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In recent years, there has been a growing interest in using archaeological marine mollusc shells as a paleoclimate archive by virtue of their ability to preserve high-resolution paleoclimatic and paleoenvironmental information in multiple biogeochemical proxies. Moreover, valuable information about past environments, human-environmental interactions, and seasonal foraging practices can be obtained via the analysis of marine gastropods from archaeological sites. Rochia nilotica is the most common shell in coral reef ecosystems across the Indo-Pacific Ocean and archaeological shell middens in the Great Barrier Reef (GBR); however, its application as a paleoclimate and paleoenvironment archive to reconstruct the Mid-to-Late Holocene ENSO (El Niño-Southern Oscillation) has not yet been investigated. In this study, we compare temporally successive oxygen isotope and trace element records (δ18O, Mg/Ca, Sr/Ca, and Ba/Ca) in modern R. nilotica shells with instrumental environmental records to test whether we can quantitively reconstruct past environmental parameters. Preliminary results show that modern R. nilotica reliably records environmental factors (e.g. sea surface temperature and salinity) in equilibrium with the surrounding environment at a seasonal scale. These proxies will ultimately be applied to reconstruct localised Mid-to-Late Holocene ENSO records at sub-seasonal scales in the Great Barrier Reef. Results obtained from this ongoing research can be used to compare with climate model simulations to provide a more robust reconstruction of paleo ENSO behavior and offers an opportunity to decipher the long-term shellfish management strategies of Indigenous peoples in the GBR environment to provide a baseline for future marine resource management in the GBR.

Ocean warming is increasing the incidence, scale, and severity of global-scale coral bleaching and mortality, culminating in the third global coral bleaching event that occurred during record marine heatwaves of 2014-2017. While local effects of these events have been widely reported, the global implications remain unknown. Analysis of 15,066 reef surveys during 2014-2017 revealed that 80% of surveyed reefs experienced significant coral bleaching and 35% experienced significant coral mortality. The global extent of significant coral bleaching and mortality was assessed by extrapolating results from reef surveys using comprehensive remote-sensing data of regional heat stress. This model predicted that 51% of the world’s coral reefs suffered significant bleaching and 15% significant mortality, surpassing damage from any prior global bleaching event. These observations demonstrate that global warming’s widespread damage to coral reefs is accelerating and underscores the threat anthropogenic climate change poses for the irreversible transformation of these essential ecosystems.