184-9 Determining Morphological Response in Benthic Ostracods to Increased Stratification and Low Oxygen Caused by Climate Change in Lake Tanganyika, East Africa

Session: Lakes of the World Through Space and Time: Archives of Climate, Paleoenvironments, Ecosystems, Geohazards, and Economic Resources (Posters)

Presenting Author:

Authors:

Abstract:

Located in the East African Rift, Lake Tanganyika is the continent’s oldest and deepest lake, supporting a diverse ecosystem of endemic species. Tanganyika is an essential source of food, water, and employment to its four surrounding nations and thus, deoxygenation is a major threat to the ecosystem, people, and economy of the region. The lake is permanently stratified with a well-established oxycline, making it an excellent system to observe fluctuating oxygen conditions. Within the three basins of the lake, the central basin has the shallowest oxycline and the southern basin has the deepest—and are the foci of this study. While known for its endemic cichlid fish flocks, the lake is also home to hundreds of species of ostracods, most of which are endemic. These small, bivalved crustaceans are useful proxy indicators due to their size, shape, and ornamental structures that can vary based on environmental conditions. Despite this, their physiological response to decreasing oxygen is not yet well understood.

In this study, we analyzed the benthic ostracod species Gomphocythere downingi and its physiological response to a range of oxygen conditions along depth transects in the central and southern Tanganyika basins. G. downingi was chosen because of  its prevalence in the lake and distinctive alae, a wing-like protrusion of the carapace. Alae and body length were measured using a Leica M205 light microscope and LasX software and compared across the transect depth gradient.

Data indicate positive trends between body length versus depth (central basin: r = 0.51, southern basin: 0.63) and alae length with depth (central basin: r = 0.37, southern basin: 0.89) Whilst both body and alae length increase with depth, they do not increase at the same rate. Body length increases by 120% in the central basin and 105% in the southern basin across the depth gradient, and alae length increases by 174% in the central basin and 118% in the southern basin. These differences in rate of change may be due to differences in oxycline dynamics between the two basins.

By understanding the relationship between morphology, oxygen availability, and depth, G. downingi can be used as a proxy to examine deoxygenation within the lake, providing a useful way to model biological response to low oxygen levels in future climate states.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.