2018 Volume 41 Issue 3 Pages 55-59
We have investigated the effects of the Great East Japan Earthquake on the water quality of brackish Lake Hinuma located in Ibaraki Prefecture. It was observed that for three years after the earthquake, the chloride ion (Cl−) concentration in the lake water was high. This can be attributed to the fact that the bottom of the lake was lowered owing to the ground subsidence due to the earthquake, which facilitated the increase in salinity. Three years after the earthquake, the bottom has recovered and the Cl− concentration in the lake water has decreased. Compared with the water quality three years before the earthquake, the chlorophyll-a concentration decreased during summer. It seems that the amount of Cyanobium, which was predominant in summer, decreased owing to the high Cl− concentration.
