The connection between Melting glaciers and Carbon emissions

Sampriti Roy, University of Calcutta

When glaciers melt, the water from the glaciers is channelled downstream, thus feeding the rivers and affecting river temperature along with the aquatic invertebrate biodiversity. Today as we gradually lose glaciers around the world due to climate change, the study of the consequences of this loss is the need of the hour. One such recently published study informs us about the effect of climate change on glacier loss and consequently, the global carbon cycle.

Led by the University of Leeds, an international team of researchers has stated for the first time that glacier-fed mountain rivers have higher rates of decomposition of plant material, the latter being one of the most significant processes in the global carbon cycle.

As stated before, water from melting glaciers is channelled downstream into rivers. However, global warming has led to the increasing loss of glaciers resulting in warmer river water temperatures and waters being less prone to the flow of sediment and water. 

 Role of fungi: Fungi are involved in processes that are an important part of global carbon cycling. The process of decomposition has been measured in 57 rivers in 6 countries (Norway, New Zealand, Ecuador, United States, France, and Austria) and according to the lead author of the study, Sarah Fell (from the Leeds’ School of Geography), similar patterns were seen worldwide. 

This is a rather unexpected form of climate feedback, mainly because glacier loss is ultimately responsible for rapid carbon recycling in rivers (warmer water leads to greater fungal growth) before the same is returned to the atmosphere.

The study: To have an understanding of the decreasing glacier cover on fungal biodiversity the team of scientists conducting the study tried to mimic plant materials that naturally accumulate in rivers through the use of canvas fabric used by artists. 

Why a canvas?

The initial idea while designing a simulation study must be to acquire items that have almost the same integrity as the one that we are studying. In this case, the canvas was taken as a test material to and compare decomposition by fungi in the different study areas (rivers) because it is made up of cotton- a substance that is predominantly composed of cellulose. Cellulose is also found in plant leaves that are found accumulating in rivers naturally. Thus, the choice of canvas was made.

The Canvas strips were placed in the rivers in the study for approximately one month, followed by testing how easily they could rip. It was found that the strips were found ripping with greater ease in the mountain rivers due to more aquatic fungi colonization. Aquatic fungal colonization occurs in warmer waters more efficiently. The observation showed that the decomposition of carbon molecules proceeded faster in rivers.

According to Alex Dumbrell of the University of Essex (whose team was responsible for analyzing the fungi from the river samples), the work conducted by the team showed that by measuring a certain gene that could underpin the activity of Cellobiohydrolase I (cbhI), which is a cellulose-degrading enzyme, the decomposition of the cotton strips could be better predicted. This would be by using the information that would be obtained about the fungal species abundance through the activity of cbhl. 

Significance of the study:

• The problem with leaf litter: Glacier loss means water flows in lesser amounts through the rivers. Rivers are also seen as being less prone to changing course as a consequence of Glacier loss and this means that bankside plants, as well as trees, will be more prone to grow in the regions surrounding them. This will lead to more leaf litter being accumulated in the rivers, which is in turn likely to accelerate fungal processing of carbon in the rivers of mountains.

This could have a great effect on carbon cycling and our climate as a whole.

• The method used for studying decomposition is especially important because it potentially opens up new avenues of research to improve carbon cycling predictions.

Also read: Zoonotic illness: Transmission between man and animal

Source: “Fungal decomposition of river organic matter accelerated by decreasing glacier cover” by Sarah C. Fell, Jonathan L. Carrivick, Sophie Cauvy-Fraunié, Verónica Crespo-Pérez, Eran Hood, Kate C. Randall, Kirsty J. Matthews Nicholass, Scott D. Tiegs, Alex J. Dumbrell and Lee E. Brown, 15 March 2021, Nature Climate Change. DOI: http://10.1038/s41558-021-01004-x

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