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More Finnish organic carbon is going to the Baltic Sea

Posted December 5, 2019

Rivers are arteries of nature. They deliver nutrients, they irrigate plants and generally are just giant flows of life. However, with climate change they are changing too. Scientists from the University of Helsinki, Aarhus University and the Finnish Environment Institute found that in the past few decades the amount of carbon transported via Finnish rivers to the Baltic Sea has increased substantially.

Organic carbon is disappearing from the Finnish soil, but its concentrations are growing in the rivers. Image credit: Sergey Ashmarin via Wikimedia (CC BY-SA 3.0)

Rivers are always carrying organic carbon – that’s just the nature of the river. That organic carbon is actually extracted from decomposing organic matter, such as plants and animals. However, it is not normal for the amount of carbon to increase so much. Scientists analysed water-quality monitoring data for 30 rivers and a period of 25 years. They found that the Finnish rivers now transport 280,000 tonnes more carbon to the Baltic Sea each year than they did in the early 1990s. This is an increase of almost 50 %.

Antti Räike, one of the authors of the study, commented on the results: “The larger the share of a catchment drained, the more TOC concentrations had increased. The rise in concentrations was approximately 20% in the least drained catchments, whereas it was twice as large in the most drained catchments”.

Increased total organic carbon has been found in pretty much all rivers. Scientists say that this phenomenon can be attributed to climate change. Temperature is rising and there is more precipitation now, which makes it easier for organic carbon to wash out into the rivers. Meanwhile acidity is reducing, which also affects the concentrations of total organic carbon. Finally, land use is also an important factor.

In fact, that is where all the carbon is coming from. The increase of total organic carbon in Finnish rivers coincides with the decreasing contents in Finnish soil. It is possible that some of the carbon was simply washed out into the Baltic Sea.

Increased carbon content in the water is not a good thing. It reduces transparency and less sunlight reaches deeper waters of the Baltic Sea. Also, it increases the risk of hypoxia in bottom waters. Although scientists are not sure what is the end result, this definitely affects the local ecosystems.

This is what scientists are going to focus on now. They want to research carbon transported to coastal waters a little bit more. Also, they want to see what are the effects of it.


Source: University of Helsinki

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