The Black Sea Is a Goldmine of Ancient Genetic Data

When Woods Hole Oceanographic Institution (WHOI) marine paleoecologist Marco Coolen was mining through vast amounts of genetic data from the Black Sea sediment record, he was amazed about the variety of past plankton species that left behind their genetic makeup (i.e., the plankton paleome).

The semi-isolated Black Sea is highly sensitive to climate driven environmental changes, and the underlying sediments represent high-resolution archives of past continental climate and concurrent hydrologic changes in the basin. The brackish Black Sea is currently receiving salty Mediterranean waters via the narrow Strait of Bosphorus as well as freshwater from rivers and via precipitation.

"However, during glacial sea level lowstands, the marine connection was hindered, and the Black Sea functioned as a giant lake," says WHOI geologist Liviu Giosan. He added that "the dynamics of the environmental changes from the Late Glacial into the Holocene (last 10,000 years) remain a matter of debate, and information on how these changes affected the plankton ecology of the Black Sea is sparse."

Using a combination of advanced ancient DNA techniques and tools to reconstruct the past climate, Coolen, Giosan, and their colleagues have determined how communities of plankton have responded to changes in climate and the influence of humans over the last 11,400 years.

Researchers traditionally reconstruct the make up of plankton by using a microscope to count the fossil skeletons found in sediment cores. But, this method is limited because most plankton leave no fossils, so instead Coolen looked for sedimentary genomic remains of the past inhabitants of the Black Sea water column.