Effects of Bioturbation by Macrobenthos Living on the Tidal Flat on the Bottom-Mud Environment and Concentration Profiles of Nutrient Salts

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The effects of bioturbation by macrobenthos living on the tidal flat on the environment in the bottom-mad and the concentration profiles of nutrient salts were investigated on the basis of field measured and analytical data. The results obtained by this research are summarized as follows :1. The species of macrobenthos and its number distribution in the study sites were grasped. Moreover, it was found that the number distributions of macrobenthos and its nesting holes on the tidal flat surface were strongly affected by air and mud temperature.2. The close relationships were observed between the redox potential (Eh) in the bottom-mud, and the number distributions of macrobenthos and its nesting hole. Therefore, it was assumed that the most important bioturbation that influenced on the environment in the bottom-mud was the nesting hole formation by macrobenthos.3. It was estimated that the vertical distributions of oxidized and reduced layers in the bottom-mud changed remarkably and periodically according to ebb and flood, and variation of bioturbation strength by macrobenthos.4. The close relationship was observed between the number distributions of macrobenthos and its nesting hole, and the vertical profiles of Eh in the bottom-mud and NH_4^+ and NO_3^- concentrations in the bottom-mud pore water.5. It was estimated that the decomposition and mineralization of organic matters, that is, the nutrient salts production processes by bacteria in the bottom-mud took place effectively under the environment variations that occurred according to ebb and flood, and nesting hole formation by macrobenthos in the bottom-mud.6. The resuspension mechanism of bottom-mud under the combined wave-current flows, which was one of physical action that affected on the concentration profiles of nutrient salts in the bottom-mud, was made clear theoretically and experimentally