Project: Development and application of a high sensitivity, ultra low volume method to measure biomarkers of terrigenous organic matter in the open ocean

NSF Award Abstract:
The distribution and fate of land-derived, or terrigenous, organic matter in the ocean has long been of interest to oceanographers, but that interest has grown considerably as research on the marine and global carbon cycle intensifies. Lignin is a major structural polymer found only in vascular plants, making lignin a unique tracer of terrigenous organic matter input to the marine environment. The current analytical tool for analyzing lignin, breaking it into a suite of identifiable phenolic compounds, is complex, time consuming and requires 10 to 30 liters of water. Given these limitations, applications of lignin phenols as tracers of terrestrial organic carbon in the ocean have been sparse. Through this project, the researchers aim to redesign existing chemical methodology together with modified instrumental detection for even 3 times greater sensitivity using a sample of less than 200 milliliters. Outfitting the scientific community with new methodology to sensitively trace this marker of terrigenous organic carbon will provide a clearer understanding of organic matter fluxes between and within terrestrial and oceanic reservoirs, and potentially establish lignin phenols as a robust oceanographic tracer. This project will support the development of the next generation of scientists, including an early career investigator, and graduate and undergraduate students.

Lignin phenol measurements have been used to study general distribution patterns and mechanisms of decomposition of terrigenous dissolved organic carbon (tDOC) in the global ocean. The distribution pattern of tDOC among ocean basins is generally consistent with the global pattern of riverine discharge to the ocean basins. However, large scale generalizations required and more fully resolved distributions of lignin as a tracer of tDOC are hampered by the difficulties and limitations associated with the present lignin phenol method. The main objectives of this project are to (1) develop methodology for measuring dissolved lignin in ultra-low volumes at high sensitivity in open ocean seawater and (2) apply the new method to study terrigenous tDOC processing and transport in the Eurasian Basin of the Arctic Ocean, where large Siberian rivers deliver the bulk of tDOC to the shelf areas. Results from this research will help evaluate lignin phenols as robust oceanographic tracers, useful to study physical mixing in the Arctic Ocean and potentially improve our understanding of the fate and removal of terrigenous organic carbon in the oceans. Addressing the second objective would provide well-constrained decay constants for lignin and tDOC in the Arctic Ocean and provide novel information on halocline formation. Integration of tDOC budgets, freshwater budgets, and circulation and atmospheric patterns will ultimately improve understanding of biogeochemical cycles in the Arctic Ocean and its role in global climate.