Calcium Phosphate Mineralization as a Nexus of Geosphere–Biosphere interactions

Abstract

There is arguably no more direct example of the dynamic relationship between the geosphere and the biosphere than the element phosphorus. Originally sourced from the rocky material of Earth, phosphorus enters the biosphere as the highly charged phosphate ion that is incorporated into every cell of every organism, and eventually returns to the geosphere in sedimentary phosphate rock. Although both igneous and sedimentary phosphate rock is mined for use in fertilizers, mineable phosphate rock is not evenly distributed across the Earth which imbues this vital resource with global economic significance and makes it an important issue in international relations, with wide-ranging implications for global human population growth trends. Phosphorus-related research is conducted in a wide variety of fields, including the medical and dental sciences, environmental and agricultural sciences, wastewater treatment technology, geology and mining. Indeed, there are many angles from which to explore the function and importance of phosphorus. In this thesis, I focus on some of the aspects of the phosphorus-related interplay between the geosphere and the biosphere through both 1) the ancient rock record, through analysis and interpretation of ~2 billion year old phosphate rock carrying an imprint of the biologically influenced cycling of phosphorus and 2) the modern, through laboratory experiments designed to elucidate details of the nucleation and precipitation of solid calcium-phosphate minerals in proximity with biological material. My work in the rock record carries significance for our understanding of the co-evolution of a relatively young, only recently oxygenated Earth and coeval life as it evolved to adapt to this changing environment. In addressing challenges inherent in determining bona fide biogenicity of putative microfossils, this work is also relevant to the field of micropaleontology. Finally, I offer a newly developed apparatus and protocol for use in the experimental examination of mineral precipitation over time and in the context of polymeric matrices such as those implicated in both biologically directed mineralization and biologically influenced precipitation of calcium-phosphate minerals and their precursors.