Lacustrine ostracodes from Nam Co (Tibetan Plateau) indicate biotic responses to Quaternary climate change (NamCore ICDP project)

A central objective of the NamCore ICDP project is to understand Quaternary biotic dynamics—specifically species diversity, distribution, and evolution—in relation to Asian monsoon variability and orbitally driven climate change. Lacustrine ostracodes are therefore ideal indicators to assess (1) whether Nam Co served as a glacial refugium for cold-adapted species during glacial periods, (2) how biota responded to glacial–interglacial environmental transitions, and (3) whether the lake exhibits a high ecological resilience to environmental change.

To address these objectives, a multi-scale analytical approach was applied. Ostracode valve analyses were conducted on 43 core catcher samples spanning depths from 8 m to 470 m b.l.f., corresponding to a stratigraphic resolution represented by intervals of 3–35 m, to provide an overview of broad-scale changes in ostracode distribution and abundance. To obtain higher-resolution data on species distribution and morphological variability, additional samples from core sections within the upper 33 m b.l.f. were analyzed at 16 cm intervals. Morphometric analyses of valve outline shape and size are intended to identify either gradual or abrupt changes in morphological variability. Environmentally driven morphological responses are expected to manifest as gradual shifts in size and/or shape, whereas re-colonization from other lakes may produce distinct morphological signatures, resulting in discontinuous variation in size or shape.

Preliminary results indicate that ostracode abundance and species composition are highly variable, with ostracodes absent below 470 m b.l.f. In total, ten species were identified, with a maximum of five species per sample. Generally, samples from the uppermost 30 m contain four species that are absent in the lower sections of the record. Although Leucocytherella sinensis and ?Leucocythere dorsotuberosa represent the most abundant taxa, no species occurs continuously throughout the sedimentary record.

Detailed analyses of species composition, combined with morphometric investigations, are expected to elucidate whether the discontinuous ostracode distribution pattern reflects repeated lake colonization events associated with, e.g. glacial–interglacial cycles. Such findings would have significant implications for understanding the role of the Tibetan Plateau as a biodiversity refugium during Quaternary climate oscillations and for reconstructing paleoenvironmental conditions from ostracode assemblages in high-altitude lake systems.