Abstract

Lake Tanganyika, in central Africa, contains a diverse and endemic fauna under threat from global climate change, overfishing, and nearshore sediment pollution. Previous studies of sediment pollution focused justifiably on impacts along rocky shorelines where diversity is high, but Lake Tanganyika also contains widespread shelly accumulations (shell beds) unprecedented in the modern East African lakes, but where impacts are less con- strained. Here we integrate multiple datasets from three sites along the Tanzanian shoreline to explore how variation in sedimentation rates and sediment quality impacts shell-bed substrate and diversity and abundance of ostracodes and sponges across sites that exhibit varying watershed characteristics. Taphonomic overprinting of the shells are similar over the three sites, suggesting lake-wide processes control their accumulation. However, shell bed distribution and sediment volume and compositions vary. There are also differences in the abundance of studied taxa. Where organic matter is diluted by clastic mud, ostracodes are less abundant and less diverse. Where sediment is pervasive and shell density is low, fewer sponges occur. Using the fallout radionuclide 210Pb, the two sites with discontinuous shell beds show sedimentation rates at least twice as high as the site where shell beds are more continuous. These differences are likely related to modest differences in watershed morphology, urbanization, and land cover. Our study suggests that modern sediment pollution creates sediment blankets that cover extant shell beds and likely reduce live populations of the snails that contribute to the accumulations. This has important conservation implications as planning must focus on large watersheds where agriculture and urbanization tend to be higher.

Document Type

Article

Publication Date

2024

Notes/Citation Information

0380-1330/© 2024 The Authors. Published by Elsevier B.V. on behalf of International Association for Great Lakes Research. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Digital Object Identifier (DOI)

https://doi.org/10.1016/j.jglr.2024.102325

Funding Information 

This work was supported by the National Science Foundation, Divi- sion of Earth Sciences [EAR-1424907] as well as the Society of Explo- ration Geophysicists Foundation Geoscientists Without Borders program (#20141005) and National Geographic Society. Financial support was provided by the OU Libraries’ Open Access Fund. Field work was sup- ported by Tanzania Fisheries Research Institute (TAFIRI) and The Na- ture Conservancy. We thank Mupape Mkuli, Athanasio Mbonde, Joseph Lucas, Anna Gravina, James Busch, Emily West and Courtney Milledge for field assistance and Aubrey Weed, and Kim Schindler and Rebecca Smiley for lab assistance. We thank Associate Editor Salzburger and two anonymous reviewers for careful reviews that provided helpful com- ments and edits to the initial manuscript submission. This research was authorized by the Tanzania Commission for Science and Technology (Permit #2016-3-1-NA-2011-87).

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