Rising temperatures have lowered fish numbers in one of Africa's great lakes, threatening food sources vital to local people.

Credit: Sue Cunningham Photographic/Alamy

Andrew Cohen at the University of Arizona in Tucson and his colleagues analysed sediments and fossils from Lake Tanganyika (pictured) to infer water temperatures and estimate species abundance going back over 1,500 years. They found population declines in fishes, molluscs and plankton that pre-dated commercial fishing, but correlated with sustained warming and falling algal production during the past 150 years.

Warming reduces the mixing of nutrient-rich deeper waters with oxygen-rich shallow waters, limiting the growth of plankton — an important food source for many fishes. Reduced mixing also lowers the area of oxygenated water at the bottom of the lake, threatening numerous fish and invertebrate species.

Proc. Natl Acad. Sci. USA http://doi.org/bnqk (2016)