Ecosystem Of Late-Carboniferous Coral Reef In Southern Guizhou Province

Carbonate rocks of plateau facies well developed in vast sea area of southern China in Late-Carboniferous, and the south of Guizhou Province was a representative region. Shallow water environment on the carbonate platform was quite favourable for organisms, especially the benthic organisms, and as a result different types of reef-building communities formed. Lithogeneous process of these organisms is intensive with organic banks, bioherms and reefs built widely, and thus it is an ideal region to study Late-Carboniferous biostratum and reef of South China. Most of these reefs developed on the platform margin, and the large-scale reef complex is the mostly representative one.The reef complex has a large size and a special architectural structure, and 3 superimposed units, U1, U2 and U3 could be recognized according to features of reef rocks. U1 is a patch reef layer involving a mud mound built by cyanobacteria, an Ivanovia cf. manchurica patch reef and a phylloid algae patch reef, and it is separated from mainbody of the reef by an overlying bioclast layer. U2 has an identical lithology and a similar biological composition with U3, that is, both of them are composed of Fomitchevella framestone and packstone, the difference is that abundance of organisms in U3 is much higher than that in U2.In the study region, the reef-building organisms are various in genera and ecotype, and their reef-building modes are diversefied. In the large-scale coral reef complex in Bianping Village, these reef-building organisms mainly include:1) Fomitchevella, frame builder; 2) phylloid algae, frame-builder and baffler; 3) Ivanovia cf. manchurica, frame-builder and covering organism; and 4) cyanobacteria, binding organism. Fomitchevella is the dominant constructor of the reef complex who grows into a phaceloid or fasciculate colony through budding and then builds reefs of diverse types. The skeletons of Fomitchevella individuals are large in the centre of the colony while small on the edge, and the individuals are viable. Ivanovia cf. manchurica develops a tabular colony and various growth forms. Their colonies get a strong power of regeneration and make a great contribution to the formation of U1. Phylloid algae is one of the most important builders in the study region which has diverse morphologies and builds different types of reefs, including the phylloid algae patch reef in U1. The other genera of colonial coral-Antheria has a low abundance and a limited distribution, and it plays a transitional role in community evolution. Cyanobacteria is a sort of autotroph with binding function, and it is the main builder of mud mound in U1. Fusulinids and brachiopods are the most common dwellers, followed by crinoids, Tubiphytes and bivalves, while bryozoans and solitary corals are few.Six reef-building communities are recognised in the reef complex, which are similar in biological diversity while different in abundance of benthos, vertical spacial zonation, impacts of the key species and so on. The organisms are divided into various groups according to their life habits, fuctions and feeding positions. The vertical zonation becomes more and more notable along with evilution of these communities. Their adaptability to the evironment and control on organisms also get an obvious development. Cyanobacteria, Tubiphytes, fusulinids, foram, brachiopods and gastropods live in the lower part of the communities, while rinoids, Ivanovia cf. manchurica and Antheria in the middle part and Fomitchevella in the upper part. The biological components of these communities are different but the maintaining mechanisms are generally accordant.Nutrient absorbing of the communities is similar to that of extant coral reef community, and one or more absorption models may be available. The energy of the whole ecosystem is derived from sunlight ultimately. Algaes, microbes, cyanobacteria, Tubiphytes and deliquescent organic materials in the water constitute the primary productivity. Energy is transferred and lost gradually through predation between organisms, and finally released into the water by decomposers. Part of the energy recycles in the ecosystem, and most is dispersed with the waterflow.Ecological relationships in the coral reef complex in Bianping Village are analysed and studied based on research findings of extant reefs. Brachiopods lived in the mats of phylloid algae, which enabled them to get more food and also avoid being hunted by natural enemies. They could coexist without competition or live independently, and thus they were in a special relationship of commensal. In order to get more space for growth, source of food and larger lighting area, the individuals in Fomitchevella colony always competed intensely with their neigbours, resulting in some bent, misshapen, inclined or even lateral individuals. As a result, these individuals lost more living resources and would be finally replaced by those erect, strong and long ones. The "unamed reef-building organisms" grew and expanded at a high rate and were good at en winding. They wraped on the colony of Ivanovia cf. manchurica, and both of them thickened tissues on the contact zone, and as a result an aggressive-wraping relationship was formed. The "unamed reef-building organisms" deprived Ivanovia cf. manchurica of living resources and would finally lead to its death. When laterally expanding, Ivanovia cf. manchurica would as much as possible avoid direct contact with individual skeletons of Fomitchevella, who was not good at occupying the substrate but could take up the space above Ivanovia cf. manchurica throgh laterally budding and overshaded it. Then an off-overshading spatial competition was formed and Fomitchevella would be the dominant at last. An overwhelming spatial competition was formed by phylloid algae and a few Fomitchevella individuals lived in the algae mat, but the outcomes would be various with the influences of environmental conditions. Ivanovia cf. manchurica lived on substrate built by phylloid algae and the was covered by phylloid algae, which suggested an alternate community replacement. Some outrunners of Fomitchevella initialized in Ivanovia cf. manchurica community and then overthrew the former dominantor and finally a gradual replacement occurred. Fomitchevella-1 community evolved into Fomitchevella-2 community, during which adjustments on biological composition and proportion occurred to make the community structure was more appropriate with high adaptability to the environment. Thus this was actually an update of community.Development of the reef is closely related to community evolution. The whole formation process could be divided into four stages and each stage involved transformation of initialization, development and decline of the communities. The patch reef layers were built in the first two stages, while the main body of the reef was built in the last two stages. Growth rate of the reef was controlled by both nutrient levels and sedimentation rate, and in a certain extent they were positively correlated. The reef would stop growing when environmental conditions changed abruptly.