The soft-shell clam in the North Sea basin: descendants of ancestors hitchhiking with the Vikings from North America to Europe?
Published: 9 March 2017
The species survived at the east coast of North America. Datings of Mya shells found in northern Denmark and the southern Baltic Sea suggest that repopulation of northwest European coasts already occurred before Columbus’ discovery of America (1492), possibly facilitated by Viking (Norse) settlers at Greenland and northeast North America , as was suggested by Petersen et al. (1992). Nowadays the soft-shell clam is common along the coasts of the North Sea, the Balthic Sea, northern Adriatic Sea, the Black Sea, Ireland, England, Atlantic France, Spain, and even in the Mediterranean Sea. It has been a very successful invader.
A recent study of the Sunken History Foundation, Deltares and the Universities of Utrecht, Groningen and Leiden (Essink et al., 2017) published in Netherlands Journal of GeoSciences dated M. arenaria shells of older coastal deposits. Using a precise isotope analysis method it was shown for four locations in the coastal landscape of the Netherlands that the shells date from the 13th to 15th century AD. It provides further evidence of the re-introduction of this invasive species from its native range in northeast America into European waters in the Medieval Period. As a consequence, it supports the hypothesis of Viking-mediated transfer of this species from northeast America to northwest European waters. To test the hypothesis by Petersen et al. (1992) Essink and Oost are currently investigating in more detail if Viking-mediated transport was indeed possible and if there could be other plausible cross-Atlantic pathways. At the moment the arguments for Mya hitchhiking with the Vikings seem the most convincing.
Albert Oost (geologist Deltares): as Mya arenaria is an invasive species it is exciting to notice that wide spreading in NW Europe already took place in the Middle Ages. It provides an excellent indicator for the age of marine deposits of the North Sea basin.