Abstract
Because reef-dwelling large benthic foraminifera (LBF) tests, which is composed of high-magnesium calcite, are the common components of modern reef sediments, and ancient reef carbonate rocks, they can provide a continuous record of the paleoenvironment of reef sediments. Evaluation of the responses of the minor element concentrations (Mg, Sr, Na, P, and S) of individual tests to ambient temperature and LBF growth modes was conducted with two cultured species, Calcarina gaudichaudii and Amphisorus kudakajimensis. The elements were assessed as tracers of temperature, salinity, nutrient concentration, and calcification rate. The Mg content of C. gaudichaudii and the Sr content of both species were controlled by temperature. It can be confirmed that the Mg of individual tests of C. gaudichaudii is a useful paleothermometer. There was a large biological modulation of Na, P, and S incorporation. In-situ XANES analysis revealed that both inorganic and organic species contributed to the P and S content of LBF tests. We observed five sulfur components with variable oxidation states.
Highlights
The reconstruction of paleoenvironmental conditions is fundamental to understanding the mechanisms of climate change
Mg concentrations of both species fell within similar concentration ranges, those of A. kudakajimensis did not show a linear relationship with temperature; at 25◦C, the Mg concentration of AMP-25-12 was an outlier
Mg concentration in C. gaudichaudii increased with length but not with test weight, and neither test weight nor length show significant difference with Mg concentrations in A. kudakajimensis (Figure 1)
Summary
The reconstruction of paleoenvironmental conditions is fundamental to understanding the mechanisms of climate change. In tropical and sub-tropical oceans, long-lived clacifiers such as massive corals and giant clams are geologically important producers of biominerals that provide high-resolution records of environmental conditions for up to hundreds of years (e.g., Gagan et al, 2000). Because LBF tests are common components of modern reef sediments and ancient reef carbonate rocks, they can provide a continuous record of paleoenvironmental changes in reef sediments, such as the Quaternary coral-reef sequences recovered by the Integrated Ocean Drilling Program Expedition 310 and 325 (Fujita et al, 2010; Yokoyama et al, 2011). Environmental proxies of high-Mg calcite LBF tests have the potential to provide continuous paleoceanographic records during climatically important periods such as the Paleogene (Evans et al, 2013). Temperature-dependent Mg incorporation is clearly apparent in cultured LBFs (Evans et al, 2013; Maeda et al, 2017), but not in LBFs collected from actual reef beds (Raja et al, 2007)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
