Field study on short-term changes in benthic environment and benthic microbial communities using pyrolyzed oyster shells.

To evaluate the effect of pyrolyzed crushed oyster shells (PCOS) on the remediation of sediments and microbial diversity, a field study was conducted in Buksin Bay, Tongyeong City, Republic of Korea. It was observed that after treatment with PCOS, the concentration of H2S in the sediment of the control site was 287 mg/L. Furthermore, it decreased up to 0 mg/L and remained so until the end of the field study, that is for a period of six months. Moreover, the concentrations of NO2-N + NO3-N, NH4-N, and PO4-P decreased sharply, and the oxidation-reduction potential (ORP) increased after PCOS treatment in pore water and overlying water. Regarding the diversity of microbial communities, the predominance of bacteria from phylum Chlorobi was observed in highly reduced (-410 mV; ORP) sediment, which is well known for the production of H2S. After PCOS treatment, the relative abundance of Chlorobi was sharply suppressed. On the other hand, the predominance of bacteria from the phyla Proteobacteria and Bacteroidetes was observed, and their relative abundance in the PCOS-treated sediment increased throughout the experiment, based on 16S rRNA sequencing. The results demonstrate that the abundance of bacterial communities in the PCOS-treated sediments of Buksin Bay is important for marine ecological functioning, especially for pollutant transformation.