Rhizophora mangle, also known as red mangroves, are native to the intertropical regions on North America, the Caribbean and parts of South America and West Africa (roughly 35°N to 5°N latitude) (Pasiecznik, 2021). Due to their physiology, red mangrove trees tolerate freshwater and saltwater, usually inhabiting mixed-water or brackish areas ("Mangrove Swamps", 2016). There has been a steady decline in red mangrove populations due to coastal development. Government initiatives have been put in place in many areas to try to counteract the decline and help preserve R. mangle populations ("Profile: Rhizophora mangle", 2021). The governments of Florida and Bermuda are planting red mangrove trees along their beaches in an attempt to preserve and promote unique coastal ecosystems from further degradation ("Red mangrove", 2013). ("Mangrove Swamps", 2016; Pasiecznik, 2021; "Profile: Rhizophora mangle", 2021; "Red mangrove", 2013)
Red mangroves cannot survive frosts or arid climates and grow in coastal environments, making their habitat a tropical or temperate climate with shallow waters and mild oceanic currents. Red mangroves inhabit coastlines, putting their roots into the soil or sand below water, while their shoots and crowns remain above water ("Mangrove Swamps", 2016). They can be found further inland from the coast in environments like estuaries because of their ability to tolerate low levels of salinity; Rhizophora mangle can survive in freshwater but are usually outcompeted and thus are found mostly in saltier water ("Profile: Rhizophora mangle", 2021). ("Mangrove Swamps", 2016; "Profile: Rhizophora mangle", 2021)
The common name red mangrove comes from the bright red color of the wood lying beneath the grey outer bark of the tree (Booker et al., 1998). The roots of the red mangrove are uniquely named prop roots for their characteristic arch. Prop roots provide stability in shallow, muddy waters, and in the shifting sands in which they are rooted. In fact, the roots of R. mangle also trap silt and sand, allowing for sturdier future growth and reinforcement of existing roots ("Red mangrove", 2013). Red mangroves produce small, yellow, radially symmetric flowers year-round. Red mangrove fruits are long (up to 20.32 centimeters), skinny tubes that mature and eventually drop in the water. The fruits will land in mud or silt, where they will begin to grow when the tide is low. High sea levels and the buoyancy of the fruit can lead to the fruit being carried in the water until suitable shoreline is reached (Booker et al., 1998). The size of R. mangle varies from 5 to 10 m tall, with many individuals reaching upwards of 20 to 30 m (Pasiecznik, 2021). (Booker, et al., 1998; Pasiecznik, 2021; "Red mangrove", 2013)
After pollination of the flowers, the fertilized ovule becomes the fruit which will fall off into the water or soil. If unable to lodge into the soil, the fruit floats due to its physiology and will be carried by the current until it reaches soil and can establish its roots. The maximum time a fruit can remain dormant is estimated to be about one year (Booker et al. 1998). Once the fruit lodges in the soil, it begins to grow and build up its root and shoot system. Roots are unable to penetrate much deeper than 50 cm in coastal areas, making the prop roots a vital stabilizer for the trees. As indicated by the genus name Rhizophora, red mangroves develop rhizophores (modified lateral branches) for above-ground structural enhancement of the main stem of the tree (Mendez-Alonzo et al., 2015). As the trees continue to mature and grow the cycle of pollination and fruit production begins again. (Booker, et al., 1998; Mendez-Alonzo, et al., 2015; "Profile: Rhizophora mangle", 2021)
As monoecious plants, Rhizophora mangle are technically capable of self-fertilization, however this is not ideal for maintaining genetic diversity and preventing the passing on of deleterious mutations. Red mangrove trees are generalists, as they are not specialized for any specific pollinators. Red mangrove trees rely on bees, butterflies, and wind to pollinate flowers (Profile: Rhizophora mangle, 2021). Flowers of R. mangle are radially symmetric and produce fragrant pollen to attract pollinators.
