The black mangrove, Avicennia germinans, is found on coasts of tropical America and West Africa. It is a member of the Verbenaceae family.
The wood of Avicennia germinans is dark-brown to black in colour, the origin of the common name black mangrove, and grows to heights of around 50 feet.
Adaptations Of The Black Mangroves To Their Habitat
The characteristic features of the black mangroves are their ‘snorkels’ called pneumatophores. The black mangroves can be found slightly in shore from the red mangroves but can still survive in saturated water thanks to these breathing tubes. They are usually found in areas that are only exposed to the salt water during the high tide, they will die if they are submerged for a long period of time due to flooding. The pneumatophores are pencil-like and extend upwards from the lateral roots. They are abundant with pores called lenticils and will often reach up to 6 inches above the water level, depending on the tide. They enable the underwater roots to obtain oxygen from the atmosphere.
Like the other mangroves, the black mangrove is tolerant to high salinity waters. The method that Avicennia germinans uses to eliminate salt from the water is via its thick leathery leaves. Unlike the red mangrove that blocks the salt water from entering its roots, the black mangrove excretes the salt once it has entered through the roots, via pores on the surface of its leaves. Salt crystals are clearly visible if you look at the leaves of a black mangrove tree.
Reproduction Of The Black Mangrove
The seed, or propagule, of the black mangrove is shaped like a teardrop, it is about an inch in length and ¾ of an inch in width. The propagules turn from bright green to yellow as they ripen and when ripe enough they fall from the parent tree, usually into water. The propagule has to be in contact with water for a period of at least 14 days before the seed coat will fall off, and a primary root will emerge. The propagules of all the mangrove species have this 'obligatory dispersal' period. A period in which embryonic development continues as the seedling floats until the root system is ready to be initiated.
Medicinal and Physical Uses Of The Black Mangrove
Black mangroves bloom clusters of white, fragrant flowers in June and July. The nectar of the flowers is ‘vigorously sought by bees’ a quote by David Nellis, from the 1994 edition of Seashore Plants of South Florida and the Caribbean, and used for ‘mangrove honey’. Mangrove honey is a very high quality clear honey.
The wood of Avicennia germinans is strong, heavy and hard and has been used for fuel as well as construction, in particularly, marine construction.
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