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Study shows how climate impacts food webs, poses socioeconomic threat in Eastern Africa

Study shows how climate impacts food webs, poses socioeconomic threat in Eastern Africa
The research team spent 12 days on Lake Tanganyika collecting core samples from the lake’s floor. They chartered a Congolese merchant vessel, seen here, and adapted it for their research project. Credit: Michael McGlue, University of Kentucky

A new study is sounding the alarm on the impact climate change could have on one of the world’s most vulnerable regions.

Michael McGlue, Pioneer Natural Resources Professor of Stratigraphy in the University of Kentucky Department of Earth and Environmental Sciences, and his team conducted the study at Lake Tanganyika—a major African fishery. The results, which published today in Science Advances, show how certain changes in climate may place the fishery at risk, potentially diminishing food resources for millions of people in this area of eastern Africa.

“Lake Tanganyika’s fish are a critically important resource for impoverished people from four nations (Tanzania, Democratic Republic of the Congo, Burundi and Zambia) and resilience to environmental change in that region is quite low,” McGlue said. “Our study revealed that high frequency variability in climate can lead to major disruptions in how the lake’s food web functions.”

Small pelagic fish, known locally as dagaa, are abundant in Lake Tanganyika, and their conservation is pivotal to the food security and economy of rapidly growing and largely impoverished segments of these four nations.

Dagaa feed on algae and plankton, which means greater algae production in the lake results in more fish. How this aquatic food web responds to external forces, like climate, is critical for identifying vulnerabilities and maintaining healthy fish stocks. But until now, very limited information existed on how Lake Tanganyika may respond to such forces.

To understand how the lake reacts to climate changes, the team would need detailed information on the lake’s upwelling—the process by which deep waters rise and fertilize surface waters, thereby increasing algae and photosynthesis. In order to observe this, the team would have to obtain data from well-preserved sediment cores within the lake.

McGlue and his team traveled to one of the most remote regions of Lake Tanganyika, the southern basin, on a 12-day trip to collect these cores from the lake floor.

“The winds were especially violent that season, so most of our cruise was spent taking refuge from the waves in bays near the shoreline,” McGlue said. “But in the narrow window when the winds dropped, we raced out to our stations and collected the cores.”

McGlue and his team would later “read” the layers of sediment.

“The chemistry and fossil content of each layer tells us a specific story about how the lake functions,” McGlue said. “Limnologists (scientists who study the lake today, like our co-author Dr. Ismael Kimirei) help us to translate the information in the sedimentary record and learn how climate change affects the lake’s food web.”

Until now, sedimentary records from Lake Tanganyika lacked the resolution needed to accurately measure the influence of frequent climatic events, such as the El Nino Southern Oscillation (ENSO). Most sedimentary datasets are low resolution, meaning that changes