Yawei Luo is a sixth year graduate student in the Brown-MBL Joint Graduate Program. He is co-advised by Dr. Hugh Ducklow at the MBL’s Ecosystems Center and Dr. Warren Prell at Brown University. His major scientific interest is ecosystem modeling and microbial ecology of the open ocean.
The world ocean has already absorbed a large amount of anthropogenic CO2 emitted by the fossil-fuel burning and the recent land-use change, and Yawei thinks that microbes may be playing important roles in the CO2 sequestration process. Here is how Yawei explains the phenomenon of CO2 sequestration in the ocean.
The primary production of marine ecosystems converts CO2 into organic matter at the ocean surface. Part of the organic matter synthesized is exported into the lower water column, where the organic matter is respired back to CO2. This process, called the biological pump, maintains a low partial pressure of CO2 at the surface ocean so that CO2 can continuously be pumped from the atmosphere into the ocean. Through this process, the marine ecosystems help reduce the atmospheric CO2 level and may cool down our warming planet. Yawei believes that heterotrophic bacteria, bacteria that consume organic matter synthesized by primary producers for energy production, are one of the key components controlling the biological pump. He thinks that about one half of the organic carbon produced by primary production is degraded by the heterotrophic bacteria and availability of a large amount of inorganic nutrients required for primary production depends on the recycling of organic matter by this degradation process.
As a graduate student in-residence at MBL, Yawei investigates the role of the heterotrophic bacteria in the ocean ecosystem and their impacts on the carbon cycle using mathematical modeling. Mathematical modeling is an essential tool in oceanography. Unlike terrestrial ecological studies, it is very difficult to operate observatories in the remote open ocean. In the past decades, oceanographers have generated enormous amount of field observation data. However, opportunities for such field observations are still very limited, compared to those in other types of ecosystems. Yawei says, “a modeling study can fill the gap when and where the observations are unavailable and can even predict the future.” He is currently optimizing his model at the Arabian Sea, Equatorial Pacific, and North Pacific Subtropical Gyre, and his initial results shows that the heterotrophic bacteria may be more important in marine ecosystems than what people normally think.
Article prepared by Yawei Luo and Yuko Hasegawa