To develop a method for forecasting fluctuations in a macrobenthic community with changes in the hypoxic environment, water temperature and dissolved oxygen saturation levels were monitored continuously and the macrobenthic community was sampled around a borrow pit in Mikawa Bay during seasons of hypoxia from 2005 to 2007. The influence of hypoxia on each species of sampled macrobenthos was expressed as a new index, oxygen-deficient sensitivity index (OSI), which was calculated from the dissolved oxygen and water temperature data. The relation between the biomass of each species and OSI was fitted using numerical formulae. The results indicate that as hypoxic water developed in June/July, macrobenthic biomass decreased; and as the hypoxic water dissipated from September to November, biomass increased. In addition, the recovery of macrobenthic biomass required higher levels of dissolved oxygen saturation than those recorded when macrobenthic biomass decreased as hypoxia developed. Additionally, fluctuations in species biomass forecasted using the OSI method and the formulae correlated well with field observations. As this method accurately forecasts changes in the macrobenthic community based on dissolved oxygen and water temperature data, it is very effective at forecasting the recovery of the macrobenthic community. It can also be used to predict the water quality purification function of the macrobenthic community after environmental restoration (for instance, backfilling borrow pits or creating artificial shallow sea areas, etc.).
