title: Coupled dynamics of iron and phosphorus in sediments of an oligotrophic coastal basin and the impact of anaerobic oxidation of methane.
abstract: Studies of phosphorus (P) dynamics in surface sediments of lakes and coastal seas typically emphasize the role of coupled iron (Fe), sulfur (S) and P cycling for sediment P burial and release. Here, we show that anaerobic oxidation of methane (AOM) also may impact sediment P cycling in such systems. Using porewater and sediment profiles for sites in an oligotrophic coastal basin (Bothnian Sea), we provide evidence for the formation of Fe-bound P (possibly vivianite; Fe3(PO4)2(·)8H2O) below the zone of AOM with sulfate. Here, dissolved Fe(2+) released from oxides is no longer scavenged by sulfide and high concentrations of both dissolved Fe(2+) (>1 mM) and PO4 in the porewater allow supersaturation with respect to vivianite to be reached. Besides formation of Fe(II)-P, preservation of Fe-oxide bound P likely also contributes to permanent burial of P in Bothnian Sea sediments. Preliminary budget calculations suggest that the burial of Fe-bound P allows these sediments to act as a major sink for P from the adjacent eutrophic Baltic Proper.
authors.affiliation: Department of Earth Sciences-Geochemistry, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands. c.p.slomp@uu.nl
authors.forename: Caroline P
authors.initials: CP
authors.lastname: Slomp
authors.forename: Haydon P
authors.initials: HP
authors.lastname: Mort
authors.forename: Tom
authors.initials: T
authors.lastname: Jilbert
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Reed
authors.forename: Bo G
authors.initials: BG
authors.lastname: Gustafsson
authors.forename: Mariette
authors.initials: M
authors.lastname: Wolthers
mesh_terms: D002244:Carbon / Q000737:chemistry; D005387:Finland; D019015:Geologic Sediments / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008697:Methane / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010758:Phosphorus / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry; D013548:Sweden; D014867:Water / Q000737:chemistry
chemical_list: D008903:Minerals; D013431:Sulfates; D014867:Water; D010758:Phosphorus; D002244:Carbon; D007501:Iron; D008697:Methane