Florida’s mysterious mangroves
Mangroves are indispensable to the health of the Charlotte Harbor estuary. They stabilize shorelines, prevent erosion during storms and provide prime real estate for nesting seabirds. But their greatest contribution occurs when they shed their leaves, which sink and rot, supplying nutrients to a huge variety of microscopic creatures and forging links in a multitude of food chains. Falling at an average rate of three and a half tons per acre, mangrove leaf litter sustains fungi, bacteria, protozoans, marine worms, copepods, amphipods, shrimp, crabs, mollusks, striped mullet and, ultimately, a sizeable portion of the local economy. At some point in its life cycle, every commercial fish or shellfish taken in Charlotte Harbor depends on the mangroves in some way.
In southern Florida, there are only three mangrove species, living more or less communally. Red mangroves, Rhizophora mangle, are typically found growing at, or a little above, mean sea level. Their long “prop roots” arch into the sea like the tines of an inverted antler, providing sanctuary for young fish and anchorage for oysters and barnacles. Black mangroves, Avicennia germinans, colonize the upper reaches of the intertidal zone. Clusters of odd breathing tubes, called “pnuematophores,” grow from their shallow, extensive root systems, projecting from the mud like thousands of slender cigars. White mangroves, Laguncularia racemosa, favor slightly higher ground, thriving in soil that’s seldom flooded, except during the highest tides and storm surges. They’re usually accompanied by a fourth species, buttonwood, Conocarpus erecta, considered a “mangrove associate” because it lacks some of the adaptations of the other three.
Mangroves are facultative halophytes, which means they can grow in either fresh or salt water. Their seedlings, called “propagules,” germinate while still on the tree. The propagules of black and white mangroves are small and short-lived, but those of the red mangrove are up to a foot in length. Like little green torpedoes, they drop into the sea, drifting for thousands of miles and remaining viable for up to a year. Eventually one end turns brown and becomes waterlogged, causing the propagule to float vertically. If it comes to rest on a tropical mudflat, the oscillations of the waves will embed the tip in the sediment and the seedling will grow.
The next time you visit the estuary, take a moment to explore the mangrove ecosystem. Keep an eye open for red mangrove propagules; as you stroll along the tide line, chances are you’ll find several. Choose one that seems viable, and stick it point-first into the mud. Plant it near mean sea level, so that it’s sometimes wet, sometimes dry.
Think of it as casting a vote for the health and productivity of the estuary. It may seem like a small gesture, but as we all know, every vote counts.
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