How do marsh and mangrove habitats compare?

In seagrass beds in Florida, nutrient supply appears to be more important than canopy complexity for epifauna. How does that conclusion apply to salt marshes in Texas?

Most Texas salt marshes are dominated by Spartina alterniflora (cordgrass). This forms a dense, complex canopy (left) that is critical habitat for a variety of animals, including snails, shrimp, and juvenile fish. But, in some parts of the Texas coast, native mangroves (Avicennia germinans) are behaving like invasives and converting marshes into dwarf mangrove forests. This change may have been influenced by climate change, which brings milder winters and less frequent freeze events to limit the spread of mangroves. Continuing climate change may accelerate mangrove proliferation, particularly in transition zones like Port Aransas.




Mangroves have aerial root structures (left) that may provide analogous habitat to salt marshes for marsh fauna. I have observed snails using marsh grasses and mangrove pneumatophores in similar ways. But will other important marsh fauna, like brown shrimp or juvenile fish, use marsh and mangrove structures in the same way? In other parts of the world, the answer is "no," but here in Texas, where we are at the transition between marsh and mangrove habitats, the answer is unknown. We will soon begin collecting fauna from both habitats to find out.