It’s an ocean of trouble out there — such were the conclusions of the U.S. Commission on Ocean Policy, which issued an interim report today at the halfway-point of an 18-month study of ocean health and marine resources. So far, the commission has found that about 40,000 acres of coastal wetlands in the U.S. are disappearing annually, threatening the spawning, feeding, and nursery areas of three-quarters of the nation’s commercial fish catches. Of the fish stocks that have been thoroughly studied, 40 percent are depleted or overfished. And a different kind of threat is being posed by invasive species spread by ballast water released from ships. “The oceans are in trouble; the coasts are in trouble; our marine resources are in trouble. These are not challenges we can sweep aside,” said James Watkins, the leader of the commission, who is a former chief of naval operations and a national-security expert. The panel expects to recommend consolidation of federal and state ocean-management policies through a national coordinating body.