Population responses of Daphnia magna, Chydorus sphaericus and Asellus aquaticus in pesticide contaminated ditches around bulb fields

Tolerance to environmental pollution in the freshwater crustacean Asellus aquaticus: A role for the microbiome

Freshwater habitats are frequently contaminated by diverse chemicals of anthropogenic origin, collectively referred to as micropollutants, that can have detrimental effects on aquatic life. The animals' tolerance to micropollutants may be mediated by their microbiome. If polluted aquatic environments select for contaminant-degrading microbes, the acquisition of such microbes by the host may increase its tolerance to pollution. Here we tested for the potential effects of the host microbiome on the growth and survival of juvenile Asellus aquaticus, a widespread freshwater crustacean. Using faecal microbiome transplants, we provided newly hatched juveniles with the microbiome isolated from donor adults reared in either clean or micropollutant-contaminated water and, after transplantation, recipient juveniles were reared in water with and without micropollutants. The experiment revealed a significant negative effect of the micropollutants on the survival of juvenile isopods regardless of the received faecal microbiome. The micropollutants had altered the composition of the bacterial component of the donors' microbiome, which in turn influenced the microbiome of juvenile recipients. Hence, we show that relatively high environmental concentrations of micropollutants reduce survival and alter the microbiome composition of juvenile A. aquaticus, but we have no evidence that tolerance to micropollutants is modulated by their microbiome.

Measuring Daphnia life history in the wild: The efficacy of individual field cages

Life-history studies are often conducted in a laboratory environment where it is easy to assay individual animals. However, factors such as temperature, photoperiod, and nutrition vary greatly between laboratory and field environments, making it difficult to compare results. Consequently, there is a need to study individual life histories in the field, but this is currently difficult in systems such as Daphnia where it is not possible to mark and track individual animals. Here, we present a proof of principle study showing that field cages are a reliable method for collecting individual-level life-history data in Daphnia magna. As a first step, we compared the life history of paired animals reared outside and inside cages to test the hypothesis that cages allow free flow of algal food resources. We then used a seminatural mesocosm setting to compare the performance of individual field cages versus glass jars refilled with mesocosm water each day. We found that cages did not inhibit food flow and that differences in life histories between three clones detected in the jar assays were also detectable using the much less labor-intensive field cages. We conclude that field cages are a feasible approach for collecting individual-level life-history data in systems such as Daphnia where individual animals cannot be marked and tracked.

A review on pesticides in flower production: A push to reduce human exposure and environmental contamination

In several countries, flower import regulations are restricted to food security, by establishing maximum residue limits (MRL) for pesticides in flower-based food products and biosafety, in order to limit the circulation of vectors, pests and exotic species across borders. In this context, the lack of limits on pesticides in flower-products for ornamental purposes can influence the pesticide overuse in production areas, as well as the transfer of contaminated products between countries. Therefore, the purpose of this review was to discuss possible adverse effects on human and environmental health of pesticides used in floriculture, evaluating regulations on the use of these pesticides in the main importing and flower-producing countries. This review included 92 documents. The use of 201 compounds was identified by interviews and analytical measurements. Among them, 93 are banned by the European Union (EU), although 46.3 % of these compounds have been identified in samples from European countries. Latin American countries have a large number of scientific publications on pesticides in flower production (n = 51), while the EU and China have less studies (n = 24) and the United States and Japan have no studies. Regarding adverse health effects, poorer neurobehavioral development, reproductive disorders, congenital malformations and genotoxicity have been reported for residents of flower production areas and workers throughout the flower production cycle. Studies including water samples show overuse of pesticides, while environmental impacts are related to water and air contamination, soil degradation and adverse effects on the reproduction and development of non-target organisms. This review points out that the absence of MRL for non-edible flowers can be crucial for the trade of contaminated products across borders, including pesticides banned in importing countries. Furthermore, setting limits on flowers could reduce the use of pesticides in producing countries.

