Mangrove wetlands are coastal forested wetlands that are periodically flooded. These wetlands form one of the most important intertidal plant communities found along low wave-energy shorelines in the tropics. As the interface between marine and terrestrial ecosystems, mangrove wetlands provide a unique and vital habitat as well as ecosystem services for both the upland and seaward environments. They are highly productive environments that support a variety of flora and fauna.
Mangroves offer critically important ecosystem services to terrestrial, coastal, and marine communities. Mangrove leaf litter and other organic matter flushed into nearby seagrass and reef habitat provide nutrient input for filter feeders and benthic scavengers (Snedaker and Getter 1985). Mangroves with extensive root systems trap sediment and debris (including trash) and play an important role in sequestering carbon, heavy metals, and other contaminants. Red mangrove propagules that float away can become established in soft-bottomed calm shallow water. These individuals can start to trap sediment and other propagules to eventually form manglar islands that are used as roosting sites by shorebirds and seabirds, such as herons and pelicans. Eventually, trapped sediments in the root systems may create conditions that become suitable for the establishment of black and white mangroves and associated species.
Mangroves support a wide range of biodiversity within the submerged root systems and among the trunks and canopy including sponge communities, shrimp, insects, fish, frogs, turtles, lizards, snakes, and birds (Kathiresan & Bingham 2001, Nagelkerken et al. 2001). Mangrove wetlands support a variety of wetland and migratory birds (Wauer and Sladen 1992). A study of bird use of mangrove and salt pond wetlands on St. Croix found that of 121 species of birds recorded, nearly 75% of them use mangrove habitats, with 26% using mangroves exclusively. Migratory warblers were noted to be the dominant species utilizing mangroves, joined by migratory shorebirds and waterfowl. A number of waders utilize mangrove trees for roosting, and waders, waterfowl, and shorebirds readily inhabit flooded mangrove forests (Knowles 1994). Resident waterbirds nest in mangroves along salt ponds (McNair et al. 2006). Submerged red mangrove prop roots are colonized by a variety of organisms, including sponges, oysters, and an abundance of coral species among the prop roots (Rogers 2009). The complexity of these prop root communities support a range of fish species and are known as a nursery ground these commercially important species (Tobias 2001). Many juveniles use detritus and mangroveassociated invertebrates and fish as a food source (Zieman et al. 1984, Thayer et al. 1987), while the complex prop-root habitat provides protection from predation (Orth et al. 1984, and Sogard and Olla 1993). These highly diverse and abundant juvenile fish communities within mangroves are linked to high diversity on nearby reefs and other habitats (Nagelkerken et al. 2001, Mumby et al. 2003, Serafy et al. 2015). This relationship could provide more resilient reef habitats after a disturbance event by reducing additional stress from algae growth (Mumby and Hastings 2008).
Mangrove wetlands of the USVI have been impacted by natural as well as anthropogenic forces. Anthropogenic sources of stress to mangroves include siltation, surface runoff, oil pollution, sewage effluent, and cooling water discharge from power plants. The threat of pollution can come in the form of large marine debris, including derelict vessels and fishing gear, but also as soluble pollution such as oil and gas. Movement of abandoned vessels during storms harm prop roots and tree growth and can leak pollutants and trap wildlife (Lord-Boring et al. 2004). Oils and gases negatively impact mangrove health and seedling survival (Kathiresan and Bingham 2001). Increased nutrients from agricultural areas and sewage decreases mangrove root system growth (Lovelock et al. 2009). In the USVI, mangrove wetlands are located on prime coastal real estate (Tobias 1996). As a result, they are often threatened by commercial and residential development.