Search

Understanding the survival of honey bees after pesticide exposure is key for environmental risk assessment. Currently, effects on adult honey bees are assessed by Organisation for Economic Co-operation and Development standardized guidelines, such as the acute and chronic oral exposure and acute contact exposure tests. The three different tests are interpreted individually, without consideration that the same compound is investigated in the same species, which should allow for an integrative assessment. In the present study we developed, calibrated, and validated a toxicokinetic-toxicodynamic model with 17 existing data sets on acute and chronic effects for honey bees. The model is based on the generalized unified threshold model for survival (GUTS), which is able to integrate the different exposure regimes, taking into account the physiology of the honey bee: the BeeGUTS model. The model is able to accurately describe the effects over time for all three exposure routes combined within one consistent framework. The model can also be used as a validity check for toxicity values used in honey bee risk assessment and to conduct effect assessments for real-life exposure scenarios. This new integrative approach, moving from single-point estimates of toxicity and exposure to a holistic link between exposure and effect, will allow for a higher confidence of honey bee toxicity assessment in the future. Environ Toxicol Chem 2022;41:2193-2201. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

In Europe, the risk assessment for bees at the European Union or national level has always focussed on potential impacts on honeybees. During the revision of the European Food Safety Authority bee guidance it was explicitly stated that bumblebees and solitary bees should be considered as well and consequently concerns were raised regarding the representativeness of honeybees for these other bee species. These concerns originate from differences in size as well as differences in behavioral and life history traits of other bee species. In response to this concern, the non-Apis working group of the International Commission for Plant-Pollinator Relationships initiated a ring-test of a semifield tunnel study design using the bumblebee Bombus terrestris. Nine laboratories participated, validating and improving the proposed design over a 2-year period. The intention of the ring-test experiments was to develop and if possible, establish a test protocol to conduct more standardized semifield tests with bumblebees. In the present study, the results of the ring-tests are summarized and discussed to give recommendations for a promising experimental design. Environ Toxicol Chem 2022;41:2548-2564. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

There are various differences in size, behavior, and life history traits of non-Apis bee species compared with honey bees (Apis mellifera; Linnaeus, 1758). Currently, the risk assessment for bees in the international and national process of authorizing plant protection products has been based on honey bee data as a surrogate organism for non-Apis bees. To evaluate the feasibility of a semifield tunnel test for Osmia bicornis (Linnaeus, 1758) and Osmia cornuta (Latreille, 1805), a protocol was developed by the non-Apis working group of the International Commission for Plant-Pollinator Relationships, consisting of experts from authorities, academia, and industry. A total of 25 studies were performed over a 2-yr period testing a replicated control against a replicated positive control using either a dimethoate or diflubenzuron treatment. Studies were regarded to be valid, if ≥30% of released females were found to occupy the nesting units in the night/morning before the application (establishment). Thirteen studies were regarded to be valid and were analyzed further. Parameters analyzed were nest occupation, flight activity, cell production (total and per female), cocoon production (total and per female), emergence success, sex ratio, and mean weight of females and males. Dimethoate was a reliable positive control at the tested rate of 75 g a.i./ha, once >30% females had established, displaying acute effects such as reduction in flight activity, increase in adult mortality (shown by nest occupation), and reproduction ability of the females (total cell and cocoon production). On the other hand, no effects on larval and pupal development were observed. The growth regulator diflubenzuron had statistically significant effects on brood development, causing mortality of eggs and larvae at a rate of approximately 200 g a.i./ha, whereas fenoxycarb did not cause any significant effects at the tested rates of 300 and 600 g a.i./ha. In conclusion, the ring-test protocol proved to be adequate once the study comprised a well-established population of female Osmia bees, and the results improved in the second year as the laboratories increased their experience with the test organism. It is noted that the success of a study strongly depends on the experience of the experimenter, the crop quality, the quality of the cocoons, and the weather conditions. Based on these finding, recommendations for a semifield study design with Osmia spp. are proposed. Environ Toxicol Chem 2021;40:236-250. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

The freshwater crayfish Pacifastacus leniusculus is among the most widespread invasive crayfish species in Europe. Pacifastacus leniusculus invaded Hungary around 1998 and here we investigated the recent expansion of this species and its impact on other aquatic macroinvertebrates. The colonization of watercourses throughout Europe by the signal crayfish resulted in negative impacts on the present aquatic communities. Our investigation (i.e. in Rába, Pinka, Gyöngyös-stream, Répce, Arany-stream and Strém systems) revealed that the distribution range of signal crayfish is still in expansion in the western part of Hungary and in all likelihood impacting the aquatic communities in these watercourses. Our results obviously demonstrated that signal crayfish densities were highest in habitats with gravel or coarse particulate organic matter, which seems to reflect a species-specific habitat preference. Our investigation proved that the presence of P. leniusculus had negative effects on a number of protected species such as Calopteryx virgo and Onychogomphus forcipatus next to a significant negative effect on the Odonata and Trichoptera species richness as well as on the abundances of Ephemeroptera, Odonata and Trichoptera. Our study in Hungary supports the notion of the significant negative impact of signal crayfish on native freshwater invertebrate communities throughout Europe. In order to assess whether these impacts are restricted to fast flowing waters only, an adequate monitoring plan providing more knowledge on this species with respect to biotic and abiotic preferences and aquatic macroinvertebrate composition is required.

Zoos increasingly transform their exhibitions from traditional one‐species enclosures to more natural exhibits, that is, environments that capture part of an ecosystem including a selection of animals and plants that occur there. Thus, enhancing the experience of its human visitors while also allowing its residents to possibly show more natural behavior. In 2017 Royal Burger's Zoo (Arnhem, The Netherlands) created and opened a mangrove‐like environment containing fiddler crabs. Fiddler crabs display a broad range of behaviors, and this research examines which wild‐type behavior and behavioral patterns can be observed on a seminatural mudflat. The behavior shown by Uca rapax and Uca tangeri on the mudflat was counted each hour between 07:00 and 17:00. An asymmetric tidal regime was present in the enclosure including two high water periods. Various known fiddler crab behaviors, including waving and combat, were observed but no copulation. A clear pattern in exposed crabs on the mudflat was found, with low numbers visible in the early morning and the highest numbers present in the early afternoon, while number of visitors did not have a significant effect on this pattern. Interestingly, the highest abundances were not observed around the ebbing tide (07:00–09:00), as observed in the wild, but somewhat later, possibly due to the asymmetric tidal scheme or the interaction of tidal and daily rhythms. This study shows that in captivity, fiddler crabs indeed show a range of natural behaviors which is linked to the tidal and possibly daily rhythm as well., Mean individuals of visible Uca rapax crabs per hour, Research Highlights Typical fiddler crab behaviors were observed on a seminatural mudflat.Distinct patterns in activity and behavior were present throughout the day.The highest number of visual crabs was observed a couple of hours after low tide.

