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Fig. 3 Effect of Ag or Pt Pt-NPs Ag-NPs
nanoparticles on the optical chlorophyll chlorophyll
density and chlorophyll content OD OD
of Pseudokirchneriella 35 0.8 10.0 0.7
subcapitata cultures 30 0.7 9.0 0.6
8.0
chlorophyll [mg/L] 20 0.5 OD chlorophyll [mg/L] 6.0 0.3
0.6
25
0.5
7.0
5.0
0.4
15
4.0
0.4 OD
0.3
10
2.0
0.1
5 0.2 3.0 0.2
0.1
1.0
0 0 0.0 0
0 20 40 60 0 20 40 60
Pt NPs [mg/L] Ag NPs [mg/L]
concentrations of the NPs were investigated. As illustrated the presence of various concentrations of Ag or Pt NPs.
by the growth curves in Fig. 2, Ag nanoparticles were The results (Fig. 3) indicate that the total chlorophyll
highly toxic to P. subcapitata even at very low concen- content of the culture is an excellent measure of the effect
trations and the total inhibition of growth was observed at of NPs on algal growth, since the NP concentrations found
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5.0 mg L , all of which agreed with the pilot data. to cause a 100 % drop of chlorophyll level were virtually
Compared to Ag nanoparticles, Pt-NPs were of remarkably identical to the EC100 values previously determined. An
lower toxicity to P. subcapitata. Substantial growth inhi- excellent correlation was found between the culture optical
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bition was only observed at C10 mg L , and for the total density, number of algal cells, and chlorophyll content
inhibition of the algal growth 22.2 mg L -1 Pt NPs was ([90 %), indicating that the chlorophyll determination is a
required. Table 1 provides the NOEC, EC50 and EC100 very good approach for the investigation of the toxicity of
values for the two types of NPs. They are, respectively, ten- NPs to algae.
, twelve- and four-fold lower for silver than for platinum. The purpose of this study was to elucidate the toxicity of
The toxicity of silver ions to aquatic invertebrates and silver and platinum nanoparticles toward the freshwater
algae has been studied extensively. The lowest recorded microalga P. subcapitata using a standardized algal growth
NOEC values varied between 0.001 lgL -1 (for daphnia) inhibition test and the determination of photosynthetic
(Bielmyer et al. 2002) and 2 mg L -1 (for freshwater algae) pigments. Silver nanoparticles were more toxic than plat-
(Ratte 1999). However, very little research has been done on inum NPs. We also found that the determination of
the effects of Ag NPs on algal growth and photosynthesis chlorophyll can replace cell counting or other methods for
(Miao et al. 2009; Navarro et al. 2008). Griffitt et al. (2009) biomass quantification.
investigated the toxicity of Ag NPs coated with sodium ci-
Open Access This article is distributed under the terms of the
trate to P. subcapitata (96-h test) and obtained an LC50 of
Creative Commons Attribution License which permits any use, dis-
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0.19 mg L , eight times lower than our result tribution, and reproduction in any medium, provided the original
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(1.63 mg L ). This difference could be related to the par- author(s) and the source are credited.
ticle size—in our studies the particles were fivefold larger.
The coating of the particles could have played a role as well.
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