Chemical Environment for Red Tides due to Chattonella antiqua:Part 2. Daily Monitoring of the Marine Environment throughout the Outbreak Period

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Environmental parameters that affect the growth ofChattonella antiquawere monitored throughout the outbreak period of this species around the le-shima Islands, the Seto Inland Sea, in the summer of 1987 (20 July-13 August). Averaged cell concentration ofC. antiquaover the water column (21 m) was below 10 cells·ml-1 on 20 July, gradually increased to reach the maximum of 250 cells·ml-1 on 7 August, and then rapidly decreased to the value of 30 cells·ml-1 on 13 August. Thermal stratifications were prominent from 20 July to 3 August and were destroyed after 4 August. Temperature and salinity were optimum for the growth ofC. antiquathroughout the survey period. At the bloom initiation period (20-21 July), concentrations of N- and Pnutrients (SNandSF) were high throughout the water column. From 22 July to 3 August, whenC. antiquaincreased its populations, SNandSPat the depth of 0-5 m were low but those at the depth of 10-20 m kept a high value. After 4 August, SN and SP at the depth of 10-20 m decreased rapidly due to wind mixing coupled with the nutrient uptake by C. antiqua. When the populations of C. antiqua reached the maximum (7-9 August), N-nutrients were depleted throughout the water column but P-nutrients were not. Concentrations of vitamin B12 were almost in the same range as those of the previous years and were optimum for the growth of C. antiqua. GP- value (growth potential of the seawater with respect to nitrogen and phosphorus) was higher than 0.6 even at the surface layer (0-5 m) at the bloom-initiation period. During the bloom development period (22 July-3 August), GP at the surface layer (0-5 m) was low (<0.2), but GP at the depth of 10-20 m kept a rather high value (>0.4). In situ growth rates of C. antiqua at the depth of 0 and 5 m estimated from bottle experiments coincided well with the values expected from GP. A high value of GP at the surface layer in the initiation period and a shallow GP-cline in the development period, combined with the ability of diurnal vertical migration seemed to be at least one reason that natural populations of C.antiqua grew at a rather high rate and formed red tides in the summer of 1987.
日本海洋学会の論文

Chemical Environment for Red Tides due to <I>Chattonella antiqua</I>:Part 2. Daily Monitoring of the Marine Environment throughout the Outbreak Period

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日本海洋学会 | 論文

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