Due to their foraging behavior, honey bees interact with the landscape. As a result, honey bees and their brood will be exposed to pesticides through nectar and pollen entering the hive. Although these pathways seem rather straightforward, there are several steps between the entry of nectar and pollen and its consumption by the colony. One of the aspects involved here is the time between collection and consumption of pollen in the hive. This is of importance for the actual exposure of nurse bees and larvae to pesticides in pollen. Although lab and short-term field studies indicated that bees prefer to consume freshly stored pollen, this has to our knowledge not been verified in a long-term field study under realistic environmental and apiculturist conditions. To study pollen consumption dynamics, influx and consumption were recorded at 3 or 4 day intervals over a six-week period in two colonies. It was demonstrated that throughout the experimental period, beebread consumption was high in the first 3 to 5 days after collection, over which approximately 70% was consumed. The remaining 30% was consumed within a 2 to 3 week period. Pollen consumption is swift and indicates that only limited time is available for potential degradation processes. As actual data on degradation of pesticides in stored pollen are not available, a justified worse case assumption would be that the actual exposure concentrations consumed by the nurse bees and larvae are the same as the concentrations in collected pollen.

Seaweed has the potential to deliver more food to an increasing world population. Diseases endanger production security and yield of any farm, seaweed farming is no exception, hence crop protection plans may be developed that include the use of chemical crop protection either directly or indirectly in co-cropping systems. This document reports a first attempt to map the extent to which chemicals are being used in seaweed production, which production systems are used, where potential risks of the use of chemicals resulting from protection of seaweed production (or co-produced products) against diseases can be anticipated, and how this could be taken into account for future work. The investigations concerning open sea production systems indicate that for the control of pests and diseases in the described cultivation systems only prevention, monitoring and mechanical/physical measures are common, at least for Indonesia. In contrast, results from closed pond- or tank-based multi-trophic systems where seaweed can be included for example as feed or filter, or for biomass production, indicate some reasons for concern. Uptake and sorption of veterinary medicinal products and other chemicals can lead to additional input to shrimp and/or fish (via feed) or to the environment (via disposal of filter material). The ERA-AQUA model, originally developed for risk assessment of aquaculture production of fish and shrimp, was identified as possible means to further explore the fate of chemicals used in land-based multi-trophic production systems, for their bioaccumulation and biomagnification potential and possible risk for the environment, the produced goods (fish/shrimp), and finally human health.

Previous studies have explored effects of imidacloprid and its metabolites on terrestrial species, such as bees, and indicated the importance of some active metabolites. However, the biotransformation of IMI and the toxicity of its metabolites to aquatic arthropods are largely unknown, especially the mechanisms driving species sensitivity differences and time-cumulative toxicity effects. To assess the potential effects of the metabolization of IMI and the toxicokinetics and toxicity of the metabolite(s) on aquatic arthropods, we first studied the acute toxicity of IMI and relevant metabolites to the mayfly species Cloen dipterum (sensitive to IMI) and the amphipod species Gammarus pulex (less sensitive to IMI). Secondly, toxicokinetic experiments were conducted using both the parent compound and imidacloprid-olefin (IMI-ole), a metabolite assessed as toxic in the acute tests and defined as bioactive. Of the four tested metabolites, only IMI-ole was readily biotransformed from the parent IMI and showed similar toxicity to C. dipterum as IMI. However, C. dipterum was hardly able to eliminate IMI-ole from its body. For G. pulex, IMI-ole was also the only detected metabolite causing toxicity, but the biotransformation of IMI to IMI-ole was slower and lower in G. pulex compared to C. dipterum, and G. pulex eliminated IMI-ole quicker than C. dipterum. Our results on internal kinetics of IMI and IMI-ole, and on biotransformation of IMI indicated that the metabolite IMI-ole was toxic and was rather persistent inside the body tissue of both invertebrate species, especially for C. dipterum. In conclusion, as IMI and IMI-ole have similar toxicity and IMI was replaced rapidly by IMI-ole which in turn was poorly eliminated by C. dipterum, the overall toxicity is a function of dose and time. As a result, no long-term threshold of effects of IMI may exist for C. dipterum as the poor elimination results in an ongoing increase of toxicity over time for mayflies as also found experimentally in previous published papers.

There are various differences in size, behavior, and life history traits of non‐Apis bee species compared with honey bees (Apis mellifera; Linnaeus, 1758). Currently, the risk assessment for bees in the international and national process of authorizing plant protection products has been based on honey bee data as a surrogate organism for non‐Apis bees. To evaluate the feasibility of a semifield tunnel test for Osmia bicornis (Linnaeus, 1758) and Osmia cornuta (Latreille, 1805), a protocol was developed by the non‐Apis working group of the International Commission for Plant‐Pollinator Relationships, consisting of experts from authorities, academia, and industry. A total of 25 studies were performed over a 2‐yr period testing a replicated control against a replicated positive control using either a dimethoate or diflubenzuron treatment. Studies were regarded to be valid, if ≥30% of released females were found to occupy the nesting units in the night/morning before the application (establishment). Thirteen studies were regarded to be valid and were analyzed further. Parameters analyzed were nest occupation, flight activity, cell production (total and per female), cocoon production (total and per female), emergence success, sex ratio, and mean weight of females and males. Dimethoate was a reliable positive control at the tested rate of 75 g a.i./ha, once >30% females had established, displaying acute effects such as reduction in flight activity, increase in adult mortality (shown by nest occupation), and reproduction ability of the females (total cell and cocoon production). On the other hand, no effects on larval and pupal development were observed. The growth regulator diflubenzuron had statistically significant effects on brood development, causing mortality of eggs and larvae at a rate of approximately 200 g a.i./ha, whereas fenoxycarb did not cause any significant effects at the tested rates of 300 and 600 g a.i./ha. In conclusion, the ring‐test protocol proved to be adequate once the study comprised a well‐established population of female Osmia bees, and the results improved in the second year as the laboratories increased their experience with the test organism. It is noted that the success of a study strongly depends on the experience of the experimenter, the crop quality, the quality of the cocoons, and the weather conditions. Based on these finding, recommendations for a semifield study design with Osmia spp. are proposed. Environ Toxicol Chem 2021;40:236–250. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC., For ecotoxicological testing of pesticides, a protocol was developed and ring‐tested by the non‐Apis working group of the International Commission for Plant‐Pollinator Relationships to conduct semifield tunnel tests with the solitary bee species Osmia bicornis (Linnaeus, 1758) and Osmia cornuta (Latreille, 1805).

