The pie charts indicate the relative spatial coverage of areas with the four different concentrations of DO, aggregated by Marine Strategy Framework Directive (MSFD) marine regions - North-East Atlantic Ocean, Baltic Sea, Mediterranean Sea and Black Sea (smaller pie charts) and for all regions combined (large pie chart in centre). Oxygen concentrations above 6mg/l are considered to support marine life with minimal problems while concentrations less than 2mg/l (hypoxia, oxygen deficiency) are considered to cause severe problems. (Source: EEA)