Carbonate mineralogy in Brazilian reefs and estimate of modern potential production of MgCO3 in coralline algae and dolomite contribution to the reefs

• Grant number: 14/22889-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2014
• End date: November 30, 2015
• Field of knowledge: Physical Sciences and Mathematics - Oceanography - Geological Oceanography
• Principal Investigator: Paulo César Fonseca Giannini
• Grantee: Ana Elisa Almeida Ayres
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The stability of the reefs structures depends on the preservation of coralline algae skeleton post mortem, since coralline algae binds the reef surface together. There are concerns about coralline algae with the ocean acidification phenomenon, because their skeleton has a high content of magnesium calcite, a mineral very susceptible to dissolution with the decline of the pH in the oceans. However, recently it was discovered other carbonate minerals in crustose coralline algae (CCA), such as dolomite and magnesite. There is a mystery about the apparent absence of dolomite in modern reefs while it was abundant in ancient fossil, phenomenon named as the "Dolomite Problem". This project aims to reanalyze and reinterpret data from previous studies for estimate the global potential magnesium carbonate production by CCA and dolomite contribution to the reefs. Also mineralogical analysis (X-ray Diffraction (XRD), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES)) in CCA from Brazilian reefs samples will be done for the first time. It is important to study the carbonate mineralogy of CCA for understanding how it can change under ocean acidification conditions, provide insights to the physical stability of coral reefs and scientific contributions to solve the Dolomite Problem.