Aquatic ecosystem changes in a global biodiversity hotspot: Evidence from the Albertine Rift, central Africa

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Date
2019Author
McGlynn, Gayle
Lejju, Julius
Dalton, Catherine
Mooney, Scott D.
Rose, Neil L.
Tompkins, Adrian M.
Bannister, Wayne
Tan, Zu D.
Zheng, Xianglin
Rühland, Katherine M.
Taylor, David
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Show full item recordAbstract
Determine the extent to which remote, high‐altitude (Afroalpine) aquatic ecosystems
in tropical Africa have been impacted by global and regional‐scale environmental
change processes.
Location: Two volcanic crater lakes (Bisoke and Muhavura) in the Afroalpine zone,
Albertine (Western) Rift, central Africa.
Methods: Sediment cores were collected from Bisoke and Muhavura lakes and dated
using radiometric techniques. A range of sediment‐based proxies was extracted from
the cores and quantified. Sedimentary data were subjected to statistical analyses
that contributed to the identification of influential environmental variables and their
effects on diatom assemblages, the determination of variations in spatial beta diversity
and estimates of the rate of compositional turnover over the last c. 1,200 years.
Results: Sediments from the two sites provide evidence of the sensitivity of remote,
Afroalpine aquatic ecosystems to perturbation. Climate variability has been a major
driver of ecological change, particularly at Bisoke Lake, throughout the c. 1,200‐
year‐long record, while Muhavura Lake has been directly impacted by and recovered
from at least one volcanic eruption during this time. The effects of climatic warming
from the mid‐ to late 19th century and especially from the late 20th century,
possibly accentuated by atmospheric deposition‐driven nutrient enrichment, appear
increasingly in lockstep. Effects include changes in diatom community composition,
increased productivity and compositional turnover, and biotic homogenization (reduced
spatial beta diversity) between the two sites.
Main conclusions: The two Afroalpine sites record changes in atmospheric conditions
and their effects on diatom assemblage composition, particularly over the last
c. 150 years. Drivers of these changes have the potential to disrupt ecosystems at
lower altitudes in the Albertine Rift, including biodiverse areas of forest, and across
tropical Africa more widely.
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- Natural Sciences [591]