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Bren PhD Student Recognized for Work on Carbon Cycling in an Amazon Lake
Conrado Rudorff attends major freshwater lake conference after publishing paper showing Amazon lowland lakes release more carbon than previously thought.

Bren student Conrado Rudorff was one of just ten students from around the world to  participate in the 3rd World Lake Student Meeting, held at Lake Tahoe in late October, and the 14th World Lake Conference, convened in Austin, Texas, several days later. The sequential events were arranged in conjunction with the International Lake Environmental Committee Foundation.


Conrado Rudorff in the Amazon

Rudorff, who is in his fourth year of doctoral study at Bren, was nominated for inclusion by his advisor, Bren professor John Melack, and was invited to participate based on the strength of his c.v. and an abstract he submitted demonstrating his “interest and ideas on the future direction of monitoring and data processing in fresh water systems.”

For his application, Rudorff was able to reference a recently completed paper. Titled “Seasonal and spatial variability of CO2 emission from a large floodplain lake in the lower Amazon” and co-authored by Melack and three others, the article appeared in the Oct. 20, 2011 issue of the Journal of Geophysical Research and was featured Nov. 15 as a "Research Spotlight" in Eos, AGU's weekly newspaper.

Rudorff found that CO2 concentrations in large Amazon lakes vary widely by location, that seasonal changes in mixing patterns affect gas production and emission from the lakes, and, perhaps most importantly, that rates of CO2 release from the lake he studied are at least two to four times the estimates provided by previous regional studies.

“Conrado has applied new models of gas exchange to Amazon lakes and shown that these habitats out-gas more carbon dioxide than previous estimates, which were already high,” says Melack. “This result further emphasizes the importance of inland waters to the global carbon cycle.”

Scientists have for years been working to understand the carbon cycle of the Amazon region and its role in sequestering carbon and releasing it back into the atmosphere.

Studies of floodplain gas cycling have been conducted previously across large regions of seasonally flooded Amazon lowlands; for his work, however, Rudorff focused on a smaller area — a single large floodplain lake in the lower reach of the Amazon River — in order to gain a more refined understanding of gas-exchange rates and the physical and biological processes that affect them.

“In a regional study, you can only do limited sampling for the lakes in the region,” Rudorff says by way of explaining his approach. “But the processes have high spatial and temporal variation. Because we looked at only one large lake, we could look at the variables in more detail.”

The project relied on extensive field measurements of CO2, a meteorological buoy that measured wind and other variables to determine heat fluxes at the surface of the lake, and remote sensing, sonar survey, and gauging station data to map areas of the lake that exist because of seasonal flooding, expanding and contracting as part of that cycle.