Marine Dissolved Organic Phosphorus Composition: Insights from Samples Recovered Using Combined Electrodialysis/Reverse Osmosis |
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Authors: | Cindy L Young Ellery D Ingall |
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Institution: | (1) School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332-0340, USA; |
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Abstract: | The dominant phosphorus compound classes were characterized in marine samples using a new, high recovery method for isolating
and concentrating bulk dissolved organic matter (DOM) called combined electrodialysis + reverse osmosis (ED/RO). In contrast
to earlier studies that use ultrafiltration (UF) to recover only the high molecular weight DOM, ED/RO is capable of isolating
both low molecular weight (LMW) and high molecular weight (HMW) DOM. Samples were collected from a broad range of marine environments:
along a transect incorporating coastal and offshore waters off the Southeastern United States, in Effingham Inlet, a Pacific
fjord located on Vancouver Island, British Columbia and in the Amundsen Sea, Antarctica. Results from phosphorus nuclear magnetic
resonance (31P NMR) analysis reveal a similar abundance of P compound classes among samples, phosphate esters (80–85%), phosphonates (5–10%)
and polyphosphates (8–13%). These samples contain significantly higher proportions of polyphosphate P and P esters and lower
proportions of phosphonates than measured in previous studies using the UF method. The much higher levels of polyphosphate
detected in our samples suggests that polyphosphate is present mainly in the LMW dissolved matter fraction. Polyphosphates
in dissolved matter may be present as (or derived from) dissolved nucleotides or organismal polyphosphate bodies, or both.
Low molecular weight P esters are possibly composed of phosphoamino acids and small carbohydrates, like simple sugar phosphates
and/or dissolved nucleotides. Phosphonates in DOM are more prevalent as HMW phosphonate compounds, which suggests that LMW
phosphonates are more readily utilized in marine ecosystems. Overall, the investigation of DOM across a size spectrum that
includes both the HMW and the LMW fractions reveals a new picture of phosphorus distribution, cycling and bioavailability. |
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