Lake Tanganyika's surface waters are currently warmer than at any time in the previous 1,500 years, a University of Arizona researcher and his colleagues report online in Nature Geoscience.
The rise in temperature during the 20th century is driving a decline in the productivity of the lake, which hosts the second-largest inland fishery in Africa.
"People throughout south-central Africa depend on the fish from Lake Tanganyika as a crucial source of protein," said study co-author Andrew S. Cohen, a UA professor of geosciences. "This resource is likely threatened by the lake's unprecedented warming since the late 19th century and the associated loss of lake productivity."
This is the first detailed record of temperature and its impacts on a tropical African ecosystem that allows scientists to compare the last 100 years with the previous 1,400 years, Cohen said.
The team attributes the lake's increased temperature and the decreased productivity during the 20th century to human-caused global warming.
"We've got a global phenomenon driving something local that has a huge potential impact on the people that live in the region and on the animals that live in the lake," he said.
The annual catch of the Lake Tanganyika fishery is estimated at about 198,000 tons per year, more than 20 times greater than the U.S. commercial fishery in the Great Lakes, he said. The nations of Burundi, Tanzania, Zambia and the Democratic Republic of Congo border the lake, which is the longest lake in the world and the second deepest.
The surface waters of Lake Tanganyika are the most biologically productive part of the lake. For the 1,400 years before 1900, those waters were no warmer than 75.7 F (24.3 degrees C). Since 1900, the lake's surface waters warmed 3 degrees F, reaching 78.8 degrees F (26 degrees C) in 2003, the date of the researchers' last measurement.
The researchers used sediment cores from th
|Contact: Mari N. Jensen|
University of Arizona