Resolving marine dissolved organic phosphorus (DOP) composition in a coastal estuary

Abstract

A mechanistic understanding of dissolved organic phosphorus (DOP) utilization, and its role in the marine P cycle, requires knowledge of DOP molecular composition. In this study, a recently developed approach coupling electrodialysis and reverse osmosis with solution 31 P-NMR analysis was used to examine DOP composition within a tidally dominated salt-marsh estuary (North Inlet, South Carolina) over seasonal and tidal time frames. The isolation technique allowed for near complete recovery of the DOP pool (90% AE 13%; n = 12) with six broad compound classes quantified: phosphonates, phosphomonoesters, phosphodiesters, pyrophosphate, diand tri-phosphate nucleotides (nucleoP α), and polyphosphate. Our results indicate that phosphomonoesters (ca. 61%) and phosphodiesters (ca. 31%) comprise the majority of the DOP pool, with relatively small contributions from pyrophosphates (ca. 4%), phosphonates (ca. 2%), nucleoP α (ca. 1%), and polyphosphates (ca. 1%). The study found no significant differences in DOP composition or concentration between tidal stages, despite significant tidal changes in dissolved organic nitrogen (DON):DOP stoichiometry. Significant seasonal variation was observed, with higher concentrations of phosphonates, nucleoP α , and monophosphates and lower phosphomonoester concentrations in Fall relative to all other seasons. We hypothesize that these seasonal variations reflect the balance between specific compound class seasonal production, lability, and local P demands associated with marine vs. terrestrial sources. Our results indicate that DOP composition exists at a dynamic equilibrium that is strongly conserved across diverse marine environments.

NMR spectroscopy of dissolved organic matter: a review

“…Thereby, 31 P NMR spectroscopy played a crucial role to secure that the samples were not biased by the extraction method. During a followup study, seasonal and tidal changes of DOP were investigated that was extracted from the water of a salt-marsh estuary located in South Carolina with the RO/ED technique described in their previous publication (Bell et al 2020). Notably, the recovery rates of DOP in this study reached 90% ± 13%.…”

“…While essentially all NMR spectroscopic studies investigating dissolved organic nitrogen used solid-state NMR spectroscopy, a few solution-state NMR studies on dissolved organic phosphorous (DOP) have already been reported Minear 1994a, b, 1997;Bell et al 2017Bell et al , 2020. Minear (1994a, b, 1997) investigated lake freshwater samples in all of their studies.…”

“…Recently, Bell et al (2017Bell et al ( , 2020 characterized DOP using solution-state 31 P NMR spectroscopy. Within the first study, they assessed the potential of RO/ED for the isolation of DOP (Bell et al 2017).…”

What are inorganic nanozymes? Artificial or inorganic enzymes

“…61–63 In the meantime, phosphate esters, particularly monoesters, are the most significant parts of the dissolved organic phosphorus in soils and waters (including the ocean) in our contemporary Earth's environment. 64–68 Many other laboratory studies have confirmed the release of orthophosphates from a variety of phosphate esters when iron oxide is present. 69–77 However, the importance of inorganic phosphatase is underestimated from the view of biogeochemistry.…”

Uptake of inorganic and organic phosphorus compounds by two marine sponges and their associated bacterial communities in aquaria

“…Radiolabelled adenosine 5 0 -triphosphate (ATP) was used to determine DOP uptake. Using 31 P-NMR analysis, studies have shown that phosphorus esters comprise the majority of high-molecular weight DOP in the ocean (75%) and in tidal salt marshes (phosphomonoesters: 61%, phosphodiesters: 31%) (Bell et al, 2020;Kolowith et al, 2001). Therefore ATP, a triphosphate monoester was used as a proxy for DOP uptake for both L. chondrodes and H. heliophila.…”