The water quality and ecological value in the Molenpolder has deteriorated sharply in recent years from clear water with a well-developed underwater vegetation to turbid water where submerged aquatic plants are completely lacking. The fish stock has also changed from a limnophilic fishing community to an eurytope fishing community. During the same period, red swamp crayfish (Procambarus clarkii) has increased in numbers. Although no causal research has been conducted between the increase in crayfish numbers and the decline of the aquatic ecosystem in the Molenpolder, the ecological profile of this crayfish indicates that that it very likely plays a role in maintaining the poor state of the ecosystem. To investigate whether the characteristic underwater vegetation of the Molenpolder can easily recover, the province of Utrecht has asked Wageningen Environmental Research to investigate the vitality of the seed bank in the sediments of the Molenpolder. De waterkwaliteit – en bijbehorende ecologie – is in de Molenpolder de afgelopen jaren sterk veranderd: van helder water met een goed ontwikkelde onderwatervegetatie naar troebel water waarin ondergedoken waterplanten ontbreken. Ook de visstand is van een limnofiele gemeenschap omgeslagen naar een eurytope visgemeenschap. Parellel aan deze omslag zijn de rode Amerikaanse rivierkreeften (Procambarus clarkii) sterk in aantallen toegenomen. Hoewel er geen causaal onderzoek gedaan is tussen de toename van kreeften en de achteruitgang van het aquatische ecosysteem in de Molenpolder is het, gezien het profiel van deze kreeft, aannemelijk dat ze ook een rol speelt bij het in stand houden van de slechte toestand van het ecosysteem in de Molenpolder. Om na te gaan of de karakteristieke onderwatervegetatie van de Molenpolder weer makkelijk terug kan komen, heeft de provincie Utrecht aan Wageningen Environmental Research gevraagd of zij de vitaliteit van de zaadbank in de onderwaterbodems van de Molenpolder kunnen onderzoeken.

Er zijn sterke aanwijzingen dat zowel de aantallen als de soortendiversiteit van bestuivers de laatste decennia sterk achteruit zijn gegaan. Een speerpunt van de Nationale Bijenstrategie is het verbeteren van het leefgebied van wilde bijen en andere bestuivers. De meeste initiatieven om leefgebied voor wilde bijen te creëren, richten zich op het aanleggen van een bloemrijke vegetatie. Belangrijk voor wilde bijen is echter dat naast voldoende voedsel ook voldoende geschikte nestlocaties aanwezig zijn. De bekende bijenhotels helpen daarbij, maar het overgrote deel van de Nederlandse wilde bijensoorten nestelt ondergronds. Nestgelegenheid voor deze bodemnestelende bijen kan o.a. worden gecreëerd door zogenaamde nestelhoopjes of nesteldijkjes vorm te geven, maar dergelijke maatregelen zijn lang niet overal mogelijk. Een voorbeeld zijn de wegbermen, waar relatief makkelijk meer bloemaanbod te genereren is, maar gezien de verkeersveiligheid minder ruimte is voor het creëren van kale bodem of taluds. Onduidelijk is in hoeverre bloemrijke grasstroken, zoals deze wegbermen, al functioneren als nestlocatie voor wilde bijen en hoe deze potentiële functie verder kan worden bevorderd. In het voorliggende onderzoek is die vraag nader onderzocht door gedurende twee jaren in wegbermen met en zonder ingezaaide bloemranden de aanwezigheid van bodemnestelende bijen te inventariseren.

As a result of the incorporation of invasive freshwater crayfish onto the European regulation on Invasive Alien Species, this group of animals has drawn the attention of water managers. Commercial fishery has been suggested as a measure to control or eradicate populations of alien crayfish. However, it is not clear how and where the commercial practices of the fisherman and the needs of water managers converge. This field study provides answers to some of the basic questions regarding the efficiency of different traps, the impact of fishing on the population and the so-called unintended by-catches. Invasieve rivierkreeften zijn op de Europese Exoten Verordening geplaatst en hebben momenteel de aandacht van waterbeherend Nederland. Om de populaties van deze invasieve exoten te beheersen, is visserij als mogelijk handelingsperspectief benoemd, maar het is vooralsnog niet bekend in hoeverre de commerciële praktijk van de beroepsvisser en de wensen van de waterbeheerder te verenigen zijn. Deze veldstudie geeft de eerste antwoorden op enkele basale vragen over de efficiëntie van verschillende vangtuigen, het effect van afkreeften ‘an sich’ en mogelijke bijvangsten.

