Exploring a link between Atlantic coral mounds and Phanerozoic carbonate mudmounds: Insights from pore water fluorescent dissolved organic matter (FDOM), Pen Duick mounds, offshore Morocco

This study explores a genetic link between modern Atlantic coral mounds and ancient, sponge-rich carbonate mudmounds based on Ca-carbonate authigenesis driven by induced-and-supported organomineralization (ISOM). The potential for ISOM in Atlantic coral mounds is tracked by peak patterns of fluorescent dissolved organic matter (FDOM) present in pore waters down to 3 m of sediment depth (Gamma mound, Beta mound, Pen Duick escarpment, offshore Morocco). re waters display a biological activity (protein-like fluorescence) with two local maxima, occurring from the surface to about 1 m of sediment depth and below 2 m of sediment depth. Protein-like fluorescence correlates well with the fluorescence of porphyrin-like compounds. A sample of bottom water displays a blue-shifted variety of protein-like fluorescence suggesting hydrolysis and diffusion from the benthic realm into the water column. A significant accumulation of refractory FDOM does not occur in shallower than 2 m of sediment depth. It is accompanied by a late stage of biodegradation of organic matter (peak Geol.-A; ex. 224 ± 2 nm; em. 385 ± 8 nm) and the occurrence of a new fluorescence peak Q that is expressed along an emission band with peak Geol.-A (peak Q; ex. 295 ± 5 nm; em. 385 ± 1 nm). With caution, peak Q represents a product of exudation from anaerobic microorganisms and/or derives from siderophore-like pigments (pyocyanine-like; from Pseudomonas species). eralizing fluids that are characteristic for ISOM are locally present within the shallow subsurface and reach a maximum intensity at about 1 m of sediment depth. However, no ISOM-related authigenic carbonate was observed. Both the lack of organic substrates that is due to the absence of degrading connective tissues from a cryptic community and the high amount of infiltrated mud that acts as a sorbent might explain the absence of ISOM in Gamma mound sediments. Labyrinthine deposits of coral rubble or current-swept coral mounds are prone to host a sponge-rich cryptic community and therefore, in their deeper parts, should provide a variety of substrates for ISOM during suboxic cycling of natural organic matter. In such a view, the modern coral-rich mound system, which by itself appears diverse and with a variety of controlling factors, maintains an excellent potential to drive ISOM and to share a crucial process of early diagenesis with Phanerozoic sponge-rich carbonate mudmounds.