Glycerol dialkyl glycerol tetraethers (GDGTs) as proxies for paleoceanographic and paleoclimatic changes in the inner shelf of São Sebastião (Southeastern Brazil)

• Grant number: 15/11923-8
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: August 31, 2015
• End date: November 29, 2015
• Field of knowledge: Physical Sciences and Mathematics - Geosciences
• Principal Investigator: Márcia Caruso Bícego
• Grantee: Amanda Mattosinhos Spera
• Supervisor: Gesine Mollenhauer
• Host Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Helmholtz Association, Germany
• Associated to the scholarship: 13/08463-0 - Record of the paleoclimatic and paleoceanographic conditions of the past 2500 years in the region of São Sebastião Island, located in the Southeastern Brazilian Continetal Shelf, through the use of geochemical proxies, BP.DR

Abstract

Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane lipids produced by bacteria and archaea living in both terrestrial and marine ecosystems. These compounds have been extensively used as proxies in paleoclimatologic and paleoceanographic studies. Among the different data obtained from GDGTs, the paleothermometer TEX86 is calculated by using the relative proportion of isoprenoid GDGTs with different cyclopentane rings, which are produced by so called Thaumarchaeota, a group of marine archaea. Culture studies have shown that the number of cyclopentane rings present in the GDGTs is a response to the growth temperature of these microorganisms. In addition to the isoprenoid GDGTs, branched GDGTs are produced by a group of anaerobic soil bacteria, and therefore can be used as a tracer of the contribution of soil organic matter to the sedimentary organic matter. BIT index is the ratio between the terrestrial branched GDGT and the crenarchaeol, a GDGT produced by marine Archaea. Values of this index can be interpreted as an indication of changes in the relative contribution of soil organic matter to the aquatic ecosystems. The present study aims to use glycerol dialkyl glycerol tetraethers as molecular organic markers to assess changes in rainfall patterns and in the sea surface temperature over the past 2500 years in the inner shelf of São Sebastião, Southeastern Brazil. (AU)