The phrase "black mangrove" refers to a type of tree that grows in coastal areas with its roots partially submerged in water. It is called "black" because its bark is dark-colored. Full definition
The river is closely lined with swamps of black mangrove, which are protected by law and provide stability for the banks as well as habitat for many species of animals and birds. (ambergrisCaye.com)
Black mangrove pneumatophores not only act as a «snorkel» for the roots to breath, they trap sediment and may remove chemicals from water running into the sea. (AmbergrisCaye.com)
Patches of dwarf red mangrove (dwarf because of the lack of phosphate in the soil in certain areas), white and black mangrove line the channel. (ambergrisCaye.com)