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Shallow Lakes

Project Description

Luke Nolby, Ann Goding, and Adrian Montes with a hydrolab covered in purple sulfur bacteria that had been deployed in a lake that was anoxic.

There is worldwide concern over increasing concentrations of carbon dioxide in the atmosphere and its influence on global climate. Managing atmospheric concentrations of carbon dioxide in the air requires understanding how ecosystems process carbon, and identifying systems that potentially store carbon for long periods of time. Carbon dynamics of the ocean are critical to atmospheric carbon remediation, but recent work has suggested that storage of carbon in freshwater systems can also be important to the global carbon cycle. Organic carbon deposited in sediments is a mechanism for removing CO2 from the atmosphere for thousands of years. Therefore, understanding the controls of carbon storage in lake and wetland sediments represents a potential regulatory mechanism for increasing atmospheric carbon removal through management practices. This project assesses the role of shallow lakes and wetlands in the global carbon cycle to determine if they can be managed to store carbon in sediments more efficiently.

Shallow lakes are dominated by either algae or submerged aquatic plants; this study tests the hypothesis that shallow lakes dominated by submerged plants store more carbon in sediments than do lakes dominated by algae. It is hypothesized that submerged plants facilitate higher carbon storage because they are more resistant to decomposition relative to algae, and they also slow decomposition of sediments by reducing sediment resuspension and oxygen concentrations. These hypotheses are being tested using both modern day measurements and records from lake sediment cores to estimate carbon storage rates over scales of years to centuries. Modern-day measurements involve both comparative and experimental approaches, including observations as lakes are manipulated to shift from algae to submerged-plant dominance.

Many shallow lakes and wetlands are already heavily managed for various goals, but not necessarily for carbon removal. This project will increase fundamental knowledge regarding sources and controls of carbon storage in these systems, and determine whether shallow lakes can be managed to increase uptake and storage of atmospheric carbon dioxide.