Field experiments on chemical and biological changes of thin-layer oyster shells capping sediments in dense aquaculture area.

Thin-layer oyster shell capping has been proposed as a method for improving contaminated coastal environments. Field experiments were conducted to investigate the effects of oyster shell capping on nutrient concentrations, microorganisms, and macrobenthic communities. The concentration of PO4-Pin the experimental area decreased by approximately 38% more than in the control, due to phosphorus fixation of oyster shells and the presence of Proteobacteria. Ammonia-oxidizing bacteria such as the order Pirellulales (phylum Planctomycetes) were related to the low ratio of NH3-N found in dissolved inorganic nitrogen in the experimental area, indicating nitrification promotion. The reduction in annular benthic organisms observed in the experimental area indicates a decline in sediment organic matter, which could potentially mitigate eutrophication. Oyster shell capping was confirmed to be an effective material for restoring coastal sediments by improving their chemical and biological properties.