Lithium elemental and isotope systematics of modern and cultured brachiopods: Implications for seawater evolution

Lithium has proven a powerful tracer of weathering processes and chemical evolution seawater. Skeletal components marine calcifying organisms, in particular brachiopods, present promising archives Li signatures. However, incorporation mechanisms potential influence from biological or environmental conditions require careful assessment. In order to constrain systematics brachiopod shells, we concentrations isotope compositions for 11 calcitic species collected six different geographic regions, paralleled with data culturing experiments where brachiopods were grown under varying seawater chemistry (pH–pCO2, temperature, Mg/Ca ratio). The recent specimens across temperate polar environments showed broadly consistent ?7Li values ranging 25.2 28.1‰ (with mean 26.9 ± 1.5‰), irrespective taxonomic rank, indicating that isotopes into shells is not strongly affected by vital effects related differences among species. This results ?7Licalcite–seawater (per mil difference 7Li/6Li between calcite shell seawater) ?2.9‰ ?5.8‰ value ?3.6‰), which larger than the calculated based on planktonic foraminifera (~0‰ ~?4‰). range further supported cultured experimentally. Under controlled simulating natural environment, Magellania venosa was ?2.5‰ an increase temperature 10 16 °C. contrast, decrease (or Li/Ca) ratio addition CaCl2 as well elevated pCO2, hence low-pH conditions, resulted increased ?7Licalcite-seawater up ?4.6‰. Collectively, our indicate represent valuable provide envelope robust Li-based reconstruction over Phanerozoic.