This paper compares the fate and effects of linuron in an outdoor plankton-dominated microcosm st... more This paper compares the fate and effects of linuron in an outdoor plankton-dominated microcosm study carried out in Thailand with those reported in temperate model ecosystem studies evaluating linuron and other photosynthesis-inhibiting herbicides. Lower linuron concentrations disappeared slightly faster from the water compartment compared to temperate conditions, which appears to be related with the experimental design rather than differences in climatic conditions. Sensitivity of primary producers and zooplankton were similar for the climatic regions, whereas effects on ecosystem functioning were less pronounced in tropical microcosms. Recovery potential of affected endpoints appears higher for tropical ecosystems compared to their temperate counterparts. These findings support the use of toxicity data generated in temperate countries in the tropics. Recommendations for the methodology of tropical model ecosystem experiments are discussed.
Effects of a single application of the photosynthesis-inhibiting herbicide linuron (0, 15, 50, 15... more Effects of a single application of the photosynthesis-inhibiting herbicide linuron (0, 15, 50, 150, and 500 microg/L) on the ecology of outdoor plankton-dominated microcosms were studied in Thailand. As a result of the decreased photosynthesis, DO and pH decreased while EC, alkalinity and nutrient concentrations increased. Chlorophytes belonging to the genera Scenedesmus, Coelastrum and Pediastrum were the most sensitive taxa, whereas several other chlorophytes, diatoms, and cryptophytes increased in abundance. Tolerant taxa appeared to be less digestable for several zooplankton taxa, which subsequently decreased in abundances. Chamaesiphon sp. (Cyanobacteria) was the most susceptible periphyton species. As a consequence of functional redundancy, effects of the herbicide on the chlorophyll-a content of periphyton and especially phytoplankton did not always reflect the effects noted on community level.
In aquatic environments, many factors determine the overall impact of a toxic event, constituting... more In aquatic environments, many factors determine the overall impact of a toxic event, constituting "exposure scenarios" that must be understood so that risk assessment strategies can be successfully applied. In this work, an experimental design was planned to investigate the influence of the organism age, duration of exposure and subsequent recovery period (after cessation of toxic exposure) on chlorpyrifos or carbendazim toxicity to Kiefferulus calligaster. The endpoints studied were cholinesterase (ChE) activity and glutathione S-transferase (GST) activity. The influence of age and exposure time and the existence of recovery depend on the chemical and the biomarkers tested, suggesting that no general rule can be applied when trying to assess overall toxicity of pesticides and that detailed knowledge has to be acquired on a case-to-case basis.
This paper compares the fate and effects of linuron in an outdoor plankton-dominated microcosm st... more This paper compares the fate and effects of linuron in an outdoor plankton-dominated microcosm study carried out in Thailand with those reported in temperate model ecosystem studies evaluating linuron and other photosynthesis-inhibiting herbicides. Lower linuron concentrations disappeared slightly faster from the water compartment compared to temperate conditions, which appears to be related with the experimental design rather than differences in climatic conditions. Sensitivity of primary producers and zooplankton were similar for the climatic regions, whereas effects on ecosystem functioning were less pronounced in tropical microcosms. Recovery potential of affected endpoints appears higher for tropical ecosystems compared to their temperate counterparts. These findings support the use of toxicity data generated in temperate countries in the tropics. Recommendations for the methodology of tropical model ecosystem experiments are discussed.
Effects of a single application of the photosynthesis-inhibiting herbicide linuron (0, 15, 50, 15... more Effects of a single application of the photosynthesis-inhibiting herbicide linuron (0, 15, 50, 150, and 500 microg/L) on the ecology of outdoor plankton-dominated microcosms were studied in Thailand. As a result of the decreased photosynthesis, DO and pH decreased while EC, alkalinity and nutrient concentrations increased. Chlorophytes belonging to the genera Scenedesmus, Coelastrum and Pediastrum were the most sensitive taxa, whereas several other chlorophytes, diatoms, and cryptophytes increased in abundance. Tolerant taxa appeared to be less digestable for several zooplankton taxa, which subsequently decreased in abundances. Chamaesiphon sp. (Cyanobacteria) was the most susceptible periphyton species. As a consequence of functional redundancy, effects of the herbicide on the chlorophyll-a content of periphyton and especially phytoplankton did not always reflect the effects noted on community level.
In aquatic environments, many factors determine the overall impact of a toxic event, constituting... more In aquatic environments, many factors determine the overall impact of a toxic event, constituting "exposure scenarios" that must be understood so that risk assessment strategies can be successfully applied. In this work, an experimental design was planned to investigate the influence of the organism age, duration of exposure and subsequent recovery period (after cessation of toxic exposure) on chlorpyrifos or carbendazim toxicity to Kiefferulus calligaster. The endpoints studied were cholinesterase (ChE) activity and glutathione S-transferase (GST) activity. The influence of age and exposure time and the existence of recovery depend on the chemical and the biomarkers tested, suggesting that no general rule can be applied when trying to assess overall toxicity of pesticides and that detailed knowledge has to be acquired on a case-to-case basis.
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