© The Author(s) 2020., The Partnership for Chemicals Risk Assessment (PARC) is currently under development as a joint research and innovation programme to strengthen the scientific basis for chemical risk assessment in the EU. The plan is to bring chemical risk assessors and managers together with scientists to accelerate method development and the production of necessary data and knowledge, and to facilitate the transition to next-generation evidence-based risk assessment, a non-toxic environment and the European Green Deal. The NORMAN Network is an independent, well-established and competent network of more than 80 organisations in the field of emerging substances and has enormous potential to contribute to the implementation of the PARC partnership. NORMAN stands ready to provide expert advice to PARC, drawing on its long experience in the development, harmonisation and testing of advanced tools in relation to chemicals of emerging concern and in support of a European Early Warning System to unravel the risks of contaminants of emerging concern (CECs) and close the gap between research and innovation and regulatory processes. In this commentary we highlight the tools developed by NORMAN that we consider most relevant to supporting the PARC initiative: (i) joint data space and cutting-edge research tools for risk assessment of contaminants of emerging concern; (ii) collaborative European framework to improve data quality and comparability; (iii) advanced data analysis tools for a European early warning system and (iv) support to national and European chemical risk assessment thanks to harnessing, combining and sharing evidence and expertise on CECs. By combining the extensive knowledge and experience of the NORMAN network with the financial and policy-related strengths of the PARC initiative, a large step towards the goal of a non-toxic environment can be taken.

The commercial farming of Atlantic salmon, Salmo salar, may require the periodic application of emamectin benzoate (EB) treatments to reduce the effects of biological pests, such as sea lice. As a result, EB is detected in sediments beneath these fish farms at considerable levels. Literature sediment toxicity data for EB for marine benthic species is only available for 10-day sediment toxicity tests, which might be too short to assess field effects. Here, we present a sediment toxicity test to determine 28-day mortality and growth effect concentrations for the non-target polychaete worm Arenicola marina, the crustacean Corophium volutator and the mollusk Cerastoderma edule using a marine microcosm setup. Results indicate that no concentration-dependent increase of mortality and growth rate was apparent to A. marina and C. edule. But for C. volutator, a concentration-dependent increase in mortality was observed, resulting in a calculated 28-d LC50 of 316 μg/kg dry sediment (95% confidence interval: 267–373 μg/kg dry sediment). There were significant effects on C. volutator growth rate at concentrations of 100 μg/kg dry sediment and above (NOEC = 30 μg/kg dry sediment). These observations show that C. volutator is more sensitive to EB than A. marina, which differs from results reported in previous studies. Comparison to the most sensitive NOEC (30 μg/kg dry sediment) found for C. volutator (organisms of 8–11 mm length), shows that the Environmental Quality Standard, derived by the Scottish Environment Protection Agency in 2017 which based on freshwater species data (NOEC = 1.175 μg/kg dry sediment), are relatively strict and is sufficiently protective for the marine species tested in this paper.

In 2019, a report was issued by Buijs en Samwel-Mantingh which claimed a possible relation between the occurrence of pesticides and veterinary drugs in manure and the decline of farmland birds, which feed on (soil) invertebrates allegedly impacted by these substances. The current research project provides an in-depth analysis of the reliability of the measured concentrations, an analysis of the potential risk to (soil) invertebrates of single compounds and mixtures and an assessment of potential pathways of these substances into the manure. In 2019 verscheen een rapport van Buijs en Samwel-Mantingh waarin een mogelijke relatie gelegd werd tussen de aanwezigheid van bestrijdingsmiddelen en diergeneesmiddelen in mest van landbouwhuisdieren en de afname van weidevogels t.g.v. een afname in evertebraten (o.a. wormen en insecten) als voedselbron voor deze vogels. In deze verdiepende analyse van de gerapporteerde concentraties wordt onderzocht hoe betrouwbaar de gemeten concentraties zijn, of er een mogelijk risico voor bodemevertebraten van individuele stoffen en mengsels is en wat mogelijke routes van deze stoffen naar mest zijn.

When entering aquatic ecosystems, hydrophobic organic chemicals like the fungicide fludioxonil partition to the sediment compartment where they pose potential risks to benthic invertebrates. To assess the ecological risk for sediment-dwelling invertebrates, nematodes are a suitable organism group, as they are abundantly present and possess key positions in the benthic food web. Therefore, the toxicity of the fungicide fludioxonil to nematodes was assessed in a standardized sediment toxicity test with Caenorhabditis elegans (ISO 10872), as well as in an outdoor sediment-spiked microcosm test system. In the microcosms, effects on the nematode species composition were studied, while exposure concentrations of fludioxonil were monitored in total sediment and pore water. Toxic effects on nematodes were better predicted using concentrations in pore water than total sediment concentrations. In laboratory single species tests, fludioxonil showed considerably lower toxicity in spiked field-collected sediment, compared to artificial ISO-sediments. Applying an assessment factor of 10 to the C. elegans 96-h EC10, a Tier-1 RACNematode of 7.99 mg kg-1 dry artificial sediment (corresponding to 69 mug l-1 in pore water) appeared to be protective for nematode communities in microcosms that showed no response in total abundance and species composition up to 39.9 mg fludioxonil kg-1 dry sediment (corresponding to 392 mug l-1 in pore water). Copyright © 2019 Elsevier B.V. All rights reserved.

This paper deals with species sensitivity distributions (SSDs) for the lipophilic insecticide lufenuron and benthic arthropods based on sediment-spiked laboratory toxicity tests. This compound that inhibits chitin synthesis and moulting of arthropods persists in sediment. Using field-collected sediment, toxicity tests were conducted with three macro-crustaceans and six insects. The Hazardous Concentration to 5% of the tested species, the HC5 (and 95% confidence limit), derived from an SSD constructed with 10d-LC50′s was 2.2 (1.2–5.7) μg/g organic carbon (OC) in dry sediment. In addition, HC5 values derived from SSDs constructed with 28d-LC10 and 28-d LC50 values were 0.13 (0.02–1.50) μg/g OC and 2.0 (1.3–5.5) μg/g OC, respectively. In 28d toxicity tests with Chironomus riparius and Hyalella azteca, a higher sensitivity was observed when using lufenuron-spiked field-collected sediment than in lufenuron-spiked artificial sediment. Overall, the non-biting midge C. riparius appeared to be a representative and sensitive standard test species to assess effects of lufenuron exposure in sediment. The Tier-1 (based on standard test species), Tier-2 (based on standard and additional test species) and Tier-3 (model ecosystem approach) regulatory acceptable concentrations (RACs) for sediment-spiked lufenuron did not differ substantially. The Tier-2 RAC was the lowest. Since to our knowledge this study is the first in the open literature that evaluates the tiered approach in the sediment effect assessment procedure for pesticides, we advocate that similar evaluations should be conducted for pesticides that differ in toxic mode-of-action.

