Implications of dietary carbon incorporation in fish carbonates for the global carbon cycle

• Published in: The Science of the total environment 2024-03, Vol.916, p.169895-169895, Article 169895
• Main Authors: Oehlert, Amanda M., Garza, Jazmin, Nixon, Sandy, Frank, LeeAnn, Folkerts, Erik J., Stieglitz, John D., Lu, Chaojin, Heuer, Rachael M., Benetti, Daniel D., del Campo, Javier, Gomez, Fabian A., Grosell, Martin
• Format: Article
• Language: English
• Subjects: Biological pump; Carbonate pump; Global carbon cycle; Marine fish; Osmoregulation; Stable carbon isotope ratios
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.169895

Marine bony fish are important participants in Earth's carbon cycle through their contributions to the biological pump and the marine inorganic carbon cycle. However, uncertainties in the composition and magnitude of fish contributions preclude their integration into fully coupled carbon-climate models. Here, we consider recent upwards revisions to global fish biomass estimates (2.7–9.5×) and provide new stable carbon isotope measurements that show marine fish are prodigious producers of carbonate with unique composition. Assuming the median increase (4.17×) in fish biomass estimates is linearly reflected in fish carbonate (ichthyocarbonate) production rate, marine fish are estimated to produce between 1.43 and 3.99 Pg CaCO3 yr−1, but potentially as much as 9.03 Pg CaCO3 yr−1. Thus, marine fish carbonate production is equivalent to or potentially higher than contributions by coccolithophores or pelagic foraminifera. New stable carbon isotope analyses indicate that a significant proportion of ichthyocarbonate is derived from dietary carbon, rather than seawater dissolved inorganic carbon. Using a statistical mixing model to derive source contributions, we estimate ichthyocarbonate contains up to 81 % dietary carbon, with average compositions of 28–56 %, standing in contrast to contents