The kinetics of phytoplankton is complicated function of phytoplankton present and their differing reactions to solar radiation, temperature and balance between nutrient availabilities and phytoplankton requirements. Computers program for water quality problems helps users interpret and predict water quality responses to natural phenomena. But model parameters and initial condition needs hydrodynamic and hydrologic measures in long time interval, with combination of laboratory studies. Lake Gracanka (Serbia, Yugoslavia) is good example for description of the processes kinetics of phytoplankton. But, simulation model can not be used to guide future monitoring efforts without needing measuring and developing network of measuring station.

International audience | Background, aim and scope Agricultural landscapes comprise cultivated fields and semi-natural areas. Biological components of these compartments such as weeds, insect pests and pathogenic fungi can disperse sometimes over very large distances, colonise new habitats via insect flight, spores, pollen or seeds and are responsible for losses in crop yield (e.g. weeds, pathogens) and biodiversity (e.g. invasive weeds). The spatiotemporal dynamics of these biological components interact with crop locations, successions and management as well as the location and management of semi-natural areas such as roadverges. The objective of this investigation was to establish a modelling and simulation methodology for describing, analysing and predicting spatiotemporal dynamics and genetics of biological components of agricultural landscapes. The ultimate aim of the models was to evaluate and propose innovative cropping systems adapted to particular agricultural concerns. The method was applied to oilseed rape (OSR) volunteers playing a key role for the coexistence of genetically modified (GM) and non-GM oilseed rape crops, where the adventitious presence of GM seeds in non-GM harvests (AGMP) could result in financial losses for farmers and cooperatives. Material and methods A multi-year, spatially explicit model was built, using field patterns, climate, cropping systems and OSR varieties as input variables, focusing on processes and cultivation techniques crucial for plant densities and pollen flow. The sensitivity of the model to input variables was analysed to identify the major cropping factors. These should be modified first when searching for solutions limiting gene flow. The sensitivity to model processes and species life-traits were analysed to facilitate the future adaptation of the model to other species. The model was evaluated by comparing its simulations to independent field observations to determine its domain of validity and prediction error. Results The cropping system study determined contrasted farm types, simulated the current situation and tested a large range of modifications compatible with each farm to identify solutions for reducing the AGMP. The landscape study simulated gene flow in a large number of actual and virtual field patterns, four combinations of regional OSR and GM proportions and three contrasted cropping systems. The analysis of the AGMP rate at the landscape level determined a maximum acceptable GM OSR area for the different cropping systems, depending on the regional OSR volunteer infestation. The analysis at the field level determined minimum distances between GM and non-GM crops, again for different cropping systems and volunteer infestations. Discussion The main challenge in building spatially explicit models of the effects of cropping systems and landscape patterns on species dynamics and gene flow is to determine the spatial extent, the time scale, the major processes and the degree of mechanistic description to include in the model, depending on the species characteristics and the model objective. Conclusions These models can be used to study the effects of cropping systems and landscape patterns over a large range of situations. The interactions between the two aspects make it impossible to extrapolate conclusions from individual studies to other cases. The advantage of the present method was to produce conclusions for several contrasted farm types and to establish recommendations valid for a large range of situations by testing numerous landscapes with contrasted cropping systems. Depending on the level of investigation (region or field), these recommendations concern different decision-makers, either farmers and technical advisors or cooperatives and public decision-makers. Recommendations and perspectives The present simulation study showed that gene flow between coexisting GM and non-GM varieties is inevitable. The management of OSR volunteers is crucial for containing gene flow, and the cropping system study identified solutions for reducing these volunteers and ferals in and outside fields. Only if these are controlled can additional measures such as isolation distances between GM and non-GM crops or limiting the proportion of the region grown with GM OSR be efficient. In addition, particular OSR varieties contribute to limit gene flow. The technical, organisational and financial feasibility of the proposed measures remains to be evaluated by a multi-disciplinary team.

Fucus virsoides is an ecologically important canopy-forming brown algae endemic to the Adriatic Sea. Once widespread in marine coastal areas, this species underwent a rapid population decline and is now confined to small residual areas. Although the reasons behind this progressive disappearance are still a matter of debate, F. virsoides may suffer, like other macroalgae, from the potential toxic effects of glyphosate-based herbicides.Here, through a transcriptomic approach, we investigate the molecular basis of the high susceptibility of this species to glyphosate solution, previously observed at the morphological and eco-physiological levels. By simulating runoff event in a factorial experiment, we exposed F. virsoides to glyphosate (Roundup® 2.0), either alone or in association with nutrient enrichment, highlighting significant alterations of gene expression profiles that were already visible after three days of exposure. In particular, glyphosate exposure determined the near-complete expression shutdown of several genes involved in photosynthesis, protein synthesis and stress response molecular pathways. Curiously, these detrimental effects were partially mitigated by nutrient supplementation, which may explain the survival of relict population in confined areas with high nutrient inputs.

