Microbial Activities in the Decay of Rhizophora Mangle Leaves
Red mangrbve (Rhizophora mangle L.) leaf fall has been estimated at approximately three tons (dry wt)/acre/year. The degradation of these leaves is a combination of bacterial, fungal and meiofaunal activities. Initiating with the living leaves and following through the decay process in the water, there is a definite sequence of fungal invaders. The role of the fungi is considered to be the conversion of leaf carbon compounds to microbial protein. Absolute nitrogen values in decaying leaves increase at an approximate rate of 30µg/day/gm dry wt of leaf. This microbial protein is utilized by a variety of meiofaunal organisms including nematodes, copepod’s, amphipods, polychaetes, forams, eta. These invertebrates inhabit the leaf surface within the first 24 hours after leaf fall; durin later stages of decay the animals invade the internal leaf layers. Animal numbers reach a peak of about 70 animals/cm2 of leaf surface within 4 weaks of submergence The animals feed on the microbial protein either by direct consumption of the microbes or indirectly through leaf fragmentation. The rate of decay appears to be. dependent on temperature. Laboratory studies of the individual components of the system indicates optimal rates at from 24 to 33°C, whereas 37°C and above may retard or possibly stop the decay process. This leaf degradation system is important in the production of organic materials required to drive certain estuarine food chains. It is also of interest in connection with the fate of leaf tissue that alternatively becomes incorporated into peat.
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This publication represents the proceedings, of a symposium on The Geology, Paleobotany, Geochemistry, and Microbiology of Peats." The symposium was held during the Annual Meeting of the Geological Society of America and associated societies, which took place in Miami, 18-20 November, 1974, and was jointly sponsored by the Coal Geology Division of the Society and the Organic Geochemistry Division of the Geochemical Society. Fourteen papers were presented, and nine are included in this publication. Five authors elected to make other arrangements for publishing their work; but the abstracts of these five papers, as submitted for inclusion in Abstracts with Programs, volume 6, number 7, 1974, are included here for completeness. Peats are of interest to scientists in a variety of disciplines: coal geology, organic geochemistry, soil science, plant ecology, the general ecology of food chains, agronomy, and environmental studies. Workers in many of these fields contributed to this symposium, but it is perhaps fair to say that the central unifying core is the consideration of peat as the precursor of coal. From a broad and general earth science point of view, peats and coals are of special interest because (a) such sediments contain higher concentrations of organic matter than any other common sedimentary deposits, and (b) in most peat beds and coal seams, the greater part of the organic matter and part of the mineral matter are autochthonous in the strictest sense, so that the many biological and chemical fossils that they contain are valid indicators of the organisms from which the organic matter was derived or of the environment of deposition. By contrast, although the reservoir and source rocks of petroleum do contain chemical fossils indicating their origin, reservoir rocks at least, cannot, of their nature, contain relevant fossils in the ordinary biological sense.