It is characterised by low salinity, low water temperatures, a long period of ice cover, low primary productivity, low levels of nutrients (particularly phosphorus), and large amounts of riverine runoff adding organic matter and industrial-sourced nutrients (Kronholm et al., The Bay lacks many of the key species of the Baltic, such as bladder wrack, seagrass, blue mussels, cod and sprat. It is characterised by a combination of freshwater and salt-water species and has low biodiversity (Fig. Common starfish (Asterias rubens) and common shore crab (Carcinus maenas) are only present in Kattegat and The Sound (0resund).