While many people see the carbon cycle as vertical, with CO2 moving up and down between soil, plants and the atmosphere, new research has shown that water moves large amounts of carbon laterally through ecosystems. The findings have implications for climate change and water quality.
Carbon in the environment – specifically dissolved organic carbon (DOC) – influences many of our planet’s fundamental processes, including water chemistry, greenhouse gas emissions and pollutant transport across land and water.
It is typically seen as moving vertically, but new research from Michigan State University has now shown how water moves massive amounts of carbon laterally through ecosystems – especially during floods.
The findings, which analyzed more than 1,000 watersheds covering about 75 per cent of the contiguous USA, have implications for climate change and water quality.
“When water flows through ecosystems, it picks up organic carbon from plants and soils, and in many cases, water determines whether the ecosystem is a net carbon source or sink,” explained study lead author Jay Zarnetske in a statement.
“The massive amount of carbon that leaks out of ecosystems as DOC is about as big as the net amount of carbon taken up from the atmosphere each year. So accurate accounting is crucial when managing the ‘carbon bank account.’”
The scientists found that rather than diluting DOC, floods readily flush carbon from landscapes in diverse ecosystems – a behaviour that was primarily related to the acreage of wetlands in a watershed, according to the statement. Wetlands act as buffers or storage zones for DOC in watersheds. If floodwaters rise, water and DOC in the wetlands closest to the river can rapidly spill over.
“Wetlands are major controls for carbon balance and water quality, and they’re also some of the most vulnerable landscapes,” commented Zarnetske. “If you move them, you’re changing a region’s plumbing and the chemistry.”
For the research, the scientists used data collected over decades by state and federal government agencies.
Photo credit: Leonie/ CC BY-NC 2.0