Application of 3-hydroxy fatty acids and GDGTs as seawater temperature proxy in sediment samples from southeast Brazillian slope region (Santos Bifurcation)

• Grant number: 25/18590-6
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: March 15, 2026
• End date: March 14, 2027
• Field of knowledge: Physical Sciences and Mathematics - Oceanography - Chemical Oceanography
• Principal Investigator: Márcia Caruso Bícego
• Grantee: Cristian Taboada Timoszczuk
• Supervisor: Yi Yang
• Host Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: China University Of Geosciences, China
• Associated to the scholarship: 23/17753-3 - Paleoceanographic variations in the Santos Bifurcation: molecular organic markers as indicators of seawater temperature and organic matter input, BP.DR

Abstract

The study of marine biomarkes as proxies for sea surface temperature (SST) is constantly evolving and novel proxies are continually being developed and implemented, enhancing multiproxy paleo studies and deeping the knwoledge about past ocean conditions. Traditional SST proxies, which include alkenones, GDGTs and diols, are widely used and well established as sea surface and sub-surface temperature proxies. Gram-negative bacterial 3-hydroxy fatty acids (3-OH-FAs) were recently revealed as a new potential paleoclimate proxy. The ratio of anteiso to normal 3-OH-FAs with 13 carbons (RAN13) as well as the ratio combining normal, iso and anteiso 3-OH-FAs with 12 to 14 carbons (RANs), has shown good correlation with SST values, while the ratio of anteiso to iso C15 isomers (RAI15) correlated well with bottom water temperatures (BWT). This proposal aims to implement and evaluate the application of 3-OH-FAs as a sea temperature proxy in sediment samples from the southeast Brazilian slope. This novel proxy has never been evaluated in the South Atlantic region, and possess a great potential to understand changes not only in SST, but possibly in BWT. Along with 3-OH-FAs, samples will also be analyzed for GDGTs. For this, sediment from a core sampled in the southeast Brazillian margin will be analyzed in the State Key Laboratory of Geomicrobiology and Environmental Changes in the China University of Geosciences. These results will complement the multiproxy approach with the SST data already obtained from alkenones and diols, enhancing the discussion of these results and possibly bringing new insights from temperatures deeper in the water column.