Metal pollution left over from mining in the 19th century is weakening the shells of scallops off of the coast of the Isle of Man, a study has warned. Researchers led from York analysed shells from six areas around the island, looking at their thickness, strength and internal mineralogical composition. They said that the seabed off of the coast of Laxey -- a village on the eastern side of the island -- has been contaminated with copper, lead and zinc. While it is not clear how, the result of this appears to be that scallops are growing more brittle shells -- leaving them vulnerable to the claws of crabs and lobsters. Scallops -- as well as other molluscs -- play a key role in maintaining marine ecosystems, as they help to filter the water around them.