Potential imprint of Spörer and Maunder solar minima on coral skeleton carbon isotopes
Abstract. Despite being routinely measured with δ18O in corals, records of δ13C are seldom presented in paleoceanographic studies. Numerous factors influence the biologically-mediated fractionation of carbon isotopes during skeletogenesis, resulting in a complex behaviour of this tracer. Here we present a long coral δ13C series, dating back to 1475, and showing the potential impact of solar activity. We note a significant decrease of δ13C during the Spörer and Maunder minima. We argue for a change in metabolical processes, from an autotrophical pattern to a more heterotrophical mode of feeding guided by change in sun irradiation. In addition, nearby volcanic eruptions might also have an impact and cause δ13C shifts, depending on the dust load associated with the eruption. Following previous work, we advocate the systematic presentation of δ13C vs. δ18O plots in coral studies to identify whether isotopic fractionation might have been affected by change in mode of feeding.