Project: Collaborative Research: DOC removal in the ocean according to polymer gel theory

NSF abstract:
Research on carbon cycling in the ocean has received much attention in recent years due to the importance of carbon dynamics in terms of global climate change. A significant portion of the marine carbon reservoir is made up of dissolved organic carbon (DOC), yet much still needs to be learned about the processes controlling its removal (sinks). Especially crucial is identifying how DOC get incorporated into the microbial loop, or the cycling of carbon through biological processes. This project aims to study the creation of microgels from pools of DOC. Microgels are the product of DOC aggregating to form a particle-type of a DOC conglomerate, which makes it more biologically accessible. About 10-30% of the DOC pool is estimated to form these microgels, so a significant segment of the marine carbon cycle will be illuminated more clearly through this research. A vast variety of processes could influence the development of these microgels, so the researchers are including a study of various environmental controls such as temperature and pH. With these parameters and more, the investigators will potentially be able to not only develop and explain the mechanisms of microgel formation, but also the effect which climate change (warming and acidification of the ocean) will have on this process and how that will affect marine biological processes. Additionally, a postdoctoral researcher will be supported through this project, as well as the training of 20 high school teachers, one undergraduate and two high school students. The investigators will develop a high school curriculum that will focus on connecting science to the students' local natural world, which has been shown to improve student learning.

The involvement of dissolved organic carbon (DOC) in the microbial loop is overall still a mystery due to the fact that DOC mechanics are poorly understood. The assembly of microgels from dispersed DOC pools may be a critical factor in studying the bioreactivity of DOC in the open ocean. This project aims to study the formation of DOC polymers in the North Pacific and assess their bioreactivity under a variety of environmental conditions (pH, temperature). Deep North Pacific water contains very low DOC (35 µM) yet has the oldest radiocarbon ages (up to 6000 years old) known in the open oceans, which makes it an ideal test site due to the low bioreactivity end member. The goal of this research is to develop mechanistic models of the aggregation of DOC polymers into microgels under a variety of environmental conditions and potentially use that information to describe the potential climate change effects on these processes.