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84 result(s) for "Köhler, Heinz-R."
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Wildlife Ecotoxicology of Pesticides: Can We Track Effects to the Population Level and Beyond?
During the past 50 years, the human population has more than doubled and global agricultural production has similarly risen. However, the productive arable area has increased by just 10%; thus the increased use of pesticides has been a consequence of the demands of human population growth, and its impact has reached global significance. Although we often know a pesticide's mode of action in the target species, we still largely do not understand the full impact of unintended side effects on wildlife, particularly at higher levels of biological organization: populations, communities, and ecosystems. In these times of regional and global species declines, we are challenged with the task of causally linking knowledge about the molecular actions of pesticides to their possible interference with biological processes, in order to develop reliable predictions about the consequences of pesticide use, and misuse, in a rapidly changing world.
Plastic pollution in agricultural landscapes: an overlooked threat to pollination, biocontrol and food security
Ecosystem services such as pollination and biocontrol may be severely affected by emerging nano/micro-plastics (NMP) pollution. Here, we synthesize the little-known effects of NMP on pollinators and biocontrol agents on the organismal, farm and landscape scale. Ingested NMP trigger organismal changes from gene expression, organ damage to behavior modifications. At the farm and landscape level, NMP will likely amplify synergistic effects with other threats such as pathogens, and may alter floral resource distributions in high NMP concentration areas. Understanding exposure pathways of NMP on pollinators and biocontrol agents is critical to evaluate future risks for agricultural ecosystems and food security. Ecosystem services such as pollination and biocontrol are affected by increasing plastic pollution with potential implications for food security. Here the authors synthesize the little known effects of nano- and microplastics on pollinators and biocontrol agents at the organismal, farm and landscape scale.
Snails in the sun: Strategies of terrestrial gastropods to cope with hot and dry conditions
Terrestrial gastropods do not only inhabit humid and cool environments but also habitat in which hot and dry conditions prevail. Snail species that are able to cope with such climatic conditions are thus expected to having developed multifaceted strategies and mechanisms to ensure their survival and reproduction under heat and desiccation stress. This review paper aims to provide an integrative overview of the numerous adaptation strategies terrestrial snails have evolved to persist in hot and dry environments as well as their mutual interconnections and feedbacks, but also to outline research gaps and questions that remained unanswered. We extracted relevant information from more than 140 publications in order to show how biochemical, cellular, physiological, morphological, ecological, thermodynamic, and evolutionary parameters contribute to provide an overall picture of this classical example in stress ecology. These mechanisms range from behavioral and metabolic adaptations, including estivation, to the induction of chaperones and antioxidant enzymes, mucocyte and digestive gland cell responses and the modification and frequency of morphological features, particularly shell pigmentation. In this context, thermodynamic constraints call for processes of complex adaptation at varying levels of biological organization that are mutually interwoven. We were able to assemble extensive, mostly narrowly focused information from the literature into a web of network parameters, showing that future work on this subject requires multicausal thinking to account for the complexity of relationships involved in snails' adaptation to insolation, heat, and drought. Mechanisms of terrestrial snails to cope with radiation, heat, and drought range from behavioral and metabolic adaptations, including estivation, to the induction of chaperones and antioxidant enzymes, mucocyte and digestive gland cell responses and the modification and frequency of morphological features, particularly shell pigmentation. In this context, thermodynamic constraints call for processes of complex adaptation at varying levels of biological organization which are mutually interwoven. Future work on this subject therefore requires multicausal thinking to account for the high complexity of relationships.
Growth-Promoting Gold Nanoparticles Decrease Stress Responses in Arabidopsis Seedlings
The global economic success of man-made nanoscale materials has led to a higher production rate and diversification of emission sources in the environment. For these reasons, novel nanosafety approaches to assess the environmental impact of engineered nanomaterials are required. While studying the potential toxicity of metal nanoparticles (NPs), we realized that gold nanoparticles (AuNPs) have a growth-promoting rather than a stress-inducing effect. In this study we established stable short- and long-term exposition systems for testing plant responses to NPs. Exposure of plants to moderate concentrations of AuNPs resulted in enhanced growth of the plants with longer primary roots, more and longer lateral roots and increased rosette diameter, and reduced oxidative stress responses elicited by the immune-stimulatory PAMP flg22. Our data did not reveal any detrimental effects of AuNPs on plants but clearly showed positive effects on growth, presumably by their protective influence on oxidative stress responses. Differential transcriptomics and proteomics analyses revealed that oxidative stress responses are downregulated whereas growth-promoting genes/proteins are upregulated. These omics datasets after AuNP exposure can now be exploited to study the underlying molecular mechanisms of AuNP-induced growth-promotion.
