Molecular Level Characterization of Diatom and Coccolithophore-Associated Biopolymers That Are Binding 210Pb and 210Po in Seawater

Through a combination of selective extractions and molecular characterization techniques including Isoelectric Focusing Chromatography Electrospray Ionization Fourier-Transform Ion Cyclotron Resonance Mass spectrometry, structures diatom ( Phaeodactylum tricornutum ) coccolithophore Emiliania huxleyi )-associated biopolymers that are responsible for the distinct partitioning behavior between 210 Pb Po were determined. Our results show diatom-derived have distinctive elemental grouping distributions as compared to those excreted by coccolithophore, with former consisting more heterogeneous elements (i.e., nitrogen, sulfur phosphorus-containing organic compounds). For culture, two Pb-enriched (non-attached exopolymeric substances coccosphere shell-associated biopolymers) higher abundance CHO-type compounds, suggesting CHO-only-type compounds main binding moieties Pb. In contrast, such association was not evident in culture. Different Pb, enrichment coccolithophore-derived attached Fe-Mn-associated metabolites coincided nitrogen/sulfur-containing these biopolymer fractions, strong parallel production nitrogen-rich matter well sulfur-containing amino acids. These different associations Pb/ functional groups further explored separating or Po-labeled via isoelectric focusing. This technique suggests phosphate group-containing molecules but other contain (e.g., CHONS, CHON, CHOS) strongest agents while hydrophobic (high protein carbohydrate ratio) nitrogen/sulfur-enriched acted Po-binding ligands. It is concluded deficiency respect can be influenced relative nitrogen/sulfur-depleted water column. constrains application Po- approach quantify particulate carbon (POC) export flux ocean. also explains differences chemical radionuclides thorium-234) factor. That decay half-lives physical factors less important when nuclides applied estimate POC