A freshwater amphipod toxicity test based on postexposure feeding and the population consumption inhibitory concentration

Holistic evaluation of the environmental impacts of shipping in the sensitive region of Ria de Aveiro

Shipping activity can be a substantial source of pollution and impact on the environment, including air, water and ecosystems, as well as adverse health and climatic effects. Due to the distribution of maritime transport activity routes in the EU, a large portion of the population is exposed to shipping pollution throughout Europe. The ongoing European project EMERGE aims to investigate and quantify these impacts over Europe, and in more detail, in specific case studies regions. The Aveiro lagoon region in Portugal is one of these case studies. This region is a Natura 2000 area, and also includes a medium-sized port. Both air quality and water modelling tools were applied to assess the impact of the emissions and discharges from shipping (to air and water) in the region in 2018. Additionally, ecotoxicological impacts were determined by bioassays to evaluate the impact of scrubber-water discharges on the most sensitive stages of marine invertebrates, and on the post-exposure feeding inhibition of crustacean and bivalve species. The results show that there was a substantial increase in atmospheric pollutant concentrations due to emissions attributed to shipping, which was most relevant for NOx and SO2 (up to a 30 % shipping contribution). There was no significant degradation of the water quality, mainly as the ships operating in this area did not have scrubber equipment. The ecotoxicological tests were performed with three samples of scrubber water, including one artificial sample and two samples collected on-board ships. If scrubber water would have been discharged in this area, the results indicated that the majority of the tested species would be exposed to lowest observed effect concentration (LOEC) for the different scrubber-water samples, as well as to substantial concentrations of metals, PAHs, and alkylated PAHs.

Changes in metabolic profiles of amphipods Allorchestes compressa after acute exposures to copper, pyrene, and their mixtures

Amphipods are ideal indicators for biomonitoring and ecotoxicological studies of environmental contaminants because they are extensively distributed in aquatic environments, are easy to collect and are important in nutrient cycling. Marine amphipods (Allorchestes compressa) were exposed to two concentrations of copper and pyrene, and their mixtures, for 24 and 48 h. Changes in polar metabolites were assessed using Gas Chromatography Mass Spectrometry (GC-MS)-based untargeted metabolomics. Generally, limited metabolite changes were observed for copper and pyrene single exposures (eight and two significant metabolites, respectively), while 28 metabolites had changed following exposures to mixtures. Furthermore, changes were mainly observed after 24 h but had seemingly returned to control levels after 48 h. Multiple types of metabolites were affected including amino acids, Tricarboxylic acid (TCA) cycle intermediates, sugars, fatty acids, and hormones. This study highlights the sensitivity of metabolomics in assessing the impacts of low concentrations of chemicals compared to traditional ecotoxicological endpoints.

Experimental study on effects of prometryn exposure scenarios on Microcystis aeruginosa growth and N and P concentrations

Single exposure toxicity tests of herbicides like prometryn are commonly applied in studying ecological and environmental issues, but they are more likely exposed to microalgae through multiple applications of irrigation and water flow. The toxicity of prometryn towards Microcystis aeruginosa (M. aeruginosa) at different growth stages (different exposure period) was determined by single and multiple exposures (different exposure mode) through 39-day batch-experiment comparison study. Inhibition rates showed that M. aeruginosa growth was greatly inhibited by exposure to prometryn in a final concentration of 80 and 160 μg·L^-1 (p < 0.05). Specifically, with the same prometryn exposure periods (lag or exponential phase) and concentrations, a single exposure displayed larger toxicity on M. aeruginosa than repetitive additions of prometryn in general according to inhibition rates. Moreover, with the same prometryn exposure modes and concentrations, inhibitory effect was higher with prometryn exposure in lag phase than that in exponential phase according to M. aeruginosa densities and inhibition rates. In general, variations of total dissolved phosphorus (TDP) and total dissolved nitrogen (TDN) with time responded negatively to M. aeruginosa growth, and added prometryn inhibits the utilization rate of both P and N. Logistic function was well used to describe algae densities (R² = 0.979 ~ 0.995), growth rates (R² = 0.515 ~ 0.731), specific growth rates (R² = 0.301 ~ 0.648) and inhibition rates (R² = 0.357 ~ 0.946) along with its combination with Monod function. In addition, results showed that shifts of limiting nutrients could be prompted by not only M. aeruginosa growth but also prometryn exposure scenarios. This study provides a basis for studying the potential harm of prometryn to the ecological environment.

