δ<sup>11</sup>B as monitor of calcification site pH in marine calcifying organisms

Abstract

Abstract. The isotope composition of boron (B) in marine biogenic carbonates has been predominantly studied as a proxy 15 for monitoring past changes in seawater pH and carbonate chemistry. In order to derive seawater pH from boron isotope ratio data, a number of assumptions related to chemical kinetics and themodynamic isotope exchange reactions are necessary. Furthermore, the boron isotope composition (

Atmospheric CO2 estimates for the last 17 million years based on foraminiferal δ11B at Ocean Drilling Program Sites 806 and 807 in the Western Equatorial Pacific

“…coral (NEP). The boron isotopic composition of JCP-1 211 was measured at 24.06 ± 0.20‰ (2 SD, n=6) within error of published values of 24.37 ± 0.32‰, 24.11± 0.43‰ and 24.42 ± 0.28‰ from Holcomb et al (2015), Farmer et al (2016 and Sutton et al (2018), respectively. Average values are δ 11 BNEP = 25.72 ± 0.79‰ (2 SD, n=31) determined over 13 different analytical sessions, with each number representing a separately processed sample from this study.…”

Regulation of calcification site pH is a polyphyletic but not always governing response to ocean acidification

“…Boron isotopic compositions of the coralline red algae, pencil urchins, purple urchins, temperate corals, and serpulid worms were measured on a Thermo Finnigan Neptune MC-ICPMS (multicollector-inductively coupled plasma mass spectrometer) at Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), France, following the method from Sutton et al (19).…”

Calibration of the pH-δ11B and temperature-Mg/Li proxies in the long-lived high-latitude crustose coralline red alga Clathromorphum compactum via controlled laboratory experiments

“…Many species of calcium carbonate precipitating organisms elevate their calcifying fluid pH (pH cf ) to promote calcification, as revealed by pH-microelectrode, pH-sensitive dyes, and/or boron isotope studies (Al-Horani et al, 2003;Anagnostou et al, 2012;Holcomb et al, 2014;Krief et al, 2010;McCulloch et al, 2012;Ries, 2011;Sutton et al, 2018;Venn et al, 2011;Venn et al, 2013). Therefore, to estimate pH sw from skeletal δ 11 B (δ 11 B cc ) of coralline algal calcite, which prior studies suggest occurs primarily as borate ion, (Cornwall et al, 2017;Donald et al, 2017), species-specific relationships must be empirically defined between seawater δ 11 B borate and δ 11 B cc .…”

“…compactum, the elevated δ 11 B of the coralline algal skeleton relative to that expected from the δ 11 B borate -pH sw relationship suggests that pH within the alga's zone of calcification is higher than pH of the surrounding seawater (shown as pH cf vs. pH sw in Figure 4a and ΔpH and Δ[H + ] in Figure 4b). This could promote calcification in a manner similar to foraminifera (De Nooijer et al, 2014), corals (Al-Horani et al, 2003;Holcomb et al, 2014;Krief et al, 2010;McCulloch et al, 2012;Venn et al, 2011), and other species of marine calcifiers (Sutton et al, 2018).…”