Tracking Baltic hypoxia and cod migration over millennia with natural tags

摘要

Hypoxia, or the occurrence of low-oxygen conditions, is increasing worldwide in marine, estuarine, and freshwater ecosystems. The Baltic, a semi-enclosed brackish sea, experiences both seasonal and chronic hypoxia and anoxia (zero oxygen) in various parts, and it is the world's largest anthropogenic "dead zone," with increasing severity of episodes during the 2000s (1). We have found a connection between hypoxia in the Baltic Sea and the chemical composition within the ear-stones, or otoliths, of Baltic Sea cod, Gadus morhua.