Population Dynamics of Harmful Phytoplankton Causing Bleaching of Cultured Nori in the Shiota River Estuary in Innermost Ariake Sea, Japan

• Published in: Bulletin on Coastal Oceanography Vol. 55; no. 2; pp. 139 - 153
• Main Authors: Matsubara, Tadashi, Mine, Takayuki, Ito, Shiro
• Format: Journal Article
• Language: Japanese
• Published: Tokyo Coastal Oceanography Research Committee, the Oceanographic Society of Japan 2018
• Subjects: Akashiwo sanguinea; Brackish; Dangerous organisms; Discoloration; Estuaries; Eucampia zodiacus; Fibrocapsa japonica; Light transmission; Marine; Microalgae culture; Phytoplankton; Population dynamics; Pyropia; Seaweed culture; Skeletonema; Japan, Kyushu, Saga Prefecture, Shiota River; INW, Ariake Sea
• ISSN: 1342-2758; 2434-4036
• DOI: 10.32142/engankaiyo.55.2_139

Diatoms Skeletonema spp. and Eucampia zodiacus, and dinoflagellates Akashiwo sanguinea and raphidophyte Fibrocapsa japonica are harmful phytoplankton and causative organisms in the bleaching of cultured nori（Phyropia）. The relationships between the population dynamics of these four phytoplankton and environmental factors were examined in the Shiota River estuary in the innermost part of the Ariake Sea, Japan between April 2008 and March 2013. Blooms of the diatoms Skeletonema spp. and E. zodiacus occurred during June to September and from January to March, mainly during February to March, respectively. Blooms of flagellate genera were also found : those of the dinoflagellate A. sanguinea mainly during September to November, and of the raphidophyte F. japonica during August to September and in November. This suggested that the winter blooms of Skeletonema spp. and E. zodiacus were triggered by an increase in transmitted light in the water column. Furthermore, the increase in transmitted light confirmed that stratification was formed due to flush and neap tide even in the mixing period. It wasalso suggested that A. sanguinea and F. japonica tended to bloom when diatom densities were low.