Elements Magazine Past Issues

Marine calcium carbonate biominerals, especially the shells and skeletons produced by molluscs, corals, and the immeasurably numerous calcifying phytoplankton and zooplankton, are of both societal and environmental importance for two key reasons. Firstly, the mineralised remains of these organisms are one of the largest long­term sinks of carbon on Earth’s surface. Secondly, and perhaps more practically, the (trace) element and isotopic composition of these biominerals probably represents the most widely applied tool for quantitatively reconstructing past environmental conditions on timescales from days to millions of years. It has been known for some time that the processes of biomineralisation imprint on these ‘proxy’ systems, shifting their behaviour away from thermodynamic equilibrium, such that they typically require empirical calibration to an environmental variable of interest. The generally poor understanding of the physics and chemistry of these biomineralisation processes therefore introduces uncertainty both into our palaeo­ reconstructions and provides significant limits to our ability to accurately predict the future response of the marine carbon cycle to anthropogenic ocean acidification. However, it has recently become apparent that this biological imprint also offers a unique opportunity—skeletal and shell geochemical information can be leveraged to constrain various aspects of physiology including the biomineralisation process to non­invasively understand the organisms themselves. In this issue of Elements, a series of articles showcase how low­temperature proxy systems can offer insights into both paleoenvironmental change, as well as the mechanistic processes involved in biomineral formation. Ultimately, our aim is to highlight how the two fields could be more closely connected via research into the controls on biomineral chemistry.