Unusual distribution of floating seaweeds in the East China Sea in the early spring of 2012.
Floating seaweeds play important ecological roles in offshore waters. Recently, large amounts of rafting seaweed have been observed in the East China Sea. In early spring, juveniles of commercially important fish such as yellowtail accompany these seaweed rafts. Because the spatial distributions of seaweed rafts in the spring are poorly understood, research cruises were undertaken to investigate them in 2010, 2011, and 2012. Floating seaweed samples collected from the East China Sea during the three surveys contained onlySargassum horneri. In 2010 and 2011, seaweed rafts were distributed only in the continental shelf and the Kuroshio Front because they had become trapped in the convergence zone of the Kuroshio Front. However, in 2012, seaweed was also distributed in the Kuroshio Current and its outer waters, and massive strandings of seaweed rafts were observed on the northern coast of Taiwan and on Tarama Island in the Ryukyu Archipelago. Environmental data (wind, currents, and sea surface height) were compared among the surveys of 2010, 2011, and 2012. Two factors are speculated to have caused the unusual distribution in 2012. First, a continuous strong north wind produced an Ekman drift current that transported seaweed southwestward to the continental shelf and eventually stranded seaweed rafts on the coast of Taiwan. Second, an anticyclonic eddy covering northeast Taiwan and the Kuroshio Current west of Taiwan generated a geostrophic current that crossed the Kuroshio Current and transported the rafts to the Kuroshio Current and its outer waters. Such unusual seaweed distributions may influence the distribution of fauna accompanying the rafts.
5-1-5, Kashiwanoha, Kashiwa, 277-8564 Japan.
Teruhisa
T
Komatsu
5-1-5, Kashiwanoha, Kashiwa, 277-8564 Japan.
Shizuha
S
Mizuno
5-1-5, Kashiwanoha, Kashiwa, 277-8564 Japan.
Alabsi
A
Natheer
5-1-5, Kashiwanoha, Kashiwa, 277-8564 Japan.
Attachai
A
Kantachumpoo
5-1-5, Kashiwanoha, Kashiwa, 277-8564 Japan.
Kiyoshi
K
Tanaka
Hydrospheric Atmospheric Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
Akihiko
A
Morimoto
Marine Fisheries Division, Fisheries Research Institute of Taiwan, 199, Hou-Ih Road, Keelung, 20246 Taiwan.
Sheng-Tai
ST
Hsiao
5-1-5, Kashiwanoha, Kashiwa, 277-8564 Japan.
Eva A
EA
Rothäusler
Kagoshima Prefectural Fisheries Technology and Development Center, Ibusuki, Kagoshima 891-0315 Japan.
Hirotoshi
H
Shishidou
Division of Applied Aquatic Bio-Science, Graduate School of Agricultural Science, Tohoku University, 1-1 Amamiya-machi, Tsutsumidori, Aoba-ku, Sendai, Miyagi 981-8555 Japan.
Masakazu
M
Aoki
Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwakecho, Sakyoku, Kyoto 606-8502 Japan.
Tetsuro
T
Ajisaka
East China Sea; Ekman drift current; Floating seaweed; Kuroshio; Phaeophyta; SSH; Sargassum horneri; Transport