Chemical properties and fluorescence of DOM in relation to biodegradation in the interconnected Marmara–North Aegean Seas during August 2008

Abstract

The dynamics of dissolved organic matter (DOM) in the Marmara Sea–Dardanelles Straits–North Aegean Sea were investigated using measurements of dissolved organic carbon and nitrogen (DOC, DON), PARAFAC modeling of 3-D excitation–emission fluorescence spectra and bacterial production (BP) and respiration (BR) rates. In the surface brackish waters, chemical parameters showed an increase from the Aegean to the Marmara (DOC: 65–217μmolL−1; DON: 3.08–9.34μmolL−1; Dissolved Inorganic Nitrogen (DIN): 0.044–1.38), followed by an increase in BP rates (7.2–195nmolL−1d−1). In the subsurface waters, DIN also showed an increase in the Marmara basin (0.085–9.79μmolL−1) followed by an increase in BP rates (3.3–17.4nmolL−1d−1). PARAFAC modeling revealed three fluorescent components: λex/λem: <260(330)/464nm, humic-like; λex/λem: <(260) 285/364nm, quinone-like; λex/λem: 270/308nm, tyrosine-like. DOC:DON ratios were found similar for the Marmara (21±3) and the N. Aegean Sea (19±2). The slopes ΔDOC:ΔDON suggested that in the Marmara Sea mineralization processes require more carbon relative to nitrogen (22.3), whereas in the N. Aegean there is preferential removal of nitrogen over carbon (5.66). The lack of significant correlation between DOC and AOU (apparent oxygen utilization) in the deep Marmara waters indicates that particulate organic matter is important in deep mineralization processes.