Information from effects of pesticides in sediments at an ecosystem level, to validate current and proposed risk assessment procedures, is scarce. A sediment-spiked outdoor freshwater microcosm experiment was conducted with fludioxonil (lipophilic, non-systemic fungicide) to study exposure dynamics and treatment-related responses of benthic and pelagic macroinvertebrates and zooplankton. Besides blank control and solvent control systems the experiment had six different treatment levels (1.7–614 mg a.s./kg dry sediment) based around the reported 28-d No Observed Effect Concentration (NOEC) for Chironomus riparius (40 mg a.s./kg dry sediment). Twelve systems were available per treatment of which four were sacrificed on each of days 28, 56 and 84 after microcosm construction. Fludioxonil persisted in the sediment and mean measured concentrations were 53–82% of the initial concentration after 84 days. The dissipation rate increased with the treatment level. Also exposure concentrations in overlying water were long-term, with highest concentrations 28 days after initiation of the experiment. Sediment-dwelling Oligochaeta and pelagic Rotifera and Cladocera showed the most pronounced treatment-related declines. The most sensitive sediment-dwelling oligochaete was Dero digitata (population NOEC 14.2 mg a.s./kg dry sediment). The same NOEC was calculated for the sediment-dwelling macroinvertebrate community. The most sensitive zooplankton species was the cladoceran Diaphanosoma brachyurum (NOEC of 1.6 μg a.s./L in overlying water corresponding to 5.0 mg a.s./kg dry sediment). At the two highest treatments several rotifer taxa showed a pronounced decrease, while the zooplankton community-level NOEC was 5.6 μg a.s./L (corresponding to 14.2 mg a.s./kg dry sediment). Zooplankton taxa calanoid Copepoda and Daphnia gr. longispina showed a pronounced treatment-related increase (indirect effects). Consequently, an assessment factor of 10 to the chronic laboratory NOECs of Chironomus riparius (sediment) and Daphnia magna (water) results in a regulatory acceptable concentration that is sufficiently protective for both the sediment-dwelling and pelagic organisms in the microcosms.

Exposure patterns in ecotoxicological experiments often do not match the exposure profiles for which a risk assessment needs to be performed. This limitation can be overcome by using toxicokinetic-toxicodynamic (TKTD) models for the prediction of effects under time-variable exposure. For the use of TKTD models in the environmental risk assessment of chemicals, it is required to calibrate and validate the model for specific compound–species combinations. In this study, the survival of macroinvertebrates after exposure to the neonicotinoid insecticide was modelled using TKTD models from the General Unified Threshold models of Survival (GUTS) framework. The models were calibrated on existing survival data from acute or chronic tests under static exposure regime. Validation experiments were performed for two sets of species-compound combinations: one set focussed on multiple species sensitivity to a single compound: imidacloprid, and the other set on the effects of multiple compounds for a single species, i.e., the three neonicotinoid compounds imidacloprid, thiacloprid and thiamethoxam, on the survival of the mayfly Cloeon dipterum. The calibrated models were used to predict survival over time, including uncertainty ranges, for the different time-variable exposure profiles used in the validation experiments. From the comparison between observed and predicted survival, it appeared that the accuracy of the model predictions was acceptable for four of five tested species in the multiple species data set. For compounds such as neonicotinoids, which are known to have the potential to show increased toxicity under prolonged exposure, the calibration and validation of TKTD models for survival needs to be performed ideally by considering calibration data from both acute and chronic tests.

28-Day sediment-spiked laboratory toxicity tests with eight benthic macroinvertebrates and the lipophilic fungicide fludioxonil were conducted to verify the proposed tiered sediment effect assessment procedure as recommended by the European Food Safety Authority (EFSA). The test species were the oligochaetes Lumbriculus variegatus and Tubifex tubifex, the insects Chironomus riparius and Caenis horaria, the crustaceans Hyalella azteca and Asellus aquaticus and the bivalves Corbicula fluminalis and Pisidium amnicum. Toxicity estimates were expressed in terms of total concentration of dry sediment as well as in pore water concentration. Field-collected sediment, also used in a previously performed sediment-spiked microcosm experiment, was used in tests with all species. L. variegatus and C. riparius had similar lowest 28d-L(E)C10 values when expressed in terms of total sediment concentration, but in terms of pore water concentration L. variegatus was more sensitive. Three of the six additional benthic test species (A. aquaticus, C. horaria, C. fluminalis) had 28d-EC10 values a factor of 2–6 lower than that of L. variegatus. Comparing different effect assessment tiers for sediment organisms, i.e. Tier-0 (Modified Equilibrium Partitioning approach), Tier-1 (Standard Test Species approach), Tier-2 (Species Sensitivity Distribution (SSD) approach) and Tier-3 (Model Ecosystem approach), it is concluded that the tiers based on sediment-spiked laboratory toxicity tests provide sufficient protection when compared with the Tier-3 Regulatory Acceptable Concentration (RAC). Differences between Tier-1 and Tier-2 RACs, however, appear to be relatively small and not always consistent, irrespective of expressing the RAC in terms of total sediment or pore water concentration. Derivation of RACs by means of the SSD approach may be a challenge, because it is difficult obtaining a sufficient number of valid chronic EC10 values with appropriate 95% confidence bands for sediment-dwelling macroinvertebrates. Therefore, this paper proposes a Tier-2 Weight-of-Evidence approach to be used in case an insufficient number of valid additional toxicity data is made available. Similar studies with pesticides that differ in fate properties and toxic mode-of-action are necessary for further validation of the tiered effect assessment approach for sediment organisms.

