Mangrove forest showing the tree's exposed root system. Mangroves are salt-tolerant plants (halophytes) that contain a complex salt filtration system and complex root system to cope with salt water immersion and wave action. They are adapted to the low oxygen (anoxic) conditions of waterlogged mud. As the oxygen level in the water-logged ground is extremely low, they use upward extensions (pneumatophores) of the underground root system to obtain oxygen from the air. Photographed in Los Haitises National Park, Dominican Republic.