Absorption and fluorescence of dissolved organic matter in the waters of the Canadian Arctic Archipelago, Baffin Bay, and the Labrador Sea

The optical properties of dissolved organic matter (DOM) were investigated for the first time in the Canadian Arctic Archipelago (CAA), Baffin Bay (BB), and Labrador Sea (LS) as part of the International Polar Year Canada's Three Oceans project (C3O). The dynamics and composition of absorbing DOM (i.e., colored DOM, or CDOM) and fluorescent DOM (FDOM) were evaluated in several distinct water masses occupying the three regions: surface waters, Arctic outflow waters, West Greenland Intermediate waters (WGIW), upper Labrador Sea waters (uLSW), and Bottom Baffin Deep Water (BBDW). Four fluorescent components were identified by applying parallel factor analysis (PARAFAC) to 522 excitation emission matrix (EEM) spectra: three humic-like and one protein-like. The FDOM in surface waters of the CAA and BB differed considerably in character from those of the LS, with higher fluorescence intensity in the former. The fluorescence intensities of the two terrestrial humic-like components (C1 and C3) were linearly correlated with apparent oxygen utilization (AOU) in the CAA Arctic outflow and the WGIW whereas only humic-like C3 was significantly correlated with AOU in uLSW. These findings suggest that the humic-like components were produced in situ as organic matter was bio-oxidized. The slopes of the linear relationship between humic-like intensity and AOU were significantly greater in the WGIW relative to the Arctic outflow waters, which implies that FDOM in the Arctic-derived deeper layer was less prone to mineralization.