An Ecopath with Ecosim model for the Pacific coast of eastern Japan: Describing the marine environment and its fisheries prior to the Great East Japan earthquake

A mass balance model of the marine ecosystems is presented for the four prefectures of Japan prior to the Great East Japan earthquake. The Ecopath with Ecosim food web modelling approach and its Ecotracer routine were used to simulate the concentrations of ¹³⁷Cs in the ocean and the biota in order to serve as baseline, and to estimate the initial conditions for impact scenarios. Results of the Ecopath model were checked against pre-balance [PREBAL] diagnostics for integrity. ¹³⁷Cs was shown to bioaccumulate with increases in trophic level, and has a tendency to biomagnify. Generally, for fish species, the dominant pathway of contaminant accumulation was through diet, whereas for invertebrates it was through respiration. Ecotracer was able to accurately model the expected concentrations in organisms that had existing concentration ratio data from field measurements, and also make predictions on biota lacking concentration data. In 2010, using national fishery landing statistics for the four prefectures and predicted whole body concentrations of ¹³⁷Cs, it is estimated that the apparent direct and indirect human food supply of ¹³⁷Cs from fisheries to the market was 46.1 MBq.