Time resolved data unveils the complex DOM dynamics in a Mediterranean river.

Mediterranean rivers experience distinct seasonal changes in flow and water quality. Prior research has shown that these rivers transport significant amounts of dissolved organic matter (DOM) to coastal waters. However, the specific mechanisms driving DOM dynamics in such systems remain unclear. This gap motivated the need for long-term, high-frequency data collection. No prior work had resolved the seasonal and event-based variability of DOM in a Mediterranean river with torrential hydrology. Understanding DOM dynamics is essential for modeling carbon fluxes in coastal ecosystems. This study provides a new dataset that fills a key gap in the literature. The findings may improve predictions of carbon export from Mediterranean rivers.

The aim of this study was to investigate the temporal dynamics of dissolved organic matter (DOM) in a Mediterranean river. The researchers focused on the Arno River, which has torrential hydrology and medium-high human impact. They collected weekly samples over two years to capture seasonal and event-based changes in DOM. The goal was to identify the main drivers of DOM concentration and quality. The study also aimed to estimate the river's contribution to the Mediterranean Sea's carbon budget. This approach allows for a more detailed understanding of DOM dynamics than previous studies. The researchers sought to quantify the role of hydrological events in DOM transport. Their findings may support future modeling efforts in similar river systems.

The study used a two-year dataset of dissolved organic carbon (DOC) and optical properties of DOM collected weekly from the Arno River. Optical measurements included absorbance and fluorescence to assess DOM quality. The researchers analyzed seasonal patterns in DOC concentrations and DOM composition. They compared terrestrial and autochthonous sources of DOM across different seasons. The study also examined the influence of hydrological events such as floods on DOM transport. A statistical approach was used to estimate annual DOC fluxes to the Mediterranean Sea. The dataset includes both water quantity and quality parameters. These methods enabled a detailed assessment of DOM dynamics in a Mediterranean river.

The study found a clear seasonal cycle in DOM dynamics, with DOC concentrations ranging from 170 to 490 μM. Terrestrial humic-like substances dominated in winter, when high discharge and floods influenced DOM quality. In spring and summer, autochthonous protein-like substances were more prevalent. The researchers estimated an annual DOC flux of 9.6 × 10⁹ g to the Mediterranean Sea. The flux varied between 5.12 × 10⁹ g and 12.95 × 10⁹ g annually. Autumn and winter accounted for 80% of the annual DOC flux. Single flood events contributed up to 26% of the annual flux in 2014. These results highlight the importance of hydrological events in DOM transport.

The study provides a detailed dataset on DOM dynamics in a Mediterranean river with torrential hydrology. The findings suggest that seasonal changes in DOM composition are linked to hydrological and biological processes. The researchers propose that terrestrial sources dominate in winter, while autochthonous sources prevail in spring and summer. Their estimates of DOC fluxes to the Mediterranean Sea may inform future modeling efforts. The data show that flood events significantly influence DOM transport. The results may improve understanding of carbon cycling in Mediterranean rivers. The study highlights the need for high-frequency monitoring to capture DOM variability. These conclusions align with the observed patterns in the dataset.