Posted by: Hourglass PJ14 APR 2010
My father, who had an enormous interest in shipwrecks, told me that those in the Baltic Sea are distinguished from those in many other places by their lack of deterioration. But I never knew why.
I was therefore interested to read in an Associated Press report of a dozen unusually well preserved shipwrecks recently found in the Baltic. The oldest is believed to date from medieval times and could be up to 800 years old, and others are thought to date from the 17th and 19th centuries. The 12 wrecks were found in a 30-mile long and two-mile wide corridor east of the Swedish island of Gotland by a gas company building an underwater pipeline between Russia and Germany.
But why are the wrecks so well preserved? Because of the near absence of the so-called shipworm (actually a small clam), which burrows into and gradually destroys the wooden structures in saltier oceans. However, one species of shipworm, Teredo navalis, is now apparently spreading to the Baltic to a greater extent than previously.
It has largely avoided the Baltic as it does not do well in its low salinity waters, needing a relatively high salinity to reproduce. But Scandinavian researchers have speculated that a combination of warmer summers, milder winters and higher nutrient inputs into the water (eutrophication) may help the shipworm to tolerate a lower salinity.
Currently, around 100,000 well preserved shipwrecks lie in the Baltic Sea, all at risk of damage from these “termites of the sea”. An EU project, Wreck Protect, is examining their spread in the Baltic and plans to develop guidelines for protecting its submerged cultural heritage.