Biophysical processes affecting DOM dynamics at the Arno river mouth (Tyrrhenian Sea)

Dissolved organic carbon (DOC) and optical properties (absorption and fluorescence) of chromophoric dissolved organic matter (CDOM) were measured in October 2012, at the Arno river mouth and in a coastal station close to it. The data reported indicates that the Arno river represents an important source of DOC and CDOM to this coastal area, with a total DOC flux of 11.23-12.04·109 g C·y- 1. Moving from the river to the sea, CDOM absorption and fluorescence decreased, while the spectral slope increased, suggesting a change in the molecular properties of CDOM. Mineralization experiments were carried out in order to investigate the main processes of DOM removal and/or transformation in riverine and coastal water. DOC removal rates were 20 μM·month- 1 in the river and 3 μM·month- 1 in the seawater, while CDOM was released during the first 30 days and removed in the following 40 days.