Extended calibration of cold-water coral Ba/Ca using multiple genera and co-located measurements of dissolved barium concentration

Abstract

Extended calibration of cold-water coral Ba/Ca using multiple genera and co-located measurements of dissolved barium concentration. Chemge (2018), Abstract Biological productivity and ocean circulation are both important oceanographic variables that control the distribution of dissolved barium in the ocean interior ([Ba] sw ). The ability to accurately reconstruct [Ba] sw will provide key constraints on these processes in the past. The geochemistry of cold-water corals has the potential to unlock paleoceanographic records at spatial and temporal resolutions not available using other sedimentary archives. Previous studies have suggested that the Ba/Ca ratio of coral skeletons is linearly related to [Ba] sw .However, these efforts have used a limited number of species, sparse global seawater databases, or have not explicitly measured the Ba/Ca ratio. Here we investigate the Ba/Ca ratio in a well-constrained set of cold-water scleractinian (aragonitic) corals as a proxy for[Ba] sw , using 58 specimens from 7 coral genera along with co-located measurements of [Ba] sw . We find that traditional chemical cleaning procedures do not significantly affect the Ba/Ca ratio of cold-water coral skeletons, allowing rapid sample throughput. We also determine that intra-sample variation in Ba/Ca ratios can be reduced by using larger sample sizes (e.g. 20 mg). By combining our results with existing data, we find that cold-water coral Ba/Ca is linearly related to [Ba] sw according to the relationship: Ba/Ca µmol/mol = [0.15 ± 0.02] [Ba sw nmol/kg] + [2.5 ± 1.4], (R 2 = 0.7). We observe no species-specific 'vital effects' in cold-water coral Ba/Ca ratios, but site-specific effects could be a factor. Nevertheless, our results highlight the potential of Ba/Ca in cold-water corals to reconstruct biological and physical changes in the ocean interior.

Constraining past environmental changes of cold‐water coral mounds with geochemical proxies in corals and foraminifera

“…This could be shown for foraminiferal calcite (Hönisch et al, 2011) as well as for scleractinian CWC (Anagnostou et al, 2011;Hemsing et al, 2018;. However, Ba/Ca ratios in foraminifera sometimes reveal a strong sample heterogeneity (Hathorne et al, 2009) and exhibit different sensitivities in scleractinian CWCs, which may indicate that other parameters also exert a control on Ba incorporation (Anagnostou et al, 2011;Hemsing et al, 2018) or it may be a location effect (Spooner et al, 2018).…”

Cold-water corals as archives of seawater Zn and Cu isotopes

“…Note that reported Zn concentrations in and around the active hydrothermal vent site of the Reykjanes Ridge range widely from 1.4 to 6 nmol/kg (Lemaitre et al, 2020), while Cu concentrations at this location are poorly defined. Previous work has also found that Ba partitioning in these Icelandic corals is unusual compared to corals from elsewhere in the Atlantic and Southern Ocean, indicating a possible site-specific effect in this location (Hemsing et al, 2018;Spooner et al, 2018). Therefore, the two Icelandic corals are excluded from the description of elemental partitioning that follows.…”

Glacial-aged development of the Tunisian Coral Mound Province controlled by glacio-eustatic oscillations and changes in surface productivity

“…A total of 7, 6 and 1 additional dated corals in cores GM2AA-GC403, GM2AA-GC406 and GM2AA-GC409 were also analysed to acquire Li/ Ca, Mg/Ca and Ba/Ca ratios. These fragments were 10-30 mg in mass to average different structural features largely following the sampling approach of others for Li/Mg and Ba/Ca (Spooner et al, 2018;Stewart et al, 2020;Corbera et al, 2021). With the aim of removing any Fe -Mn crust and visible borings, the coral fragments were mechanically cleaned using a circular saw and ultra-sonicated to detach any loose sediments trapped within the coral skeleton.…”