Environmental Engineering Reference
In-Depth Information
membranedisruptionandheavycellulardamage(Table
5
), which may have resulted
fromdirectcontactbetweentheNPsandorganismalcells(Palomaresetal.
2011
).
A similar interaction was observed for
Desmodesmus subspicatus
with photoactive
TiO
2
NPs(25nm)andtheeffectswereconirmedbyilluminationmeasurements.In
particular, the main effects were growth reduction, which was enhanced with
increased levels of TiO
2
NPs(Hund-RinkeandSimon
2006
).
The dearth of information on the effects of ENPs on both bacteria and algae
makescleartheneedfornewresearchtostrengthenknowledgeinthisdomain.
5.1.3
Protozoa
Toxicity testing on the living unicellular protozoan
Stylonychia mytilus
revealed
that exposure to MWNTs resulted in uptake by the protozoa.Absorbed MWNTs
weresubsequentlypassedonaftercelldivisionandwereultimatelyexcretedfrom
the cell (Zhu et al.
2006b
). A dose-dependent growth inhibition was observed as
MWNT exposure concentrations increased. It was observed by using fluorescence
and electron microscopy that the MWNTs caused damage to the macronucleus and
externalmembranesofcells.Moreover,MWNTsremainedexclusivelylocalizedin
cellmitochondria(Table
5
).Zhuetal.(
2006b
) proposed that the deleterious effects
on the micronucleus, macronucleus and the cell membrane may be attributed to
mitochondrial damage.
Zhu et al. (
2006a
) performed a similar study with the unicellular protozoan
Tetrahymena pyriformis
, and in contrast to previous results, showed a growth stimu-
lation from exposure to MWNTs-peptone conjugates in a proteose peptone yeast
extractmedium(PPY).However,growth inhibition from exposure to MWNTs was
observed in presence of filtered pond water. Furthermore, measurements of MDA
(malondialdehyde)levels,andSOD(superoxidedismutase)activitydemonstrated
that MWNTs may be toxic or nontoxic depending on the medium used to cultivate
Tetrahymena pyriformis
.
5.2
Animals
5.2.1
Invertebrates
Crustacea
Templetonetal.(
2006
) performed a chronic life cycle bioassay with the estuarine
copepod
Amphiascus tenuiremis
with SWNTs. No significant effects on mortality,
developmentandreproductionwasobservedacrossexposures(<0.05)withpuriied
SWNTs (Table
5
). However, an AP-SWNT (As prepared) complex significantly
increasedthelifecyclemortalityandreducedthefertilizationrate.Theresultsof
this study suggested increased life cycle mortality and delayed copepod develop-
mentatvarioussizesandconcentrationsofAP-SWNT(Templetonetal.
2006
).
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