The ability to withstand short-term heat shocks and long-term elevated ambient temperatures suggests different sensitivity to future climatic changes for two sympatric Mediterranean land snail species, Theba pisana and Xeropicta derbentina (Helicoidea)
In the 1940s, Xeropicta derbentina was introduced to the Provence region in south-eastern France. Since then, it has coexisted sympatrically with the native species Theba pisana . X. derbentina ‘s successful establishment in Provence is commonly attributed to the hot and dry climate there. In the context of continually rising temperatures and increasing aridity resulting from global change, we conducted open-top chamber (OTC) experiments with both species to simulate extreme heat conditions to be expected in the context of climate change. After exposure in the OTCs, the temperatures on the shell surface did not differ between the two species. Nevertheless, differences in the survival of the species following heat shocks, which were induced by transferring the snails to the hot soil, were striking. An initial heat shock at the start of the OTC exposure was survived significantly better by T. pisana than by X. derbentina . However, the prevailing conditions in the OTC apparently weakened T. pisana to such an extent that only few individuals survived another heat shock a week later. In contrast, X. derbentina exhibited heat hardening induced by the OTC conditions, meaning that a heat shock after a week of adaptation to the OTCs resulted in much lower mortality than in individuals of the same species that had not adapted to OTC conditions before the heat shock. After a week of exposure to OTCs, the survival rate following heat shock was also significantly higher in X. derbentina than in T. pisana . These results suggest that X. derbentina will have a selective advantage over T. pisana as their environment continues to warm up unless more heat-tolerant phenotypes of the latter species evolve or immigrate. Graphical Abstract
How glyphosate and its associated acidity affect early development in zebrafish ( Danio rerio )
Glyphosate is among the most extensively used pesticides worldwide. Following the ongoing highly controversial debate on this compound, its potential impact on non-target organisms is a fundamental scientific issue. In its pure compound form, glyphosate is known for its acidic properties. We exposed zebrafish ( ) embryos to concentrations between 10 μM and 10 mM glyphosate in an unbuffered aqueous medium, as well as at pH 7, for 96 hours post fertilization (hpf). Furthermore, we investigated the effects of aqueous media in the range of pH 3 to 8, in comparison with 1 mM glyphosate treatment at the respective pH levels. Additionally, we exposed zebrafish to 7-deoxy-sedoheptulose (7dSh), another substance that interferes with the shikimate pathway by a mechanism analogous to that of glyphosate, at a concentration of one mM. The observed endpoints included mortality, the hatching rate, developmental delays at 24 hpf, the heart rate at 48 hpf and the malformation rate at 96 hpf. LC , EC and, if reasonable, EC values were determined for unbuffered glyphosate. The results revealed high mortalities in all treatments associated with low pH, including high concentrations of unbuffered glyphosate (>500 μM), low pH controls and glyphosate treatments with pH < 3.4. Sublethal endpoints like developmental delays and malformations occurred mainly at higher concentrations of unbuffered glyphosate. In contrast, effects on the hatching rate became particularly prominent in treatments at pH 7, showing that glyphosate significantly accelerates hatching compared with the control and 7dSh, even at the lowest tested concentration. Glyphosate also affected the heart rate, resulting in alterations both at pH 7 and, even more pronounced, in the unbuffered system. In higher concentrations, glyphosate tended to accelerate the heart rate in zebrafish embryos, again, when not masked by the decelerating influence of its low pH. At pH > 4, no mortality occurred, neither in the control nor in glyphosate treatments. At 1 mM, 7dSh did not induce any mortality, developmental delays or malformations; only slightly accelerated hatching and a decelerated heart rate were observed. Our results demonstrate that lethal impacts in zebrafish embryos can be attributed mainly to low pH, but we could also show a pH-independent effect of glyphosate on the development of zebrafish embryos on a sublethal level.
Glyphosate- and aminomethylphosphonic acid (AMPA)-induced mortality and residues in juvenile brown trout (Salmo trutta f. fario) exposed at different temperatures
Background Glyphosate is a broad-spectrum, non-selective systemic herbicide with a commonly assumed low potential for accumulation in biota. Nevertheless, glyphosate has been shown to bioaccumulate in the tissues of several organisms. To understand the bioconcentration dynamics of glyphosate in fish, brown trout ( Salmo trutta forma fario ) of different age were exposed to different concentrations of glyphosate, the formulation Roundup® LB Plus, and the major transformation product aminomethylphosphonic acid (AMPA) for two, three, or four weeks at different temperatures in the laboratory. Mortality rates were determined, and tissue samples were collected at the end of the experiment to ascertain concentrations of glyphosate and AMPA residues by liquid chromatography coupled to mass spectrometry (LC–MS/MS). Results Brown trout mortality during exposure to glyphosate or AMPA was considerably higher at 15 °C than at 7 °C. Also, a significant increase in glyphosate concentrations in samples containing muscle, head, backbone, and caudal fin tissue with increasing exposure concentrations and temperatures was observed. Six-month-old fish contained more glyphosate per kg wet weight after exposure than ten-month-old fish. The bioconcentration factors (BCFs) for glyphosate and AMPA were much higher at 15 °C than at 7 °C, but in both cases decreased with higher glyphosate concentrations. The BCF for glyphosate formulated in Roundup® was higher than the one for the parent compound. Approximately 30–42% of the organ-absorbed glyphosate and AMPA remained in the tissues even when the fish were kept in clean water lacking the test substances for three weeks after termination of exposure. Conclusion Our study demonstrated that there is an interaction between glyphosate and ambient temperature in terms of toxicity. Further it was shown that increasing concentrations of glyphosate and AMPA in the surrounding media lead to significantly increased concentrations of these substances in brown trout tissues, although neither bioconcentration nor bioaccumulation of glyphosate in animal tissues is expected due to the high water solubility of this chemical. As a consequence, the uptake of glyphosate by humans through the consumption of contaminated edible fish is very likely.
