Introduction:
American mangrove (Rhizophora mangle) in an American Swamp.
Rhizophora mangle (the red mangrove) is a coastal, estauarine species that can tolerate saltwater and extended flooding. It commonly forms monoculture stands in its native range, or is associated with two other common species of mangrove; the black mangrove and the white mangrove. It can flower year-round and the seed remains on the parent plant where it is in constant development until it germinates on the plant and then is released for dispersal. The red mangrove has a large native range and has been introduced to Hawaii where it is considered an invasive species.
Description:
Rhizophora mangle is a small aquatic tree or shrub, that can reach heights between 5-20m and a trunk diameter between 20-50cm. The bark is gray to brown, thin when a sapling, becoming thick and furrowed with maturity. The leaves are evergreen, opposite, simple, entire, elliptical, thick and leathery, the tops dark green, glossy to glabrous, with undersides yellow-green with black dots and no visible veination. Leaf width 2.5-6cm and length 6-12cm. Prop roots originate from the stem or trunk of the plant about 2-4.5m high and function in stabilizing the plant in the ground and facilitate gas exchange for respiration during periods when it is completelt submersed in standing water.
Habitat description:
The red mangrove is found in five different topographical communities in subtropical to tropical coastal regions: fringe, riverine, overwash, basin, and supra-tidal flats. The differences amongst these classifications is due to elevation and its respect to the rise and fall of the water-level and its approximatey to the ocean. The red magrove can survive under permanent submersion, resulting from flooding, due to its unique anatomy and physiology. However, the red mangrove cannot tolerate arid conditions during seedling establishment, so often communities develop around spatial and temporal water patterns. The red magrove can tolerate salinity ranges from 0-90 parts per thousand, with higher salinity contents of the sediment impacting red mangrove establishment . Temperature ranges are from 21.6 °C - 25.6 °C and sub-freezing temperature is what limits this species’ range to below the 28° latitude in both hemispheres. Sedimentation type varies widely and pH ranges fall between 5.3-8.5. The red mangrove can tolerate full sun and grows best under these conditions, however, seedlings can survive in the understory until a gap forms in the overtsory.
Geographical range:
Native range:
North Carolina, South Carolina, Florida, United States, Mexico, Costa Rica, Panama, Belize, Bermuda, Colombia, Brazil, Ecuador, Galapagos Islands, Guyana, Puerto Rico, Netherlands Antilles, Trinidad-Tobago, Suriname, Venezuela, Peru, French Polynesia, Polynesia, Melanesia, Nigeria, Benin, Togo, Ghana, Ivory Coast, Liberia, Sierra Leone, Guinea, Guinea-Bissau, Gambia, Senegal, Angola.
Known introduced range:
Hawaii, United States, Queensland, Australia.
Distribution Map:
Distribution of American mangrove (Rhizophora mangle) in Green.
Management information:
Integrated management:
To know the extent of the population of the red mangrove in a given region mapping techniques are recommended to quantify the severity of the problem. This information not only could be used classifying forest communities but also attmept to further explain the distribution pattern of the species. This may lead to local involvement in either a restoration project in areas where mangrove forests are being dessimated or in locales like Hawaii where management options focus on eradication.
Physical:
Close up image of American mangrove (Rhizophora mangle).
Physical control options are expensive, timely and moderately to highly effective. Cutting back vegetation with machinery, hand tools, and dredging canals and pools where it grows are all an effective means of reducing the population pool and allowing native species to return. If cutback to 10cm above the ground it is not likely to resprout, and if young mangroves in standing water are cutback to the waterline, they too are not likely to resprout.
Chemical:
The chemical Garlon 4 has been shown to be successful at eradicating the red mangrove with basal treatments .
Biological:
A possible biological control is a species of fungus Cystospora rhizophorae which enters the red mangrove through wounded tissue and forms cankers on stem tissue. The fungus has been reported to cause a 33% mortality rate in seedlings when inoculated in the field.
