Plankton living in the Mediterranean Sea some 2000 years ago have helped researchers to uncover a correlation between climate change and the spread of disease in ancient Roman Italy and into the early Middle Ages.
Using a sediment core recovered from the Gulf of Taranto, in the arch of Italy’s boot, Karin Zonneveld of the University of Bremen in Germany and colleagues reconstructed the regional climate from 200 BCE to 600 CE. The sediment record reveals that periods of rapid cooling and drying in the heart of the Roman Empire align with documented major disease outbreaks, the researchers report in a new study.
The core’s plankton fossils are from dinoflagellate cysts, also known as dinocysts. Dinoflagellates bloom in late summer and early fall, with thousands of species that thrive under varying surface temperatures and nutrient levels. By comparing the ratios of dinocyst species that flourish in warmer waters with those that flourish in cooler waters, researchers can precisely estimate historical temperatures. Dinocysts also respond to the water’s changing nutrient levels, which are controlled by precipitation. Rain and snowfall over the Italian Peninsula are channeled by rivers into the Adriatic Sea, where currents carry the nutrient-enhanced water southward around Italy’s heel and into the gulf.
Gerard Versteegh and Karin Zonneveld, coauthors of the new study on climate change and pandemics, process a sediment core from the Gulf of Taranto. (Courtesy of Karin Zonneveld.)
The core was recovered from a location with a rather high deposition rate, with 1 cm of sediment deposited roughly every 10 years (compared with about 1 cm/1000 yr in the open Mediterranean Sea)…
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