Advances in giant clam (Tridacnidae spp.) sclerochronology and sclerochemistry as a high-resolution palaeoenvironmental archive

Abstract

Reconstructions of Quaternary environmental change using high-resolution proxies are important for testing and refining climate models to enable better adaptations to current and future global changes. Giant clams (Tridacnidae spp.), the largest bivalve mollusc in the Indo-Pacific region, comprise important palaeoenvironmental archives, being characterised by a long lifespan, rapid growth rate, and wide distribution habitat, and possessing shells that preserve a high-resolution growth pattern and stable geochemical composition. In this paper, we review all sclerochronology studies of giant clams published between 1986 and 2023. These studies show that isotopic and trace elements proxies, including δ18O, δ13C, Sr/Ca, Mg/Ca, Ba/Ca, and Fe/Ca, can reliably reconstruct palaeoclimate records including sea surface temperature, dissolved inorganic carbon, insolation, extreme weather events and primary productivity at ultra-high resolution. These proxies have been successfully employed for palaeoclimatic and palaeoenvironmental reconstructions from the Miocene to the present across a range of shallow marine areas including southern Japan, northern Australia and the Red Sea. These studies have shed light on changes in interannual climate cycles, climate variation, and human migrations over thousands to millions of years. They have generated quantitative records that are valuable for testing and refining numerical climate models, understanding the relationship between past climate cycles and future climate variability, and providing insights into human-environment interactions over time. This review paper also addresses some of the challenges of employing Tridacnidae proxy analysis, and we provide recommendations for future research. Specifically, we highlight gaps in our understanding of the influence of microstructure on the shell, age dating of fossil samples, uncertainty in proxies, the need for tank experiments, and access to ultra-high resolution palaeoenvironmental records.