Higher mean and fluctuating temperatures jointly determine the impact of the pesticide chlorpyrifos on the growth rate and leaf consumption of a freshwater isopod

There is growing evidence that both increases in mean temperature and the widespread daily temperature fluctuations (DTF) may increase pesticide toxicity. Nevertheless, the likely more stressful, realistic combination of the two warming-related stressors has rarely been considered in ecotoxicology. Moreover, we have little knowledge on whether these stressor combinations could impair ecosystem functioning. We examined the effect of the pesticide chlorpyrifos under an increased mean temperature (+4 °C, from 18 °C to 22 °C) and in the presence of DTF (constant and 8 °C) on two life-history traits (mortality and growth rate) and one ecologically important behavioural trait (feeding rate) in the freshwater isopod Asellus aquaticus. The chlorpyrifos concentration used, 0.2 μg/L, did not cause mortality in any thermal condition, nor did it cause sublethal effects at the mean temperature of 18 °C. A key finding was that growth rate was strongly reduced by the pesticide only under the combination of both a higher mean temperature and DTF, highlighting the importance of testing toxicity under this realistic thermal scenario. The leaf consumption of chlorpyrifos-exposed isopods increased at the higher mean temperature when this was kept constant, however, it lowered again towards control levels when DTF was induced, thereby contributing to the growth reduction at this most stressful condition. These alterations of growth and leaf degradation rates may impact nutrient recycling, a key ecosystem function. Our results highlight the importance of integrating both increases in mean temperature and in DTF to improve current and future ecological risk assessment of pesticides.

Novel Protocol for Acute In Situ Ecotoxicity Test Using Native Crustaceans Applied to Groundwater Ecosystems

Current standardized laboratory test protocols use model species that have limitations to accurately assess native species responses to stressors. We developed and tested a novel acute in situ protocol for testing field-collected organisms. We used Asellus aquaticus and NaCl as a reference toxicant to test for the effects of location (laboratory vs. in situ), medium (synthetic vs. field water), substrate (presence vs. absence), and protocol replicability. We further tested the protocol using groundwater-adapted isopods: Proasellus assaforensis for the effect of location, P. cavaticus of medium and P.lusitanicus of substrate. Our results showed that A.aquaticus’ lethality obtained with the novel acute in situ protocol did not significantly differ from those from laboratory testing. However, laboratory tested P.assaforensis showed a higher sensitivity, suggesting that its acclimation to laboratory conditions might have pernicious effects. A. aquaticus and P. cavaticus showed a higher mortality using synthetic medium in situ and under laboratory conditions, which overestimated the stressor’s effect. Besides, substrate use had no significant effect. The novel acute in situ protocol allows the use of native species under realistic scenarios. It is particularly well adapted for assessing the risk of groundwater ecosystems but it can be applied to a wide range of ecosystems.

The freshwater isopod Asellus aquaticus as a model biomonitor of environmental pollution: A review

Anthropogenic substances pollute freshwater systems worldwide, with serious, long-lasting effects to aquatic biota. Present methods of detecting elevated levels of trace metal pollutants are typically accurate but expensive, and therefore not suitable for applications requiring high spatial resolution. Additionally, these methods are not efficient solutions for the determination of long-term averages of pollution concentration. This is the rationale for the implementation of a biomonitoring programme as an alternative means of pollutant detection. This review summarises recent literature concerning the past and potential uses of the benthic isopod Asellus aquaticus as a biomonitor for pollution in freshwater systems. Recent studies indicate that A. aquaticus is well suited for this purpose. However, the mechanisms by which it bioaccumulates toxins have yet to be fully understood. In particular, the interactions between coexisting trace metal pollutants in the aquatic environment have only recently been considered, and it remains unclear how a biomonitoring programme should adapt to the effects of these interactions. It is evident that failing to account for these additional stressors will result in an ineffective biomonitoring programme; for this reason, a comprehensive understanding of the bioaccumulation mechanisms is required in order to reliably anticipate the effects of any interferences on the outcome.

Assessment of the environmental impact of an abandoned mine using an integrative approach: A case-study of the "Las Musas" mine (Extremadura, Spain)

The mine abandonment is generally associated with the release of potentially toxic metals into the environment, which may depend on metals speciation, soil properties and climate conditions. The goal of the present work was to assess the environmental impact of the abandoned Pb-Zn mine "Las Musas" (Spain) using an integrative approach. The impact on soils and surface waters was performed using: chemical parameters, quantification of potentially toxic metals (Cd, Cu, Pb and Zn), and ecotoxicological responses using lethal and sub-lethal bioassays with organisms' representative of different trophic level ((soil: Eisenia fetida (mortality and reproduction test); Latuca sativa and Lollium perenne (seedling emergence); and water: Vibrio fischeri (luminescence inhibition), Daphnia magna (immobility and reproduction test), Thamnocephalus platyurus (mortality), Pseudokirchneriella subcapitata (growth inhibition)). The results showed soils with neutral to slight alkaline pH (7.64-8.18), low electric conductivity (125-953 μS/cm) and low organic matter levels (0.20-1.85%). For most of the soil samples, Pb was the only metal which surpassed the limit proposed by the Canadian soil quality guidelines, with values ranging from 42.2 to 181.4 mg/kg. The ecotoxicological results showed that the soils with the highest levels of Pb induced a decrease on E. fetida reproduction and on L. sativa germination, indicating negative impacts on the habitat function. The analysis of the surface waters showed levels of Zn surpassing the legal limit adopted from the Water Framework Directive (37.0 to 69.0 μg/L). The ecotoxicological results highlight the importance of bioassays that evaluate the behavior of species, when assessing the risk of mining areas with non-acid soils and waters with high nutrients/organic matter concentrations and low concentrations of potentially toxic metals. The results indicated a moderate environmental risk from potentially toxic metals, at the areas analyzed around the Azuaga mine.

