Fluctuations of sulfate, S-bearing amino acids and magnesium in a giant clam shell

Abstract

Abstract. We used micro-X-ray fluorescence combined with X-ray photoabsorption spectroscopy to investigate speciation-specific sulfur profiles in the inner shell layer of a giant clam (Hippopus hippopus). The sulfate, S-bearing amino acids, and total sulfur profiles indicated that inorganic sulfate was the dominant component in the shell of this bivalve. Sulfur profiles in the inner shell layer showed clear annual fluctuations that varied by more than one order of magnitude, from < 50 to 1420 ppm, and sulfate and total sulfur maxima became higher with age, whereas no ontogenetic trend was noticeable in the profile of S-bearing amino acids. A change in the carbonate ion concentration in the calcifying fluid would suggest that an ontogenetic increase in the relative activity of sulfate ions to carbonate ions in the calcifying fluid affects sulfate concentrations in the shells. These results suggest that trace sulfur profiles in the shell of the giant clam may reflect both cyclic shell growth related to environmental factors such as insolation and temperature and ontogenetic changes of the calcifying fluid chemistry mediated by physiological processes. The observed S profile implies a clear change in calcifying fluid chemistry towards less alkaline condition with age. Magnesium fluctuations suggested that Mg was incorporated into the shells at high growth rates during warm seasons. The spectrum of Mg K-edge X-ray absorption near edge structure (XANES) and comparison of Mg and S-bearing amino acids profiles indicated that a pronounced effect of the organic fraction or disordered phases were observed in aragonitic shell of H. hippopus rather than regulated substitution into the aragonite crystal lattice.

Carbonate Associated Sulfate Extraction Method Using Weakly Acidic Cation Exchange Resins

“…2014, Yoshimura et al . 2014, van Dijk et al . 2017), and it is presumed that JCp‐1 (modern coral) and JCt‐1 (Holocene giant clam) also contain organic S. JLs‐1 is Mesozoic limestone and contains clastic minerals (e.g., quartz, feldspar) and barite (BaSO 4 ; Aizawa and Akaiwa 1989).…”

“…2008) and S‐bearing amino acids (Yoshimura et al . 2014), and pyrite is also formed diagenetically (Richardson et al . 2019).…”

“…In addition to CAS, S can be incorporated into biogenic and geological carbonates as sulfated polysaccharides (Cuif et al 2008) and S-bearing amino acids (Yoshimura et al 2014), and pyrite is also formed diagenetically (Richardson et al 2019). These contaminants should be removed before measuring CAS contents and S isotope ratios.…”

Ultradian rhythms in shell composition of photosymbiotic and non-photosymbiotic mollusks

“…Similarly, Mg/Ca ratios in tridacnids were previously thought to primarily record water temperature (e.g., Batenburg et al, 2011) but detailed investigation shows here large differences in Mg concentration within tridacnid shells. and a strong anticorrelation of Mg with sulfur compounds associated with the organic matrix in the shell (see section 4.1; Dauphin et al, 2003), has been put forward as evidence for a strong control of calcification and microstructure on Mg composition in tridacnid shells (Yoshimura et al, 2014). However, evidence from studies on foraminifera calcification demonstrate that the sulfur in biocarbonates is not organically bound and that the covariation with Mg might instead be caused by lattice distortion due to incorporation of Mg favoring simultaneous S incorporation (van Dijk et al, 2017).…”

Partitioning and Chemical Environments of Minor Elements in Individual Large Benthic Foraminifera Cultured in Temperature-Controlled Tanks

“…A. kudakajimensis tests were enriched in both S and P. As for the structural SO 4 2− substitution, an increased activity of sulfate ions relative to carbonate ions in the calcifying fluid would have affected sulfate concentrations in the skeletons [the sulfate-carbonate link of Berry (1998) and co-workers]. A growth-related change in the carbonate ion concentration in the calcifying space affects the relative activity of sulfate ions to carbonate ions, which would be recorded as sulfate concentrations in the biogenic carbonates (Yoshimura et al, 2014). The impact of seawater [CO 3…”