Elemental concentrations of waters and bivalves in the fresh to hypersaline Coorong Lagoons, South Australia: Implications for palaeoenvironmental studies. (5th July 2021)

• Record Type: Journal Article
• Authors: Chamberlayne, Briony K.; Tyler, Jonathan J.; Gillanders, Bronwyn M.
• Is Part Of: Estuarine, coastal and shelf science. Volume 255(2021)
• Publication Date: 2021-07-05
• Subjects: Arthritica helmsi -- Bivalve -- Trace element -- Proxy -- Coorong lagoon; Estuarine oceanography -- Periodicals; Coasts -- Periodicals; Estuarine biology -- Periodicals; Seashore biology -- Periodicals; Coasts; Estuarine biology; Estuarine oceanography; Seashore biology; Periodicals; 551.461805
• DOI: 10.1016/j.ecss.2021.107354
• Languages: English
• ISSNs: 0272-7714

Abstract

Abstract: Element-to-calcium ratios of bivalve shells are potentially useful proxies for environmental change, provided the relationship between the environmental variable and element ratio are calibrated using modern specimens. In this study we investigate the utility of trace elemental ratios in the estuarine micromollusc Arthritica helmsi as (palaeo)environmental proxies. Sr/Ca, Mg/Ca and Ba/Ca ratios were measured in waters (n = 137) and live bivalves (n = 125) were collected along a salinity gradient from fresh to hypersaline in the Coorong Lagoon and Lake Alexandrina, at the terminus of the Murray River, South Australia. Water Mg, Sr and Ca exhibited linear relationships with salinity, while Ba showed no relationship. Mg/Ca and Sr/Ca in water both showed positive logarithmic responses to increasing salinity, while the response of Ba/Ca was best explained by a negative power function. The Sr concentration and Sr/Ca of water collected between 2016 and 2018 were elevated compared to a previous study conducted between 2007 and 2008, possibly due to a higher river flow regime in the more recent period. The range of Sr/Ca, Mg/Ca and Ba/Ca measured in A. helmsi were in agreement with previous studies, as were the range of partition coefficients. However, the incorporation of Sr/Ca, Mg/Ca and Ba/Ca did not correlate with water elemental ratios, temperature, salinity or pH and are therefore likely to be more heavily influenced by biological processes. As a consequence, while the elemental composition of other carbonate fossils within the Coorong system may hold potential to reconstruct past climate and environmental change, the trace element geochemistry of A. helmsi aragonite shells, and possibly other similar micro-bivalve molluscs, should be treated with caution as a palaeoenvironmental tracer. Highlights: Mg/Ca in the Coorong Lagoon waters were stable in comparison to previous studies. Sr/Ca and Ba/Ca in the Coorong Lagoon waters were influenced by changes in hydrological regime. Elemental incorporation into Arthritica helmsi was not controlled by temperature, salinity or water element ratios. Element ratios and element partitioning in Arthritica helmsi were in good agreement with previous studies.