Ostracodes as indicators of Late Quaternary aquatic and monsoon system changes on the southern Tibetan Plateau
Knowledge on micro-crustaceans in high mountain-ecosystems and their potential in palaeoclimatic research is still limited. The study contributes to: 1) Ecology of Recent (living + dead) Ostracoda (‘Seed Shrimp’) from the southern Tibetan lakes (Tangqung Co, Tangra Yumco, Monco Bunnyi, and Xuru Co, ~ 4500 m a.s.l) and their adjacent waters. Ostracod associations can be used to classify types of water bodies: i) Leucocytherella sinensis dominates Ca-depleted brackish waters although adaptable to diverse aquatic habitats; ii) Leucocythere? dorsotuberosa lives in lacustrine fresh to brackish waters; iii) Limnocythere inopinata predominates in mesohaline to polyhaline waters; iv) Fabaeformiscandona gyirongensis lives in brackish lacustrine deeper waters; v) Candona candida populates freshwaters; vi) Tonnacypris gyirongensis and Ilyocypris sp. occur in shallow temporary waters; and vii) Heterocypris incongruens occurs in ponds. Conductivity is the best environmental predictor for the presence/absence and abundance of ostracods in continental waters of southern Tibet. 2) Shell geochemistry (δ13C, δ18O, Mg/Ca, Sr/Ca, Fe/Ca, Mn/Ca and U/Ca) of L. sinensis, L.? dorsotuberosa, L. inopinata and T. gyirongensis shows species-specific variability. 3) Ostracoda provides evidence of subaqueous flow dynamics and specific sediment deposition in Tangra Yumco. Lower abundance of ostracods occurs within sediment event layers (turbidites) than in the overlying and underlying sediments. 4) Late Holocene environmental variability in Tangra Yumco is elucidated by: i) The predominance of L. sinensis suggests a highest lake level and lowest salinity in 3.3 until 2.3 ka cal BP; ii) the prevalance of L.? dorsotuberosa suggests lower lake level and variable salinity in 0.8 to 0.4 ka cal BP and iii) the dominance of L. inopinata indicates the lowest lake level and highest salinity in 0.7 ka cal BP. Ostracoda are excellent indicators for environmental reconstructions.