Geochemical Proxies in Coral Ecosystems

Coral skeletons incorporate a variety of trace elements and isotopes that reflect ambient seawater composition and environmental conditions at the time of calcification. These geochemical proxies include element‐to‐calcium ratios such as Sr/Ca and Ba/Ca, and stable isotopes of oxygen and carbon, which can be resolved at sub‐annual to centennial scales. By analysing these signatures, researchers reconstruct past sea surface temperatures, rainfall patterns, riverine sediment and nutrient flux, oceanographic events, and anthropogenic impacts. High‐resolution techniques such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and luminescence scanning enable detailed records from massive and branching coral species across diverse reef settings. This approach has shed light on the intensification of hydroclimatic extremes under global warming, the legacy of seismic‐driven uplift and land development, and the influence of industrial pollutants and heavy metals. Integrating multi‐proxy data from coral archives informs models of climate variability, reef resilience and coastal management strategies worldwide.

Research from Nature Portfolio

Recent studies have extended coral rainfall reconstructions in the Great Barrier Reef back to the mid‐eighteenth century by calibrating multiple skeletal proxies against instrumental records. This work reveals a ten per cent increase in wet‐season precipitation and a doubling in its variability since 1750, linked to strengthening Pacific temperature anomalies under warming. In a separate investigation, time-series measurements of Mn/Ca, Y/Ca and Ba/Ca in Porites corals affected by coseismic uplift following a major earthquake in Indonesia demonstrate how reef geochemistry responds to altered sediment delivery and hydrographic regimes. Elevated Mn/Ca and Y/Ca ratios at uplifted sites reflect increased suspended sediment flux, while lagoonal corals record additional influences of phytoplankton blooms and wind-driven resuspension, illustrating the dynamic adaptation of reef communities to episodic vertical displacement.

Geochemical Proxies in Coral Ecosystems publication trend

The graph below shows the total number of articles in geochemical proxies in coral ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Geochemical proxy: A chemical signature preserved in coral skeletons that reflects environmental conditions such as temperature, salinity or sediment flux at the time of deposition.

Ba/Ca ratio: The barium-to-calcium ratio in coral skeletons, commonly used as an indicator of terrestrial sediment or nutrient input from river discharge.

Sr/Ca ratio: The strontium-to-calcium ratio in coral skeletons, often employed as a proxy for past sea surface temperature variations.

LA-ICP-MS: Laser ablation inductively coupled plasma mass spectrometry, a high-resolution analytical technique for measuring trace element concentrations in solid samples.

Partition coefficient (D): The ratio of an element’s concentration in coral aragonite to its concentration in ambient seawater, indicating uptake efficiency and proxy calibration.

References

1. Rainfall variability increased with warming in northern Queensland, Australia, over the past 280 years. Communications Earth & Environment (2024).
2. Coral geochemical response to uplift in the aftermath of the 2005 Nias–Simeulue earthquake. Scientific Reports (2024).
3. Century‐Long Records of Sedimentary Input on a Caribbean Reef From Coral Ba/Ca Ratios. Paleoceanography and Paleoclimatology (2024).
4. Incorporation of Dissolved Heavy Metals Into the Skeleton of Porites Corals Based on Multi‐Element Culturing Experiments. Geochemistry Geophysics Geosystems (2024).