Calculating Dissolved Marine Oxygen Values Based on an Enhanced Benthic Foraminifera Oxygen Index.

Marine oxygen minimum zones (OMZs) trap greenhouse gases, reduce livable habitats, a critical factor for these changes is the amount of dissolved oxygen (DO). The frequently used tool to reconstruct DO values, the Benthic Foraminifera Oxygen Index (BFOI), showed major shortcomings and lacks effectiveness. Therefore, we enhanced the BFOI and introduce enhanced BFOI (EBFOI) formulas by using all available data benthic foraminifers provide, calculating the whole livable habitat of benthic foraminifers, including bottom water oxygenation (BWO) and pore water oxygenation (PWO). Further, we introduce for the first time a transfer function to convert EBFOI vales directly into DO values, increasing efficiency by up to 38%. All formulas are calibrated on modern samples and applied to fossil datasets. Our new approach provides a major improvement in defining and reconstructing marine oxygen levels and eutrophication, by, providing a new toolset for understanding past changes and tracking actual and predicted future expanding OMZs.