Influence of hydrological parameters on hydroxylated tetraether lipids in a deep Lake Fuxian, China: Implications for their use as environmental proxies

Abstract

Hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers (OH-GDGTs) have shown their potential in environmental reconstructions. However, the unclear underlying mechanism challenges their application. To elucidate the effects of water parameters on OH-GDGT-derived indices and understand their environmental implications, we investigated the core OH-GDGTs of suspended particulate matter (SPM) from water columns in a year cycle and surface sediments at different water depths along a nearshore-offshore transect in Lake Fuxian, a deep and large lake in southwestern China. OH-GDGTs were primarily found in the hypolimnion and were produced in situ by Group I.1a Thaumarchaeota. The relative abundance of OH-GDGTs (%OH-GDGTs) and ring indices (RI-OH and RI-OH′) in the hypolimnion were significantly influenced by dissolved oxygen (DO) and pH, particularly DO, which regulated the inverse physiological functions of the hydroxyl and cyclopentane moieties of archaea. %OH-GDGTs values in SPM were positively correlated with DO and negatively correlated with pH levels, while RI-OH values exhibited an inverse relationship with DO and positive correlation with pH levels. OH-GDGTs in surface sediments appeared to be homologous to that of water columns, indicating that their inferred proxies could be regulated by the configuration of water parameters. The sedimentary %OH-GDGTs values increased as the RI-OH values decreased with water depth along the transect from the lakeshore to the lake center, suggesting their potential as lake-level proxies.