A silicon depleted North Atlantic since the Palaeogene: Evidence from sponge and radiolarian silicon isotopes

A Review of the Stable Isotope Bio-geochemistry of the Global Silicon Cycle and Its Associated Trace Elements

“…This includes short time scales such as anthropogenic impacts (not only on Si, but also on other nutrients e.g., N, P, Fe) and possibly to an extent large enough to impact wholeocean isotopic signatures on the timescale of Quaternary glacial cycles. Thus, the sensitivity of biogeochemical Si cycling to anthropogenic pressure, especially in coastal regions, will likely be highlighted in the future (Laruelle et al, 2009;Bernard et al, 2010) and the continental Si cycle should not be neglected when interpreting pre-Quaternary long-term δ 30 Si bSiO2 records from marine sediment records (Egan et al, 2013;Fontorbe et al, 2016).…”

Biosilicification Drives a Decline of Dissolved Si in the Oceans through Geologic Time

“…Recently, Fontorbe et al (2016) used δ 30 Si from sponge spicules and radiolarian tests to derive the first long term empirical reconstruction of ocean DSi concentrations in the North Atlantic during the Paleocene and Eocene. Using a calibrated relationship between spicule δ 30 Si and sponge Si isotope fractionation (Wille et al, 2010;Hendry and Robinson, 2012), they show that from 60 to 30 Ma DSi concentrations in the North Atlantic were consistently low, meaning that the transition to a low DSi ocean had to have begun prior to the Early Cenozoic ( Figure 4A).…”

Competition between Silicifiers and Non-silicifiers in the Past and Present Ocean and Its Evolutionary Impacts

“…Recent studies have robustly demonstrated the presence of very low oceanic silicic acid concentrations since at least 60 Ma, most likely as a result of the drawdown of silicic acid by diatom biomineralization (Fontorbe et al, 2016, which is tens of millions of years before the time period envisioned by Siever (1991) and others. Conley et al (2017) have hypothesized that if such a global decrease in oceanic silicic acid concentrations Sims et al, 2006;Fontorbe et al, 2016Fontorbe et al, , 2017 Diatoms and sponges Post-Mesozoic decline of certain sponge spicule morphologies Maldonado et al, 1999 Diatoms and radiolarians; Diatoms and silicoflagellates Silicificaton and shell-thickness/spine morphology, decline of radiolarians in the low latitudes throughout the Cenozoic (reason still debated) Lazarus et al, 2009;van Tol et al, 2012;Cermeño et al, 2015 Ecology in modern oceans…”

“…Fossil sampling and isotopic analyses of new sediment records have modified our view of the geological history of silicon biogeochemistry (Fontorbe et al, 2016). The massive increase in large-scale sequencing data has greatly aided research into the molecular biology of silica biomineralization, both through whole-genome sequencing within groups like diatoms and plants, and via transcriptome sequencing of new and previously poorly researched siliceous taxa (Keeling et al, 2014;Beisser et al, 2017;Caron et al, 2017;Tirichine et al, 2017).…”