TDA-IME Project Final Report June, 2013 Asia and Australia. Many species are inadequately described (Davie, 1982). In the Indo- Pacific sesarmid crabs play an important role in the ecology of the mangroves through their selective destruction of propagules, as well as consuming and breaking down leaf litter (Robertson, 1986; Smith, 1987). Chansang and Poovachiran (1990) confirmed the important role played by the feeding activities of crabs and other crustaceans in breaking down mangrove litter to detritus in a Thai mangrove forest. They also showed that mangrove litter and detritus export occurred mainly during outgoing spring tides, where it is presumed to enrich coastal waters and serve as food for marine species. Mangrove sesarmid crabs are also important economically in Cambodia and Thailand, where they are collected in huge numbers for processing as “boo samae”, a delicacy used to flavour traditional dishes, like papaya salad. Mangrove-dwelling Ocypodidae include the familiar fiddler crabs (Uca spp.). They are predominantly deposit feeders that ingest organic matter from the mud at low tide and assimilate the bacteria, diatoms and meiofauna that grow on the detritus fraction. Fiddler crabs must process large amounts of soil from the mangrove floor surface to obtain this food material. Because fiddler crabs are often very abundant in mangroves, occurring in densities up to 80/m2 (Macintosh, 1984), they are capable of turning over large amounts of surface soil. Their feeding activity plays a major role in modifying the soil environment (retexturing the soil and altering its chemical composition). Fiddler crabs also have another important role in the mangrove ecosystem as a food source for numerous predators, including monkeys, birds, snakes, fish and other crabs (Macintosh, 1977). Other mangrove crustaceans include a variety of burrowing species, such as mud lobsters (Thalassina), amphipods and isopods. The mud lobster is a subterranean deposit-feeder that forms large mounds up to 2 m high. Together with crabs in the mangrove forest, mud lobsters play an important role as “ecosystem engineers” (Jones et al., 1994). Large Thalassina mounds create “small islands” of drier habitats above the highest tidal level that are suitable for a variety of other, more terrestrial, species. Their burrows also increase the surface area of the mud. This has benefits to the mangrove plants by increasing diffusion of gases. It also allows the forest to be flushed more easily at high tide promoting nutrient exchange (Lee, 1998). Experiments have shown that crabs can significantly affect the growth and productivity of mangrove trees (Smith et al., 1991). Other crustaceans may cause significant damage to mangroves. Burrowing isopods can affect mangrove root growth and development (Ellison and Farnsworth, 1990). Barnacle settlement on mangrove seedlings can be a major cause of mortality in mangrove rehabilitation projects, because the sheer weight of many barnacles can bend and kill the seedlings (Maxwell and Li, 2006). Some mangrove crustaceans have considerable commercial value, particularly swimming crabs of the family Portunidae; they include the mud crab Scylla spp. and blue swimmimg crab Neptunus (Portunus) pelagicus. Crabs of the genus Scylla are the largest invertebrate predators in mangroves and they are commercially important in many countries because they are exported to meet the high demand for live seafood in Asia’s major cities. Penaeid shrimps (Penaeus merguiensis and P. indicus), depend heavily on mangroves for feeding and breeding habitats (Ronnback et al., 2002). They are also very important commercially with catches having strong positive correlations with mangrove area (Chong et al., 1990 and Loneragan et al., 2005). Mantis shrimps, or stomatopods, live in burrows in the mud on mangrove foreshores; they are collected for food mainly on a subsistence level. Molluscs live on and in mangrove mud, or attach to roots, or forage in the forest canopy. They are mainly gastropod and bivalve species. In turn, these molluscs contribute to supporting higher trophic levels in the mangrove food web. Gastropod snails are the most conspicuous group; most species are deposit feeders that scrape organic particles from the surface of the mangrove soil or vegetation. In some places gastropods are collected as a local food source, for example Cerithidea in Southeast Asia and Telescopium in India. In the 37
Transboundary Diagnostic Analysis of Indochina Mangrove Ecosystems
To see the actual publication please follow the link above