The role of sediment microorganisms in the productivity, conservation, andrehabilitation of mangrove ecosystems: an overview

Mangrove communities are recognized as highly productive ecosystems that pr ovide large quantities of organic matter to adjacent coastal waters in the form of detritus and live animals (fish, shellfish). The detritus serves as a nutrient source and is the base of an extensive food web in which organi sms of commercial importance take part. In addition, mangrove ecosystems se rve as shelter, feeding, and breeding zones for crustaceans, mollusks, fish of commercial importance, and resident and migratory birds. Although mangr oves in the United States are protected, the systematic destruction of thes e ecosystems elsewhere is increasing. Deforestation of mangrove communities is thought to be one of the major reasons for the decrease in the coastal fisheries of many tropical and subtropical countries. There is evidence to propose a close microbe-nutrient-plant relationship that functions as a mec hanism to recycle and conserve nutrients in the mangrove ecosystem. The hig hly productive and diverse microbial community living in tropical and subtr opical mangrove eco-systems continuously transforms nutrients from dead man grove vegetation into sources of nitrogen, phosphorus, and other nutrients that can be used by the plants. In turn, plant-root exudates serve as a foo d source for the microorgranisms living in the ecosystem with other plant m aterial serving similarly for larger organisms like crabs. This overview su mmarizes the current state of knowledge of microbial transformations of nut rients in mangrove ecosystems and illustrates the important contributions t hese microorganisms make to the productivity of the ecosystems. To conserve the mangrove ecosystems, which are essential for the sustainable maintenan ce of coastal fisheries, maintenance and restoration of the microbial commu nities should be undertaken. Inoculation of mangrove seedlings with plant-g rowth-promoting bacteria may help revegetate degraded areas and create reco nstructed mangrove ecosystems.