Numerous biotic mechanisms can control ecosystem nutrient cycling, but their full incorporation into ecological models or experimental designs can result in inordinate complexity. Including ...organismal nutrient limitation in models of highly dimensional systems (i.e., those with many nutrient pools/species) presents a critical challenge. We evaluate the importance of explicitly considering microbial and animal nutrient limitation to predict ecosystem nitrogen cycling across plant-based and detritus-based food chains. We investigate how eight factorial scenarios of microbial, herbivore, and microbi-detritivore (i.e., omnivores consuming microbes and detritus) nitrogen or carbon limitation alter the stocks and flows of nitrogen in an ecosystem model. We used a combination of partial derivatives of model equilibrium solutions and numerical simulations using randomly drawn parameter sets to explore the impact of each nutrient limitation scenario on nutrient stocks and flows. We show that switching microbes, herbivores, or microbi-detritivores from nitrogen to carbon limitation consistently altered the ecosystem response to changes in inorganic nitrogen supply, plant C:N ratio, and microbial C:N ratio. Organism nutrient limitation changed ecosystem nitrogen flows by altering the feedbacks between the abiotic and biotic pools. For example, microbi-detritivore nutrient limitation determined whether the microbial response to changes in inorganic nitrogen supply and C:N ratios was dependent on the size of detrital carbon or detrital nitrogen pool. Such correlated responses among biotic and abiotic pools set up a network of predictable changes in ecosystem properties sensitive to organism nutrient limitation. Scenarios with microbial limitation were generally sufficient to capture the suite of ecosystem responses to increasing inorganic nitrogen supply, while scenarios with animal limitation added new behavior whenever C:N ratios changed. We make the case for explicitly considering both microbial and animal nutrient limitation when predicting the flow and distribution of nitrogen across green and brown food chains.
Stable isotope mixing models are increasingly used to quantify consumer diets, but may be misused and misinterpreted. We address major challenges to their effective application. Mixing models have ...increased rapidly in sophistication. Current models estimate probability distributions of source contributions, have user-friendly interfaces, and incorporate complexities such as variability in isotope signatures, discrimination factors, hierarchical variance structure, covariates, and concentration dependence. For proper implementation of mixing models, we offer the following suggestions. First, mixing models can only be as good as the study and data. Studies should have clear questions, be informed by knowledge of the system, and have strong sampling designs to effectively characterize isotope variability of consumers and resources on proper spatio-temporal scales. Second, studies should use models appropriate for the question and recognize their assumptions and limitations. Decisions about source grouping or incorporation of concentration dependence can influence results. Third, studies should be careful about interpretation of model outputs. Mixing models generally estimate proportions of assimilated resources with substantial uncertainty distributions. Last, common sense, such as graphing data before analyzing, is essential to maximize usefulness of these tools. We hope these suggestions for effective implementation of stable isotope mixing models will aid continued development and application of this field.
•A narrative review is presented of the potential toxicity of plastic particles to humans.•Nanoparticles are more readily absorbed than microparticles.•Atmospheric pollution and ingestion of ...shellfish are major sources of plastic particles.•Toxicity is unlikely unless absorption of plastic particles is high and continuous.
Macro-plastic pollution is found in terrestrial and marine environments and is degraded to micro-particles (MP) and nano-particles (NP) of plastic. These can enter the human food chain either by inhalation or by ingestion, particularly of shellfish and crustaceans. Absorption across the gastrointestinal tract is relatively low, especially for MPs, which appear to have little toxicity. However, NPs are more readily absorbed and may accumulate in the brain, liver and other tissues in aquatic species and other animals. Studies using nanoparticles of other materials suggest that toxicity could potentially affect the central nervous system and the reproductive system, although this would be unlikely unless exposure levels were very high and absorption was increased by physiological factors.
Resistance to 3rd-generation cephalosporins in Escherichia coli is mostly mediated by extended-spectrum beta-lactamases (ESBLs) or AmpC beta-lactamases. Besides overexpression of the species-specific ...chromosomal ampC gene, acquisition of plasmid-encoded ampC genes, e.g. bla
, has been described worldwide in E. coli from humans and animals. To investigate a possible transmission of bla
along the food production chain, we conducted a next-generation sequencing (NGS)-based analysis of 164 CMY-2-producing E. coli isolates from humans, livestock animals and foodstuff from Germany.
