Reproducibility of Ba/Ca variations recorded by northeast Pacific bamboo corals

Abstract

Trace elemental ratios preserved in the calcitic skeleton of bamboo corals have been shown to serve as archives of past ocean conditions. The concentration of dissolved barium (BaSW), a bioactive nutrientlike element, is linked to biogeochemical processes such as the cycling and export of nutrients. Recent work has calibrated bamboo coral Ba/Ca, a new BaSW proxy, using corals spanning the oxygen minimum zone beneath the California Current System. However, it was previously unclear whether Ba/Cacoral records were internally reproducible. Here we investigate the accuracy of using laser ablation inductively coupled plasma mass spectrometry for Ba/Cacoral analyses and test the internal reproducibility of Ba/Ca among replicate radial transects in the calcite of nine bamboo corals collected from the Gulf of Alaska (643–720 m) and the California margin (870–2054 m). Data from replicate Ba/Ca transects were aligned using visible growth bands to account for nonconcentric growth; smoothed data were reproducible within ~4% for eight corals (n = 3 radii/coral). This intracoral reproducibility further validates using bamboo coral Ba/Ca for BaSW reconstructions. Sections of the Ba/Ca records that were potentially influenced by noncarbonate bound Ba phases occurred in regions where elevated Mg/Ca or Pb/Ca and coincided with anomalous regions on photomicrographs. After removing these regions of the records, increased Ba/Cacoral variability was evident in corals between ~800 and 1500 m. These findings support additional proxy validation to understand BaSW variability on interannual timescales, which could lead to new insights into deep sea biogeochemistry over the past several centuries.

Century‐Long Records of Sedimentary Input on a Caribbean Reef From Coral Ba/Ca Ratios

“…Sinclair et al. (1998) observed organic enrichments of Ba/Ca on the outer edges of the coral skeleton, agreeing with our data that displays extreme Ba/Ca peaks at the top of the coral core, coinciding with the discolored tissue layer (Marks et al., 2017) (see Figure S4 in Supporting Information ). These extreme peaks (>1000 μmol/mol) starkly contrast the rest of the data in the cores (∼4–∼20 μmol/mol).…”

“…Using a similar approach to Marks et al. (2017) and Sinclair et al. (2011) to reduce analytical noise, a 40‐point (35 μm window) running mean was applied to coral Ba/Ca as it yielded the greatest reproducibility between repeat line‐transects (Welch's unequal variance paired t ‐test, p > 0.05).…”

“…Using a similar approach to Marks et al (2017) and Sinclair et al (2011) to reduce analytical noise, a 40-point (35 μm window) running mean was applied to coral Ba/Ca as it yielded the greatest reproducibility between repeat line-transects (Welch's unequal variance paired t-test, p > 0.05). For all laser ablation data, values outside of three times the interquartile range were identified as outliers and removed (<0.01% of data).…”

Chasing Interannual Marine Paleovariability

“…By our count, subannually resolved, continuous geochemical records have been generated from upwards of 14 different extant hermatypic coral genera, including Montastrea/Orbicella (Goreau, 1977), Pocillopora (Dunbar & Wellington, 1981), Porites (Schneider & Smith, 1982), Pavona (E. Druffel, 1985), Platygyra (Quinn et al., 1993), Favia (Chakraborty & Ramesh, 1998), Diploastrea (Watanabe et al., 2003), Acropora (Gallup et al., 2006), Diploria/Pseudodiploria (Hetzinger et al., 2006), Siderastrea (Maupin et al., 2008), Isopora (Lemley, 2012), Stylophora (Ross et al., 2019), Turbinaria (Ross et al., 2019), and Cladocora (Spreter et al., 2020). More recent work has also attempted to develop subannual geochemical records from ahermatypic and deep‐sea corals (Montagna et al., 2005; Saenger et al., 2017; Serrato Marks et al., 2017; Thresher et al., 2009). By far, the most popular choice for tropical SST reconstructions has been the stony coral genus, Porites , partly owing to the regular growth patterns of certain species and their ability to form massive structures over several decades to centuries.…”

Octocorals (Alcyonacea and Pennatulacea) from Paleogene deep-water strata in western Washington State, USA

“…Another genus within the Keratoisidinae, Acanella Gray, 1870, also branches from the nodes, and is similar to Isidella , but differs in branching pattern; whether pattern of branching is a stable character that can be used to differentiate genera within the Keratoisidinae is doubtful (e.g., Verrill, 1883; France, 2007; Duenas et al, 2014). Assignment of the fossils from the Pysht Formation to Isidella is somewhat provisional, but Isidella lives and is common in deep parts of the North Pacific Ocean, forms large individual colonies, and can form dense thickets (Etnoyer, 2008; Andrews et al, 2009; Serrato Marks et al, 2017).…”