EU-funded researchers are reconstructing how the chemical composition of the world’s sea water evolved, using brachiopod shells. Their findings should advance understanding of recent changes to our climate.

The chemical composition of ocean water reflects the balance between the Earth’s crust, surface water and atmosphere. Data on sea-water composition has previously provided researchers with important insights into the evolution of life, land-ocean interaction, ecosystem adaptation to climate change, and ocean trace-metal cycling, to name but a few phenomena.

Reconstructing the evolution of sea water over time can shed light on current biological, geological and chemical (bio-geochemical) cycles and their impact on the Earth’s climate. But the chemical conditions in ancient sea water can no longer be measured directly. Instead, scientists need to reconstruct these conditions using trace element measurements and isotopes acting as chemical indicators, or proxies. For this study, they will use brachiopods, which are marine invertebrates comprised of lamp shells.

The BASE-LiNE Earth project is looking into the trace elements and isotope time series depicted in brachiopod shells. Reliable data on the ratios of elements and isotopoes stored in fossil shells will help the team decode the information stored in the shells, which dates back millions of years. BASE-LiNE Earth will then use this information to reconstruct sea-water composition throughout the Phanerozoic period, i.e. the 541 million years since the Earth’s surface became populated with animals and plants, and hard-shelled animals first appeared.

Brachiopods were chosen because of their presence in geological records, the stability of their calcite shells, and their potential for preserving primary chemical signals. BASE-LiNE Earth will also use them to test new archives, proxies and analytical methods to better characterise ocean evolution.

By painting a clearer picture of the chemical composition of our oceans over the Phanerozoic period, BASE-LiNE Earth hopes to shed light on a number of important current Earth cycles – such as carbon cycles – and their impact, past and present, on our climate.

Source: EC Research & Innovation