Learn about Mangrove Ecology
Mangroves are tropical tidal forests that occur exclusively along the land/water interface. They generally develop on low energy coastlines, where they are protected from waves’ action. They typically occupy large intertidal zones, which are characterized by very fine sediment substrates. As a result of their particular place in the landscape, mangroves have adapted structural modifications like aerial roots and salt excluding or excreting organs to survive the coastal environment. Despite their salt tolerance, mangroves develop best in environments where freshwater is also present, either from river discharge or precipitation and runoff.
The large tidal range occupied by mangroves generally displays a flood frequency gradient within the forest, where the lowest lying parts are flooded daily, and where the uppermost locations of the forest are only flooded during spring tides (the highest high tides happening on full moon and new moon). Similarly, a salinity gradient generally develops between the source of freshwater and the zones of tidal influence. These two gradients are the major abiotic factors determining the distribution of mangrove species within a forest, which typically exhibit clear zonation parallel to the coastline.
While species assemblage varies across different regions of the world, distinct mangrove “classes” composed of morphologically similar species occupy two major zones:
- Plants displaying adventitious roots, like species of the genus Rhizophora (red mangroves for example), tend to occur at the lowest elevation, where flooding intensity and frequency are the highest.
- Plants displaying pneumatophore roots, like species of the genus Avicennia (black mangroves for example), tend to occur at higher elevation, where both flooding intensity and frequency are reduced.
Go to the Surviving the Coastal Environment page to see pictures of the roots of both red and black mangroves!