Effects of post-fire contamination in sediment-dwelling species of riverine systems

Wildfires are an important environmental problem in forested watersheds and can significantly alter water quality. Besides the reported ecotoxicological effects on pelagic species, the accumulation of post-fire contaminants in river sediments can also impair the benthic species. In this study, three sediment-dwelling species, Chironomus riparius, Atyaephyra desmarestii and Echinogammarus meridionalis, with different sensitivities, habitats, behaviours and/or feeding strategies, were exposed to water and sediments, in in-situ and in laboratory. Four sites were selected in a partially burnt basin (Alfusqueiro river basin), within and upstream the burnt area. The sites within the burnt area showed higher metal burden in both water and sediment, as well as changes in water physico-chemistry, consistently with the typical effects of incoming post-fire runoff. Both in-situ and laboratory exposures to water and sediments affected by the wildfire induced post-exposure feeding inhibition in the three tested macroinvertebrates. In fact, laboratory and field bioassays have produced generally consistent post-exposure feeding inhibition responses, but the most impactful response could be recognised after in-situ bioassays at the river site within the burnt area, where the species respond to the physico-chemical fluctuations during the exposure period. This comparative perspective supports the importance of using in-situ bioassays as a more realistic approach when dealing with complex and intermittent natural samples such as those affected by post-fire runoff. Overall, our results reinforce the awareness about the negative effects of wildfires on benthic biota, with significant feeding depression and consequent reduction in the available energy budget to ensure successful detoxification, growth and reproduction signalling potential trophic and functional disruption at the ecosystem level. In addition, the duality conditions of sediments as a sink and source of contaminants reinforce concerns, as the exposure of benthic organisms may persist in the long term, even after runoff income ceases due to the resuspension of contaminated sediments.

Feeding inhibition following in-situ and laboratory exposure as an indicator of ecotoxic impacts of wildfires in affected waterbodies

Among the various environmental disturbances caused by wildfires, their impacts within burnt areas and on the downhill aquatic ecosystems has been receiving increased attention. Post-fire rainfalls and subsequent runoffs play an important role in transporting ash and soil to aquatic systems within the burnt areas. These runoffs can be a diffuse source of toxic substances such as metals. The present work aims at assessing the effects of ash-loaded runoff on feeding rates of three representative aquatic invertebrates (Daphnia magna, Corbicula fluminea and Atyaephyra desmarestii) and the mosquitofish, Gambusia holbrooki, through post-exposure feeding inhibition bioassays carried out in-situ and in the laboratory using water collected from the experimental field sites. Four sites were selected in a partially burnt basin for bioassay deployment and sample collection: one site upstream of the burnt area (RUS); three sites receiving runoff directly from the burnt area, one immediately downstream of the burnt area (RDS) and two in permanent tributary streams within the burnt area (BS₁ and BS₂). The in-situ exposure lasted four days and began following the first post-fire major rain events. At sites affected by the wildfire, post-exposure feeding rates for D. magna, A. desmarestii and G. holbrooki were lower, which is consistent with the highest levels of metals found at these sites compared to the unaffected site, although the individual concentrations of each metal were generally below corresponding ecological safety benchmarks. Thus, interactions between metals and/or between metals and other environmental parameters certainly played a role in modulating the ecotoxic effects of the runoffs; this was further supported by a Toxic Units Summation exercise. Even if direct causal links between the ecotoxicological effects observed in D. magna, A. desmarestii and G. holbrooki and the physicochemical parameters of the water samples could not be established, the results suggest an important role of major and trace elements in explaining post-exposure feeding rate variation.