Traditional toxicity tests assess stressor effects on individuals, while protection goals are focused on the population-level and above. Additionally, these tests ignore common ecological factors such as resource levels and population growth phase. The objective of this research was to explore effects of – and interactions between – resource availability and stress response at the individual and population levels using Daphnia magna as a model. We hypothesized that density-dependent changes in resources at various phases of population growth would cause different population responses to the same toxicant stress. Laboratory populations of Daphnia magna were exposed to a 48-h pulse of 20 or 30 μg/l pyraclostrobin in one of four distinct phases of laboratory population cycles: growth, peak, decline, and stable. Population size and recovery were observed throughout the 51-day study. Populations exposed to pyraclostrobin during the growth phase had the least mortality and fastest recovery, while populations in the peak phase had the greatest mortality and slowest recovery. These data suggested that high density and low food at the peak phase resulted in more sensitive daphnids. To further test this hypothesis, a resource-amended acute toxicity study was conducted to quantify the effects of food resource on pyraclostrobin toxicity to Daphnia magna. Three age classes of Daphnia magna (neonate, subadult, adult) were fed low or high food levels and exposed to pyraclostrobin for 48 h. Toxicity was greater, as shown by lower 48 h LC50s, for smaller Daphnia magna age classes and lower food levels comporting results in the population study. Importantly, the acute toxicity studies generally yielded lower effect levels than the population studies suggesting that while the standard acute studies are ecologically unrealistic, they may be protective of toxicity under some circumstances. Collectively, these data point to the importance of population phase and the resource environment in modulating toxicity.

Molting is a crucial physiological process in arthropods development, growth, and adult reproduction, where the chitinolytic enzyme chitobiase (CB) and the apoptosis process (caspase-3 activity) play crucial roles. Both molecular endpoints have been observed to be affected by different toxics that may be present in aquatic environments. However, the role of ultraviolet radiation (UVR) in the molting process remains with poor evidence and the possible effect of the previous exposure on F1 generation is unknown. Here, we conducted laboratory experiments with chronic UVR exposure to test the effect on the molting process of Daphnia commutata. Our results showed a clear negative effect of the UVR that affected the molting process with a reduction in individual growth. This trend was also observed in CB and caspase-3 activities. Our results also suggest that the UV dose received by the mother and eggs has an additive effect with the dose received by the offspring. These results imply that the cumulative impact of small UVR doses (2 h per day, daily dose: 2520 J m⁻² of 340 nm) on mothers and eggs (which cannot be discriminated in our experiments) can have an additive or synergistic effect along with the generations through a potential increase in lethal effect. Finally, the observed desynchronization in the molting process by UVR will affect the fitness of individuals and population dynamics.

The increasing demand for clean water resources for human consumption, is raising concerning about the sustainable worldwide provisioning. In Mexico, rivers near to high-density urbanizations are subject to irrational exploitation where polluted water is a risk for human health. Therefore, the aims of this study are to analyze water quality parameters and bacterial community dynamics to understand the relation between them, in the Apatlaco river, which presents a clear environmental perturbance. Parameters such as total coliforms, chemical oxygen demand, harness, ammonium, nitrite, nitrate, total Kjeldahl nitrogen, dissolved oxygen, total phosphorus, total dissolved solids, and temperature were analyzed in 17 sampling points along the river. The high pollution level was registered in the sampling point 10 with 480 mg/L chemical oxygen demand, 7 mg/L nitrite, 34 mg/L nitrate, 2 mg/L dissolved oxygen, and 299 mg/L of total dissolved solids. From these sites, we selected four samples for DNA extraction and performed a metagenomic analysis using a whole metagenome shotgun approach, to compare the microbial communities between polluted and non-polluted sites. In general, Proteobacteria was the most representative phylum in all sites. However, the clean water reference point was enriched with microorganism from the Limnohabitans genus, a planktonic bacterium widespread in freshwater ecosystems. Nevertheless, in the polluted sampled sites, we found a high abundance of potential opportunistic pathogen genera such as Acinetobacter, Arcobacter, and Myroides, among others. This suggests that in addition to water contamination, an imminent human health risk due to pathogenic bacteria can potentially affect a population of ∼1.6 million people dwelling nearby. These results will contribute to the knowledge regarding anthropogenic pollution on the microbial population dynamic and how they affect human health and life quality.