Ecological and ecotoxicological responses in the assessment of the ecological status of freshwater systems: A case-study of the temporary stream Brejo of Cagarrão (South of Portugal)

The objective of the study was to assess the integrated use of macroinvertebrate indexes and ecotoxicological parameters in the evaluation of the ecological status of a temporary stream with a strong agricultural influence. Water quality was analysed at two sampling sites along the stream, considering: chemical supporting parameters; hazardous substances (pesticides); benthic macroinvertebrate communities, through quality (Iberian Biological Monitoring Working Party and Iberian Average Score Per Taxon) and multi-metric indices (Southern Portuguese Index of Invertebrates and Ecological Quality Ratio); and ecotoxicological responses using lethal and sub-lethal bioassays. The water chemical characterization showed high levels of organic matter and nutrients, mainly in the dry period ((biochemical oxygen demand (BOD₅): 18.5-25.5mgL^-1, chemical oxygen demand (COD): 60.8-193.7mgL^-1; total phosphorus (TP): 0.17-0.33mgL^-1)), which may compromise the support of biological life. In accordance with the physicochemical results, the stream had an ecological status less than good. Of the 25 pesticides analysed, only five, namely terbuthylazine, 2-methyl-chlorophenoxyacetic acid, bentazone, mecoprop and metolachlor were quantified. In general, the concentrations of pesticides detected were low, except at the source of the stream in January 2012 (sum of pesticides 2.29μgL^-1), mainly due to the concentration of bentazone (1.77μgL^-1), both values surpassing the European Commission threshold values. The analysis of benthic macroinvertebrates showed low levels of abundance and family diversity, with communities dominated by resistant groups to organic pollution and pesticides, such as the Chironomidae family. In general, the reproduction ecotoxicological results showed a very marked decrease in the number of juveniles per female. The Spearman correlation identified pesticides, namely MCPA (R=-0.89; p<0.05), as the main responsible for the observed effect. The results showed the linearity and complementarity of the two groups of biological responses, allowing to cover the interactions between the ecosystem's species and the different types of pollutants.

Thiacloprid-induced toxicity influenced by nutrients: Evidence from in situ bioassays in experimental ditches

Many studies show that neonicotinoid insecticides cause toxicity to aquatic invertebrates. Some studies report that insecticide toxicity may differ in combination with other agrochemicals under realistic field conditions. To explore such altered toxicity further, we aimed to determine the single and combined effects of environmentally relevant levels of the neonicotinoid thiacloprid and nutrients on different endpoints of 4 aquatic invertebrate species. Animals were exposed to these agrochemicals using a caged experiment within experimental ditches. We observed thiacloprid-induced toxicity for 2 crustaceans, Daphnia magna and Asellus aquaticus, and for 1 out of 2 tested insect species, Cloeon dipterum. We observed no toxic effects for Chironomus riparius at the time-weighted average test concentration of 0.51 μg thiacloprid/L. For D. magna, the observed toxicity, expressed as the lowest-observed-effect concentration (LOEC), on growth and reproduction was present at thiacloprid concentrations that were 2456-fold lower than laboratory-derived LOEC values. This shows that these species, when exposed under natural conditions, may exhibit neonicotinoid-induced toxic stress. Contrary to the low nutrient treatment, such toxicity was often not observed under nutrient-enriched conditions. This was likely attributable to the increased primary production that allowed for compensatory feeding. These findings warrant the inclusion of different feeding regimes in laboratory experiments to retrieve the best estimates of neonicotinoid-induced toxicity in the natural environment. Environ Toxicol Chem 2018;37:1907-1915. © 2018 SETAC.

