South Korea's first international seaweed-themed expo on Wando island is undergoing the finishing touches before its opening one week from now, organizers said Friday. The Wando Seaweeds Expo 2014 will open on the island off the country's southeastern coast on April 11 for a month-long run under the theme of "seaweeds and their role in mankind's future."    The expo's main exhibition hall was opened to the press for the first time on Thursday, the organizing committee said, adding that it is in the final stage of fine-tuning other venues and security measures.