Food up-take and reproduction performance of Daphnia magna under the exposure of Bisphenols

Because the application of Bisphenol A (BPA) was restricted, many substitutes, such as Bisphenol F (BPF) and Bisphenol S (BPS), were developed as BPA substitutes. Therefore, environmental impacts of BPA and its substitutes on aquatic organisms should be concerned, especially their combined toxicity. In this study, the impacts of BPA, BPF, BPS and their mixture on the feeding behavior, reproduction and physiological function of daphnids were synthetically evaluated, involving the duration and mode of exposure. In short-term exposure tests, feeding rates of D. magna decreased after exposure to BPA, BPF, BPS and their mixture, while the inhibition reversed into stimulation in the recovery period. It may benefit from overcompensation of D. magna. In long-term exposure tests, the inhibition effect on the reproduction and growth of the exposed D. magna was difficult to recover, and only some experimental groups have a certain recovery. In conclusion, environmental risk of BPA, BPF, BPS and their mixture on the behavior of D. magna increased with prolonged exposure time. Moreover, relative activities of trypsin, amylase (AMS), acetylcholinesterase (AChE), carbonic anhydrase (CA), glutathione peroxidase (GPx) and super oxidase dimutase (SOD) of the exposed daphnids decreased in most treatment groups, indicating the disorder of digestive, nervous and antioxidative system of D. magna. Interestingly, inhibition of enzymes activities decreased with the increase of the exposure time, which implied the tolerance may be occurred.

Correlation between antibiotic-induced feeding depression and body size reduction in zooplankton (rotifer, Brachionus calyciflorus): Neural response and digestive enzyme inhibition

The study analyzed the correlation between the antibiotic-induced feeding depression and body size reduction in rotifer, Brachionus calyciflorus, involving exposure, post-exposure and re-exposure periods. The filtration and ingestion rates of the rotifers were inhibited in these three exposure periods at any given concentration of the antibiotic sulfamethazine (SMZ). As food for rotifer, the cell size of the green algae was unchanged, which indicated that it could not drive feeding depression. Secondly, several corresponding physiological responses were considered. Reactive oxygen species (ROS) levels increased in the post-exposure and the re-exposure; acetylcholinesterase (AChE) activity was significantly decreased in the exposure and the re-exposure, whereas it was induced in the post-exposure. The activities of amylase and lipase were always inhibited in these three exposure periods. Additionally, significant decreases in lorica length, width and biovolume of rotifers occurred after the feeding depression. Statistical analysis indicated a positive correlation between the activity of the digestive enzyme and the body size. Our results demonstrated that SMZ could influence the neurotransmission, inhibit the activity of the digestive enzyme, and finally result in body size reduction. These results provided an integrated perspective on assessing the toxicity effects of antibiotic in non-lethal dosage on the feeding behavior of non-target aquatic organisms.

Comprehensive assessment of three typical antibiotics on cyanobacteria (Microcystis aeruginosa): The impact and recovery capability

This innovative study provided a comprehensive evaluation of the effects of three typical antibiotics exposures (cefradine, norfloxacin and amoxicillin) on Microcystis aeruginosa in two periods (exposure and post-exposure) at a new perspective. The results indicated that the irreversible growth inhibition of M. aeruginosa attributed to the norfloxacin in the exposure and the re-exposure stages. In contrast, although the algal cell size recovered to the control level after the exposure of 20 mg/L of cefradine, the significant stimulation on glutathione (GSH) still persisted even if the contaminants were removed. On the other hand, amoxicillin inhibited the activities of superoxide dismutase (SOD), GSH contents and the algal cell size in the exposure period while malonaldehyde (MDA) contents increased significantly in two periods.

