title: Biogenic fish-gut calcium carbonate is a stable amorphous phase in the gilt-head seabream, Sparus aurata.
abstract: The main source of calcium carbonate (CaCO₃) in the ocean comes from the shells of calcifying planktonic organisms, but substantial amounts of CaCO₃ are also produced in fish intestines. The precipitation of CaCO₃ assists fish in intestinal water absorption and aids in whole body Ca²⁺ homeostasis. Here we report that the product formed in the intestinal lumen of the gilt-head seabream, Sparus aurata, is an amorphous calcium carbonate (ACC) phase. With FTIR spectroscopy and SEM imaging, our study shows that the fish-derived carbonates from S. aurata are maintained as a stable amorphous phase throughout the intestinal tract. Moreover, intestinal deposits contained up to 54 mol% Mg²⁺, the highest concentration yet reported in biogenic ACC. Mg is most likely responsible for stabilizing this inherently unstable mineral. The fish carbonates also displayed initial rapid dissolution when exposed to seawater, exhibiting a significant increase in carbonate concentration.
authors.affiliation: Interuniversity Institute for Marine Sciences, Eilat 88103, Israel Israel. ellieraeforan@gmail.com
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Foran
authors.forename: Steve
authors.initials: S
authors.lastname: Weiner
authors.forename: Maoz
authors.initials: M
authors.lastname: Fine
mesh_terms: D000818:Animals; D002119:Calcium Carbonate / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism*; D044367:Phase Transition; D021541:Sea Bream / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D002119:Calcium Carbonate