Interdecadal variations in the inorganic phosphorus content in the Atlantic Water and their possible impact on commercial resources of the Barents Sea

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Since the second half of the last century interdecadal variations in the content of inorganic phosphorus in the southern Barents Sea waters occurred quasi-synchronously with similar variations in the active layer of the Atlantic Water over a large area from the Irminger Sea to the Baltic Sea and from the Porcupine Plateau to the Norwegian Sea. Interdecadal structural changes in the Barents Sea ecosystem, manifested as variations in the total biomass and catches of some fish species, are caused by changes in the “cumulative” properties of seawater, in particular, stratification and inorganic phosphorus content. In line with general eutrophication-related trends, an increased content of phosphates in the Barents Sea and adjacent areas of the Atlantic coincided with a decrease in biomass and catches of relatively long-lived species (cod and herring) and a simultaneous increase in those for capelin, a short-lived plankton-eater. So, in the periods of low inorganic phosphorus content in seawater, the Barents Sea ecosystem can be classified as a continental shelf temperate marine ecosystem. When the total level of inorganic phosphorus in the environment was high, the food chain structure was closer to that typical of biological communities inhabiting the Arctic seas and upwelling areas.