The grazing of Acartia spinicauda Giesbrecht on Alexandrium catenella Taylor in Dapen Bay, Guangdong

The grazing of adult females of Acartia spinicauda(Copepoda), the dominant species in Dapeng Bay, Guangdong, on Alexandrium catenella was determined under experimental conditions. Grazing rates increased with the increasing cells concentration of Alexandrium untill a maximum was reached, beyond which the rate declined. On the other hand, maximum grazing rates increased within the temperature 15~25℃, while in lower food concentration, maximun rate appeared at higher temperature. The photoperiod was found to be a more important factor affecting feeding rate than the bioluminescence of Alexandrium. In mixture cells of Alexandrium catenella and platymonas subcordiformis with varying concentrations of the two foods, copepod fed electively on the latter. Theoretically, the elective capacity can be expressed as: y=12 707.68-2.907 3x+0.000 180 055x~(2), where y is the grazing rate of copepod on Alexandrium, x is the concentration of Platymonas.