Assessing the effects of carboxylated amino acids and polysaccharides on the fluid-calcite element partitioning

University Of Hawaii, Honolulu

Investigators

Abstract

Many marine organisms build elaborate skeletons and shells made of carbonate minerals. Organic molecules such as amino acids and carbohydrates play important roles in regulating the structure and texture of these carbonates. Recent studies show that certain amino acids enhance magnesium uptake in carbonates and thereby influence the overall chemical composition. It is likely that these organic molecules influence the uptake of other elements as well, though this idea has not been tested. Using carefully controlled laboratory experiments, this study will investigate the effect of organic molecules on the abundance of several trace elements in carbonates. Trace element compositions of marine biogenic carbonates are widely used as tools ("proxies") to infer the temperature and the chemistry of ancient seawater, though it is known that biological processes also influence the shell chemistry. The outcome of this study will improve the reliability of trace element proxies by providing insights into biological controls on carbonate formation. This should advance our ability to reconstruct the dynamics, biology, and chemistry of the oceans in the past, which is a key to understanding the Earth's climate system. The research outcomes should be also relevant to other areas, such as removal of toxic heavy metals from the environment, engineering of new synthetic materials for industrial purposes, and geological CO2 sequestration. Based on inorganic calcite precipitation experiments using a pH-stat system, the research team will determine if and by how much element/Ca ratios in CaCO3 and precipitation rates depend on the types and concentrations of organic molecules at a constant saturation level. The research team will also address whether such effects are due to modulation of precipitation rates (kinetic effects) or due to direct molecular/ionic interactions by performing additional experiments using a known calcite precipitation inhibitor. This project provides support for an early-career investigator as well as research opportunities for undergraduate students at the University of Hawaii, where the student population has an exceptionally diverse ethnic background.