open access

https://hdl.handle.net/2115/60652

Seasonal distribution of Heterosigma akashiwo in Funka Bay, Hokkaido, Japan

日本語

water temperature

2015-02

日本プランクトン学会

Bulletin of the Plankton Society of Japan

62(1)

1-7

The raphidophyte Heterosigma akashiwo is well known to be a fish-killing red tide species, and the distribution of this species in Japan has reported from Otaru（ 43.2°N）, Hokkaido to Okinawa（ 26.1°N）. Occurrences of the red tide of H. akashiwo have been mainly reported in the Pacific coastal areas from Honshu to Kyushu, such as Sanriku coast, Tokyo Bay, Seto Inland Sea and Shikoku. However, there is a paucity of information on dynamics of this species in northern Japan. This is the first report to reveal the seasonal distribution of H. akashiwo in Funka Bay, Hokkaido, northern Japan. Monthly surveys were conducted at two fixed stations in the inner part of the bay during the period from April 2011 to July 2013, and the cell density of H. akashiwo and environmental factors（ water temperature, salinity, Chl. a, DIN, PO4-P, and SiO2-Si） were measured. H. akashiwo was detected every summer with the maximum cell density reaching 1.9×104 cells L－1 from 0 m depth in August 2012. At the same time, H. akashiwo also accounted for 74.4％ of the total cell density of phytoplankton. On the other hand, H. akashiwo was not detected from every autumn to next spring. H. akashiwo cell density and water temperature showed a significantly positive correlation （r ＝ 0.53）, while salinity or DIN showed significantly negative correlation （r＝－0.33, －0.25, respectively）. It is concluded that H. akashiwo commonly appears in summer with a rise of water temperature and overwinters in cyst form. Furthermore, it is suggested that this species sometimes occupies a potential important primary producer in the bay during summer when the primary produce changes relatively at a low level.

学術雑誌論文

Version of Record

0387-8961