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What happens to the organic material and iron in the Baltic Sea?

27.04.12, 17:53 (comments: 1)

The dissolved organic matter and iron that comes from river mouths along the coast can potentially generate large effects on the organisms and processes in the Baltic Sea. One example is that iron is at times the element that is limiting the production of toxic cyanobacterial blooms that are reported in the newspapers most summers. That iron is limiting these blooms suggest that an increase in iron may result in increased production of the toxic cyanobacteria, or blue-green algae that they are also known as. 


Flocculation of iron at 23 permil.


Both organic matter and especially iron are known to aggregate and sediment in more saline waters. The question then is if the salinity of the Baltic Sea is high enough for the iron to fall out of the water into the sediments near the coasts. If that is the case than increasing export of iron will not really affect the open Baltic sea. To test this we are starting a project looking at aggregation and what factors are determining to what extent organic matter and iron is sedimented in estuaries. The pictures show water from Lyckebyån with four different salinities: 0, 5, 12 and 23 permil. This covers more or less the salinity from the Bothnian Bay in the north all the way to the Öresund. We were intrigued to see that there is no flocculation at 5 permil which is the salinity all the way down to Gotland. This suggests that the iron may, in fact, reach quite far beyond the estuaries in the eastern Baltic Sea.

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Comment by Enis Hrustić | 21.08.12

I am interested into floculation of iron and organic matter from the sea, separately or togehther, and I wonder do you have any recommendations from the literature or your papers and new results. We have to prepare some sea water with no iron and no organic matter inside.

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