首页|Potassium incorporation and isotope fractionation in cultured scleractinian corals
Potassium incorporation and isotope fractionation in cultured scleractinian corals
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NSTL
Elsevier
Potassium (K) participates in coral biological activities and accumulates in their skeletons, driving the fractionation of stable K isotopes (K-41/K-39). Constraining the influences of biotic and abiotic controls on K isotope fractionation is important for interpreting coral records. However, the processes and mechanisms regulating K incorporation into coral skeletons and K isotope fractionation between seawater and coral skeletons remain unknown. Here, we combined isotopic and synchrotron-based spectroscopic analyses to evaluate the phase distribution and corresponding isotope variation of K in the skeleton of scleractinian (Porites australiensis) corals at a seawater temperature range from 20 to 29 degrees C in aquaria culture experiments. Potassium in coral skeletons exists mainly as organic-K (K hosted in soluble and insoluble organic matrices) and carbonate-K (K incorporated into K2CO3 and aragonite) phases of various proportions. Coral delta K-41 values vary substantially in both direction and magnitude from the modern seawater delta K-41 composition (similar to 0.12 parts per thousand), showing marked deviations ( delta K-41(Coral-Sea)) from -2.00 to 0.67 parts per thousand. As seawater temperature increases, the organic-K fraction increases, whereas delta K-41(Coral) decreases. The variation in delta K-41(Coral) reflects the relative proportions of organic-bound K to carbonate-associated K. In most cases, coral intracrystalline organic matrices preferentially sequester isotopically lighter K whereas carbonate phases prefer heavier K. Distinguishable inter-colony difference in skeletal delta K-41 of corals growing under the same culturing conditions reveals the influence of physiological controls on K partitioning and isotope fractionation. Although calcification rate correlates with temperature to different degrees in the studied corals, likely reflecting control of the difference in zooxanthellae density, we infer that calcification rate is not a major controlling factor on skeletal delta K-41. Rather, skeletal delta K-41 correlates closely with K phase partitioning, which is ascribed to temperature-sensitive physiological modulation (c) 2022 Elsevier B.V. All rights reserved.
NSTL
Elsevier
