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Benzalkonium bromide is a high-efficiency algaecide. Its concentration in seawater was measured by the method of spectrophotometer. The results indicated that the deposition appeared if the concentration of benzalkonium bromide in seawater was more than 50 mg.L-1, and affected the detection of benzalkonium bromide. But, there was a good linear relationship between concentration and absorbance when the concentration was lower than 50 mg.L-1 (R2 = 0.9996). Therefore, spectrophotometer could be used to detect benzalkonium bromide in seawater.

In the past decade, the Prorocentrum bloom was the most frequently occurred bloom in the East China Sea. It occurred every one year or two years, and covered huge areas. There were arguments on the identification of Prorocentrum bloom causative species. Some scientists thought the species being P. dentatum Stein, but the others thought that it was a new species, P. donghaiense Lu. For achieving the proper classification of the species, an "International Workshop on HAB Causative Species--Taxonomic View on a species of Prorocentrum in the East China Sea" was held in Shenzhen, China in November, 2002. By reviewing as much as available references, and by comparing the Prorocentrum specimen from the East China Sea with those from Japan, Korea and USA, scientists participated in this Workshop agreed that: 1) the specimens from Japanese and Korean waters, and from CCMP, USA were the same species; 2) the features of anterior projection and cell surface marking were similar to those of originally described P. dentatum Stein; 3) the major difference is the cell size. The specimens from the East China Sea were mostly less than 20 microns long, whereas the size of the original described P. deatatum was larger than 50 microns; 4) the minor difference is the shape of the cell end. The original described P. deatatum was with a pointed end, whereas the cells from the East China Sea were mostly with a rounded end. There was no final agreement for the species identification at the Workshop. By summing all views of scientists from the Workshop, the authors suggested that the bloom causative species of Prorocentrum in the East China Sea, as well as so-called species of P. dentatum from other East Asian waters, should be the same species. They are all P. donghaiense Lu.

In this paper, the detailed morphology of Prorocentrum donghaiense was studied. Taxonomic comparison was made between P. donghaiense and other relevant Prorocentrum species. The results suggested that distinct differences existed among them with respect to their conservative characteristics of morphology and cell sizes. This kind of discrepancy was far beyond that of individual variations within same species due to environmental factors. Therefore, the high biomass bloom-forming species in the East China Sea was not real Prorocentrum "dentatum" Stein, but P. donghaiense Lu that was re-described in the present paper. P. donghaiense appeared in the East China Sea, and P. "dentatum" occurred in Japanese and Korean waters should be the same species.

53 water samples were collected from 28 stations in typical regions where redtide frequently occurred in the Changjiang River estuary during Spring, 2002. In total, 80 diatom species and varieties belonging to 31 genera were identified, among which, genera with high species biodiversity included Coscinodiscus which contained 17 species and Pleurosigma which contained 8 species and varieties. Quantitative analysis of diatom cell density showed that Pseudo-nitzschia delicatissma (3.48 x 10(3) cells.L-1, 28.54%), Melosira sulcata (1.43 x 10(3) cells.L-1, 16.98%) and Pseudo-nitzschia pungens (0.71 x 10(3) cells.L-1, 9.85%) were dominant species, which occurred at almost all stations. Higher cell density of Pseudo-nitzschia delicatissma and Pseudo-nitzschia pungens occurred at stations along 123 degrees E, while that of Melosira sulcata occurred at stations around Changjiang River at 31-32 degrees N. The total diatom cell density ranged from 0.43 x 10(3)-23.3 x 10(3) cells.L-1, with average of 4.61 x 10(3) cells.L-1. At station DD15 located at 123 degrees E and 30.5 degrees N, the highest diatom cell density was found, which was 1.85 x 10(4) cells.L-1 at surface water layer, and 2.33 x 10(4) cells.L-1 at middle water layer (30 m) respectively. Horizontally, the diatom cell density showed scattered distribution, while vertically, it was commonly higher at surface water layer than that at middle water layer.

The relationships between temporal dynamics of phytoplankton density and nutrients (NO3-, NH4+, PO4(3-), SiO3(2-), Fe) contents in the water body at Aotou waters of Daya Bay during red tide were comprehensively analysed based on the fixed position investigation of red tide in the summer of 2000 and the several years investigation data by using grey linear regression model. The relationships between phytoplankton cell density and chlorophyll a content were also analysed. The results showed that the predicted values were well consistent with the measurement values, and their correlation coefficients were between 0.51-0.83. Red tide might break out if chlorophyll a contents in water body were larger than 5.8 micrograms.dm-3. The study could provide a simple effective method to forecast red tide by sampling water samples to analyse chlorophyll a concentration, or using SeaWiFS data, and then, to calculating phytoplankton density. In addition, the primary productivity of the water areas was controlled by phosphorus.

In order to understand the potential of algal blooms, surface sediments were collected from 12 stations in the Changjiang River estuary with longitude from 122 degrees to 123.5 degrees E and latitude from 29 degrees to 32 degrees N from April to May 2002 to investigate the distribution of dinoflagellate resting cysts, 29 different cyst morphotypes representing 19 genera and 6 groups were identified. Among them, there were 11 autotrophic species and 18 heterotrophic ones. The number of species observed in each sample was low, and varied from 10 to 21. Cyst concentrations varied from 11.7 to 587 cysts per gram dry weight. Cyst concentrations and species diversity were higher in offshore areas, and increased from the west to the east, and from the north to the south within the studied area. Cysts of Alexandrium distributed widely in the Changjiang River estuary, with the maximum concentration of 40.4 cysts per gram dry weight. Cysts of harmful algal bloom causative species such as Alexandrium, Gymnodinium catenatum, Lingulodinium polyedra, Scrippsiellla trochoidea, Polykrikos kofoidii and P. schwartzii were also observed in this survey.

Studies on the removal and control of red tide algae Phaeoecystis globosa by povidone-iodine and isothiozolone algaecide showed that Phaeoecystis globosa could be killed and controlled by povidone-iodine and isothiozolone. The effective concentration of povidone-iodine was 30 mg.L-1, and that of isothiozolone was 0.30 mg.L-1. Using povidone-iodine and isothiozolone together could improve the effect, and the ideal composite ratio of povidone-iodine and isothiozolone was 1.0:0.15.