An Illinois State University scholar said climate change is raising the water temperature of a 10-million-year-old lake in East Africa.
ISU Professor of Geography-Geology Catherine O'Reilly has been studying Lake Tanganyika for 15 years. O'Reilly hopes that a buoy measuring temperatures in the lake will help gauge climate change effects and allow people in the region to adjust to a changing ecology. O'Reilly said rising temperatures are reducing wind speeds and accelerating temperature increases in the lake. Fisheries are being threatened.
"There is increased pressure from human society to extract fish from this resource and at the same time the lake itself is able to provide fewer and fewer fish. Because it is such a large lake and it is bordered by four different countries, fisheries management is very challenging," said O'Reilly.
Lake Tanganyika is very big and very deep. It is about the size of Lake Superior. Because it is a tropical lake, O'Reilly said, winds help create underwater turbulence, mixing the warmer upper layers with colder deeper water. Without as much wind, there is less turbulence, and the surface layers heat more. With more heat in that layer, the sharper the thermocline, or temperature barrier between layers, said O'Reilly.
O'Reilly said this project will also help determine fish-growth rates and the number of fish being caught. She said when local fishermen know lake conditions, they can catch more fish and know when to fish and when not to. The buoy will be operational at the end of the year, streaming temperature data on the internet. And yes, O'Reilly said, there's an app for that.
"Because these fishermen are very smart and already have an intuitive sense of what kinds of conditions are good for fishing and what are bad, we're hoping that we can learn from them about the decisions they make and how that connects and relates to the actual conditions on the lake," said O'Reilly.
O'Reilly says fishermen in that area historically have earned two or three times what workers outside the fishery make and the lake provides 40 to 50% of the protein consumed by the surrounding countries. Fish from Lake Tanganyika in the middle of Africa, she says, even go to market in Dar Es Salaam on the Indian Ocean.
O'Reilly said this will help scientists understand a changing ecology and help fishermen manage their crop without crashing the fish population, by deciding when not to fish based on changing growth rates and fertility linked to temperature changes.
A grant from a Danish government development agency is paying for the temperature monitoring and streaming buoy on the lake. It will be the first such device on any African Lake. The data will eventually go into GLEON, the Global Lake Ecological Observatory Network.
A team of Tanzanian scientists and graduate students is also working with the data.
