Abstract
Seafloor structures related to the emission of different fluids, such as submarine mud volcanoes (MVs), have been recently reported to largely contribute with dissolved organic matter (DOM) into the oceans. Submarine MVs are common structures in the Gulf of Cádiz. However, little is known about the biogeochemical processes that occur in these peculiar environments, especially those involving DOM. Here, we report DOM characterization in the sediment pore water of three MVs of the Gulf of Cádiz. Estimated benthic fluxes of dissolved organic carbon (DOC) and chromophoric DOM (CDOM) were higher than in other marine sediments with an average of 0.11 ± 0.04 mmol m−2 d−1 for DOC and ranging between 0.11 and 2.86 m−1 L m−2 d−1, for CDOM. Protein-like components represented ~ 70% of the total fluorescent DOM (FDOM). We found that deep fluids migration from MVs (cold seeps) and anaerobic production via sulfate-reducing bacteria represent a source of DOC and FDOM to the overlying water column. Our results also indicate that fluorescent components can have many diverse sources not captured by common classifications. Overall, MVs act as a source of DOC, CDOM, and FDOM to the deep waters of the Gulf of Cádiz, providing energy to the microbial communities living there.
Highlights
Dissolved organic matter (DOM) is one of the Earth’s major carbon reservoirs and the largest ocean pool of reduced carbon (662 Pg C)[1]
The authors found that fluid migrating from deep sediments through mud volcanoes (MVs) could be an important source of altered fluorescent DOM (FDOM) to the overlying water column, with a total fluorescence of up to eight times higher than sediments without MVs
Our results indicate that cold seeps from MVs could be a source of dissolved organic carbon (DOC) and FDOM to shallower sediments and, eventually, to the overlying water column
Summary
Dissolved organic matter (DOM) is one of the Earth’s major carbon reservoirs and the largest ocean pool of reduced carbon (662 Pg C)[1]. Hydrothermal vents have been described as sinks of DOC, removing 1.4 ± 0.7 × 104 tons C yr−1 from the deep-ocean[11,12] They have been found to act as a source of CDOM to the seawater[9]. MVs are cone-shaped structures built up by mud breccia containing gases (mainly methane), saline water, mud, and, occasionally, oil rising from deep pressurized sources through controlled conduits[15,16]. They can be associated with the presence of chemosynthetic biological communities[17,18]. No studies have focused on the dynamic and diffusive benthic flux of DOM from these MVs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
