2026/02/01 by Addison Rice, Eunmi Park, Gesine Mollenhauer +10 · 1 voice
Environmental Science · Earth and Planetary Sciences · #Microbial Community Ecology and Physiology #Methane Hydrates and Related Phenomena #Marine and coastal ecosystems
paper · pdf · doi:10.1029/2025pa005141
Abstract Marine ammonia oxidizing archaea (AOA) produce isoprenoid glycerol dibiphytanyl glycerol tetraethers (GDGTs) which form the basis of seawater temperature proxy TEX 86 . Although most studies use TEX 86 for sea surface temperature (SST) reconstructions, maximum GDGT production occurs at and below the nitracline. Moreover, sedimentary GDGT‐2/GDGT‐3 values >5 reflect GDGT contributions of a deeper dwelling (>100 m) clade of AOA, fueling debate on export mechanisms and the water depth of TEX 86 proxy sensitivity. We investigate subseasonal variations in GDGT export depth using 4 new and 19 previously published marine sediment trap records and compare results to real‐time biogeochemical and physical hindcast/reanalysis model outputs. Due to the complexity of the biological pump and the often short time series of sediment trap records, no globally consistent pattern emerges. However, GDGT‐2/GDGT‐3 ratios imply seasonal changes in GDGT export depth, and often correlate to changes in the depth (negative) or intensity (positive) of maximum net primary production (NPP). Increased/shallower maximum NPP also correlate positively with GDGT flux at several sites, indicating that NPP exerts a strong control on GDGT origin depth. Mechanistically, increased/shallower maximum NPP incorporates relatively more shallow clade GDGTs into sinking particles, leading to lower GDGT‐2/GDGT‐3 values. Additionally, GDGT‐2/GDGT‐3 values correlate with TEX 86 in most sediment traps, suggesting that, on sub‐annual timescales, mixing of shallow and deep‐clade derived GDGTs rather than SST changes causes variations in TEX 86 . TEX 86 ‐based temperatures are up to 0.5°C lower per unit increase in GDGT‐2/GDGT‐3, but the North Atlantic deviates from this global trend with a positive correlation.