Tons of bombs and missiles dumped in the Baltic Sea after World War II are contaminating the seabed and causing mutations in fish populations, researchers say. At the end of the war the Soviet Union and Britain dumped thousands of tons of captured German chemical weapons and agents into the Baltic Sea with many of them ending up on the seabed of the Gotland Basin between Sweden and the Baltic countries. \"Our research has shown that in the Gotland Deep there are about 8,000 shells and missiles that could pollute the environment,\" Jacek Beldowski of the Institute of Oceanology at the Polish Academy of Sciences said. \"We have now confirmed that these objects are contaminating the seabed.\" Mustard gas, accounting for 80 percent of the dumped chemicals, has been turned into a heavy substance by the colds water temperatures, but European scientists warn it may still pose a certain threat to the local fish species and the marine life. Beldowski said studies have already revealed some genetic defects and diseases of the fish population, RIA Novosti reported. The researcher was part of the European Union\'s Chemical Munitions Search and Assessment project, which has discovered additional previously unknown dumping zones of the chemicals weapons in the Baltic. \"When the Russians learned that the goods they transport[ed were] dangerous, they were throwing them overboard as soon as the land was out of sight,\" Beldowski said.