Exploring sediment porewater dissolved organic matter (DOM) in a mud volcano: Clues of a thermogenic DOM source from fluorescence spectroscopy

Submarine mud volcanoes as a source of chromophoric dissolved organic matter to the deep waters of the Gulf of Cádiz

“…Anaerobic production of DOM via sulfate-reducing bacteria might also be a source of DOM in AN and, to a lesser extent, in PT, providing energy to the microbial communities living there. These processes were also suggested as one of the responsible of FDOM composition in other MVs 20 .…”

“…One possible source could be the production of thermogenic DOM together with the production of methane. More than 2.4% of DOM compounds in the ocean are thermogenic 7 , and a previous work suggests that the FDOM coming from the deep sediments of MVs fluids was mainly thermogenic 20 . According to the authors, the lower DOC-normalized fluorescence in the MVs, compared to those found in a reference site (without MVs), may be due to the thermal quenching of the fluorophores.…”

“…The deep DOC in fluid seepage may stimulate the microbial community to release autochthonous organic matter and enhance heterotrophy in seep environments 39 . Based on BIX values, Retelleti et al 20 suggested that MVs have more abundance of DOC from biological sources than sediments without MVs, which has been attributed to the direct release of DOC from microorganisms. This could explain the highest BIX values observed in AN (> 1 up to 3), which corresponds to the presence of DOM recently released 40 .…”

“…A recent study in the South China Sea suggests that MVs are an important source of DOC to the deep waters through benthic fluxes, and these could represent up to 24% of the total annual flux from the largest river that drains into this sea 19 . Moreover, Retelleti et al 20 also measured a high concentration of DOC and FDOM in pore water from MVs (1–6 mM and 0.01–0.06 RU, respectively). The authors found that fluid migrating from deep sediments through MVs could be an important source of altered FDOM to the overlying water column, with a total fluorescence of up to eight times higher than sediments without MVs.…”

Do early diagenetic processes affect the applicability of commonly-used organic matter source tracking tools? An assessment through controlled degradation end-member mixing experiments

“…All the identified components were consistent with those previously reported and/or matched well with the Open Fluor database with similarity scores > 0.95 (Table S3). Component 1 (C1), which had a R e v i s e d m a n u s c r i p t 11 maximum at 220/430 nm (Ex/Em), can be assigned to a typical terrestrial humic-like component 228 (Graeber et al, 2012;Retelletti Brogi et al, 2019b;Yamashita et al, 2010). Component 2 (C2), 229 which exhibited the maxima at 220/547 nm (Ex/Em) can be associated with a humic-like 230 component or aromatic conjugated macromolecular substances of terrestrial origin (Galletti et 231 al., 2019;Osburn et al, 2016b;Wünsch et al, 2017).…”