Abstract
Primary water quality factors influencing the long-term change of blue-green algal growth in Lake Kasumigaura were investigated using water quality data surveyed by the public sector. Blue-green algae tended to grow when the dissolved oxygen (DO) concentration at the sediment surface decreased and the dissolved Mn (D-Mn) concentration increased. With a statistical analysis of the water quality data, the influence of D-Mn released from the sediment on the growth of the blue-green algae was discussed. Furthermore, seawater intrusion was inferred to be the major environmental factor behind the decrease in the DO concentration at the sediment surface. For the clarification of the mechanisms of the changes in the growth of blue-green algae, surveys and research needed in the future were proposed.
