Interannual variability in dissolved organic matter (DOM) concentration and quality in shallow water bodies of Tierra del Fuego (Argentina)

Dissolved organic matter (DOM) is a crucial component of the global carbon cycle, significantly influencing aquatic ecosystems through its quantity and quality, which are shaped by abiotic factors such as precipitation, runoff, and solar radiation. Recently, the role of winter conditions, particularly ice cover, has gained attention due to the ongoing biogeochemical processes that occur during this period. This study explores the effect of winter precipitations on DOM dynamics in humic shallow lakes and beaver ponds in Tierra del Fuego over two consecutive years. Higher accumulated precipitation in 2021 compared to 2022 led to differences in DOM properties. While dissolved organic carbon (DOC) levels were higher in 2022, likely due to concentration effects from reduced precipitation, shallow lakes and beaver ponds exhibited distinct responses. Absorbance-based (water color, SUVA and spectral slope) assessments revealed a slight increase in DOM molecular size in shallow lakes during 2022, whereas fluorescence-based indices (HIX and BIX) indicated greater humification in 2021 but fewer humic components, suggesting complex patterns of allochthonous DOM mobilization. These findings highlight the importance of precipitation regimes and runoff in shaping DOM dynamics in subantarctic aquatic systems, with significant contribution from the surrounding soils and vegetation.