THE ROLE OF BACTERIA IN NUTRIENT RECYCLING IN TROPICAL MANGROVE AND OTHER COASTAL BENTHIC ECOSYSTEMS

Sedimentary bacteria have generally been recognized as an essential food for protists and invertebrates, forming the base of benthic food webs. This trophic role has been well documented, but bacteria play an equally important role as mineralizers of organic detritus and recyclers of essential nutrients. Recent evidence suggests that this latter role is more important than their trophic function in tropical mangrove and coastal sediments. Bacteria in these systems are, on average, more abundant and productive than their counterparts in higher-latitude systems. They account for a disproportionate share of nutrient uptake to the extent that bacterial communities act as a sink for carbon, processing most of the energy and nutrients in tropical aquatic systems. Most bacteria remain unconsumed in tropical deposits, dying naturally and lysing, with the next generation of cells consuming, mineralizing and recycling this material either into new biomass or dissolved material. Bacteria in tropical aquatic sediments are ultimately controlled by inputs of dissolved and particulate detritus, natural mortality and recycling. To replenish damaged ecosystems in the tropics, restoration of the natural geochemical profile in the sediments is necessary to re-initiate the growth of bacteria in order to restore the essential recycling processes which assist in the conservation of nutrients.