Robert Spencer sampling the Yukon River at the Yupik village of Pilot Station, Alaska, during the peak of spring thaw. Credit: Courtesy of Robert Spencer, Florida State University
Key points:
- A study of plants and small organisms in Arctic rivers better defines how carbon cycles through watersheds.
- This study highlights the abundance of life and amount of organic material being exported in these rivers.
- In fact, organisms in the Arctic’s major rivers are a crucial contributor to carbon export, accounting for about 40 to 60 percent of the particulate organic matter—much more than previously thought.
The cycling of carbon through the Earth’s environment is essential to life, and many plants and animals use this important element for cellular growth. It can be stored in rocks and minerals or in the ocean.
In a new study led by Florida State University, researchers studied plants and small organisms in Arctic rivers to better understand how carbon cycles through watersheds. Their research, published in Proceedings of the National Academy of Sciences, shows that organisms in the Arctic’s major rivers are a crucial contributor to carbon export, accounting for about 40 to 60 percent of the particulate organic matter.
“When people thought about these major Arctic rivers and many other rivers globally, they tended to think of them as sewers of the land, exporting the waste materials from primary production and decomposition on land” said Rob Spencer, a professor in the Department of Earth, Ocean and Atmospheric Science. “This study highlights that there’s a lot of life in these rivers themselves and that a lot of the organic material that is exported is coming from production in the rivers.”
The researchers collected data from six major rivers flowing in the Arctic Ocean: The Yukon and Mackenzie in North America, and the Ob’, Yenisey, Lena and Kolyma in Russia. Spanning almost a decade, the team used the data to build models that used the stable and radioactive isotope signatures of carbon and the carbon-to-nitrogen ratios of the particulate organic matter to determine the contribution of possible sources to each river’s chemistry.
Particulate organic matter is created differently and varies depending on whether it gets washed downstream or is produced within a river. The latter carbon is more likely to stay floating in the ocean, be eaten by organisms and eventually breathed out as carbon dioxide.
That means a small increase in a river’s biomass could be equivalent to a larger increase in organic material coming from the land.
“This study found something new in the way that these big Arctic rivers work and how they export carbon to the ocean,” said Spencer. “We have to understand the modern carbon cycle if we're really going to begin to understand and predict how it's going to change. This is really relevant for the Arctic at the rate that it's warming and due to the vast carbon stores that it holds.”