The impact assessment of anticancer drug imatinib on the feeding behavior of rotifers with an integrated perspective: Exposure, post-exposure and re-exposure

The anticancer drugs are getting increasing attention as an emerging contaminant in the aquatic environments. In the present study, feeding behavior of the rotifer Brachionus calyciflorus under the impact of anticancer drug imatinib was evaluated. Traditional toxicological studies usually focus on dose-effect relationship at a given exposure time, while ignore the possible impact after the exposure. Thus, how the impact varied in the post-exposure and re-exposure was also considered in the present study. The feeding depression of the rotifers was attributed to the increased concentration of imatinib. Although the filtration and ingestion rate of the rotifers recovered to a certain extent after the exposure, the significant feeding inhibition still persisted even if the exposure was ended. In the re-exposure period, the feeding behavior was less depressed than those of the exposure period, which implied that rotifers might develop a tolerance to the same toxics. The activities of acetylcholine esterase (AchE) and the levels of reactive oxygen species (ROS) in rotifers were also detected. Imatinib inhibited the activities of AchE in the exposure and re-exposure while ROS levels increased significantly in the re-exposure period. Our present study provided an integrated assessment the potential environmental risks of imatinib at a new perspective.

Physiological effects of essential metals on two detritivores: Atyaephyra desmarestii (Millet) and Echinogammarus meridionalis (Pinkster)

Freshwater ecosystems are essential for humans; however, input of several types of contamination has led to the degradation of these ecosystems. Thus, it is urgent to assess their health to allow actions for prevention and remediation. The level of trace metals can be enhanced by natural or anthropogenic sources. Essential metals, such as copper and zinc, become toxic when present in the environment above threshold concentrations. To evaluate the physiological effects of these 2 essential metals for 2 freshwater detritivores, the shrimp Atyaephyra desmarestii and the amphipod Echinogammarus meridionalis, acute tests were performed. Forty-eight hour median lethal concentration (LC50) values were estimated for these species using static bioassays with copper and zinc. Sublethal assays for both metals with several phases were also done to evaluate the effects on feeding behavior. The LC50 values of copper for the shrimp A. desmarestii and amphipod E. meridionalis were 0.128 mg/L and 0.050 mg/L and those of zinc were 7.951 mg/L and 11.860 mg/L, respectively. The results indicated that copper is more toxic to both species. Only E. meridionalis showed deleterious effects of copper on feeding rate. Zinc showed some tendency for feeding inhibition in both species. Environ Toxicol Chem 2016;35:1442-1448. © 2015 SETAC.

Assessing estuarine quality: A cost-effective in situ assay with amphipods

In situ assays based on feeding depression can be powerful ecotoxicological tools that can link physiological organism-level responses to population and/or community-level effects. Amphipods are traditional target species for toxicity tests due to their high sensitivity to contaminants, availability in the field and ease of handling. However, cost-effective in situ assays based on feeding depression are not yet available for amphipods that inhabit estuarine ecosystems. The aim of this work was to assess a short-term in situ assay based on postexposure feeding rates on easily quantifiable food items with an estuarine amphipod. Experiments were carried out under laboratory conditions using juvenile Echinogammarus marinus as the target individual. When 60 Artemia franciscana nauplii (as prey) were provided per individual for a period of 30 min in dark conditions, feeding rates could be easily quantified. As an endpoint, postexposure feeding inhibition in E. marinus was more sensitive to cadmium contamination than mortality. Assay calibration under field conditions demonstrated the relevance of sediment particle size in explaining individual feeding rates in uncontaminated water bodies. An evaluation of the 48-h in situ bioassay based on postexposure feeding rates indicated that it is able to discriminate between unpolluted and polluted estuarine sites. Using the harmonized protocol described here, the in situ postexposure feeding assay with E. marinus was found to be a potentially useful, cost-effective tool for assessing estuarine sediment and water quality.

