Melting glaciers in the Arctic are in rapid recession, and microscopic organisms are colonizing the newly exposed landscapes. Dr. James Bradley, Honorary Reader in Arctic Biogeochemistry at the School of Biological and Behavioral Sciences at Queen Mary University of London, and his team, have revealed that yeasts play an important role in soil formation in the Arctic after glaciers have melted.
About 10% of the Earth’s land surface is covered by glacial ice. However, glaciers are retreating further and faster due to global warming. As they do, they reveal new landscapes that have been covered in ice for thousands of years. After the glacial ice disappears, microscopic life forms colonize the now accessible rock, gathering nutrients and forming new soils and ecosystems. Because soils can be a significant carbon store under the right conditions, the question of how exactly new soils form after glaciers melt is a matter of great scientific and social relevance.
To study the formation of Arctic soils, a team led by Dr. Bradley to Spitsbergen – an archipelago of islands about halfway between the North Pole and the north coast of Norway, and well above the Arctic Circle. Here the climate is warming seven times faster than the rest of the world, and the glaciers are shrinking rapidly. The arid landscapes exposed offer very little ability to support any form of life: the rocky terrain is lacking in nutrients, temperatures drop well below freezing for months and due to the high latitude there is a complete lack of sunlight. winter polar night. The very first pioneer settlers of the inhospitable terrain are microorganisms such as bacteria and fungi. These microbes determine how much carbon and nitrogen can be stored in the soil, but very little is known about the exact processes behind this stabilization of nutrients through microbial activity. Bradley and his team studied these soils to better understand how microbes contribute to the process of soil formation when glaciers disappear.
Colonization timeline
The research focuses on the foreland of Midtre Lovénbreen, a retreating valley glacier in the northwest of Spitsbergen. Dr. James Bradley, who first worked at the site in 2013, said: “Ten years ago I was walking on the ice and drilling ice cores into the glacier. When we returned in 2021, the glacier had shrunk and instead of ice there were barren, seemingly lifeless soils.” But from laboratory analyzes of these soils, the researchers found that they contained incredibly diverse communities of microbes, the smallest and simplest life forms on Earth.
The newly exposed areas are ideal for research into incremental changes in soils, as they provide a natural laboratory for observing the different stages of soil development. The soil closer to the glacier edge is the youngest, and the soil further away from the retreating glacier becomes incrementally older – where more time has passed allowing life to colonize the terrain. “These are some of the most pristine, delicate and fragile ecosystems on the planet, and they are rapidly colonized by specialized microbes, even though they are subject to extremes of temperature, light, water and nutrient availability,” said Dr. Bradley.
Adapting to the midnight sun and often changeable weather, the scientists spent weeks working on the rocky and uneven terrain of the glacier area, surrounded by ice crevasses, a fjord home to minke whales and seals, and the tundra shared by arctic foxes, reindeer and polar bears . The researchers are trained to recognize polar bear behavior and safely handle firearms in the event of a bear encounter while working in the remote Arctic environment.
Pioneer fungi fix carbon in the soil
Bradley’s team examined the microbial composition of soil through DNA analysis, while also measuring the cycling and flow of carbon and nitrogen. Through experiments with isotope-labeled amino acids, they were able to accurately monitor microbial assimilation and metabolism of organic carbon. “We were particularly interested in what proportion of carbon microorganisms lock up in the soil as biomass and how much they release back into the atmosphere as carbon dioxide,” says Juan Carlos Trejos-Espeleta, the lead author of the study from Ludwig Maximilian University of Munich. , Germany.
Their main focus was on fungi – a group of microorganisms known to be often better adapted than bacteria to storing and keeping a lot of carbon in the soil. The fungi/bacteria ratio is an important indicator of carbon storage: more fungi means more carbon in the soil, while more bacteria usually means that the soil emits more CO2. “In high Arctic ecosystems, the diversity of fungi is particularly high compared to that of plants, which increases the possibility that fungal communities there could play a key role as ecosystem engineers,” says author Professor William Orsi from the Ludwig Maximilian University of Munich. Germany. Discovering more about the carbon assimilation processes of fungal and bacterial populations and carbon flow processes in the ecosystem is crucial for making accurate predictions about how terrestrial ecosystems in the Arctic will respond to future warming.
And indeed, the researchers were able to demonstrate that fungi – or more precisely, specific basidiomycete yeasts – play a decisive role in the early stabilization of the assimilated carbon. According to the study, they are the fungal pioneers in the young postglacial soils and make a decisive contribution to the enrichment of organic carbon. “We discovered that these specialized fungi are not only able to colonize the rugged Arctic landscapes before any other, more complex life, but that they also provide a foothold for soil development by building a base of organic carbon that can sustain other life can use,” the researchers said. Dr. Bradley. In the elderly, bacteria increasingly dominate amino acid assimilation, leading to a significant reduction in biomass formation and an increase in CO2 emissions from respiration. “Our results show that fungi will play a crucial role in future carbon storage in Arctic soils as glaciers continue to shrink and more of the Earth’s surface becomes covered by soil,” summarizes Prof. Orsi.
The results of the study, which involved other researchers from Germany, the United States and Switzerland, have now been published in the journal Proceedings of the National Academy of Sciences (PNAS). The research was funded by the UK Natural Environment Research Council (NERC), the US National Science Foundation (NSF) and the German National Science Foundation (DFG).
