Extreme strontium concentrations reveal specific biomineralization pathways in certain coccolithophores with implications for the Sr/Ca paleoproductivity proxy.

The formation of the coccolith biominerals by a group of marine algae (the Coccolithophores) offers fascinating research avenues both from the biological and geological sides. It is surprising how biomineralisation by a key phytoplanktonic group remains underconstrained, yet is influential on ocean alkalinity and responsible for the built up of our paleoclimatic archive over the last 200 Myrs. Here, we report two close relative coccolith taxa exhibiting substantial bioaccumulation of strontium: Scyphosphaera and Pontosphaera grown in the laboratory or retrieved from Pliocene sediments.

Fossil evidence for serpentinization fluids fueling chemosynthetic assemblages.

Among the deep-sea hydrothermal vent sites discovered in the past 30 years, Lost City on the Mid-Atlantic Ridge (MAR) is remarkable both for its alkaline fluids derived from mantle rock serpentinization and the spectacular seafloor carbonate chimneys precipitated from these fluids. Despite high concentrations of reduced chemicals in the fluids, this unique example of a serpentinite-hosted hydrothermal system currently lacks chemosynthetic assemblages dominated by large animals typical of high-temperature vent sites. Here we report abundant specimens of chemosymbiotic mussels, associated with gastropods and chemosymbiotic clams, in approximately 100 kyr old Lost City-like carbonates from the MAR close to the Rainbow site (36 °N).