Climate Change Results to Microbial Awakening in Arctic Ecosystems; Food Webs Get Restructured As Fungi Become Primary Energy Source

Alaska experiences some of the fastest rates of global warming, more than any other place in the world. This vast high-latitude region spanning 113 million acres (457,295 square kilometers) has warmed its interior by 4-7 degrees Fahrenheit (2.2 - 3.9 degrees Celsius) over the last century.

As the permafrost in Alaska thaws, it releases large amounts of carbon dioxide into the atmosphere and triggers a significant decay process.

Climate Change Hotspot

The accelerating decomposition of permafrost soils can infuse above- and below-ground food webs with carbon, altering the energy flow and affecting the species that rely on these systems. This phenomenon was explored by scientists from the USDA Forest Service in collaboration with experts from the University of New Mexico and the University of Texas.

Led by research wildlife biologist Philip Manlick, the team focused on four Arctic and boreal forest animals like the tundra vole. Their findings are discussed in the paper "Climate warming restructures food webs and carbon flow in high-latitude ecosystems."

The core of the study involves the analysis of carbon isotope "fingerprints" in essential amino acids produced exclusively by plants, bacteria, and fungi. They serve as biomarkers that enable scientists to trace the movement of carbon between "green" plant-supported and "brown" microbe-driven food webs.

By understanding the movement of energy through food webs, experts can understand how ecosystems function and how animals respond to stressors such as climate change. In high-latitude ecosystems, climate change results in melting permafrost and flourishing microbes. However, very little is known about the impact of this phenomenon on food webs and the animals that rely on them.

Manlick and his team analyzed bone collagen from specimens of tundra and red-backed voles and masked shrews from the Bonanza Creek Experimental Forest. These samples represent animals who were exposed to long-term global warming. Meanwhile, Arctic wolf spiders near Toolik Lake were sampled to study the effects of short-term climate warming on animals.

Based on isotope analyses, the researchers detected significant changes in carbon assimilation in mammals as they shifted from plant-based to fungal-based food webs. This means that fungi replaced plants as the main source of energy.

Shifting Diet From Microbial Awakening

Small mammals, such as shrews, have been shown to assimilate up to 90% of their total carbon intake from fungal carbon. On the other hand, Arctic wolf spiders assimilate over 50% brown carbon under warming conditions.

The researchers suspect that brown carbon is transferred to above-ground consumers, like mammals and spiders, in predation events called trophic pathways. Increased global warming results in increased decomposition in permafrost in tundra and boreal forest. The decomposing plant matter is consumed by fungi, which, in turn, are eaten by arthropods, mites, and earthworms. Finally, the fungal carbon is transferred upward in the food web as the voles, spiders, and shrews consume the small animals.

According to Manlick, the shifts in these interactions can indirectly affect nutrient cycling and ecosystem function. For instance, if voles get more energy from below-ground sources, they would consume fewer plants, which could increase carbon storage in above-ground ecosystems.

Check out more news and information on Food Web in Science Times.