Growth variations in Arctica islandica L. (Mollusca): A reflection of hydrography-related food supply

Abstract

The growth lines in shells of Arctica islandica from the Fladen Ground have been used to construct long-term chronologies of growth variations. Individual specimens showed characteristic sequences of periods in high and low growth rates. Because the deviations were strongly synchronized, an environmental factor is held responsible. Inter-annual variations in either temperature or phytoplankton abundance could not explain the observed variations. The hypothesis is therefore put forward that the occurrence of dense patches of Arctica and the variations in growth result from variations in import and accumulation of organic matter by an eddy system overlying the area. Evidence for this hypothesis is provided by the correlation between the estimated inter-annual influx of Atlantic water into the North Sea and the observed growth variations.