In the higher tiers of pesticide risk assessment, the Species Sensitivity Distribution (SSD) concept is often used to establish the effect threshold defined as the concentration protecting 95% of the species (Hazardous Concentration 5%, HC5). The toxicity data included in SSDs are normally established using a constant exposure regime. However, the exposure of pesticides in the field is often characterised by a variable exposure regime. Toxicokinetic-toxicodynamic (TKTD) models can be used to extrapolate the toxic effects of a chemical to a specific, time-variable exposure regime. The aim of this paper was to develop Exposure Pattern Specific SSDs (EPS-SSDs) for three insecticides using TKTD models and to compare the HC5 of different exposure patterns with the same time-weighted average concentration to evaluate whether the use of EPS-SSDs would change the outcome of the ecological risk assessment. The EPS-SSDs were developed by estimating TKTD parameters for the compounds chlorpyrifos, imidacloprid and lambda-cyhalothrin using results from standard, 96 h, single species tests. These parameter estimates were used for TKTD modelling to determine toxicity thresholds (e.g. LC10 and LC50) for contrasting exposure patterns after certain evaluation times (4, 10 or 100 days). HC5 values were constructed with TKTD-predicted LC10- and LC50- values for different exposure patterns characterised by similar time-weighted average concentrations. Differences between those HC5 values ranged from a factor 1 to a factor 2.3 for the short evaluation period (4 d). This difference was smaller when using an evaluation period of 10 days instead of 4 days and selecting the TKTD-predicted LC10 instead of TKTD-predicted LC50 based HC5s. For the long term evaluation period (100 d), a maximum difference of a factor of 30 was found.

Three native crayfish species, i.e. Astacus astacus , Astacus leptodactylus and Austropotamobius torrentium , occur in Hungary. Lately, however, non-indigenous crustaceans have also invaded the country Their most recent distribution and impact on the occurrences of the native species is not clear. Consequently, the first object of the present study was to investigate the present-day distribution and habitat preference of the native and invasive crayfish and crab species in Hungary according to water types and surface water velocity values. The second aim was to investigate the changes in the distribution patterns of all species over the last 20 years and to identify potential risks for native species in Hungary. Although A. astacus was discovered on several new locations the overall distribution of the species is decreasing. The rarest crayfish is A. torrentium which was found only at three locations, making this the most endangered crayfish in Hungary. Although A leptodactylus used to occur especially in the main branches of the Danube and Tisza Rivers it shifted towards its tributaries after O. limosus appeared here. Despite their overlapping habitat preference and the fact that O. limosus is a carrier of the lethal crayfish plague, both species still co-occur at a few locations in Hungary Pacifastacus leniusculus is invading the country from the West and although it is not present in large numbers yet, it has replaced the local A. astacus populations and may further impact its distribution when it further increases its range in the future. Although occurrences of the Chinese mitten crab ( Eriocheir sinensis ) the marbled crayfish ( Procambarus fallax f. virginalis ) and the red swamp crayfish ( Procambarus clarkii ) have been reported in the literature, these species were not encountered during the survey Thus indicating that their occurrence in Hungary is not widespread yet. The increasing distribution of the invaders forms a constant threat to native crayfish populations in Hungary To ensure the survival of the native species it is important to keep track of the ongoing changes in crayfish distributions. Nevertheless, additional protection measures will be required to safe-guard the survival of the native crayfish populations in Hungary.

A major problem with risk assessment of chemicals is the extrapolation of laboratory single-species toxicity tests, which oversimplify the actual field situation by ignoring species interactions, to natural communities. The authors tested if the bioavailability-normalized 5% hazardous concentration (HC5) estimated from chronic planktonic single-species toxicity data (HC5plankton ) for zinc (Zn) is protective for a plankton community and investigated the direct and indirect effects of Zn (at HC5 and HC50) on a freshwater community's structure and function. Microcosms were exposed to 3 different Zn concentrations (background, HC5plankton = 75 μg Zn/L and HC50plankton = 300 μg Zn/L) for 5 wk. The planktonic groups revealed a consistent no-observed-effect concentration for the community of 75 μg Zn/L, similar to or higher than the HC5plankton , thus suggesting its protectiveness in the present study. At 300 μg Zn/L a significant reduction in cladocerans resulted in increases of rotifer, ciliate, and phytoplankton abundance. In addition, the phytoplankton community shifted in dominance from grazing-resistant to edible species. Contrary to the species sensitivity distribution (SSD) prediction, which identified phytoplankton as the most sensitive group, only the total chlorophyll and the abundance of 2 phytoplankton species were adversely affected at 300 μg Zn/L. Thus, although the HC5 estimated from the bioavailability-normalized SSD was overall protective for the plankton community, the SSD was not able to correctly predict the species sensitivity ranking within their community context at the HC50. Environ Toxicol Chem 2016;35:2698-2712. © 2016 SETAC.

Mayfly nymphs are among the most sensitive taxa to neonicotinoids. The present study presents the acute and chronic toxicity of 3 neonicotinoids (imidacloprid, thiacloprid, and thiamethoxam) to a mayfly species (Cloeon dipterum) and some notes on the seasonality of the toxicity of imidacloprid to C. dipterum and 5 other invertebrate species. Imidacloprid and thiamethoxam showed equal acute and chronic toxicity to a winter generation of C. dipterum, whereas thiacloprid was approximately twice as toxic. The acute and chronic toxicity of imidacloprid was much higher for the C. dipterum summer generation than for the winter one. The acute toxicity differs by a factor of 20 for the 96-h 50% effective concentration (EC50) and by a factor of 5.4 for the chronic 28-d EC50. Temperature had only a slight effect on the sensitivity of C. dipterum to imidacloprid because we only found a factor of 1.7 difference in the 96-h EC50 between tests performed at 10 °C and 18 °C. The difference in sensitivity between summer and overwintering generations was also found for 3 other insect species. The results indicate that if the use and environmental fate of the 3 neonicotinoids are comparable, replacing imidacloprid by another neonicotinoid might not reduce the environmental impact on the mayfly nymph C. dipterum. The results also show the importance of reporting which generation is tested because sensitivity values of insects in the summer might be underestimated by the experiments performed with neonicotinoids and an overwintering population.

