Climate change makes Lake Tanganyika warmest in over a century

Lake Tanganyika, the second-oldest and second-deepest lake in the world, has recorded unprecedented high temperatures during the last 100 years.

Situated in East Africa, the lake's surface waters are the warmest on record, according to geologists.

This will inevitably affect fish stock and consequently, human life amounting to 10 million, around the area.

Up to 200,000 tons of sardines and four other fish species are harvested annually from Lake Tanganyika.

"This result is in addition to those from other African lakes showing that changes in regional climate have a significant impact on the lakes, and on the human populations that depend on the lakes' resources," said Paul Filmer, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

Core samples from the lakebed that laid out a 1,500-year history of the lake's surface temperature showed that 26 degrees Celsius (78.8 F), last measured in 2003, is the warmest the lake has been for a millennium and a half.

"Our data show a consistent relationship between lake surface temperature and productivity such as that of fish stocks," said Jessica Tierney of Brown University, the paper's lead author. "As the lake gets warmer, we expect productivity to decline, and we expect that it will affect the fishing industry."

The lake holds a complete ecosystem that faces danger currently. It depends on wind to churn its waters and send nutrients from the depths toward the surface. These nutrients are food for algae, which supports the lake's entire food web.

But increasing temperatures have prevented the mixing of waters - causing fewer nutrients to be funneled from the depths to the surface.

Although some researchers say that overfishing may be a reason for stock depletion, they note that warming of the lake is exacerbating the fish stocks' decline.

The study is published in this week's on-line issue of the journal Nature Geoscience.