Climate warming coupled with local disturbances within lakes is an accelerating global problem. This issue is acute at Lake Tanganyika (eastern Africa), where warming and overfishing have resulted in declining rates of pelagic fish catches and structural damage to diverse littoral cichlid communities. This deterioration has fueled demand for alternative livelihoods, and thus conversion of shoreline-adjacent forests to agricultural fields and oil palm orchards, which in turn heightens the threat of siltation on nearshore benthic habitats. The spatial variability of sediment pollution is unknown, however, posing a barrier to effective conservation. This paper assesses the spatial patterns of nearshore sediment accumulation within the Tuungane Project co-managed area of Lake Tanganyika in Tanzania. Analysis of lead-210 data show that the mean nearshore mass-based sediment accumulation rate is 0.06 g * cm−2 * year-1 (g cm-2 yr-1) across six sites adjacent to deforested watersheds, double the mean rate (0.03 g cm-2 yr-1) at a comparable but undisturbed control site. Spatial variance among rates is best explained by distance to deltaic point sources and bathymetric gradients. Data documenting carbon flux demonstrate that organic matter burial is higher in surface sediments offshore from deforested watersheds, consistent with onshore land use changes that promote erosion. Knowledge of sediment pollution patterns, coupled with maps of rocky benthic habitats, provide the necessary framework for effective conservation planning of fisheries in the present era of accelerated human interactions with the lake and its watershed. Findings provide a model for improved integrated management practices in large tropical artisanal fisheries in other parts of Africa.
|State||Published - Mar 2021|
Bibliographical noteFunding Information:
This research was supported by the Society of Exploration Geophysicists (SEG) Geoscientists Without Borders Program award #201401005 and the U.S. National Science Foundation (NSF) ( EAR-1424907 ). Our research was permitted by The Tanzania Commission for Science and Technology (COSTECH) and the Tanzania Wildlife Research Institute (TAWIRI). Logistical support was provided by the Tuungane Project, the Tanzania Fisheries Research Institute-Kigoma, and the Tanzania Fisheries Enforcement patrol at Mahale. We thank LacCore for sediment core curation and assistance with sampling. We are grateful to the superintendent and staff of Mahale National Park, M. Mukuli, P. Ryan, J. Busch, K.J. Schindler, and E. Ryan for their assistance. We appreciate the efforts of our reviewers and editors in improving the manuscript.
© 2021 Elsevier Ltd
- Lake Tanganyika
- Sediment accumulation rates
- Sediment pollution
ASJC Scopus subject areas
- Global and Planetary Change
- Earth and Planetary Sciences (miscellaneous)