| Abstract: | Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (Ωc). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and Ωc=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10−4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10−4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates. |
| Genre: | Article |
| ProdID: | 70042984 |
| Citation Author: | Michael M Reddy |
| Citation Contributing Office: | Branch of Regional Research CR |
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| Citation Day: | 1 |
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| Citation End Page: | 154 |
| Citation Issue: | 1 |
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| Citation Language: | English |
| Citation Larger Work Title: | Journal of Crystal Growth |
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| Citation Month: | 8 |
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| Citation Publisher: | Elsevier |
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| Citation Search Results Text: | Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation; 2012; Article; Journal; Journal of Crystal Growth; Michael M Reddy |
| Citation Start Page: | 151 |
| Citation Volume: | 352 |
| Citation Year: | 2012 |
| Type: | citation/reference |
| Text: | Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation; 2012; Article; Journal; Journal of Crystal Growth; Michael M Reddy |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1016/j.jcrysgro.2011.12.069 |
| Date Other: | Sat, 1 Sep 2012 00:00 -0500 |
| Publisher: | Elsevier |
