Roundup: Oxygen Isotope, Non-biting Midges and Prokaryotes

Holocene Atmospheric Circulation in the Central North Pacific

From ScienceDirect: “The North Pacific is a zone of cyclogenesis [the development of an area of low pressure in the atmosphere, resulting in the formation of a cyclone] that modulates synoptic-scale atmospheric circulation. We present the first Holocene oxygen isotope record (δ18Odiatom) from the Aleutian Islands supported by diatom assemblage analysis. Our results demonstrate distinct shifts in the prevailing trajectory of storm systems that drove spatially heterogeneous patterns of moisture delivery and climate across the region.”

Read more about the new Holocene oxygen isotope record from the Aleutian Islands here.

A satellite picture of the Aleutian Island Range
Aerial view of the Aleutian Islands amidst the clouds (Source: NASA).


The Enigma of Survival Strategies in Glacial Stream Environments

From Freshwater Biology: “Glacier retreat is a key component of environmental change in alpine environments, leading to significant changes in glacier-fed rivers. The species compositions of Diamesinae and Orthocladiinae (of the non-biting midges family) are diverse and strongly affected by the changing habitat conditions upon glacier retreat. Here, we show that Diamesinae have extremely flexible feeding strategies that explain their abundance, high body-mass and predominance in glacier-fed streams.”

Discover more about the insects that live within the glacier-fed streams here.

A winter-emerging midge (Source: Flickr).


Phylogenetic Diversity of Prokaryotes on Lewis Glacier in Mount Kenya

From African Journal of Microbiology Research: “The seasonal snowpack of the temperate glaciers are sources of diverse microbial inoculi. However, the microbial ecology of the tropical glacial surfaces is endangered, hence posing an extinction threat to some populations of some microbes due to rapid loss of the glacier mass. The aim of this study was to isolate and phylogenetically characterise the prokaryotes from the seasonal snow of Lewis glacier in Mt. Kenya. Analyzing snow samples, the results confirm that the seasonal tropical snowpack of Lewis glacier is dominated by the general terrestrial prokaryotes (e.g. Bacillus with 53%) and a few glacier and snow specialist species (e.g. Cryobacterium with 5.9%).”

Find out more about these cellular organisms living on the surface of a Mount Kenya glacier here.

Cryobacterium (Source: Reddy et al.).


How Life Arrives on Glacier Barrens

The crust that forms on the top layer of the soil that is exposed after a glacier retreats is a rich, important place and can support new plant growth in a tough alpine environment.

Salix arctica
Salix arctica (Credit: Arctic Flora of Canada and Alaska)

A study published in the Canadian Journal of Biology suggests that biological soil crusts can help larger plants grow and colonize the area, a process called succession. The authors, Katie Breen  and Esther Lévesque of the University of Québec (Trois-Rivières), found that the land covered by biological crusts after a glacier retreats usually supports more plants than places that aren’t covered by soil crusts. The most dominant and thriving plant species can usually be found there, like Salix arctica, a tiny low shrub that grows in Arctic regions.

In the middle of the 19th century, after the end of the Little Ice Age, temperatures increased, which led to a decrease in the mass of glaciers in the Canadian High Arctic. As glaciers retreated, microorganisms and plants had new opportunities to colonize the surface that appeared. The primary colonization of the barren terrestrial environment usually starts on the microbial scale, which is an often-overlooked fact in vegetation studies. The first to move in are the pioneering organisms, such as green algae, lichens, mosses, fungi and heterotrophic bacteria.

Biological soil crusts
Biological soil crusts (Credit:INNSPUB)

As time goes by, the pioneering organisms in the soil can form a solid yet flexible layer no more than 1 cm deep close to the upper layer surface, called the biological or microbiotic soil crust. The microbiota nurtured in the biological soil are very resilient and can survive the most extreme living conditions on earth, such as glacial ice. However, it’s harder for larger plants to grow in the High Arctic; they favor habitats with higher soil temperature, lower wind speed, higher soil moisture content, and increased soil nitrate level.

Luckily, biological soil crusts can provide higher plants with all the necessary growing conditions. Cyanobacteria, a type of bacteria, are able to fix nitrogen in soil crusts and improve nutrients levels in soil; some crusts have a gluey composition, which helps the soil retain moisture and protect it from erosion by wind and water. The rougher surface created by soil crusts is able to absorb more sunlight and thus increase temperature. The process of plants helping each other grow is called facilitation.

Dryas integrifolia
Dryas integrifolia (Credit:Flickriver)

In the early stage of succession, soil crusts are comparatively thin. Within four years of glacier retreat, the plant densities above the crusts are low. Nevertheless, as time goes by, the crusts help the plants grow and the variety of plants increases. Surprisingly, the researchers discovered that a few specific species benefit the most from soil crusts than other species. Those species are represented in much higher densities than the others and account for more of the land cover, such as Dryas integrifolia, a tiny shrub in the rose family. Dominant and long-lived species also seem to do especially well in the crust environment.

According to the authors, as global temperature continues to grow, more glaciers are going to melt in the future and continue to make impacts on the development of communities left in the wake of glaciers. This trend may potentially influence the direction of succession. The study refers to this process as the “greening of the north.”