Succes of foraminiferal calcification mechanisms depend on ocean chemistry

Abstract:

Although the relationship between Phanerozoic changes in seawater Mg/Ca and the evolutionary history of many marine calcifyers has been analyzed, the response of foraminifera to changes in Mg/Ca_sw is only sparsely investigated. Geological longevity, areal distribution and importance in the global carbon cycle, however, make foraminifera particularly suitable to study the interplay between seawater chemistry and biogenic mineralogy. We assess global foraminifera abundances in the geological record from fossil species occurrences in the Paleobiology DataBase (PaleoDB; www.paleodb.org). Here, we present an analysis of the distribution of major groups of foraminifera through the Phanerozoic by comparing dominance of taxa producing aragonite or (low- and high-Mg) calcite in relation to changes in Mg/Ca_sw and mass marine extinction events (P/T, T/J and K/Pg). This allows relating the effect of ocean chemistry to the relative success of foraminifera with different calcification strategies. We show for the first time that the success of foraminifera with different calcification mechanisms (i.e. aragonite versus calcite producers) is governed by Mg/Ca_sw, potentially making foraminifera with unfavored mineralogy more vulnerable to major environmental perturbations. Furthermore, we suggest that planktic foraminifera, which are currently calcifying in a period with unfavorable sea water chemistry, might be more sensitive to on-going ocean acidification and associated environmental perturbations than currently assumed.