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The mangrove forest — All about my home
Hello! I’m Lucie, Sebastian Snook’s sister. You have probably noticed that our comfy little nook is a home in the mangroves. Many of my neighbors also spend time in the mangroves because the intricate root systems of mangroves provides great places to escape from predators.
Though mangroves can grow in freshwater, they avoid having to compete with other plants for light and space by growing where most other plants can’t grow: in the brackish (somewhat salty) water of estuaries like the Indian River Lagoon.
Because mangroves grow right at the water’s edge, their roots are wet or under water most of the time. That makes them great habitat (living area) for species like barnacles, mussels and oysters that have to live attached to a surface. For creatures that can move around, mangrove roots are excellent feeding and sheltering areas where young fish like me can find plenty of food and a hiding place from bigger fish, crabs and birds that could try to eat me. In areas of the Indian River Lagoon where there are many mangroves, you will find all kinds of creatures living the good life.
You may not realize it, but mangrove leaves are an important part of the food web here in the lagoon. The mangrove tree crab (Aratus pisonii) eats the leaves of the red mangrove right off the tree, but most other species have to wait until the leaves fall.
When leaves fall from the trees, fungi and bacteria decompose the leaves and turn them into “detritus.” Detritus forms the base of the food web in the lagoon, and many species such as crabs, shrimps, oysters, clams, anchovies and mullet depend on detritus for food. These creatures are preyed upon by larger crabs, birds and big fish like snook, seatrout, red drum and tarpon. Sharks, dolphins and alligators then eat the bigger fish. Let's not forget you humans. You are part of the food web too when you eat crabs, shrimp and fish.
In Florida, mangroves are protected and there are rules that prevent people from cutting them down or removing them. That’s a good thing. Why? The thick tangles of mangrove trees and their roots help protect the coasts from wave and wind damage during hurricanes and tropical storms.
Mangrove roots also slow down the flow of tidal water so that sediments in the water sink to the bottom. So in a way, mangroves use the sediments they trap to build their own environment!
You can find three kinds of mangroves
in the Indian River Lagoon.
The red mangrove is known as the “walking tree” because its prop roots look like legs walking in the water. The roots of this tree actually grow from the trunk and branches of the tree down into the water. This mangrove has reddish bark on the trunk and has the largest, shiniest leaves of all the Florida mangrove species. The leaf color is dark green on the top, but lighter green on the underside.
The red mangrove flowers nearly all year long and produces unique string bean-shaped fruits called propagules that grow into seedlings while still attached to the parent tree. When they are ready to grow on their own, propagules drop off into the water where they either take root in the ground or float and drift for as long as a year until they find a suitable place to grow.
The black mangrove is usually found at higher elevations than red mangrove. The base of a black mangrove is surrounded by pneumatophores (pronounced “new-mat-afores”), finger-like twigs that grow straight up out of the ground. Pneumatophores are a kind of air root, which extend above the high water line and help the trees to breathe by moving air into the roots. The bark of the black mangrove is dark and its leaves are narrow and pointed at the tips. Leaf color is a shiny dark green on top and silvery green on the underside. The propagules are light green in color and shaped like lima beans.
Black mangroves have one other interesting trait: the leaves of a black mangrove nearly always have white crusts on them, especially on the backs of the leaves. Want to guess what these crusts are? They’re salt! Go ahead and taste it for yourself if you like. You see, black mangroves take in salt water, but they don’t use the salt, so it gets released through the leaves.
The white mangrove is usually found at higher elevations than either red or black mangroves. You can identify the white mangrove by its light green leaves, which are the most rounded of the Florida mangroves. Leaves have a small notch at the tip and two tiny glands at the leaf base. These glands release both salt and nectar, which encourages insects like ants or bees to come visit the tree.
The almond-shaped propagules of a white mangrove are about the size of a nickel and whitish in color.
As you can see, mangroves are very special trees. They thrive under salty conditions that would kill many other plants, and because they live right along the shoreline, their roots provide habitat for lots of lagoon animals like me and my friends. The next time you see mangroves in the lagoon, take a minute to check out all the creatures that live on mangrove roots and feed under the protection that mangroves provide.
Remember there is much more happening here than meets the eye.