In order to study the effect of pond and paddy field cultivation mode on the flavor substances of C.carpio var. Quanzhouensis, headspace solid phase microextraction method was used to detect the contents of E-2-nonenal, 2-methylisothiol (2-MIB), and geosmin (GSM) in muscles and hepatopancreas. The content of hypoxanthine nucleotides (IMP) was determined by high performance liquid chromatography tandem mass spectrometry. The results showed that in terms of earthy smell substances, the contents of 2-methylisoalloxal and geosmin in the muscle of C.carpio var. Quanzhouensis cultured in paddy fields were extremely significantly higher than those in pond cultivation mode, and the contents of e-2-nonenal and geosmin in the hepatopancreas of C.carpio var. Quanzhouensis cultured in paddy fields were extremely higher than those in pond cultivation mode (P<0.01). In terms of umami substances, IMP contents in the muscles of C.carpio var.Quanzhouensis cultured in paddy fields were extremely higher than those in ponds (P<0.01); no significant differences were found in the IMP content of the hepatopancreas. In conclusion, C.carpio var. Quanzhouensis cultured in paddy fields had a higher umami taste, but also a heavier earth odor; C.carpio var. Quanzhouensis cultured in ponds had a weak soil flavor, but umami taste was not strong.

Based on the marine monitoring buoy data of the red tide process of Karlodinium digitatum in Putian sea area in 2022 and the manual monitoring data,potential reasons of outbreak of red tide were discussed.Before the red tide,the water temperature and salinity in Putian sea area were lower than that in the same period of previous years.With the rapid rise of water temperature and salinity,K.digitatum rapidly proliferated and accumulated to form a red tide under the favorable conditions of weak light conditions,relatively stable hydrological conditions,abundant nutrients(especially ammonia nitrogen)brought by precipitation,and aggregation caused by meteorology and tide.It was suggested that this K.digitatum red tide in Putian sea area might have been triggered by a synchronous appearance of optimal climatic,nutritional and hydrographic conditions.The concentration of chlorophyll-a reached 63.90 μg/L,while DO and pH significantly increased during the red tide,with the maximum value reaching 10.83 mg/L and 8.34,respectively.During the extinction period of red tide,with the continuous decrease of water temperature,wide fluctuation of salinity,the breaking of relatively stable hydrological conditions and the low nitrogen phosphorus ratio in the sea area,the red tide of K.digitatum rapidly disappeared.The K.digitatum red tide originated from Gangnan sea area,and spread to other sea areas with tide and current.Huge mortality of fish has been caused by K.digitatum in Putian sea area,when the cell density was higher than 10⁵ cell/L.