Threatened species are susceptible to irreversible population decline caused by adverse sub-lethal effects of chemical contaminant exposure. It is therefore vital to develop the necessary tools to predict and detect these effects as early as possible. Biomarkers of contaminant exposure and effect are widely applied to this end, and a significant amount of research has focused on development and validation of sensitive and diagnostic biomarkers. However, progress in the use biomarkers that can be measured using non-destructive techniques has been relatively slow and there are still many difficulties to overcome in the development of sound methods. This paper systematically quantifies and reviews studies that have aimed to develop or validate non-destructive biomarkers in wildlife, and provides an analysis of the successes of these methods based on the invasiveness of the methods, the potential for universal application, cost, and the potential for new biomarker discovery. These data are then used to infer what methods and approaches appear the most effective for successful development of non-destructive biomarkers of contaminant exposure in wildlife. This review highlights that research on non-destructive biomarkers in wildlife is severely lacking, and suggests further exploration of in vitro methods in future studies.

The life cycle parameters of the benthic invertebrate Chironomus riparius make it a relevant organism for use in multi-generation chronic ecotoxicology tests. Since studies on chronic exposures with fullerene carbon nanoparticles have revealed adverse effects at lower concentration ranges, it is crucial to gain understanding of the consequences in following generations. The aims of this study were to investigate whether sediment-associated fullereneC60 impacts on C. riparius emergence and breeding, thus affecting the growth of the second generation. Larvae were exposed to fullerene-spiked sediment at concentrations of 0.5, 10 and 40 mg/kg sediment dw. Total emergence and breeding success were monitored after the first generation and the newly hatched larvae from the first generation exposure were transferred either to continuous exposure or to pristine sediments without fullerene. Findings indicate that the presence of fullerenes have major impacts on the first generation, mainly shown as delayed emergence time of females. Increased larval growth was observed in the second generation, and we conclude that the C. riparius response to fullerene exposure indicated significant signs of recovery in second-generation larval growth. The result shows the effects to be important for population dynamics, revealing delayed female emergence time, which leads to situation where adults’ breeding is inhibited.

With current global changes, the combination of several stressors such as temperature and contaminants may impact species distribution and ecosystem functioning. In this study, we evaluated the combined impact of two metals (Ni and Cr) with a thermal stress (from 12 to 17 °C) on biomarker responses in two bivalves, Dreissena rostriformis bugensis and Dreissena polymorpha. Biomarkers are informative tools to evaluate exposure and effects of stressors on organisms. The set of 14 biomarkers measured here was representative of both physiologic (filtration activity) and cellular antioxidant and detoxification mechanisms. Our aim was to study the response pattern of both species, and its meaning in terms of invasive potential. The implications for the use of these mussels in environmental monitoring are also discussed. Results evidenced that the two species do not respond to multiple stressors in the same way. Indeed, the effects of contamination on biomarker responses were more marked for D. polymorpha, especially under nickel exposure. While we cannot conclude as to the effect of temperature, invasiveness could be influenced by species sensitivity to contaminants. The physiological and cellular differences between D. polymorpha and D. r. bugensis might also be of concern for environmental risk assessment. The two species present differential bioaccumulation patterns, filtration activity and cellular biomarker responses. If D. polymorpha populations decline, their substitution by D. r. bugensis for biomonitoring or laboratory studies will not be possible without a deeper understanding of biomarker responses of the new invasive.

Models can be used to assess long-term risks of sediment-bound contaminants at the population level. However, these models usually lack the coupling between chemical fate in the sediment, toxicokinetic-toxicodynamic processes in individuals and propagation of individual-level effects to the population. We developed a population model that includes all these processes, and used it to assess the importance of chemical uptake routes on a Chironomus riparius population after pulsed exposure to the pesticide chlorpyrifos. We show that particle ingestion is an important additional exposure pathway affecting C. riparius population dynamics and recovery. Models ignoring particle ingestion underestimate the impact and the required recovery times, which implies that they underestimate risks of sediment-bound chemicals. Additional scenario studies showed the importance of selecting the biologically relevant sediment layer and showed population effects in the long term.