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  • 1
    Language: English
    In: Environmental Toxicology and Chemistry, August 2004, Vol.23(8), pp.1984-1990
    Description: We investigated the acute (5 d) effects of particle‐associated azinphosmethyl (AZP) in multispecies microcosms and assessed the results in the context to data obtained from a parallel field study undertaken in the Lourens River, South Africa. A runoff simulation was carried out in stream microcosms containing the macroinvertebrate fauna of an uncontaminated Lourens River site exposed to particle‐associated AZP (control and 200, 1,000, 5,000, 20,000 μg/kg; three replicates each) for 1 h. Measured AZP concentrations in filtered microcosm water resulted in the following values: Not detectable (control) and 0.03, 0.2, 1.1, and 6.9 μg/L, respectively. The two highest treatments resulted in significantly (analysis of variance [ANOVA]) reduced total numbers of individuals, while the number of taxa was affected in the 20,000 μg/kg treatment only. A comparison with previous data suggests that observed effects partly resulted from particle‐associated AZP. Particularly affected were six out of 14 macroinvertebrate taxa such as mayfly and stonefly taxa. In parallel, the distribution of macroinvertebrates at a pesticide‐free and a contaminated stretch of the Lourens River was monitored five times during the spraying season in 2001 and 2002. Out of the 14 core taxa found in the microcosm study as well as in the field approach, 10 showed comparable reactions in the microcosm experiment and in their field distribution; they were either classified as affected or unaffected in both studies. Thus, we conclude that particle‐associated AZP has the potential to affect the invertebrate community structure of the Lourens River and that microcosm studies employing fieldrelevant exposure scenarios may be valuable for a local risk assessment of pesticide‐related community disruptions in the Lourens River.
    Keywords: Aquatic Macroinvertebrates ; Community Structure ; Microcosms ; Particle‐Associated Azinphosmethyl ; Runoff
    ISSN: 0730-7268
    E-ISSN: 1552-8618
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  • 2
    Language: English
    In: Environmental Toxicology and Chemistry, 2001, Vol.20(9), p.2088
    Description: We studied the chronic effects of 4-nonylphenol (4-NP) on reproductive status of medaka (Oryzias latipes) over two generations of continuous exposure. The exposure study of the parental (F0) medaka was begun on embryos within 24 h post-fertilization and continued with monitoring through embryological development, hatching, posthatch survival, growth, sexual differentiation, and reproduction under flow-through exposures to mean measured 4-NP concentrations of 4.2, 8.2, 17.7, 51.5, and 183 µg/litre for up to 104 d. Eggs spawned from the F0 fish at 102 and 103 d posthatch were also examined for hatchability, survival after hatching, growth, and sexual differentiation until 60 d posthatch. The 183-µg/litre treatment significantly reduced the embryo survival and swim-up success of the F0 fish. The cumulative mortality after swim-up of the F0 fish exposed to 17.7 and 51.5 µg/litre were significantly higher than the control mortality. No concentration-related effect of 4-NP was observed on the growth of surviving F0 fish at 60 d posthatch. However, the sex ratio estimated from the appearance of their secondary sex characteristics was skewed toward female in the 51.5-µg/litre treatment. Additionally, gonadal histology showed that 20% of the fish in the 17.7-µg/litre treatment and 40% in the 51.5-µg/litre treatment had testis-ova, indicating that 4-NP affects the gonadal development and survival of medaka at similar concentrations in juveniles. The sex ratio of the F0 fish in the 51.5-µg/litre treatment was completely skewed toward female; subsequently, the effects on fecundity and fertility in this generation were monitored at mean measured concentrations of 4.2, 8.2, and 17.7 µg/litre from 71 to 103 d posthatch. Fecundity was unaffected by any of the treatments examined. The mean fertility in the 17.7-µg/litre treatment was reduced to 76% of that in the controls, although no statistically significant differences were determined. Overall, these results indicate that the lowest-observed-effect concentration (LOEC) and no-observed-effect concentration (NOEC) of 4-NP through the life cycle of the F0 medaka were 17.7 and 8.2 µg/litre, respectively. In the F1 medaka, no significant effects were observed on hatching success, posthatch mortality, or growth, but sexual differentiation at 60 d posthatch was affected. Induction of testis-ova in the gonads of the F1 fish was observed in both the 8.2- and the 17.7-µg/litre concentrations. The results indicate that 4-NP can have significant effects on reproductive potential of medaka at concentrations as low as 17.7 µg/litre.
    Keywords: Aquatic Animals ; Aquatic Organisms ; Embryonic Development ; Embryos ; Growth ; Mortality ; Nontarget Effects ; Ovaries ; Reproduction ; Sex Differentiation ; Survival ; Testes ; Toxic Substances ; Toxicity ; Toxicology ; Aquatic Species ; Death Rate ; Embryo Development ; Embryo Growth ; Nonylphenols ; Poisons ; Testicles ; Oryzias Latipes ; Oryzias ; Adrianichthyidae ; Beloniformes ; Osteichthyes ; Fishes ; Vertebrates ; Chordata ; Animals ; Eukaryotes;
    ISSN: 0730-7268
    E-ISSN: 1552-8618
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  • 3
    Language: English
    In: Environmental Toxicology and Chemistry, September 1999, Vol.18(9), pp.1948-1955
    Description: The study aims to evaluate the impact of insecticides associated with rainfall‐induced surface runoff from arable land on macroinvertebrate populations. These effects of insecticides were distinguished from the hydraulic stress also associated with surface runoff. Transient increase in discharge and insecticide contamination (maximum 6 μg/L parathion‐ethyl in stream water, 302 μg/L fenvalerate in suspended particulates) was observed in a headwater stream subsequent to surface runoff from arable land. In the aquatic macroinvertebrate community, eight of the eleven abundant species disappeared, and the remaining three were reduced significantly in abundance following the insecticide‐contaminated runoff. Recovery within 6 months was observed for four species and recovery within 11 months for nine species. Two species remained at a low population density for over a year. The effects of insecticides were distinguished from other parameters, such as hydraulic stress associated with surface runoff, as well. The causal connection between insecticide contamination and biological response was established by eliminating increased hydraulic stress during surface runoff using in‐parallel bypass microcosms containing the dominant species and . The mortality of these species was similar to that of the same species in the stream. Additional microcosms, disconnected from the stream during runoff events, served as a control. Thus, the toxic potential of the runoff water is considered to be responsible for the observed effect on the macroinvertebrates. It is concluded that agricultural insecticide input may alter the dynamics of macroinvertebrate communities in streams.
    Keywords: Pesticides ; Headwater Stream ; Macroinvertebrates ; Recovery ; Microcosm
    ISSN: 0730-7268
    E-ISSN: 1552-8618
    Source: John Wiley & Sons, Inc.
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