Estimates of the extent of hypoxia and anoxia in Autumn 2007.

When this reaction occurs, oxygen concentrations are considered negative Over time, there has been a steady increase in the area affected by hydrogen sulphide in the East and West Gotland Basins, and the outer Gulf of Finland. Water from the Gulf of Finland does not enter into the Gulf of Bothnia. As a result, despite its depth, it remains well oxygenated, even during autumn.