Blackwater rivers crucial in carbon cycle

Published 5:12 am Thursday, June 23, 2016

They may be slow-moving, but that doesn’t mean blackwater rivers aren’t an important part of the carbon cycle, says a Longwood University researcher.

Deep and slow-moving, blackwater rivers drain the forested swamps and wetlands of the southeastern United States and are known for their dark brownish-orange color, derived from the large amount of decomposing plant matter — mostly organic carbon — that washes into them from surrounding land.

A recent study, published in the journal Aquatic Sciences by Longwood biologist Dr. Dina Leech, found that the blackwater Chowan River in North Carolina contributes as much organic carbon to the coastal ocean as much larger non-blackwater rivers, like the Potomac and Susquehanna.

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“More attention should be given to blackwater rivers when calculating how much organic carbon is moving from land to the ocean,” said Leech.

Understanding the movement, or cycling, of carbon among the land, ocean and atmosphere is important because these movements play a major role in regulating climate and the productivity of the earth’s ecosystems.

That’s why scientists pay close attention to where carbon is located on the planet and how much is moving from one place to another.

“Coastal rivers serve as vital conduits that process and transport dissolved organic carbon between two main carbon reservoirs — the land and the ocean,” said Leech.

“Quantifying this exchange of carbon between rivers and the coastal ocean is essential to an accurate understanding of global carbon fluxes between the land, ocean and atmosphere.”

Although blackwater rivers transport a lot of carbon, they have historically been overlooked by researchers because of their relatively small watershed size and slow flow, said Leech, a specialist in the study of inland waters whose research interests include organic carbon.

Leech is not through studying the movement of dissolved organic matter from land to ocean.

For the past three years, she has studied carbon export from streams at the Longwood-managed Hull Springs Farm in Westmoreland County to the nearby Chesapeake Bay.

She also plans to continue her research on carbon dynamics in the Chowan River watershed by focusing on the Meherrin River, which begins in Southside Virginia and joins the Chowan in North Carolina.

Before joining the Longwood faculty, Leech was a research associate for two years.