Abstract
Abstract. Here we present a comprehensive attempt to correlate aragonitic Na∕Ca ratios from Desmophyllum pertusum (formerly known as Lophelia pertusa), Madrepora oculata and a caryophylliid cold-water coral (CWC) species with different seawater parameters such as temperature, salinity and pH. Living CWC specimens were collected from 16 different locations and analyzed for their Na∕Ca ratios using solution-based inductively coupled plasma-optical emission spectrometry (ICP-OES) measurements. The results reveal no apparent correlation with salinity (30.1–40.57 g kg−1) but a significant inverse correlation with temperature (-0.31±0.04 mmolmol-1∘C-1). Other marine aragonitic organisms such as Mytilus edulis (inner aragonitic shell portion) and Porites sp. exhibit similar results highlighting the consistency of the calculated CWC regressions. Corresponding Na∕Mg ratios show a similar temperature sensitivity to Na∕Ca ratios, but the combination of two ratios appears to reduce the impact of vital effects and domain-dependent geochemical variation. The high degree of scatter and elemental heterogeneities between the different skeletal features in both Na∕Ca and Na∕Mg, however, limit the use of these ratios as a proxy and/or make a high number of samples necessary. Additionally, we explore two models to explain the observed temperature sensitivity of Na∕Ca ratios for an open and semi-enclosed calcifying space based on temperature-sensitive Na- and Ca-pumping enzymes and transport proteins that change the composition of the calcifying fluid and consequently the skeletal Na∕Ca ratio.
Highlights
Sodium-to-calcium ratios (Na/Ca) have been proposed as a new tool in paleoceanography to reconstruct seawater salinities
We investigate the impact of different seawater parameters on the incorporation of Na into the aragonitic skeleton of the scleractinian cold-water coral D. pertusum, M. oculata and a caryophylliid species from the Red Sea
Outliers were identified by the average ± 1.5 SD per oceanic region (Norwegian margin, Bay of Biscay– Irish margin, Mediterranean Sea, Red Sea, Gulf of Mexico– Bahamas)
Summary
Sodium-to-calcium ratios (Na/Ca) have been proposed as a new tool in paleoceanography to reconstruct seawater salinities. Cultured benthic and planktonic foraminifera as well as living planktonic foraminifera from the Red Sea showed the potential of calcitic Na/Ca ratios as a salinity proxy (Mezger et al, 2016; Wit et al, 2013). About half of the known scleractinian coral species do not live in tropical, shallow water (< 50 m) but in deeper waters, including deep-sea environments (> 200 m) (Roberts et al, 2009). These deep or cold-water corals lack phototrophic symbionts and, are azooxanthellate.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
