Mangroves are entanglements of many trees and shrubs of the family Rhizophoraceae that thrive in the intertidal zone, that is to say, the zone which is subjected to low tide and high tide in the coastal ecosystem. Mangroves are found in the tropical areas, along marine shorelines and estuaries, 25° north and 25°south of the equator. The mangrove habitat is extremely salty due to deposition of salt water during high tide and subsequent evaporation, which further increases water salinity. The variations in salinity, temperature and moisture allow only a selected number of plants and trees to inhabit the mangrove ecosystem; however, the mangrove plants and trees provides the habitat for a great number of other living organisms.
Mangroves are usually found in the tropical and subtropical regions of the world, covering an area of around 137,760 km² (53,190 miles²). While mangroves can be found in the latitudes ranging in between 2 5° north to 25° south of the equator, they're more abundant in the lower latitudes, comprising 5° north and 5° south of the equator. Approximately 3/4 of the world's mangroves are located in the territories of Asia, Africa, North America, Central America, South America and Oceania. Though, they're more abundant in Asia.
Unlike plants that grow in environments free of water, mangrove trees have developed a mechanism that allows them to reproduce in the harsh environment of brackish water. Mangrove trees are oviparous, in other words, their seeds germinate without having to fall to the ground or while they're still attached to their parent tree. Once the seedling germinates, it forms a propagule. The mature propagule, then, drops down to the water, where it can remain for long periods of time, before it finds favorable conditions of mud in where to root. If the conditions are not met, the propagule can wander to a more suitable place.
Mangrove plants and trees have developed physiological adaptations to cope with the harsh conditions found in their habitat within the estuary ecosystem. To cope with inundation, some species of mangrove trees, such as red mangroves stay above the water level by the use of stilt roots. The pores in the bark of the roots allow them to breathe oxygen. Other species of trees, such as black mangroves have developed aerial roots, known as pneumatophores, which stick out of the soil, allowing them to take up oxygen from the atmosphere. Pneumatophores can reach hights ranging from 30 cm (12 inches) to 3 meters (10 ft.).
Elimination of salt
Some mangrove trees eliminate the excess content of salt through an ultra-filtration mechanism in their roots. Other tree species secret salt content through two glands situated at the base of their leaves, leaving the salt content visible on the surface of the leaves. To limit the amount of water lost through evaporation, mangrove trees limit transpiration by restraining the pores of their stomata. They also point their leaves away from the sun, especially during times of intense insolation. Their long roots allow them to take the necessary nutrients from the soil.
Mangroves provide great benefits for both animals and humans. The great entanglement of tree roots help to slow the motion of tidal waters entering the system, allowing the sedimentation of more layers of mud. The great mesh of mangrove roots provide the habitat to a number of organisms, including oysters, sponges, barnacles, algae, shrimps and mud lobsters. Crocodiles and snakes hunt within them. They also provide nursery grounds for fish. According to noaa ocean service education, mangrove forests help stabilize the coastline, reducing erosion from storm surges, ocean currents, waves and tides.