3-OH-FA- and branched GDGT-based temperature calibrations from a transect of lakes in the eastern USA

Lipid biomarkers preserved in lacustrine archives provide valuable insights into past climate change. In recent decades branched glycerol dialkyl glycerol tetraethers (brGDGTs) have been used as paleoclimate proxies in lake settings. More recently, 3-hydroxy fatty acids (3-OH-FAs) have emerged as a novel approach for paleolimnology. However, region-specific temperature calibrations and applications for 3-OH-FAs have only been developed in China and remain underdeveloped globally. In this study, we analysed 3-OH-FAs from Gram-negative bacteria and brGDGTs from heterotrophic bacteria in a latitudinal transect of lake surface sediments along the densely populated and economically vital East Coast (EC) region of the United States. RAN 13 (the ratio of anteiso to normal C 13 3-OH-FA), previously proposed as a novel 3-OH-FA-based lake temperature proxy in Chinese lakes, shows a strong linear correlation with mean annual air temperature (MAAT) in 21 EC lakes (R 2 = 0.68, RMSE = 2.33 ℃). Whilst the brGDGT-based MBT’ 5ME temperature proxy shows a somewhat weaker correlation for MAAT (R 2 = 0.48, RMSE = 2.95 ℃). When calibrated to mean temperature of months above freezing (MAF) in EC lakes the MBT’ 5ME correlation improves (R 2 = 0.55, RMSE = 1.13 ℃), but RAN 13 weakens slightly (R 2 = 0.63, RMSE = 1.03 ℃). Our results also indicate that the 3-OH-FA-based soil temperature proxies, RAN 15 (previously applied to a stalagmite) and RAN 17 , are unsuitable for calibrating mean annual air temperatures (MAAT) in EC lakes. In addition, pH proxies derived from 3-OH-FAs—the Branching Ratio, Branched Index, RIN, and RIAN (R = ratio; I = iso ; N = normal ; A = anteiso )—demonstrate linear relationships with lake water pH; however, the brGDGT-based CBT 5ME index outperforms these indicators in pH reconstruction. When applied to the topmost portion of a sediment core from Lake Blauvelt located in northern New Jersey (USA), MAAT reconstructed from the RAN 13 proxy more closely resembles other reconstructed regional temperature trends (over the last ∼2 ka), while absolute temperatures from both RAN 13 and MBT’ 5ME fall within calibration uncertainty ranges and are broadly consistent with modern observations. These findings highlight the potential of novel 3-OH-FA-based proxies for paleolimnology and the value of combining both 3-OH-FA and brGDGT proxies (e.g., constraining a common temperature signal) for climate reconstruction in EC lakes in future studies.