Sediment remediation materials such as Mg and Ca were added to a microcosm (a mixed flask culture) consisting of bacteria, Cyclidium, Lecane, Philodina, Aeolosoma, Chlorella, Scenedesmus and Tolypothrix; and the respiration rate (R) and the production rate (P) were determined. The environmental impact risk assessment on aquatic ecosystem was conducted with the production/respiration ratio (P/R ratio) as the functional parameter and the succession of microbiota as the structural parameter in the flask-size microcosm system, in comparison with no addition system (control). The influence of each substance was different from each other, and being the sediment remediation materials, the risk of Mg was estimated as half of Ca. The m-NOEC (microcosm-NOEC) were estimated as less or equal to 10.0 mg/L Mg and as less or equal to 5.0 mg/L Ca with the P/R ratio as the functional parameter of the ecosystem.
