A red-tide bloom of Chattonella antiqua (Raphidophyceae) in the Seto Inland Sea, Japan, in 1987 analysed as changes in photosynthetic pigments determined by high-performance liquid chromatography

A severe red-tide bloom of Chattonella antiqua (Raphidophyceae) was observed in the Seto Inland Sea (Japan) in summer 1987. The C. antiqua bloom was monitored from beginning to end at the 0, 5, 10, 15 m and bottom layers of a fixed sampling station almost every two days. Carotenoids and chlorophyllous pigments were measured by reversed-phase high-performance liquid chromatography before and during the bloom. Before the C. antiqua bloom, some diatoms were dominant, with a chlorophyll a (Chla) concentration ranging between 2 and 8 μg litre−1 at the surface. The maximum Chla concentration reached 27 μg litre−1 at the surface during the bloom, this being due to C. antiqua. Violaxanthin, which is a constituent carotenoid of C. antiqua, varied in line with cell concentration of the species. The relative abundance of C. antiqua was estimated as its Chla contribution to total Chla; the Chla contributions of Raphidophyceae, Bacillariophyceae and Dinophyceae were calculated from pigment ratios obtained by multiple regression analysis of pigment concentrations. The relative abundance of C. antiqua at the surface was calculated to be 0–16% before the bloom and 83–100% during the bloom.