Aquaculture, sea-to-table, aqua-tourism, merroir: Larry Hughes loves using expressive terms for the Lowcountry Oyster Trail. “Why can’t we have aqua-tourism? We have ecotourism,” he said. “It’s just tourism focused on our special marine ecosystem.” When it comes to oysters, “merroir” is the maritime version of what terroir is to wine — the environmental factors that …