Nature article published December 5, 2013:
The coastal areas of the world’s oceans, once thought to be a source of atmospheric carbon dioxide, now absorbcarbon, according to a new paper [http://researchnews.osu.edu/archive/coastcarbon.htm] published in the journal Nature.
In a comprehensive review of the latest research into the carbon cycle of coastal regions, a team of researchers, including Thomas S. Bianchi, the Jon L. and Beverly A. Thompson Chair of Geological Sciences at the University of Florida, contends that human activities have transformed the role these systems play in the global carbon budget. Bianchi was responsible for the continental shelves in this paper.
They add, however, that much additional research and monitoring is necessary to calculate just how much these activities are affecting carbon flux from these coastal subsystems.
The coastal ocean consists of rivers, estuaries, tidal wetlands and the continental shelf.
“The effects of climate change, including sea-level rise, will add even more uncertainty over how coastal oceans affect the global carbon cycle,” said Bianchi.
Using the latest available data, the researchers estimate that the coastal ocean absorbs as much as two-thirds more carbon than it emitted during the pre-industrial era. According to their findings, coastal areas released about 150 million metric tons of carbon annually a century ago. Now, these waters absorb about 250 million metric tons of carbon per year.
One major factor is the increased growth of microscopic plants, fed by fertilizer runoff from rivers, which absorb carbon dioxide, carrying it to the ocean floor when the plants die.
Bianchi also emphasized that “the highly variable coastal margins of the world process carbon in different ways which in turn affects how much is buried in coastal sediments and what is lost to the atmosphere in CO2, climate change will affect these processes and we need to better understand how.”
“Humans have changed the rate of these coastal fluxes, but we’re still trying to figure out the extent,” said Peter A. Raymond, a co-author from the Yale School of Forestry and Environmental Studies, whose research was focused on the role of rivers in the global carbon cycle. “This is almost more of a call to arms to figure out that anthropogenic component.”
The lead author of the paper is James E. Bauer, a professor of evolution, ecology and organismal biology at Ohio State University.
“Compared to the open ocean, we know less about the coastal ocean’s carbon cycle even though it’s right in front of us,” Bauer said. “There is an intense need for more research because we don’t currently have the data to know exactly what’s going on everywhere.
“The methods are there now that weren’t available 50 years ago,” he said. “We just have to commit to increasing the number and types of coastal regions being studied.”
In a study published last month [http://news.yale.edu/2013/11/20/carbon-hotspots-rivers-and-streams-leak-more-co2-thought], Raymond reported that the planet’s rivers and streams are leaking more carbon dioxide than previously believed.