Given the clear waters and the dazzling calm stretching this spring morning from Villananitos beach to the wall of residential buildings on La Manga, a sandspit on the far side of the lagoon, it is hard to recall how the Mar Menor collapsed exactly 10 years ago. A biological breakdown known as the “green soup” devastated the iconic wetland, located in the region of Murcia in southeastern Spain. To this day, although remarkably recovered, the nat…