Late twentieth-century warming of the surface of Lake Tanganyika, the largest of the East African rift lakes, is the biggest temperature change in the past 1,500 years, according to a study published online this week in Nature Geoscience. Lake surface warming is linked to declining growth and abundance of the plankton that form the base of the lake’s food chain, which could have negative effects on the region’s fisheries.

Jessica Tierney and colleagues used lake sediment cores to reconstruct temperatures and primary productivity at the surface of Lake Tanganyika. They report a number of temperature fluctuations during the past 1,500 years, but the highest temperatures in their record occurred during the past few decades. In addition, they show that warmer surface temperatures were consistently associated with lower primary productivity, which they attribute to stratification between the lake’s surface and the nutrient-rich waters below.

The team describes the field work that supported these conclusions in an accompanying Backstory.