Are iron-phosphate minerals a sink for phosphorus in anoxic Black Sea sediments?

PLoS One. 2014 Jul 2;9(7):e101139. doi: 10.1371/journal.pone.0101139. eCollection 2014.

Abstract

Phosphorus (P) is a key nutrient for marine organisms. The only long-term removal pathway for P in the marine realm is burial in sediments. Iron (Fe) bound P accounts for a significant proportion of this burial at the global scale. In sediments underlying anoxic bottom waters, burial of Fe-bound P is generally assumed to be negligible because of reductive dissolution of Fe(III) (oxyhydr)oxides and release of the associated P. However, recent work suggests that Fe-bound P is an important burial phase in euxinic (i.e. anoxic and sulfidic) basin sediments in the Baltic Sea. In this study, we investigate the role of Fe-bound P as a potential sink for P in Black Sea sediments overlain by oxic and euxinic bottom waters. Sequential P extractions performed on sediments from six multicores along two shelf-to-basin transects provide evidence for the burial of Fe-bound P at all sites, including those in the euxinic deep basin. In the latter sediments, Fe-bound P accounts for more than 20% of the total sedimentary P pool. We suggest that this P is present in the form of reduced Fe-P minerals. We hypothesize that these minerals may be formed as inclusions in sulfur-disproportionating Deltaproteobacteria. Further research is required to elucidate the exact mineral form and formation mechanism of this P burial phase, as well as its role as a sink for P in sulfide-rich marine sediments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Black Sea
  • Deltaproteobacteria / physiology*
  • Iron Compounds / chemistry*
  • Iron Compounds / metabolism
  • Minerals / chemistry*
  • Minerals / metabolism
  • Phosphates / chemistry*
  • Phosphates / metabolism
  • Sulfides / chemistry
  • Sulfides / metabolism
  • Water Microbiology*

Substances

  • Iron Compounds
  • Minerals
  • Phosphates
  • Sulfides

Grants and funding

This research was funded by the Netherlands Organisation for Scientific Research (NWO Vidi grant 86405.004 and Open Competition grant 822.01013), the Max-Planck-Gesellschaft and the European Research Council under the European Community's Seventh Framework Programme for ERC Starting Grant #278364 to C.P. Slomp. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.