Magnetotactic bacterial activity indicates redox conditions in an upland lake in southwest China since the last glaciation

Magnetofossils have recently been used to indicate paleo-redox conditions of ocean water. However, the scarcity of research into their favored environments and potential relationships with temperature and precipitation in terrestrial setting such as lakes hampers a deep understanding of magnetotactic bacteria (MTB). Here, we present a 90-kyr long record of magnetofossil abundance from a lake sediment sequence of the Tengchong Qinghai Lake (Yunnan Province, Southwestern China). The results demonstrate that MTB activity in the lake was higher during glacial periods with elevated lake levels and weak hydrodynamic conditions. Compared to marine systems, MTB activity in smaller sedimentary catchments is more susceptible to redox condition changes caused by hydrodynamic variations. We propose that high lake levels resulted in water stratification associated with relatively wetter climates and rich organic inputs, which produced favorable environments for MTB to thrive during glacial stages. Magnetofossil contents reflect lake redox variations, with a complex relationship with temperature or precipitation.