The data of the 164 sequenced isolates revealed 59 different sequence types (STs); the most prevalent ones were ST38 (n = 19), ST131 (n = 16) and ST117 (n = 13). Two STs were present in all reservoirs: ST131 (human n = 8; food n = 2; animal n = 6) and ST38 (human n = 3; animal n = 9; food n = 7). All but one CMY-2-producing ST131 isolates belonged to the clade B (fimH22) that differed substantially from the worldwide dominant CTX-M-15-producing clonal lineage ST131-O25b clade C (fimH30). Plasmid replicon types IncI1 (n = 61) and IncK (n = 72) were identified for the majority of bla
-carrying plasmids. Plasmid sequence comparisons showed a remarkable sequence identity, especially for IncK plasmids. Associations of replicon types and distinct STs were shown for IncK and ST57, ST429 and ST38 as well as for IncI1 and ST58. Additional β-lactamase genes (bla
, bla
, bla
, bla
) were detected in 50% of the isolates, and twelve E. coli from chicken and retail chicken meat carried the colistin resistance gene mcr-1.
We found isolates of distinct E. coli clonal lineages (ST131 and ST38) in all three reservoirs. However, a direct clonal relationship of isolates from food animals and humans was only noticeable for a few cases. The CMY-2-producing E. coli-ST131 represents a clonal lineage different from the CTX-M-15-producing ST131-O25b cluster. Apart from the ST-driven spread, plasmid-mediated spread, especially via IncI1 and IncK plasmids, likely plays an important role for emergence and transmission of bla
between animals and humans.
Heavy metal pollution threatens human and ecological health. Heavy metals can exist in the soil for a long time and migrate to organisms along the food chain. However, only a few studies have ...investigated the effects of a single stress on broad beans. Here, we aimed to characterize Cd and Pb bioaccumulation, at varying concentrations, in the broad bean, Vicia faba L. We also determined how the bioaccumulated metals are impacted by aphids that consume the plant. No significant difference was noted in the germination rates of broad beans at the early stage of planting (after 8 days), but eventually, the germination rates of broad beans at all time points first decreased and then increased, and the highest inhibition efficiency was observed in the T3 group (12.5 mg/L Cd2+ + 50 mg/L Pb2+). Fourteen days after planting, there was no significant difference in seedling height between the T5 (50 mg/L Cd2+ + 200 mg/L Pb2+) and control groups; however, that in the other groups decreased significantly and there was no dependence between stress concentration and inhibition efficiency. In addition, both Cd and Pb in the soil could be transferred to broad beans, and the concentration of Pb in the roots of broad beans was greater than that of Cd, whereas the opposite was observed in the stems and leaves. Notably, under mixed stress, aphids could significantly reduce the content of Cd in broad beans; similarly, the Pb content in the roots and stems of broad beans decreased significantly after being infested with aphids but increased significantly in the leaves. Further, the aphid infestation decreased the Pb content in the soil and the soil Cd content in the highest concentration group (T5 group) (50 mg/L Cd2+ + 200 mg/L Pb2+). These results highlight the necessity of focusing on the effect of insects on heavy metal remediation in plants and provide a new perspective for reducing plant Cd toxicity.
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•Parts of the broad bean bioaccumulate lead and cadmium differently.•Lead was more enriched in the roots of the broad bean.•Heavy metal exposure reduced the germination rate of the broad bean.•Aphids consuming the broad bean reduced heavy metals in the roots and stems.
