in northwest Greenland.” Bulletin of Glaciological Research 32 (2014): 85-94.  Spatial variations in impurities (cryoconite) on the glacier surface were investigated on Qaanaaq Ice Cap and Tugto Glacier in the northwest Greenland in the melting season of 2012. Abundance of impurities ranged from 0.36 to 119 g m-2 (dry weight, mean:18.8 g m-2) on bare ice and from 0.01 to 8.7 g m-2 (mean:3.6 g m-2) on snow surface at the study sites. On Qaanaaq Glacier (an outlet glacier of Qaanaaq Ice Cap) impurity abundance was greatest at mid-elevations, with fewer impurities at upper and lower sites. Surface reflectivity was lowest in the mid-elevation area, suggesting that impurities substantially reduce ice surface albedo at mid-elevations on glacier surfaces. Organic matter content in the impurities ranged from 1.4 to 12.0% (mean:5.4%) on the ice and from 3.2 to 10.6% (mean:6.7%) on the snow surface. Microscopy revealed that impurities in the ice areas mainly consisted of cryoconite granules, which are aggregations of mineral particles, filamentous cyanobacteria and other microbes and organic matter, while those in snow areas consisted of mineral particles and snow algae. Results suggest that the spatial variation in the abundance of impurities is caused by supply of mineral particles both from air and ice, and microbial production of organic matter on the glacier surface.

 

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