A short-term sublethal toxicity assay with zebra fish based on preying rate and its integration with mortality

Contaminant-induced feeding inhibition has direct and immediate consequences at higher levels of biological organization, by depressing the population consumption and thus hampering ecosystem functioning (e.g. grazing, organic matter decomposition). Thus, similarly to lethality and avoidance, feeding is mechanistically linked to ecosystem processes and is therefore an unequivocal ecologically meaningful response. The objective of the present study was to develop a short-term assay with the small freshwater fish Danio rerio, based on feeding. For this, a methodology to easily and precisely quantify feeding was first optimized: each fish was allowed to prey on ten live Daphnia magna juveniles, for 1h, just before the end of a 48-h exposure test period. Secondly, copper sensitivity of feeding relatively to survival and growth was evaluated. At the growth EC20 (40 μg L(-1)), feeding was inhibited by 53%, and at the feeding EC50 (36 μg L(-1)), mortality was negligible (1.3%). Integrating feeding and survival revealed a 97% depression in the population consumption at the LC50 (61 μg L(-1)). Thirdly, the influence of pH, conductivity and hardness on the feeding background variability was assessed by assaying waters collected at eight reference sites and was found to be negligible, within tested ranges. Fourthly, feeding assays with natural waters contaminated with acid mine drainage confirmed the integration of lethality and feeding to be pertinent at estimating contaminant effects at higher levels of biological organization.

The process-dependent impacts of dimethoate on the feeding behavior of rotifer

Traditional toxicological studies usually depict the dose-effect relationship at the given exposure time while ignore how toxic effects vary during and after the exposure. In the present study, feeding depression of the rotifer Brachionus calyciflorus under the impact of dimethoate was evaluated not only in the exposure time but also in the post-exposure time. Both the filtration rates (F) and the ingestion rates (I) of the rotifers varied during the exposure period under any concentration of dimethoate. A three-stepwise stress was observed when the rotifers were exposed to 0.2 and 1.0 mg L(-1) of the pesticide respectively, whereas 1.8 mg L(-1) dimethoate caused only one-step stress on the rotifers during the whole period. In addition, although the feeding behaviors of the rotifers recovered after the exposure, two feeding rates both got even more depressed at 8h in the post-exposure time. The latent inhibition after exposure was related to the exposure concentrations and the exposure time. Our works indicated that the impact of dimethoate on the feeding behavior of the rotifers was highly process-dependent that caused the stepwise stress during the exposure period and the latent stress after the exposure.

Effect of salinity on the toxicity of road dust in an estuarine amphipod Grandidierella japonica

Urban runoff can reach coastal aquatic environments; however, little is known about the effect of salinity on road runoff toxicity. The objective of this study is to investigate the toxicity of highway road dust over a salinity gradient from 5 to 35‰, in an estuarine benthic amphipod, Grandidierella japonica. Road dust toxicity was evaluated by assessing mortality after 10 days of exposure and short-term microbead ingestion activity of the amphipod. For all road dust samples considered, amphipod mortality increased with increasing salinity, whereas no significant difference in mortality was observed among test salinities in the reference river sediment. Ingestion activity during exposure to road dust decreased with increasing salinity. In fact, none of the individuals ingested any microbeads at salinity of 35‰. If assumed microbead ingestion is a proxy for feeding activity, high mortality at 35‰ could be attributed to aquatic exposure and not to dietary exposure. These findings suggest that road dust may have considerable impact on benthic organisms at high salinity levels.

Identification of the first neuropeptides from the Amphipoda (Arthropoda, Crustacea)