Ecotoxicological studies mainly consist of single-species experiments evaluating the effects of a single stressor. However, under natural conditions aquatic communities are exposed to a mixture of stressors. The present study aimed to identify how the toxicity of zinc (Zn) is affected by increased temperature and increased phosphorus (P) supply and how these interactions vary among species, functional groups, and community structure and function. Aquatic microcosms were subjected to 3 Zn concentrations (background, no Zn added, and 75 and 300 μg Zn/L), 2 temperatures (16-19 and 21-24 °C), and 2 different P additions (low, 0.02, and high, 0.4 mg P L-1 wk-1 ) for 5 wk using a full factorial design. During the study, consistent interactions between Zn and temperature were only rarely found at the species level (4%), but were frequently found at the functional group level (36%), for community structure (100%) and for community function (100%; such as dissolved organic carbon concentrations and total chlorophyll). The majority of the Zn × temperature interactions were observed at 300 μg Zn/L and generally indicated a smaller effect of Zn at higher temperature. Furthermore, no clear indication was found that high P addition by itself significantly affected the overall effects of Zn on the community at any level of organization. Interestingly, though, 90% of all the Zn × temperature interactions observed at the species, group, and community composition level were found under high P addition. Collectively, the results of our study with the model chemical Zn suggest that temperature and phosphorus loading to freshwater systems should be accounted for in risk assessment, because these factors may modify the effects of chemicals on the structure and functioning of aquatic communities, especially at higher levels of biological organization. Environ Toxicol Chem 2018;37:2413-2427. © 2018 SETAC. ispartof: ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY vol:37 issue:9 pages:2413-2427 ispartof: location:United States status: published

One central goal of conservation biology is to conserve the genetic diversity of species in order to protect their adaptive potential. The main objective of this study was to identify management units (MUs) for the threatened noble crayfish (Astacus astacus) in Western Europe by utilizing sequence and microsatellite analysis to determine populations in need of focused conservation programs. With the analysis of noble crayfish from 31 sampling sites from Belgium, France, The Netherlands and Germany, and further comparison of this data with a European-wide dataset, we propose four distinct MUs: the French Meuse (MU 1), the French Rhine (MU 2), the Belgian Scheldt and Meuse (MU 3) as well as populations from the French Seine (MU 4). This knowledge enables advanced A. astacus conservation management practises in these catchments by distinguishing between outbreeding and inbreeding populations and by preserving the maximum genetic diversity. When required, a high genetic diversity can be conserved by strengthen existing populations via stocking with populations that either bear the most common haplotype or population-specific private haplotypes in order to maintain recent and regional adaptions. Above all, stocking with populations that exhibit haplotypes from outside Western Europe should be avoided in these catchments. This study supports the preservation of the genetic diversity of noble crayfish in Western Europe and provides thus a proposition for advanced conservation management.

Several species of invasive crayfish have become established in the Netherlands, the most recent addition being Orconectes virilis. Since crayfish are known to impact water quality and aquatic macrophytes in areas they invade, this study investigated whether this was also the case for this species under Dutch conditions and if so, whether a crayfish density producing “no effects” could be established. We focussed on the potential impact of O. virilis on water quality variables (pH, electrical conductivity, dissolved oxygen and turbidity), as well as their impact on submerged and emergent macrophytes. In a compartment experiment with different densities of O. virilis, statistically significant effects were observed at crayfish densities of 1.25 crayfish/m2 on electrical conductivity, turbidity, submersed macrophyte biomass, and the emergent plant Sagittaria sagittifolia, due to crayfish actively severing plants and physically disturbing the sediment. No statistically significant differences with controls were observed at a density of 0.63 crayfish/m2. Since densities of 0.03 to 5 crayfish/m2 have been found in different water types in the Netherlands, this indicates that the water quality and macrophyte biomass in Dutch waters are being negatively impacted by invasive crayfish. As a consequence, attempts to reach a good ecological status as required in the Water Framework Directive will be frustrated by the presence of this invader.

A field trial was set up to simulate a field margin environment to analyze sub-lethal effects of the herbicide metsulfuron-methyl on several endpoints of non-target terrestrial plants (NTTPs). Both vegetative and reproductive endpoints were evaluated. The experiment was conducted in an experimentally established field strip with sown species. The treatments consisted of five dosages and a control: 0, 0.0097, 0.0193, 0.058, 0.174, and 0.348 gram active ingredient per hectare (g a.i./ha). The plant cover, number of (flowering) individuals per species and fruit collection were performed and estimated weekly for a period of 4 months. At the end of the growing season, the total dry biomass per species was obtained and the collected fruits were weighed, counted, and sieved to obtain the seeds. The seeds were counted and weighed as well, before they were used in a germination experiment to test the seed emergence of the F1 generation. The herbicide only affected the biomass of Matricaria recutita at the treatment levels tested (0.058 g a.i./ha and higher). Field dosages of 0.174 and 0.348 g a.i./ha differed significantly in the endpoint "plant cover" compared to lower dosages and controls. The F1 generations of Sinapis alba, Centaurea cyanus, and Phacelia tanacetifolia were particularly affected at field dosages of 0.0193 g a.i./ha and higher, showing significantly lower seed germination rates. This would imply that spray drift of metsulfuron-methyl might lead to shifts in species compositions and succession in vegetation in off-crop areas adjacent to arable fields. Conducting germination experiments is necessary to investigate a herbicide's effect on the full life cycle of plants.

North American crayfish species as hosts for the crayfish plague pathogen Aphanomyces astaci contribute to the decline of native European crayfish populations. At least six American crayfish species have been reported in the Netherlands but the presence of this pathogenic oomycete with substantial conservational impact has not yet been confirmed in the country. We evaluated A. astaci prevalence in Dutch populations of six alien crustaceans using species-specific quantitative PCR. These included three confirmed crayfish carriers (Orconectes limosus, Pacifastacus leniusculus, Procambarus clarkii), two recently introduced but yet unstudied crayfish (Orconectes cf. virilis, Procambarus cf. acutus), and a catadromous crab Eriocheir sinensis. Moderate levels of infection were observed in some populations of O. limosus and P. leniusculus. Positive results were also obtained for E. sinensis and two Dutch populations of O. cf. virilis. English population of the latter species was also found infected, confirming this taxon as another A. astaci carrier in European waters. In contrast, Dutch P. clarkii seem only sporadically infected, and the pathogen was not yet detected in P. cf. acutus. Our study is the first confirmation of crayfish plague infections in the Netherlands and demonstrates substantial variation in A. astaci prevalence among potential hosts within a single region, a pattern possibly linked to their introduction history and coexistence.

