A collection of mangroves, which are tree-like shrubs that are tolerant to saltwater
and brackish conditions, mangrove forests are most common between the latitudes of 30° on either side of the equator
. The mangrove
plants take approximately 20 years to reach maturity and can reach a height of 30 meters, though they are usually shorter than that. Most notably, mangroves have large root
systems which anchor them into the soft oceanbed; these roots are usually specifically adapted to take in oxygen
There are approximately 12 genera of mangrove trees and shrubs with about 60 species. However, the most dominant genera are as follows.
- red mangroves (Rhizophora): Produce what are known as "stilt roots," which sprout from the lower section of the trunk in order to compensate for low oxygen levels. They grow sideways and downwards in order to remain stable in the loose mud.
- black mangroves (Avicennia): Produce "pencil roots," which grow under the ground and then surface again in a series of spikes which surround the tree. This adaptation, as well as stilt root systems, are useful at low tide when they are uncovered; then they can readily take in oxygen.
The seeds of mangrove trees germinate on the tree itself; the young plants detach when they are self-sufficient and take root elsewhere. The actual size of mangrove forests varies. The most important factor affecting size is tidal range. Areas with large ranges and flat oceanbeds have huge areas of forest that are host to intertidal organisms. Brackish mangrove forests tend to have a less various animal population that those in saltwater conditions.
Organisms find homes in the muddy sediment, the oceanbed surface, the trunks and roots of the trees and the canopy of the forest above the waterline. Animals found in these habitats include many sessile creatures like barnacles, tunicates, oysters and sponges. Other organisms found there are snails and crabs, particularly the fiddler crab (Uca dussumieri). Also, certain species of mudskippers (particularly Periophthalmodon schlosseri), polychaete worms, shrimps and amphipods live in mangrove forests.
Many initiatives are being taken on behalf of the preservation of these habitats. The U.S. Geological Survey is paying considerable attention to the mangrove forests along the Florida coastline. Other groups have recognized the importance of this resource as well:
"The Mangrove Replenishment Initiative (MRI) began as a local project along the central east coast of Florida; however, in the last few years it has contributed to a wide range of habitat creation and restoration programs that are international in scope. In addition, MRI directed and coordinated programs have been conducted to achieve educational objectives for participants involved in restoration projects. Mangrove trees offer significant and unique habitat to birds, mammals, crustaceans, and fish populations through a complex marine food chain. They create breeding habitat and establish restrictive areas for the protection of maturing offspring. ... To have any potential of establishing shoreline mangroves when using conventional methods, the seedlings must be planted only in areas well shielded from any substantial wave action or upland run-off. These conditions translate into restrictions not simply on the geographic location of a potential replenishment project, but also on the relative size and range of any planting. Many shorelines that would be desirable for mangrove establishment, present formidable factors prohibiting the successful introduction of the tree with conventional methods. Much of the initial work done by MRI volunteers was in support of research efforts to develop and define a methodology for establishing self-sustaining, mangrove-stabilized shorelines; particularly shores that had been modified by shoreline hardening (revetments, bulkheads, retaining structures) or areas where topography has been artificially changed, such that physical shoreline conditions were no longer favorable for natural mangrove recruitment."
*Quotation from http://mangrove.org/video/mri.htm.
Thanks to Anark for alerting me to the restoration projects in Florida. =)