Seafloor Desertification – A Future Scenario for the Gulf of Finland? - The Baltic Sea Basin - page 371

Fig. 17.6 Schematic map of concretion fields in the Russian part of the northern Gulf of Finland.
1 = concretion fields, 2 = islands, 3 = Russian-Finnish border line, 4 = isobath (from Zhamoida

et al. 2007 )

The scenario explained above is a worst-case scenario and might sound fictitious.
But in many sea areas around the world, anoxia has been reported to intensify and
extend during the last decades, even though often those areas are not so closed and
sensitive as the Baltic Sea and especially the Gulf of Finland. Such episodes have
been reported for example by Chan et al. ( 2008 ) from the coast of Oregon, Naqvi
et al. ( 2000 ) from the western coast of India, and Scavia et al. ( 2003 ) , Justi´cetal.
( 2005 ) and Turner et al. ( 2006 ) from the well-known Gulf of Mexico-Mississippi
River delta anoxic zone.
Also, when taking into account that the seasonal anoxia in the Gulf of Finland
has since the 1950s propagated to shallower bottoms from decade to decade, now
reaching bottoms of less than 20 m (Kotilainen et al. 2007 ) , it can also be speculated
that the more or less permanent anoxia below the halocline, at about 60 m depth,
can propagate to shallower bottoms, if conditions remain favourable for it.

17.6 Discussion

Climate change is affecting the whole human environment. In the seas, these
changes are slow and often unpredictable with today's knowledge and methods.
Thus it is important to speculate with different scenarios such as the one explained
in this chapter. The authors understand that much of the scenario presented here
is speculative and perhaps not possible. However, as long as there are such large
amounts of phosphorus lying on the seafloor of the eastern Gulf of Finland, these
factors should be taken into account in future Gulf of Finland management and
political decision making in addition to reduction of external phosphorus loads and
other measures.