Prediction of Gymnodinium type' 65 Red Tide by Means of Red Tide Map Akira OUCHI and Haruyoshi TAKAYAMA

Abstract

The principal component analysis was made using the six variables (WT, SAL, TDP, DIN, DON and PON) which were obtained from six or nine stations in the northern part of Hiroshima Bay since 1976. The accumuated proportion of the first three principal components is 70%, with only 30% loss of information, the distrbution of all station (N=499) in six-dimensional space can be projected into a three-dimensional subspace defined by the first three principal components.
In plotting the scores in this three-dimensional space, three kinds of scores were used; 1) the current scores from the latest observations on August 3, 1982, 2) the scores from stations where a red tide was observed in August in August in the past and 3) those of preliminary observations of Gymnodinium type' 65 red tide in the years 1977 and 1979.
In this way we could obtain a red tide map and easiy compared the position of current scores with precursice scores of Gymnodinium type' 65 red tide in 1977. we assume in this paper that Gymnodinium type' 65 red tide will occur under similar encironmental conditions as in the past. When a red tide occurs, therefore, the past Gymnodinium type' 65 redtide. Since current scores werelocated separetely from precursive scores of Gymnodinium type' 65 red tide on the red tide map, we could successfully predict that Gymnodinium type' 65 red tide would not occur in the year 1982.