Abstract
Aquatic ecosystems in tropical regions remain understudied and their long-term dynamics poorly understood. In East Africa, a better understanding of how natural communities of primary producers in small freshwater ecosystems respond to climatic variability is needed to improve management and conservation of aquatic resources. This study explored the response of algae and bacteria communities to marked hydrological variation over the past 1500 years in a small western Ugandan crater lake, Lake Nkuruba. We analyzed sedimentary algal and bacterial pigments to evaluate the magnitude and direction of change in the autotrophic community in response to severe climatic perturbations in the region. The lithology of the Lake Nkuruba sediment core indicated that external forcing in the form of a major drought, associated with the Medieval Climate Anomaly, caused a heavy, short-lived detrital pulse to the basin that led to a brief but substantial disruption of the lake system in the second half of the 13th century. The system appears to have recovered rapidly, and then transitioned to a more productive state than the one preceding the drought. The considerable variation observed in the sedimentary pigment biomarkers is likely linked with climatically-induced changes in the water column structure of this small crater lake. Our results highlight the challenge of defining appropriate baselines or reference conditions in climatically-sensitive East African aquatic ecosystems and disentangling long-term anthropogenic impacts from the strong regional hydrological flux at the decadal to centennial scale.
Highlights
Small lakes can be hotspots of biodiversity (Strayer and Dudgeon, 2010) and are critical to ecosystem service delivery; they remain some of the least investigated freshwater systems globally and are largely excluded from management planning (Biggs et al, 2017)
The date obtained from the bottom of the long core indicates that it covers the last ∼1,500 years, going back to the Sixth century common era (CE)
There is no available information on direct historical anthropogenic impacts at our study site beyond the early Twentieth century (Saulnier-Talbot et al, 2014), charcoal and pollen content of a sediment core from nearby (
Summary
Small lakes can be hotspots of biodiversity (Strayer and Dudgeon, 2010) and are critical to ecosystem service delivery; they remain some of the least investigated freshwater systems globally and are largely excluded from management planning (Biggs et al, 2017). SaulnierTalbot et al (2014) showed that these small tropical crater lakes can be very sensitive to climatic changes at the annual and decadal scale and provided a perspective of Twentieth century variability in crater Lake Nkuruba They found that temperature-driven increases in water column stability can have detrimental consequences for primary production, such as the expansion of the anoxic zone, which may limit the ability of lakes to support adequate fish populations and increase the proliferation and blooms of cyanobacteria (Saulnier-Talbot et al, 2014). Restoration, and conservation of these vital ecosystems, a more in-depth understanding of their dynamics on longer timescales is necessary, with a particular focus on identifying the timing and magnitude of the principal drivers of regional environmental change (Gelorini and Verschuren, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
