Black mangroves use “pneumataphores” to take up oxygen in harsh, low oxygen waters. (Photo Credit: Aaron Adams)
Mangrove Nurseries: Part 2
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.
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.