| 1 Effects of N, P and Mn on the growth of Karenia mikimotoi and Amphidinium sp.The cell density and relative growth rate of Karenia mikimotoi MACC/D23 and Amphidinium sp. MACC/D31, cultivated in f/2 medium under different concentration of NaNO3(0.35,0.70,1.76,8.82,15,35.30×10-3 mol/L) and NaH2PO4(0.04,0.07, 0.18,0.37,0.73,1.47×10-3 mol/L) were examined. The results showed that different concentration of NaNO3 and NaH2PO4 had significant effects on the relative growth rate of K. mikimotoi and Amphidinium sp. (P<0.05). The optimal growth NaNO3 and NaH2PO4 concentration for K. mikimotoi is 8.82×10-3 mol/L and 0.18×10-3 mol/L respectively whilst 1.76×10-3 mol/L and 0.07×10-3 mol/L for Amphidinium sp. respectively.Several studies reported that the trace element manganese, which had significant effect on the growth of microalgae, was correlated with the formation of the red tide. Karenia mikimotoi and Amphidinium sp. are common dinoflagellates which could cause harmful algal blooms. In this study, the effects of different manganese concentrations (10-12—10-4 mol/L) on the cell density of K. mikimotoi and Amphidinium sp. were studied. The results showed that manganese had significant effects on the cell density of K. mikimotoi and Amphidinium sp. (P<0.05). The cell densities of K. mikimotoi and Amphidinium sp. under 10-4 mol/L manganese concentration were significantly lower than those in other treatment groups. Under 10-12—10-8 mol/L manganese concentrations, the cell densities of K. mikimotoi increased with the increasing manganese concentration, while it under 10-8—10-4 mol/L decreased.2 Effect of manganese on the chlorophyll parameters of Karenia mikimotoi and Amphidinium sp.Chlorophyll fluorescence has been widely used in studies of photosynthesis in marine microalgae. There are several chlorophyll fluorescence parameters which correlate to photosynthetic processes, including the ratio of variable to maximal chlorophyll fluorescence(Fv/Fm), the potential activity of PSII (Fv/Fo), the actual photochemical efficiency of PSII in the light (ΦPSII), the electron transport rate (ETR), the photochemical quenching (qP) and the non-photochemical quenching (NPQ). In this study, the effects of different manganese concentrations (10-12—10-4 mol/L) on above fluorescence parameters of K. mikimotoi and Amphidinium sp. were studied by using chlorophyll fluorescence technology. The results showed that manganese had significant effects on the fluorescence parameters(Fv/Fm, Fv/Fo,ΦPSII, ETR, qP and NPQ) of K. mikimotoi and Amphidinium sp. (P<0.05). The effect of manganese on the fluorescence parameters relied on the range of manganese concentrations and the microalgal culture age. Under 10-12-10-8 mol/L manganese concentrations, the parameters Fv/Fm, Fv/Fo,ΦPSII and ETR increased with the increase of manganese concentrations from day 3 to day 9, while Fv/Fm and F/Fo increased with the increasing culture age from day 2 to day 7. The value of qP decreased with the increasing manganese concentration during the entire experimental period. NPQ showed the tendency that decreased first and increased later. Some fluorescence parameters (Fv/Fm, Fv/Fo,) also showed significant correlations with manganese concentration. The fluorescence parameters Fv/Fm and Fv/Fo both showed significant positive correlations with manganese concentrations (10-12—10-8 mol/L) on day 4 and day 5, and the same correlations were found under 10-8—10-4 mol/L from day 3 to day 6.The chlorophyll content of Amphidinium sp. under 10-12 and 10-4 mol/L was significantly lower than that of 10-8 and 10-6 mol/L on the third day, and under 10-12 it was significantly lower than that of 10-10 and 10-4 mol/L on the eighth and tenth days. Fv/Fm and Fv/Fo of Amphidinium sp. under 10-12 mol/L were significantly lower than other concentrations from the first day to the fourth day andΦPSII and ETR were significantly lower than other concentrations from the first day to the third day while under 10-4mol l-1 Fv/Fm and Fv/Fo were significantly higher than other concentrations from the sixth day to the ninth day andΦPSII and ETR were significantly higher than other concentrations from the sixth day to the seventh day. The values of qP and NPQ under 10-12 mol/L were significantly higher than other concentrations on the third day. Fv/Fm and Fv/Fo increased with the manganese concentrations (10-12-10-4 mol/L) from the third day to the sixth day whilst OPSII and ETR varied slightly with the manganese concentrations (10-10-10-6 mol l-1). Fv/Fm, Fv/Fo, OPSII, NPQ and ETR under each concentration increased in earlier experimental period and decreased later. The values of qP and NPQ decreased with manganese concentrations except for that from the fourth day to the sixth day. There were significant positive correlations between Fv/Fm, Fv/Fo and manganese concentrations (10-12-10-6 mol l-1) from the first day to the fourth day after inoculation. Moreover, Fv/Fm. Fv/Fo, OPSII and ETR all showed significant positive correlations with manganese concentrations (10-6-10-4 mol l-1) from the sixth day to the ninth day of the experimental period.3 Effect of manganese on the antioxidative enzyme activity in Karenia mikimotoi and Amphidinium sp.The antioxidant enzyme (Superoxide Dismutase, SOD and Catalase, CAT) activities in K. mikimotoi and Amphidinium sp. under different manganese concentration were examined. One-way analysis of variance showed that different concentration of manganese had significant effects on SOD and CAT activities in mikimotoi and Amphidinium sp. (P<0.05). The SOD and CAT activities K. mikimotoi and Amphidinium sp. under 10-4 mol/L manganese concentration were significantly higher than those in other treatment groups. The SOD and CAT activities in K. mikimotoi and Amphidinium sp. under 10-12 mol/L manganese concentration were significantly lower than those in other treatment groups. The SOD and CAT activities in K. mikimotoi and Amphidinium sp. all increase with manganese concentration at 10-12-10-8 mol/L. |
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