Despite being used as models in the field of ecotoxicology, including use in studies of endocrine disruption, little is known about the hormonal systems of amphipods, particularly their peptidergic signaling systems. Here, transcriptome shotgun assembly (TSA) sequences were used to predict the structures of the first neuropeptides from members of this crustacean order. Using a well-established workflow, BLAST searches of the extant amphipod TSA data were conducted for putative peptide-encoding transcripts. The pre/preprohormones deduced from the identified TSA sequences were then used to predict the mature structures of amphipod neuropeptides. In total, 43 putative peptide-encoding transcripts were identified from three amphipods, Echinogammarus veneris, Hyalella azteca and Melita plumulosa. Collectively, 139 distinct mature peptides (110 from E. veneris alone) were predicted from these TSA sequences. The identified peptides included members of the adipokinetic hormone/red pigment concentrating hormone, allatostatin A, allatostatin B, allatostatin C, bursicon α, bursicon β, crustacean hyperglycemic hormone, diuretic hormone 31, FLRFamide, molt-inhibiting hormone, myosuppressin, neuroparsin, neuropeptide F, orcokinin, pigment dispersing hormone (PDH), proctolin, RYamide, SIFamide, sulfakinin and tachykinin-related peptide families. Of particular note were the identifications of orcokinins possessing SFDEIDR- rather than the typical NFDEIDR- amino-termini, e.g. SFDEINRSNFGFN, a carboxyl-terminally amidated orcokinin, i.e. SFDEINRSNFGFSamide, PDHs longer than the stereotypical 18 amino acids, e.g. NSELLNTLLGSKSLAALRAAamide, and a 13 rather than 12 amino acid long SIFamide, i.e. GPYRKPPFNGSIFamide. These data not only provide the first descriptions of native amphipod neuropeptides, but also represent a new resource for initiating investigations of peptidergic signaling in the Amphipoda.

Predator-prey imbalances due to a pesticide: density and applicability timing as determining factors for experimental assessments

Predator-prey relationships are determining factors in sustaining community structure but xenobiotics, including pesticides, have the potential to alter them, causing imbalances at the ecosystem level. Although invertebrate predation on zooplankton is of high importance in shallow lakes, there is still little information regarding disturbances on this trophic interaction. This work assessed the potential effects of a chlorpyrifos-based pesticide (CLP) on the interaction between prawns Macrobrachium borellii and cladocerans Ceriodaphnia dubia, taking into account prey densities, specific time of exposure and contamination level. The analysis was focused on the specific sensitivity of both species and, especially, on the predation rate of M. borellii on C. dubia. The latter was evaluated through different treatments that combined predator and/or prey exposure to the insecticide, before (lapse of 12 h) or during the interaction. Under low prey density, when prawns were previously exposed to the insecticide, their consumption rate was lower than that of controls. Conversely, when cladocerans or both species were previously exposed, the prawns' feeding rate was higher. Under high prey density, there were no substantial differences among treatments. Comparatively, cladocerans were significantly more consumed when the exposure of both species was performed before rather than during the interaction. From the results obtained, it can be assumed that the trophic interaction under study is sensitive to CLP and that individual density and specific time of exposure are important variables to be considered in similar studies in order to obtain realistic results.

A laboratory and in situ postexposure feeding assay with a freshwater snail

Contaminant-driven feeding inhibition has direct and immediate consequences at higher levels of biological organization, by depressing the population consumption and thus hampering ecosystem functioning (e.g., grazing, organic matter decomposition). The present study aimed at developing a short-term laboratory and in situ assay based on the postexposure feeding of the freshwater snail Theodoxus fluviatilis. A method to precisely quantify feeding rates was first developed, consisting of a 3-h feeding period, in darkness, on 150 defrosted nauplii of the brine shrimp Artemia franciscana. Postexposure feeding after a 48-h exposure to cadmium was approximately as sensitive as survival, with the median effective concentration (EC50) and median lethal concentration (LC50) being 85 µg/L and 102 µg/L, respectively, and the 20% effective concentration (EC20) and 20% lethal concentration (LC20) being 41 µg/L and 77 µg/L, respectively. Together, both effects at the LC20 reduced population consumption by 56%. In situ experiments at reference sites covering broad ranges of current velocity, hardness, conductivity, sediment organic matter content, and sediment particle size distribution revealed the influence of these abiotic conditions on postexposure feeding, in the absence of contamination, to be negligible. The effectiveness of the in situ assay was evaluated at 5 sites contaminated with acid mine drainage. Surviving organisms at the single partially lethal site (37% mortality) presented a 54% feeding inhibition relative to the reference, whereas the population consumption would be inhibited by 71%, confirming the integration of survival and feeding to be pertinent for estimating contaminant effects at higher levels of biological organization.