In this study, we performed a sediment elution experiment to evaluate water quality in terms of phosphorus, as influenced by the dissolved oxygen consumed by sediments. Three separate model column treatments, namely, raw, calcined, and sonicated oyster shell powders, were used in this experiment. Essential phosphorus fractions were examined to verify their roles in nutrient release from sediment based on correlation analyses. When treated with calcined or sonicated oyster shell powder, the sediment-water interface became “less anaerobic,” thereby producing conditions conducive to partial oxidation and activities of aerobic bacteria. Sediment Oxygen Demand (SOD) was found to be closely correlated with the growth of algae, which confirmed an intermittent input of organic biomass at the sediment surface. SOD was positively correlated with exchangeable and loosely adsorbed phosphorus and organic phosphorus, owing to the accumulation of unbound algal biomass-derived phosphates in sediment, whereas it was negatively correlated with ferric iron-bound phosphorus or calcium fluorapatite-bound phosphorus, which were present in the form of "insoluble" complexes, thereby facilitating the free migration of sulfate-reducing bacteria or limiting the release from complexes, depending on applied local conditions. PCR-denaturing gradient gel electrophoresis revealed that iron-reducing bacteria were the dominant species in control and non-calcined oyster shell columns, whereas certain sulfur-oxidizing bacteria were identified in the column treated with calcined oyster powder.

Abstract
1. Introduction
2. Materials and Methods
    2.1. Preparation of CaO2 originated from oyster shells
    2.2. Preparation of samples and test columns
    2.3. Analysis
    2.4. Microbial assay using PCR-denaturinggradient gel electrophoresis (DGGE)
    2.5. Statistical Analysis
3. Results and Discussion
    3.1. Physicochemical changes in response to ORCtreatments
    3.2. Changes in water quality in response to ORCtreatments
    3.3. Correlation between SOD and phosphorusfractions
    3.4. Phosphate releases with ORC treatments
    3.5. Microbial community
4. Conclusion
References

• Beom-geun Kim(Department of Ocean system Engineering, College of Marine Science, Gyeongsang National University)
• Md Akhte Khirul(Department of Ocean system Engineering, College of Marine Science, Gyeongsang National University)
• Dae-chul Cho(Department of Energy Environmental Engineering, Soonchunhyang University)
• Sung-Hyun Kwon(Department of Marine Environmental Engineering, College of Marine Science, Engineering Research Institute, Gyeongsang National University) Corresponding author