Sediment DSi and DIP fluxes under changing oxygen availability in bottom waters

In the present study, we investigated how sediment fluxes of dissolved silica (DSi) and dissolved inorganic phosphorus (DIP) were affected by dissolved oxygen (DO) availability in bottom waters. Sediments from two sites in the Baltic proper were incubated under changing oxygen conditions. Our results show that when DO availability decreased from oxic to hypoxic level, the average DSi fluxes decreased significantly at the two sites from 2.12 ± 0.04 to 0.87 ± 0.18 and from 2.37 ± 0.09 to 1.91 ± 0.55 mmol Si m–2 d–1, respectively. Average DIP fluxes increased significantly at one site from 0.06 ± 0.01 to 0.14 ± 0.02 mmol P m–2 d–1, but not at the other (from 0.06 ± 0.01 to 0.07 ± 0.01 mmol P m–2 d–1). These results indicate that a change from highly oxic to hypoxic conditions in bottom waters may decrease DSi fluxes and increase DIP fluxes. However, sediment characteristics can lead to spatial differences in the response of DSi and DIP fluxes to oxygen availability.