Red Mangrove (Rhizophora mangle)
Figure 7. Red mangrove ecosystem, Puerto Rico.
The most common species of mangrove in Puerto Rico is the red mangrove. It is usually found in direct contact with the sea, thus becoming the first mangrove species encountered on the coastline, going from the sea towards the land (Figure 6).
Main characteris cs: Leaves: Red mangrove leaves are large (8-10 cm in length, 4-5 cm in width), thick and with a waxy texture, which prevents water loss and slows decomposi on. The leaves are simple, opposite (Figure 8) and are usually grouped at the ps of the branches.
Figure 8. Red mangrove leaves.
Figure 9. Red mangrove aerial prop roots.
Figure 10. Bark on the red mangrove roots.
Roots: The red mangrove is the only mangrove presen ng aerial prop roots, which branch out of the trunk or from the lateral branches and droop towards the ground like s lts (Figures 7 and 9). These roots provide the tree with more stability, allowing it to become established in finelysedimented, poorly consolidated soils. Furthermore, the aerial roots fulfill vital func ons such as nutri on, aera on and salt filtra on. The roots filter the salt through osmosis so that the tree can absorb the water necessary to survive. If the mangrove absorbed salt, it would dehydrate. Bark: The bark covering this mangrove’s roots (Figure 10) contains tannins, organic substances which protect it against bacterial decomposi on and give it a characteris c reddish coloring (tannins are also present in red wine). Also, the bark on the roots and trunk feature pore-like structures called len cels (Figure 11), which aid in the mangrove’s gas exchange (breathing). This is an adap ve response, since the trees grow in poorly-oxygenated or anoxic soils. Red mangrove bark is complete and uniform, differing from other mangrove species.