Figure 1.
Location map of the study sites in the Bothnian Sea.
Site characteristics are given in Table 1. Simplified bathymetric overlay and bottom sediment type are adapted from [73] and [72], respectively.
Table 1.
Characteristics of the 6 study sites based on conditions at the time of sampling in October 2008 and June 2009.
Figure 2.
Porewater profiles of key components for June 2009 and October 2008.
Units are in µmol/l. Note the different scales for group 1 and groups 2 and 3.
Figure 3.
Porewater profiles of SO42− and CH4 for sites US2 and US5b for June 2009.
Figure 4.
Sediment depth profiles of CDB Fe, total Fe, total Mn and total S (in µmol/g).
CDB-Fe is typically used as a measure of total Fe-oxide Fe in the sediment but may include vivianite-Fe [33] and Fe-sulfides [26].
Figure 5.
Sediment phosphorus speciation (in µmol/g) and organic carbon contents (Corg in wt%) for all sites.
Figure 6.
Depth profiles of sediment P, Fe and Mn (in µmol/g).
Sediments for sites US5B and SR5 were extracted with CDB (filled circles) and ascorbate (open circles).
Figure 7.
Compilation of key sediment and porewater profiles for US5B.
Depth profiles of sediment contents of CDB-Fe, total sulfur (Stot), reactive Fe oxides (Fereac; see text) and Fe-bound P in units of µmol/g, and depth profiles of porewater concentrations of methane, sulfate and dissolved Fe2+ and PO4 (in µmol/l) for site US5B. Data are for October 2008, unless indicated otherwise.
Figure 8.
Schematic of key processes affecting S, Fe, CH4 and P in and below the SMT.
The dotted lines indicate how the release of Fe2+ and PO4 from Fe-oxides lead to Fe(II)-P formation.
Table 2.
Reactive P burial in the Bothnian Sea.