Red mangrove is most easily recognized by its prop roots, arching stilt-like growths that support it and lift it above the level of the water. It can be found in a wide range of coastal environments, including west Africa, the Atlantic coast from northern Brazil through southern Florida, various parts of the Caribbean, the Pacific coast from Ecuador to Baja California, and the Hawaiian islands.
Its scientific name is rhizophora mangle: “rhizo” from the Greek for root and “phora” from the Greek for carry, referring to the roots that support the plant, “mangle” from the same word in Spanish meaning mangrove.
Red Mangroves are specially adapted plants that can exist in water with varying amounts of salinity. These mangroves are found closer to the water than others due to their salt tolerance. They grow in estuarine environments where sea water is brought in by the tide and fresh water arrives as run-off from the mainland. Depending on tide levels and the amount of run-off, salinity can range from .5 parts per thousand up to 35 parts per thousand, which is the approximate salinity of ocean water. Mangroves survive this salinity because they are able to aerate the roots buried deep in the muck by absorbing oxygen from the air into the aerial roots above water and sending it down to the submerged roots below.
The prop roots serve another function, anchoring the plant in a shifting and unstable seabed. The multitude of roots collects silt and debris to build up a soil base beneath the plant.
In true tropics, the Red Mangrove can reach a height of eighty feet, but in subtropical areas like Florida, it most often grows to about twenty feet. Its leaves are in an opposite arrangement, three to five inches long, one to two inches wide, dark green, with a thick waxy quality that reduces the amount of fresh water lost to evaporation.
This plant bears a unique type of seedling, called viviparous. The seeds actually germinate and begin to grow before they drop from the tree. When mature, the seedlings sprout and grow into a six to twelve inch cylindrical pod. This really consists of a long tap root with a small bud at the top, known as a propagule. If the propagule drops into the estuarine muck, the root will quickly sink in and begin to grow a new plant. If the propagule falls into deeper water, it can float around for up to a year before taking root.
Scientists now understand how important mangroves are to coastal ecosystems. In areas susceptible to hurricanes, mangroves provide stability and resist storm erosion. Red Mangrove forests shed over three tons of leaves per acre in a year. This vegetation provides food for a myriad of small creatures that exist and breed in the estuary. Those small creatures feed bigger creatures, supporting the food chain. The sheltered waters under the mangroves are an ideal nursery for juvenile fish. Many species of birds make their home in the tangled growth of the mangroves.
The next time you are along the coast, maybe out for a day of fishing, notice the Red Mangroves. They are not beautiful plants, with their bushy lump of leaves on top and awkward protruding roots below, but they are an important part of sustaining and protecting the coastal environment.
