Impact of Penguin Guano on Dissolved Organic Matter in East Antarctic Lake Sediments

Abstract Antarctica's sensitivity to climate warming expands ice‐free terrestrial environments, where lakes act as key reservoirs of organic carbon (OC). Penguins deliver nutrients from marine to terrestrial environments, which can in turn boost lake productivity near penguin colonies. However, the mechanisms by which penguin guano inputs impact sedimentary dissolved organic matter (DOM) remain unclear. Here, we analyzed three types of sediment cores (microbial mats, ornithogenic, and mixed sediments) from ice‐free areas of the Ross Sea region in East Antarctica. Combining ultraviolet‐visible spectroscopy, excitation‐emission‐matrix spectra, and pyrolysis gas chromatography‐mass spectrometry, we characterized water‐extractable DOM composition and assessed its potential for OC release. Results show that the ratios of Antarctic sedimentary dissolved organic carbon to total organic carbon (DOC:TOC) exceed those in most cold regions globally. Ornithogenic sediments exhibit the highest DOC:TOC ratio (12%), significantly higher than microbial mat sediments (7%), indicating that penguin guano contributes highly soluble organic matter to sediments—a process driven by differences in carbon‐nitrogen composition between solid phase and DOM. DOM from aquatic microbial mats presents low‐molecular‐weight and primarily consists of tryptophan‐like compounds (54%), whereas the solid‐phase components are predominantly lipids. Guano inputs contribute substantial nitrogen‐containing compounds, forming a relatively high‐molecular‐weight DOM pool with humic‐like properties and high aromaticity. Additionally, ultraviolet parameters and fluorescence indices can be used as novel proxies for reconstructing penguin activity and primary productivity. This study demonstrates that guano rapidly dissolves from sediment into water, providing key scientific evidence for evaluating the organic matter‐biological activity‐climate feedback mechanism under global change.