Green tide formed by free-floating Ulva spp. at Yatsu tidal flat, Japan
2009
Yabe, Tohru | Ishii, Yuichi | Amano, Yoshimasa | Koga, Tsunenori | Hayashi, Seiji | Nohara, Seiichi | Tatsumoto, Hideki
Green tides at Yatsu tidal flat, Tokyo Bay, Japan, were first reported in 1995 and formed by a bloom only of free-floating Ulva species. On the tidal flat, the bloom area in well-developed periods increased after 1995 and covered 27.1 ha in May 2002. Based on vertical aerial photographs, green tide remaining in winter during 1996-2007 covered 4.7 ha when first observed in 1999 and increased to 17.5 ha in January 2002 thereafter. We found that the expansion of green tide was related to such factors as an increase in Kira's Warmth Index, a decrease in annual cumulative hourly air temperatures below 7°C in December, an increase in salinity, and unintentional introduction of Ulva ohnoi. We also found that green tide at Yatsu tidal flat occurred in the course of the improvement of water quality.
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