Stochastic model for recovery prediction of macroinvertebrates following a pulse-disturbance in river

A macroinvertebrate community having been pre-assessed to have lower resilience against anthropogenic pulse-disturbance in river (e.g. muddy water from construction site) should be given intensive preservation efforts. Using stochastic population dynamics model with density-dependant and environmental fluctuation, a recovery prediction model for macroinvertebrates’ total biomass following its decline due to pulse-stressors have been developed. In this recovery model, the inherent resilience was determined by three parameters: carrying capacity, specific growth rate and environmental fluctuation intensity. The parameters were estimated from the time–series data of the total biomass. Using the application of the recovery model for a hypothesized scenario, the recovery index (RI) and the ecological time loss (ETL) were calculated. Both RI and ETL can evaluate the recovery process of the total biomass after an anthropogenic pulse-disturbance. study was done in 70 communities in Tokyo using the indexes of both RI and ETL. Recovery processes were simulated by administering a virtual pulse stressor to decrease the total biomass to 8%. As a result, 80% among the total number of communities performed a higher resilience within 3 years of the ETL. RI revealed that geographically neighboring community possesses extra-high resilience. Multiple regression analysis also proved that ETL was significantly explained by five environmental variables: specific conductivity, width of low-water channels, catchment area, suspended solid and stream order. As the results implied, macroinvertebrate community can recover quickly in total biomass when supplied from non-damaged upstream reaches. The case study also demonstrated the high potentialities of RI and the ETL for impact assessments in the river ecosystems.