Figure 1
Map of the Gdańsk Basin with the location of sampling sites (contour lines are depth in meters)
Figure 2
Variability profile of salinity, temperature and concentration of dissolved oxygen along with depth in the water column in the area of the Gdańsk Deep in August 2015 and February 2016
Table 1
Temperature (T), salinity (S), dissolved oxygen (DO) concentration, oxygen saturation (DOsat), oxidation reduction potential (Eh), pH and the concentrations of sulfate (SO42–), hydrogen sulfide (H2S), phosphate (PO43–) and ferrous iron (Fe(II)) in water above the sediment measured in the Gdansk Deep during the summer and winter voyages (T, S and DO was measured 1 m and other parameters several cm above the sediment surface)
| Voyage | Site | T (°C) | S | DO (cm3 dm–3) | DOsat (%) | Eh (mV) | pH | SO42– (mmol dm–3) | H2S (μmol dm–3) | PO43– (μmol dm–3) | Fe(II) (μmol dm–3) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| VIII 2015 | P1 | 7.27 | 13.37 | 0.86 | 11 | 162 | 7.81 | 16.19 | 1.10 | 12.56 | 0.13 |
| P1A | 7.32 | 13.21 | 1.43 | 18 | 224 | 7.80 | 14.90 | 0.00 | 8.21 | 0.18 | |
| P1B | 7.22 | 13.39 | 1.51 | 19 | 247 | 7.78 | 15.59 | 0.00 | 12.66 | 0.23 | |
| II 2016 | P1 | 6.32 | 12.31 | 0.58 | 7 | 92 | 7.90 | 4.99 | 27.22 | 27.27 | 0.42 |
| P1A | 6.63 | 11.44 | 1.17 | 15 | 194 | 7.90 | 11.04 | 17.80 | 24.66 | 0.51 | |
| P1B | 6.35 | 11.45 | 1.37 | 17 | 217 | 7.88 | 10.63 | 20.85 | 25.68 | 0.53 |
Figure 3
Changes in water content (WC) and loss on ignition (LOI) along with sediment depth in the Gdańsk Deep in August 2015 (a) and February 2016 (b)
Figure 4
Changes of the oxidation reduction potential (Eh) with sediment depth in the Gdańsk Deep in August 2015 and February 2016
Figure 5
Changes in the concentration of sulfates (SO42–), hydrogen sulfide (H2S), total iron (Fetot), ferrous iron (Fe(II)) and phosphates (PO43–) with sediment depth in the Gdańsk Deep in August 2015 and February 2016
Table 2
Benthic fluxes of phosphate (FPO43–) and ferrous iron (FFe(II)) and parameters used for calculations
| Voyage | Site | Porosity | Diffusion coefficient in sediment (10–6 cm2 s–1) | Concentration gradient in surface sediment (δC δz–1) (μmol dm–3cm–1) | Benthic flux (μmol m–2 hr–1) | |||
|---|---|---|---|---|---|---|---|---|
| PO43– | Fe(II) | PO43– | Fe(II) | FPO43– | FFe(II) | |||
| VIII 2015 | PI | 0.975 | 5.034 | 4.932 | 9.468 | 0.018 | 1.67 | 0.31 × 10–2 |
| P1A | 0.975 | 4.145 | 4.060 | 18.57 | 0.046 | 2.70 | 0.62 × 10–2 | |
| P1B | 0.975 | 5.040 | 4.937 | 8.618 | 0.029 | 1.53 | 0.50 × 10–2 | |
| II 2016 | P1 | 0.983 | 4.321 | 4.233 | 10.645 | 0.021 | 1.63 | 0.31 × 10–2 |
| P1A | 0.983 | 4.322 | 4.234 | 16.888 | 0.078 | 2.58 | 1.17 × 10–2 | |
| P1B | 0.983 | 4.323 | 4.233 | 16.580 | 0.084 | 2.54 | 1.25 × 10–2 | |
Table 3
Benthic fluxes of phosphate (FPO43–) and iron (FFe(II)) in different regions of the Baltic Sea
| Region | Estimation method | FPO43– (μmol m–2 hr–1) | References |
|---|---|---|---|
| Gullmarsfjorden | Porewater gradient calculations | 5.42 | Sundby et al. 1986 |
| Gulf of Finland | 0.002–0.07 | Ignatieva 1999 | |
| Gulf of Gdansk | –0.1–7.9 | Graca 2009 | |
| Gdansk Deep | 5.3–5.7 | Graca et al. 2006 | |
| 2.12–2.56 | Łukawska-Matuszewska & Burska 2011 | ||
| Puck Bay | 0.04–3.17 | Bolatek 1992 | |
| Gotland Basin | Chamber incubations | –0.13–15.67 | Viktorsson et al. 2013 |
| 8.33–9.58 | Noffke et al. 2015 | ||
| Region | Estimation method | FFe(II) (μmol m–2 hr–1) | References |
| Gullmarsfjorden | Porewater gradient calculations | 0.83 | Sundby et al. 1986 |
| Gulf of Finland | Sediment core incubation | 3.93 | Lehtoranta & Heiskanen 2003 |
| Gulf of Finland | Chamber incubations | 5.84a) | Almorth et al. 2009 |
| 0.21a) | Pakhomova et al. 2007 | ||
| Vistula Lagoon | 4.16a) | Pakhomova et al. 2007 |
Figure 6
Filters with suspended particulate matter collected from bottom water (about 1 m above sediment surface) in the Gdańsk Deep in August 2015 and February 2016