Mangrove forests cover much of Florida’s coastline, providing protection from storms, preventing erosion, and creating essential habitat for many different species of fish during their vulnerable juvenile stages, including snook and tarpon.
Worldwide there are more than 50 species of mangrove. In Florida, we are lucky to have three species that call our peninsula home. Mangroves are often found along coastal areas and in shallow flats, thriving in the salty water through adaptations that allow them to extract fresh water in various ways. In Florida, the red, black, and white mangroves can all be found along the coast, with white mangroves rooted higher up on land, red mangroves sitting almost fully submerged in deeper waters, and black mangroves growing in the shallow waters in between. While each species occupies its own specific habitat, each provides a number of benefits to their surrounding environment.
The red mangrove is easily recognized by its long, leg-like prop roots that anchor the plant into the sand or mud bottom and keep it stable as tides sweep water in and around the plant. These prop roots drop down from the plant as the leaves grow above the water, creating a complex network of anchors that not only keep the plant stable, but stabilize the soil as well. With the soil held firmly in place by the roots of the mangrove, the surrounding habitat is protected from erosion, and the coastline may even grow as the roots disrupt the water currents, which allows sediment to drop out of the water onto the bottom. When red mangroves grow in large clusters around coastlines, they can also act as a barrier against large waves, and even protect the land from storms and hurricanes.
Red mangroves serve another important function for the animals living in and around the mangrove community. The complex network of prop roots below the surface of the water create an incredible resource for fish in their vulnerable juvenile stages. Algae, small clams, oysters, and mussels grow on the roots and in the surrounding bottom, and many species of crabs and shrimps are found here. These provide food for small fish, while the physical structure of the mangrove roots keeps larger predators from entering. As juvenile fish grow, they are able to forage close to the mangrove community, but may retreat easily to the safety of the tangled roots if predators approach. Both snook and tarpon utilize this habitat during juvenile phases, until reaching sizes where they are less vulnerable and able to move into more exposed habitats, such as those where they are commonly fished.
Red mangrove roots grow into salt and brackish water, creating complex habitats and anchoring sediment.
Black mangroves use “pneumataphores” to take up oxygen in harsh, low oxygen waters.
Black mangroves also grow in salt and brackish water, but typically shallower than red mangroves and closer to land. In the shallow waters right next to land, water often moves very little, gets very hot, and as a result, is low in oxygen and extraordinarily salty! This creates a harsh environment that is difficult for any plant to survive in, but black mangroves have unique adaptations that allow them to thrive in these habitats. Black mangroves use modified roots, called pneumataphores, that grow up out of the water and take in oxygen while collecting sand and sediments to create stabilization, similar to the red mangrove’s prop roots. In addition, the leaves of black mangroves push out salt, or “sweat,” through special salt pores, allowing the plant to survive off of the fresh water the plant extracts from the surrounding salt water. This allows black mangroves to thrive, despite living in harsh, salty waters.
The white mangrove grows the highest up on the shore and farther away from the water. This mangrove is the least tolerant of cold weather so it is mostly found from Central Florida southward, in warm, tropical areas. The white mangrove has soft leaves that have a white fuzz on them, which is where they get their name. The white mangrove, similar to the black mangrove, also sweats out salt.
Mangroves are vital to the survival of so many important recreational fish species, and are important to the coastal ecosystem. As important nurseries for fish, crustaceans, birds and more, removal of mangrove communities can harm ecosystem health and have large economic impacts. Not only do these communities stop erosion and protect coastlines, but fish species that support huge recreational fisheries around Florida, such as snook and tarpon, rely on these ecosystems as safe places to grow up.
Unfortunately, mangroves are under threat worldwide: globally, approximately 35% of mangroves have been lost, and continue to be lost at a rate of 2% per year; in Florida, approximately 50% of mangroves have already been lost, and degradation of these habitats continues. The devastating effects of losing these mangrove communities has already been seen through declining tarpon populations, even contributing to the recent classification of tarpon as a “vulnerable” species by the International Union for the Conservation of Nature (IUCN), which means that tarpon are in need of strong conservation attention.
Today, cities and towns along with the state have created laws that limit further deforestation, including strict fines and even jail time if you illegally cut or trim mangroves. Over 80% of the mangroves living in Florida today are protected by law, though enforcement of these laws is generally lacking. However, even when coastal mangroves and salt marshes are protected, much of the uplands have been developed or their freshwater flow patterns altered, thus degrading habitat quality of the adjacent mangrove and marsh habitats. So even though many mangrove habitats don’t appear to have suffered direct damage (such as from clearing or dredging), the effects of upland habitat degradation on them is just as damaging.