Lots of energy the energy of R. mangle goes into the production of seeds, which are large and well-adapted to survive in the unstable coastal environments. See the Physical Description section for more detail on the specific adaptations and characteristics of red mangrove seeds. In a study from coastal Brazil measuring conditions in which red mangroves release fruits, it was found that more propagules were released during the wettest part of the year, indicating that precipitation may be an important trigger for the reproduction of R. mangle (Ulf, 2006). ("Profile: Rhizophora mangle", 2021; Ulf, 2006)
Red mangroves are very persistent organisms, and there is little that can cause it to die, but there are strict limitations to their growth. Rhizophora mangle cannot withstand arid, dry climates or sub-freezing temperatures under any circumstances. Red mangroves are particularly adapted to being able to live fully submerged in water, withstanding salinities up to 90 parts per thousand, and survive natural disasters like severe flooding and hurricanes (Davis and Childers, 2007). (Davis and Childers, 2007)
Red mangroves are known to tolerate a range of water conditions. As red mangroves are able to inhabit both oceans and estuaries, they have a tolerance of 0 to 90 ppt of saline in water (Profile: Rhizophora mangle, 2021), however productivity may be limited during dry seasons when saline content is highest (Ulf, 2006). During the dry season, phosphorus and nitrogen content decrease in the soil and water potentially limiting nutrient uptake during this time, however the exact nutrient requirements for R. mangle are unknown (Profile: Rhizophora mangle, 2021). ("Profile: Rhizophora mangle", 2021; Ulf, 2006)
Red mangroves are vital to coastal ecosystems. The establishment of red mangroves help protect coastlines from degradation that may occur due to extreme weather like hurricanes. The root systems of Rhizophora mangle prevent erosion and create a unique habitat for other aquatic life, such as breeding, mating, and feeding grounds for many types of invertebrates, fish, and birds. The broken branches and decaying leaves provide habitat for microorganisms and leach nutrients into the water that helps stimulate primary production in the ecosystem. ("Mangrove Swamps", 2016; "Red mangrove", 2013)
Red mangrove trees provide critical protection to humans from severe coastal weather and erosion. As is noted in the Ecosystem Roles and Conservation Status section, Rhizophora mangle prevent severe erosion and degradation of the land they inhabit ("Red mangrove", 2013). Mangrove trees have also been studied for their efficiency at phytoremediation, having shown greater efficacy of degradation of contaminants such as oil from oil spills (Verâne et al., 2020). Without the stabilizing role of red mangrove trees on our coastal habitats, we would likely see more habitat degradation. ("Mangrove Swamps", 2016; "Red mangrove", 2013; Verâne, et al., 2020)
There are no known adverse effects of Rhizohphora mangle on humans.
The decline of red mangrove populations generally is not of concern, however human development of coastlines is threatening the isolated habitats that red mangroves require.
Government initiatives have been put in place in many areas to try to counteract the decline and help preserve Rhizophora mangle populations ("Profile: Rhizophora mangle", 2021). For example, the government of Bermuda has put R. mangle on the list of its Protected Species act of 2011 in attempts to promote the preservation of these coastal environments ("Red mangrove", 2013).
Melina Takvorian (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
areas with salty water, usually in coastal marshes and estuaries.
the nearshore aquatic habitats near a coast, or shoreline.
mainly lives in water that is not salty.
the area in which the animal is naturally found, the region in which it is endemic.
a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).
mainly lives in oceans, seas, or other bodies of salt water.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
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Root biomechanics in Rhizophora mangle: anatomy, morphology and ecology of mangrove’s flying buttresses. Annals of Botany, 115: 833-840. Accessed February 08, 2020 at https://colostate.primo.exlibrisgroup.com/permalink/01COLSU_INST/51l05n/cdi_pubmedcentral_primary_oai_pubmedcentral_nih_gov_4373286.
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Verâne, J., N. dos Santos, V. da Silva, M. de Almeida, O. de Oliveira, Í. Moreira. 2020. Phytoremediation of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediments using Rhizophora mangle. Marine Pollution Bulletin, 160: 111687.