Agricultural constraints on microbial resource use and niche breadth in drainage ditches

Background

Microorganisms govern important ecosystems processes, in particular the degradation of organic matter (OM). However, microorganisms are rarely considered in efforts to monitor ecosystem health and functioning. Evidence suggests that environmental perturbations can adversely affect microbial communities and their ability to use available substrates. However, whether impacted microbial efficiencies in extracting and utilizing the available resources (resource niche breadth) translate to changes in OM degradation in natural systems remains poorly understood.

Methods

Here we evaluated effects of differences in OM related to agricultural land use (OM derived from ditches adjacent to grasslands, bulb fields and a pristine dune area) on microbial functioning. We specifically assessed (1) resource niche breadths of microbial communities during initial community assembly in laboratory microcosms and already established natural communities, and (2) how changes in community resource niche breadth translates to the degradation of natural OM.

Results

A disparity existed between microbial resource niche breadth in laboratory incubations and natural microbial communities. Resource utilization and niche breadth of natural microbial communities was observed to be constrained in drainage ditches adjacent to agricultural fields. This outcome coincides with retarded degradation of natural OM collected from ditches adjacent to hyacinth bulb fields. Microbial communities in bulb field ditches further showed functional redundancy when offered grassland OM of seemingly higher substrate quality.

Discussion

Results presented in this study suggest that agricultural practices can impose constraints on microbial functional diversity by reducing OM resource quality, which can subsequently translate to confined microbial resource niche differentiation and reduced organic matter degradation rates. This hints that assessments of actual microbial resource utilization and niche differentiation could potentially be used to assess the ecological health and functioning of natural communities.

Trait modality distribution of aquatic macrofauna communities as explained by pesticides and water chemistry

Analyzing functional species' characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2-4 % to pesticides, and for 3-11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches.

Effects of agricultural practices on organic matter degradation in ditches

Agricultural practices can result in differences in organic matter (OM) and agricultural chemical inputs in adjacent ditches, but its indirect effects on OM composition and its inherent consequences for ecosystem functioning remain uncertain. This study determined the effect of agricultural practices (dairy farm grasslands and hyacinth bulb fields) on OM degradation by microorganisms and invertebrates with a consumption and food preference experiment in the field and in the laboratory using natural OM collected from the field. Freshly cut grass and hyacinths were also offered to control for OM composition and large- and small mesh-sizes were used to distinguish microbial decomposition and invertebrate consumption. Results show that OM decomposition by microorganisms and consumption by invertebrates was similar throughout the study area, but that OM collected from ditches adjacent grasslands and freshly cut grass and hyacinths were preferred over OM collected from ditches adjacent to a hyacinth bulb field. In the case of OM collected from ditches adjacent hyacinth bulb fields, both microbial decomposition and invertebrate consumption were strongly retarded, likely resulting from sorption and accumulation of pesticides. This outcome illustrates that differences in agricultural practices can, in addition to direct detrimental effects on aquatic organisms, indirectly alter the functioning of adjacent aquatic ecosystems.

Ecotoxicological endpoints, are they useful tools to support ecological status assessment in strongly modified water bodies?

Although man-made reservoirs represent an important water supply source in countries where water scarcity has become a problem, little work has been done on the evaluation of their ecological status. Taking this in account, the general aim of this study was to assess the usefulness of ecotoxicological endpoints in the potential ecological status characterization of water reservoirs, with the purpose of their possible integration in evaluation programs developed under the Water Framework Directive (WFD). To achieve this purpose, a group of bioassays were selected to evaluate both water and sediment compartments at the Alqueva reservoir (the biggest from the Iberian Peninsula), with representative species from different taxonomic and functional groups: Vibrio fischeri, Thamnocephalus platyurus, Daphnia magna and Heterocypris incongruens. The ecotoxicological assessment showed that sublethal endpoints (e.g., luminescence, growth or reproduction), would be more useful and sensitive to identify toxicity patterns in this type of water body. In general, the results from this ecotoxicological toolbox agreed with the potential ecological status established according to the WFD, which indicates that the bioassays complement the ecological assessment. Furthermore, the use of an ecotoxicological approach can be extremely useful, especially in cases where the biotic indices are difficult to establish, such as in man-made reservoirs. However, when pollutant concentrations are very low, and/or when nutrients and organic matter concentrations are high, the two approaches do not fit, requiring further research to determine which organisms are more sensitive and the best biotic indices to use under those conditions.