Black mangroves (Avicennia germinans) are becoming increasingly common in coastal wetlands along the Gulf of Mexico (USA). As mangroves displace salt marsh vegetation, there may be consequences for predator-prey interactions in these wetland ecosystems. The overall objective of my dissertation was to determine if and how mangrove expansion may affect predator-prey interactions along the Texas coast. I investigated the effects of vegetation type on predation success of the blue crab (Callinectes sapidus) and the prey refuge value for penaeid shrimp (Family Penaeidae) in a lab study. Additionally, I investigated the potential impacts of mangrove expansion on prey refuge for a vertically migrating snail, the marsh periwinkle (Littoraria irrorata), in a series of field studies. Lastly, I determined if the presence of mangroves influenced foraging habitat selection of wading birds in coastal wetlands of Galveston County, Texas. In the lab study, a matrix of rigid dowels emulating mangrove aerial roots reduced predation success of blue crabs compared to the flexible, artificial marsh vegetation. Additionally, shrimp preferred the artificial mangrove structures relative to the simulated marsh vegetation in the presence of a predator. In the field studies, more snails survived in the mangroves at the benthos where blue crabs were the primary predator. However, more snails survived in the marsh when they were tethered higher up in the canopy where they were accessible to wading birds. The presence of mangroves did not influence wading bird foraging habitat selection. The factor that most affected wading bird abundance was distance to a nesting island. These results indicate that mangroves have complex effects on predator-prey interactions, and may alter foraging activities of key predators in coastal wetlands.
