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Sources and fate of manganese in a tidal basin of the German Wadden Sea
Dellwig, O.; Bosselmann, K.; Kölsch, S.; Hentscher, M.; Hinrichs, J.; Böttcher, M.E.; Reuter, R.; Brumsack, H.-J. (2007). Sources and fate of manganese in a tidal basin of the German Wadden Sea. J. Sea Res. 57(1): 1-18.
In: Journal of Sea Research. Elsevier/Netherlands Institute for Sea Research: Amsterdam; Den Burg. ISSN 1385-1101, more
Peer reviewed article  

Available in  Authors 

    Biodegradation; Freshwater environment; Manganese; Pore water; Sediments; Sulphate reduction; Tidal flats; ANE, Germany [Marine Regions]; ANE, Wadden Sea [Marine Regions]; Marine; Brackish water; Fresh water

Authors  Top 
  • Dellwig, O.
  • Bosselmann, K.
  • Kölsch, S.
  • Hentscher, M.
  • Hinrichs, J.
  • Böttcher, M.E.
  • Reuter, R.
  • Brumsack, H.-J.

    Dissolved and particulate Mn concentrations were investigated on a seasonal scale in surface waters of the NW German Wadden Sea (Spiekeroog Island) in 2002 and 2003. As the Wadden Sea forms the transition zone between the terrestrial and marine realms, Mn was analysed in coastal freshwater tributaries and in the adjoining German Bight as well. Additionally, sediments and porewaters of the tidal flat sediments were analysed for Mn partitioning and microbial activity. Dissolved Mn concentrations show strong tidal and seasonal variation with elevated concentrations during summer at low tide. Summer values in the Wadden Sea (av. 0.7 µM) are distinctly higher than in the central areas of the German Bight (av. 0.02 µM), suggesting a possible impact of the Wadden Sea environment on the Mn budget of the North Sea. Seasonality is also observed for particulate Mn in the Wadden Sea (winter av. 800 mg kg-1; summer av. 1360 mg kg-1). Although particles are relatively Mn-poor during winter, the high SPM load during this season causes elevated excess concentrations of particulate Mn, which in part exceed those of the dissolved phase. Therefore, winter values cannot be ignored in balance calculations for the Wadden Sea system. Porewater Mn concentrations differ depending on sediment type and season. Maximum concentrations are found in surface sediments at a mixed flat site (190 µM) during summer, while winter values are distinctly lower. This indicates that enhanced microbial activity owing to higher temperature during summer leads to increased reduction of Mn-oxides in surface sediments and enhances the corresponding diffusive and advective Mn flux across the sediment-water interface. Draining of Mn-rich porewaters from sediments is also documented by analyses of tidal creek waters, which are highly enriched in Mn during summer. Furthermore, an important Mn source is freshwater discharged into the Wadden Sea via a flood-gate. The concentration of dissolved Mn in freshwater was highly variable during the sampling campaigns in 2002 and 2003, averaging 4 µM. In contrast, particulate Mn displayed a seasonal behaviour with increasing contents during summer. On the basis of salinity variations in the Wadden Sea, the total amount of Mn contributed to the Wadden Sea via freshwater was estimated. This balance shows the importance of the freshwater environment for the Mn inventory of the Wadden Sea. During winter the total Mn inventory of the Wadden Sea water column may be explained almost completely by freshwater discharge, whereas in summer the porewater system forms the dominating source.

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