Articles | Volume 11, issue 23
https://doi.org/10.5194/bg-11-7077-2014
https://doi.org/10.5194/bg-11-7077-2014
Research article
 | 
12 Dec 2014
Research article |  | 12 Dec 2014

I/Ca ratios in benthic foraminifera from the Peruvian oxygen minimum zone: analytical methodology and evaluation as a proxy for redox conditions

N. Glock, V. Liebetrau, and A. Eisenhauer

Abstract. In this study, we explore the correlation of I/Ca ratios in three calcitic and one aragonitic foraminiferal species. I/Ca ratios are evaluated as possible proxies for changes in ambient redox conditions across the Peruvian oxygen minimum zone to the ambient oxygen concentrations in the habitat of the foraminiferal species studied. Cleaning and measurement methods for the determination of I/Ca ratios are tested. All species show a positive trend in their I/Ca ratios as a function of higher oxygen concentrations. The most promising species appears to be Uvigerina striata, which shows a highly statistically significant correlation between I/Ca ratios and bottom water (BW) oxygenation (I/Ca = 0.032(±0.004) × [O2]BW + 0.29(±0.03), R2 = 0.61, F = 75, P < 0.0001). Only for the aragonitic species Hoeglundina elegans is this relationship not significant. The iodine volatility in acidic solutions, the species dependency of I/Ca–[O2]BW correlations, and the individual variability of single tests, need to be accounted for when applying the I/Ca ratio as a proxy for redox conditions.

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Short summary
Our study explores the correlation of I/Ca ratios in four benthic foraminiferal species (three calcitic, one aragonitic) from the Peruvian OMZ with bottom water oxygenation ([O2]BW), and evaluates foraminiferal I/Ca ratios as a possible redox proxy. All species have a positive trend in the I/Ca ratios as a function of [O2]BW. Only for the aragonitic species Hoeglundina elegans is this trend not significant. The highest significance has been found for Uvigerina striata.
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