LONDON (Reuters) - The threat of an al Qaeda attack from the sea remains an "absolute concern" and could intensify as operations on land are countered, the U.S. Navy's top commander in the Gulf told Reuters on Monday. Since the September 11 attacks on the United States, governments and security experts have repeatedly voiced fears about the vulnerability of the maritime industry, which carries more than 90 percent of the world's traded goods. "I don't think there is any question that as we thwart their attacks and disrupt their operations on land, that we should expect them to turn to...