seacarbx is a seacarb extension written in R, which enables to use seacarb (Gattuso et al., 2019) for deep-time carbonate system calculations or for culturing studies carried out in seawater with modified [Mg²⁺] and [Ca²⁺]. For this, the functions carb, K0, K1, K2, Ks, Kw, Kb, Kspa, and Kspc were modfied to account for the effect of seawater [Mg²⁺] and [Ca²⁺] on the dissociation constants of carbonic and boric acid. Their names are based on the original names, and suffixed with a ‘x’. In addition to the modified functions, seacarbx contains MyAMI that are tabulated parameters defining the temperature and salinity dependencies of the conditional equilibrium constants for [Mg²⁺] and [Ca²⁺] in the range 1–60 mM (from Hain et al., 2015, 2018), as well as a function for bilinear interpolation. Please read the manual for more details.

If you use seacarbx for your published research, please cite it as:

Raitzsch, M., Hain, M., Henehan, M, and Gattuso, J.-P. (2021): seacarbx - seacarb extension for deep-time carbonate system calculations, Zenodo, http://doi.org/10.5281/zenodo.4432146.

but please also acknowledge the original works of the following:

Gattuso J.-P., Epitalon J.-M., Lavigne H. and Orr J. (2019): seacarb: seawater carbonate chemistry. R package version 3.2.12. http://CRAN.R-project.org/package=seacarb.

Hain, M. P., Sigman, D. M., Higgins, J. A. and Haug, G. H. (2015): The effects of secular calcium and magnesium concentration changes on the thermodynamics of seawater acid/base chemistry: Implications for Eocene and Cretaceous ocean carbon chemistry and buffering, Glob. Biogeochem. Cyc., 29(5), 517–533, http://doi.org/10.1002/2014GB004986.

Hain, M. P., Sigman, D. M., Higgins, J. A. and Haug, G. H. (2018): Response to Comment by Zeebe and Tyrrell on “The Effects of Secular Calcium and Magnesium Concentration Changes on the Thermodynamics of Seawater Acid/Base Chemistry: Implications for the Eocene and Cretaceous Ocean Carbon Chemistry and Buffering,” Glob. Biogeochem. Cyc., 32(5), 898–901, doi:https://doi.org/10.1002/2018GB005931.

Acknowledgement
Funded by the Deutsche Forschungsgemeinschaft (DFG – German Research Foundation) through a research project (no. RA 2068/4-1) granted to Markus Raitzsch.