We present a framework to explain how prey stress responses to predation can resolve context dependency in ecosystem properties and functions such as food chain length, secondary production, ...elemental stoichiometry, and cycling. We first describe the major nonspecific physiological stress mechanisms and their ecologically relevant consequences. We next synthesize the evidence for prey physiological responses to predation risk and demonstrate that they are similar across taxa and fit well within the general stress paradigm. We then illustrate the utility of our idea by applying our understanding of the ecological consequences of stress to explain how herbivore‐prey physiological antipredator responses affect ecosystem dynamics. We hypothesize that stressed herbivores should forage on plant species with higher digestible carbohydrates than should unstressed herbivores to meet heightened energy demands. Increased consumption of carbohydrate‐rich plants should reduce their relative abundance in the community, hence altering the quantity and quality of plant litter entering the detrital pool. We further hypothesize that stress should change the elemental composition and energy content of prey excreta, egesta, and carcasses that enter the detrital pool. Finally, prey stress should lower energy and nutrient conversion efficiency and hence the transfer of materials and energy up the food chain, which should, in turn, weaken the association between ecosystem productivity and food chain length.
Review of micro- and nanoplastic contamination in the food chain Toussaint, Brigitte; Raffael, Barbara; Angers-Loustau, Alexandre ...
Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment,
05/2019, Letnik:
36, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Whereas the dramatic environmental impact of plastic waste rightfully receives considerable attention by scientists, policy makers and public in general, the human health impact of micro- and ...nanoplastics contamination of our food and beverages remains largely unknown. Indeed, most studies aim at understanding the environmental impact rather than the human health impact of a possible exposure to micro- and nanoplastics. In addition, these papers generally lack a methodological, standardised approach. Furthermore, some studies focus on the damage to and contamination level of animal species collected from the wild environment, and others investigate the rate and biology of microplastic uptake of animals fed with microplastics in laboratory. This review aims at understanding human exposure. Since there is, with few exceptions, no evidence available on the presence of micro- and nanoplastics in a normal diet, this study takes an indirect approach and analyses peer-reviewed publications since 2010 that document the presence of micro- and nanoplastics in those animals (more than 200 species) and food products that are part of the human food chain and that may thus contribute directly or indirectly to the uptake of micro- and nanoplastics via the human diet. It also addresses the question of the definitions, the methodologies and the quality criteria applied to obtain the reported results. This review suggests that, beyond a few estimations and comparisons, precise data to assess the exact exposure of humans to micro- and nanoplastics through their diet cannot be produced until standardised methods and definitions are available.
Stable isotope analysis has emerged as one of the primary means for examining the structure and dynamics of food webs, and numerous analytical approaches are now commonly used in the field. ...Techniques range from simple, qualitative inferences based on the isotopic niche, to Bayesian mixing models that can be used to characterize food‐web structure at multiple hierarchical levels. We provide a comprehensive review of these techniques, and thus a single reference source to help identify the most useful approaches to apply to a given data set. We structure the review around four general questions: (1) what is the trophic position of an organism in a food web?; (2) which resource pools support consumers?; (3) what additional information does relative position of consumers in isotopic space reveal about food‐web structure?; and (4) what is the degree of trophic variability at the intrapopulation level? For each general question, we detail different approaches that have been applied, discussing the strengths and weaknesses of each. We conclude with a set of suggestions that transcend individual analytical approaches, and provide guidance for future applications in the field.
Little information is available about the bioaccumulation and biomagnification of antibiotics in marine food webs. Here, we investigate the levels and trophic transfer of 9 sulfonamide (SA), 5 ...fluoroquinolone (FQ), and 4 macrolide (ML) antibiotics, as well as trimethoprim in nine invertebrate and ten fish species collected from a marine food web in Laizhou Bay, North China in 2014 and 2015. All the antibiotics were detected in the marine organisms, with SAs and FQs being the most abundant antibiotics. Benthic fish accumulated more SAs than invertebrates and pelagic fish, while invertebrates exhibited higher FQ levels than fish. Generally, SAs and trimethoprim biomagnified in the food web, while the FQs and MLs were biodiluted. Trophic magnification factors (TMF) were 1.2–3.9 for SAs and trimethoprim, 0.3–1.0 for FQs and MLs. Limited biotransformation and relatively high assimilation efficiencies are the likely reasons for the biomagnification of SAs. The pH dependent distribution coefficients (log D) but not the lipophilicity (log K OW) of SAs and FQs had a significant correlation (r = 0.73; p < 0.05) with their TMFs. Although the calculated estimated daily intakes (EDI) for antibiotics suggest that consumption of seafood from Laizhou Bay is not associated with significant human health risks, this study provides important insights into the guidance of risk management of antibiotics.
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