Seeking Constraints on Open Ocean Biocalcification

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Coccolithophores and foraminifera, single-celled mineralising plankton, convert atmospheric CO2 into limestone. Together, they produce over 2 billion tonnes of calcite/year. Anthropogenic change creates myriad threats to the future of marine calcifiers, the foundation of the ocean ecosystem and global carbon cycle. Much work has focussed on the impact of acidification and declining carbonate saturation state on calcifier mineralisation. But the modern ocean is four times supersaturated with respect to calcite. Hence SCOOBi asks: What limits modern marine calcification rates? How will they respond to future change? All modern marine carbonate producers are solar-powered and rely directly on photosynthesis. To understand how calcification rates are limited, it is necessary to discover how the environment controls the flow of energy from photosynthesis to calcification. Controls on calcification rates have been elusive until now. Experimental manipulations of calcifiers test only immediate physiological responses. Palaeomethods suffer from preservational artefact, including dissolution of ¾ of all calcite produced. For the first time, a unique merger of cutting-edge approaches allows the calcification efficiency of species, and calcite production rates of communities, to be reconstructed from the geological record. Using an ambitious and high risk-high reward combination of genetics, (palaeo)metabolomics, (palaeo)physiology, and stable isotope geochemistry, SCOOBi will document and build a mechanistic understanding of pelagic calcification rates and transform our ability to predict their response to environmental change. It uses the natural laboratory of sediments to reveal how environmental factors select for calcification efficiency, which can be validated experimentally. SCOOBi will test the controversial hypothesis that pelagic calcification is limited by carbon and phosphate availability in the modern ocean, and pelagic calcifiers will flourish into the future.