Interacting Effects of Polystyrene Microplastics and the Antidepressant Amitriptyline on Early Life Stages of Brown Trout (Salmo trutta f. fario)
Whether microplastics themselves or their interactions with chemicals influence the health and development of aquatic organisms has become a matter of scientific discussion. In aquatic environments, several groups of chemicals are abundant in parallel to microplastics. The tricyclic antidepressant amitriptyline is frequently prescribed, and residues of it are regularly found in surface waters. In the present study, the influence of irregularly shaped polystyrene microplastics (<50 µm), amitriptyline, and their mixture on early life-stages of brown trout were investigated. In a first experiment, the impacts of 100, 104, and 105 particles/L were studied from the fertilization of eggs until one month after yolk-sac consumption. In a second experiment, eggs were exposed in eyed ova stages to 105, 106 particles/L, to amitriptyline (pulse-spiked, average 48 ± 33 µg/L) or to two mixtures for two months. Microplastics alone did neither influence the development of fish nor the oxidative stress level or the acetylcholinesterase activity. Solely, a slight effect on the resting behavior of fry exposed to 106 particles/L was observed. Amitriptyline exposure exerted a significant effect on development, caused elevated acetylcholinesterase activity and inhibition of two carboxylesterases. Most obvious was the severely altered swimming and resting behavior. However, effects of amitriptyline were not modulated by microplastics.
Environmental Drivers of Pesticide Toxicity: Temperature and pH Shift Azoxystrobin’s Effects on Zebrafish (Danio rerio) Early Development
Azoxystrobin, a widely used strobilurin fungicide, poses a potential risk to aquatic ecosystems due to its frequent detection in surface waters. Although its toxicity to non-target organisms has been extensively studied under standardized conditions, few investigations have considered how environmental factors can modulate the adverse effects of this chemical. In this study, we examined the toxicity of azoxystrobin to zebrafish (Danio rerio) embryos under different pH (5, 7, 9) and temperature (21 °C, 26 °C, 31 °C) conditions. Embryos were exposed to azoxystrobin concentrations ranging from 0 to 1000 μg/L, and endpoints such as survival, hatching rate, heart rate, malformations, developmental delay, and Hsp70 expression were assessed over 96 h post-fertilization. Our results demonstrate that azoxystrobin induces significant malformations (including edema, eye, tail, and spinal defects) and developmental delays at 1000 μg/L across all environmental conditions. Furthermore, both pH and temperature were found to modulate azoxystrobin toxicity: elevated temperature and alkaline pH partly alleviated mortality at high concentrations. The hsp70 expression patterns revealed complex interactions between the effects of the chemical and environmental factors. These findings highlight the importance of incorporating environmental variables into ecotoxicological risk assessments of pesticides to better reflect realistic exposure scenarios and potential ecological impacts.
Lowest Environmentally Relevant Concentrations of Ionic Silver in Picograms per Liter Impair Life History Traits and Population Growth of Daphnia magna (Cladocera)
Although chronic contamination by silver ions (Ag+) can persist in aquatic systems over long periods of time and can therefore have an impact on population developments, regulatory testing commonly relies on single-generation endpoints. Here, we used Daphnia magna to quantify long-term effects of pg/L to ng/L concentrations of Ag+ across generations and to test whether recovery depends on exposure history. Using 21 d life-cycle assays over up to seven consecutive generations, we quantified survival, key life-history traits, and population fitness (intrinsic rate of natural increase, r). In our study, low environmental concentrations of Ag+ caused minimal mortality, but sublethal effects persisted or multiplied over generations. Notably, continuous exposure led to significant reductions in body length and r at 50 pg/L (nominal LOEC) by the fourth generation exposed, representing population-relevant effects of Ag+ at very low concentrations which should be given consideration in the assessment of both water quality and the chemical itself. Recovery was concentration-dependent: low-concentration-exposed lineages recovered within a few generations, whereas 15 ng/L exposure resulted in persistent deficits even through the recovery period of three generations. Exposure-history patterns indicated that long-term outcomes were dominated by the cumulative number of exposed generations. These findings highlight the limitations of acute and single-generation assays and emphasize the importance of considering information on the effects of chemicals, including Ag+, across multiple generations in risk assessments. They also highlight the need to include expectations regarding recovery after the removal of pollutants in these assessments.