However, as for natural particles, neither NP nor NPn showed any adverse effects on the animals. On the contrary, NP and NPn provided the organism with fine living conditions with the result that the animals were vivacious throughout the 7 d bioassays (Bioassay 1 and 2) when the particle concentration exceeded 200 mg L1 for NP and 50 mg L1 for NPn. That is to say, the D. magna exhibited dose-dependent survivorship for the NP and NPn treatments, and received greater benefit in the NPn suspensions (Fig. 2). Moreover, a significant difference in growth rate was observed among the 7 d sublethal tests (Fig. 3). The growth rate of the NPn treatment was significantly higher than that of the NP treatment (p = 0.025 < 0.05). Organisms exposed to NP suspensions experienced a great decrease in the number of days to gravidity from NPn (Table 2). Both NP- and NPn-exposed organisms
showed decreases in days to gravidity with the increase in
particle concentration. Many neonates were produced during the
21 d bioassays, except for when the concentration was 200 mg L1.
The population growth rates (r) and demographic parameters calculated
from the life tables are shown in Table 2. The net reproductive
rate and population growth rate increased and the generation
time decreased as the particle concentration increased, for both the
NP and NPn treatments. The population growth rates were negative when the concentration was 400 mg L1. However, when
the concentration was either 600 or 800 mg L1, D. magna can
maintain its normal life activities with the help of natural particles,
and the population growth rates were much higher in NP than in
NPn (Table 2).
However, as for natural particles, neither NP nor NPn showed any adverse effects on the animals. On the contrary, NP and NPn provided the organism with fine living conditions with the result that the animals were vivacious throughout the 7 d bioassays (Bioassay 1 and 2) when the particle concentration exceeded 200 mg L1 for NP and 50 mg L1 for NPn. That is to say, the D. magna exhibited dose-dependent survivorship for the NP and NPn treatments, and received greater benefit in the NPn suspensions (Fig. 2). Moreover, a significant difference in growth rate was observed among the 7 d sublethal tests (Fig. 3). The growth rate of the NPn treatment was significantly higher than that of the NP treatment (p = 0.025 < 0.05). Organisms exposed to NP suspensions experienced a great decrease in the number of days to gravidity from NPn (Table 2). Both NP- and NPn-exposed organismsshowed decreases in days to gravidity with the increase inparticle concentration. Many neonates were produced during the21 d bioassays, except for when the concentration was 200 mg L1.The population growth rates (r) and demographic parameters calculatedfrom the life tables are shown in Table 2. The net reproductiverate and population growth rate increased and the generationtime decreased as the particle concentration increased, for both theNP and NPn treatments. The population growth rates were negative when the concentration was 400 mg L1. However, whenthe concentration was either 600 or 800 mg L1, D. magna canmaintain its normal life activities with the help of natural particles,and the population growth rates were much higher in NP than inNPn (Table 2).
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