Hydrologic Controls on Individual Ostracode Stable Isotopes in a Desert Lake: A Modern Baseline for Lake Turkana

Stable carbon (δ13C) and oxygen (δ18O) isotope measurements in lacustrine ostracodes are widely used as paleolimnological indicators of past climate change. Previous work has individual ostracode valves to resolve seasonal subdecadal paleohydrological signals, yet replicated assessments co-occurring specimens from modern samples rare. Here we focus on sediments collected 1979 Lake Turkana, an alkaline desert lake tropical eastern Africa. Sourced the Ethiopian highlands, Omo River is dominant inflow into this lake. We present valve analyses (IOVA) δ13C δ18O (n = 329) extant benthic Sclerocypris clavularis 17 sites spanning entire (navg ∼19 specimens/site). demonstrate that pooled statistics at each site shaped by hydrology, superimposed over inter-individual isotopic variations. Within-site variance IOVA-δ13C larger (∼60%) than IOVA-δ18O. Yet, site-based averages exhibit a systematic pattern, with higher δ values toward southern part lake, away inflow. suggest latitudinal gradient may arise low riverine organic matter productivity response nutrient-rich north. The pattern be explained diminishing influence inflows more evaporation driving IOVA-δ18O windier, basin. conclude IOVA Omo-Turkana can aid interpretations regional paleohydrology its variability