Figure 1.

Lowest recorded oxygen concentration at all monitoring locations throughout the period (1955–2009) in the entire Baltic Sea with insets for the Stockholm Archipelago (upper left) and the Finnish Archipelago Sea (lower right). Oxygen concentrations in bottom waters was divided into four categories (<0 mg L^–1, 0–2 mg L^–1, 2–4 mg L^–1, >4 mg L^–1). Oxygen concentrations <0 mg L^–1 are anoxic, 0–2 mg L^–1 are considered hypoxic by definition, and 2–4 mg L^–1 are considered oxygen stressed.(26)