Insights into sources, distribution, and degradation of biogenic sterols in surface sediments and suspended particulate matter from Admiralty Bay, Antarctica

Biogenic sterols were analyzed in surface sediments and suspended particulate matter (SPM) from the three inlets of Admiralty Bay, Antarctica, to investigate the spatial distribution, sources, and degradation patterns of organic matter (OM) and to provide comparative insights into sterol composition and behavior across environmental compartments. Total sterol concentrations ranged from 0.28 to 8.10 μg g^-1 in sediments and from 5.34 to 306.88 μg g^-1 in SPM. Marine sterols, particularly brassicasterol, dominated SPM, reflecting fresh phytoplankton-derived OM, whereas sediments contained more degraded material with contributions from both marine and terrestrial sources (β-sitosterol, stigmasterol). Sedimentary sterols positively correlated with %TOC, %TN, and fine particle fractions, while sterols in SPM negatively correlated with SPM concentration, indicating dilution by inorganic and resuspended particles. Differential SPM/sediment ratios revealed selective preservation and transport of sterols, with higher degradation rates in the water column accounting for lower sedimentary concentrations. These findings highlight the integrated influence of hydrodynamics, primary productivity, and sedimentary characteristics on the distribution, composition, and preservation of OM in Antarctic coastal ecosystems.