Co-evolution of trace elements and life in Precambrian oceans: The pyrite edition

The significance of trace elements in initiating origins and driving evolution of life on Earth is indisputable. Trace element (TE) trends in the oceans through time broadly reflect their availability and allow speculation on all possible influences on early life. A comprehensive sedimentary pyrite-TE database, covering 3000 m.y. of the Precambrian, has improved our understanding of the sequence of bio-essential TE availability in the ocean. This study probed how changing availability (and scarcity) of critical TEs in the marine environment influenced early life. The pyrite-shale matrix TE sequence shows relatively elevated concentrations of Ni, Co, Cu, and Fe, Cr, respectively, in the Archean and Paleoproterozoic. Abundances of these elements in the Archean potentially facilitated their widespread utilization by prokaryotes. The Paleoproterozoic-Mesoproterozoic saw increases in Zn and Mo but a marked decline in Ni, Co, Cu, Se, and Fe. Our data suggest the evolution of the first complex cell in the Paleoproterozoic was probably triggered by this major change in TE composition of the oceans. A decline of elements prompted alternative utilization strategies by organisms as a response to TE deficits in the middle Proterozoic. An overall increase in a multitude of elements (Ni, Co, Cu, Cr, Se, V, Mo, and P) in the Neoproterozoic and Cambrian was highly advantageous to the various micro- and macro-life forms. Without questioning the importance of macronutrients and atmosphere-ocean redox state, multi-TE availability would have induced substantial heterogenous biological responses, owing to the effects of optimal, deficient, toxic, lethal, and survival levels of TEs on life.