Red mangroves live where land and ocean meet. This group of mangrove trees grew in a shallow part of the ocean and is in the process of creating its own land. By Andrew Tappert
Red mangrove trees are an important part of shoreline ecosystems in Florida and the Caribbean. Red mangrove trees grow where the land meets water, and they are able to survive with their roots mostly covered by salty ocean water. The roots are anchored in the ocean floor but reach above water level and prop the mangrove trees up so they can grow above water.
Mangrove roots trap sand and soil that are moving with ocean currents. Over time, the sand and soil can build up so much that new land is created. In some places in the Caribbean, scientists have observed that mangrove trees extended the edges of islands by more than a mile over a several hundred year period.
Red mangrove trees have an unusual way of reproducing. Like other trees, they produce flowers that turn into seeds. Unlike other trees, the seeds begin growing while they are still attached to the tree! Red mangrove seedlings, called propagules, grow up to one foot long before they drop off the tree and begin floating in the ocean.
Once a red mangrove seed is floating in the ocean water, it continues to grow by taking nutrients that it needs directly from the water. The seed may float for more than a year before it reaches land. When a seedling washes up onto land, or even a shallow sand bar out in the ocean, it begins to grow roots that attach it to the soil. It will stay in one place for the rest of its life. The seedling grows up to three feet tall in the first year that it is on land. Within three years, the young mangrove tree has a root system that begins trapping sand and soil. The process of building new shoreline has begun.
Many ocean animals spend the early stages of their lives in the shelter of a mangrove tree root system. Fish, crabs, barnacles, crayfish, shrimp, birds, and turtles are just a few of the animals that spend all or part of their lives living in red mangrove swamps.
This mangrove seedling, or propagule, grows while still attached to the tree. After it drops into the ocean, it floats until it finds a shallow location where it can begin growing roots. By Hans Hillewaert
These young mangrove trees are beginning to grow roots that will trap sand and soil. By Hans Hillewaert
For references, please see the above links and the following book:
Ocean. New York, NY: DK Publishing, 2006. Pp. 130-136.