Coupled dynamics of iron and phosphorus in sediments of an oligotrophic coastal basin and the impact of anaerobic oxidation of methane

• Published in: PloS one Vol. 8; no. 4; p. e62386
• Main Authors: Slomp, Caroline P, Mort, Haydon P, Jilbert, Tom, Reed, Daniel C, Gustafsson, Bo G, Wolthers, Mariette
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 23.04.2013; Public Library of Science (PLoS)
• Subjects: Basins (Geology); Carbon - chemistry; Chemistry; Coastal environments; Cycles; Earth science; Earth Sciences; Eutrophication; Finland; Geochemistry; Geologic Sediments - chemistry; Hostages; Iron; Iron - chemistry; Lake sediments; Lakes; Methane; Methane - chemistry; Minerals - chemistry; Oceans and Seas; Oxidation; Oxidation of methane; Oxidation-Reduction; Oxidation-reduction reactions; Oxides; Phosphorus; Phosphorus - chemistry; Pore water; Preservation; Salinity; Sediments; Sediments (Geology); Studies; Sulfate; Sulfates; Sulfates - chemistry; Sulfide; Sulfides; Sulfur; Supersaturation; Sweden; Vivianite; Water - chemistry; Water quality; Sweden; Finland; Netherlands
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0062386

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.