The long-term impact of magnesium in seawater on foraminiferal mineralogy: Mechanism and consequences
van Dijk, I.; de Nooijer, L.J.; Hart, M.B.; Reichart, G.-J. (2016). The long-term impact of magnesium in seawater on foraminiferal mineralogy: Mechanism and consequences. Global Biogeochem. Cycles 30: 438–446. dx.doi.org/10.1002/2015GB005241
In: Global Biogeochemical Cycles. American Geophysical Union: Washington, DC. ISSN 0886-6236; e-ISSN 1944-9224, meer
Foraminifera are unicellular protists, primarily known for their calcium carbonate shells thatprovide an extensive fossil record. This record, ranging from Cambrian to present shows both major shiftsand gradual changes in the relative occurrence of taxa producing different polymorphs of carbonate. Herewe present evidence for coupling between shifts in calcite- versus aragonite-producing species and periodswith, respectively, low and high seawater Mg/Ca throughout the Phanerozoic. During periods when seawaterMg/Ca is <2 mol/mol, low-Mg calcite-producing species dominate the foraminiferal community. Vice versa,high-Mg calcite- and aragonite-producing species are more abundant during periods with relatively highseawater Mg/Ca. This alteration in dominance of the phase precipitated is due to selective recovery of groupsproducing the favorable polymorph after shifts from calcite to aragonite seas. In addition, relatively highextinction rates of species producing the mineral phase not favored by the seawater Mg/Ca of that time maybe responsible for this alteration. These results imply that the current high seawater Mg/Ca will, in the longterm, favor prevalence of high-Mg and aragonite-producing foraminifera over calcite-producing taxa,possibly shifting the balance toward a community in which calcite production is less dominant
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