Population models, in particular individual-based models (IBMs), are becoming increasingly important in chemical risk assessment. They can be used to assess recovery of spatially structured populations after chemical exposure that varies in time and space. The authors used an IBM coupled to a toxicokinetic-toxicodynamic model, the threshold damage model (TDM), to assess recovery times for 4 aquatic organisms, after insecticide application, in a nonseasonal environment and in 3 spatial settings (pond, stream, and ditch). The species had different life histories (e.g., voltinism, reproductive capacity, mobility). Exposure was derived from a pesticide fate model, following standard European Union scenarios. The results of the IBM-TDM were compared with results from simpler models: one in which exposure was linked to effects by means of concentration-effect relationships (IBM-CE) and one in which the IBM was replaced by a nonspatial, logistic growth model (logistic). For the first, exposure was based on peak concentrations only; for the second, exposure was spatially averaged as well. By using comparisons between models of different complexity and species with different life histories, the authors obtained an understanding of the role spatial processes play in recovery and the conditions under which the full time-varying exposure needs to be considered. The logistic model, which is amenable to an analytic approach, provided additional insights into the sensitivity of recovery times to density dependence and spatial dimensions.

The present study evaluated the acute and chronic toxicity of imidacloprid to a range of freshwater arthropods. Mayfly and caddisfly species were most sensitive to short-term imidacloprid exposures (10 tests), whereas the mayflies showed by far the most sensitive response to long-term exposure of all seven arthropod species tested (28-d EC10 values of approximately 0.03?µg/L). The results indicated a high aquatic risk of chronic exposure of imidacloprid to mayflies.

In situ activated carbon (AC) amendment is a new direction in contaminated sediment management, yet its effectiveness and safety have never been tested on the level of entire food chains including fish. Here we tested the effects of three different AC treatments on hydrophobic organic chemical (HOC) concentrations in pore water, benthic invertebrates, zooplankton, and fish (Leuciscus idus melanotus). AC treatments were mixing with powdered AC (PAC), mixing with granular AC (GAC), and addition-removal of GAC (sediment stripping). The AC treatments resulted in a significant decrease in HOC concentrations in pore water, benthic invertebrates, zooplankton, macrophytes, and fish. In 6 months, PAC treatment caused a reduction of accumulation of polychlorobiphenyls (PCB) in fish by a factor of 20, bringing pollutant levels below toxic thresholds. All AC treatments supported growth of fish, but growth was inhibited in the PAC treatment, which was likely explained by reduced nutrient concentrations, resulting in lower zooplankton (i.e., food) densities for the fish. PAC treatment may be advised for sites where immediate ecosystem protection is required. GAC treatment may be equally effective in the longer term and may be adequate for vulnerable ecosystems where longer-term protection suffices.

Crustaceans can store excess copper in the hepatopancreas, an organ playing a role in digestive activity as well as in neurosecretory control. Here, we studied the effect of copper exposure on the level of histamine, an indicator of food spoilage in edible crustaceans. Histamine is also a neuromodulator in the intestinal nervous system of crustaceans, and a human allergen. Marbled crayfish (Procambarus fallax forma virginalis) were exposed to average measured values of 0.031 mg Cu/l and 0.38 mg Cu/l, respectively, for 14 days and then transferred to copper-free water for another 14 days. Concentrations of copper and histamine in the hepatopancreas and muscle were evaluated at different time points. Histamine levels were significantly higher in hepatopancreas and muscle tissues at the highest exposure level, but only after transfer of the animals to copper-free water. The increased histamine concentration following copper exposure may be explained by a (delayed) stress response, and by up-regulated histidine synthesis induced by copper, followed by decarboxylation to histamine.

Ecological risk assessment (ERA) has followed a taxonomy-based approach, making the assumption that related species will show similar sensitivity to toxicants, and using safety factors or species sensitivity distributions to extrapolate from tested to untested species. In ecology it has become apparent that taxonomic approaches may have limitations for the description and understanding of species assemblages in nature. Therefore it has been proposed that the inclusion of species traits in ERA could provide a useful and alternative description of the systems under investigation. At the same time, there is a growing recognition that the use of mechanistic approaches in ERA, including conceptual and quantitative models, may improve predictive and extrapolative power. Purposefully linking traits with mechanistic effect models could add value to taxonomy-based ERA by improving our understanding of how structural and functional system facets may facilitate inter-species extrapolation. Here, we explore whether and in what ways traits can be linked purposefully to mechanistic effect models to predict intrinsic sensitivity using available data on the acute sensitivity and toxicokinetics of a range of freshwater arthropods exposed to chlorpyrifos. The results of a quantitative linking of seven different endpoints and twelve traits demonstrate that while quantitative links between traits and/or trait combinations and process based (toxicokinetic) model parameters can be established, the use of simple traits to predict classical sensitivity endpoints yields little insight. Remarkably, neither of the standard sensitivity values, i.e. the LC50 or EC50, showed a strong correlation with traits. Future research in this area should include a quantitative linking of toxicodynamic parameter estimations and physiological traits, and requires further consideration of how mechanistic trait-process/parameter links can be used for prediction of intrinsic sensitivity across species for different substances in ERA. Electronic supplementary material The online version of this article (doi:10.1007/s10646-012-0962-8) contains supplementary material, which is available to authorized users.

The ecological impact of the dithiocarbamate fungicide metiram was studied in outdoor freshwater microcosms, consisting of 14 enclosures placed in an experimental ditch. The microcosms were treated three times (interval 7 days) with the formulated product BAS 222 28F (Polyram®). Intended metiram concentrations in the overlying water were 0, 4, 12, 36, 108 and 324 μg a.i./L. Responses of zooplankton, macroinvertebrates, phytoplankton, macrophytes, microbes and community metabolism endpoints were investigated. Dissipation half-life (DT50) of metiram was approximately 1–6 h in the water column of the microcosm test system and the metabolites formed were not persistent. Multivariate analysis indicated treatment-related effects on the zooplankton (NOECcommunity = 36 μg a.i./L). Consistent treatment-related effects on the phytoplankton and macroinvertebrate communities and on the sediment microbial community could not be demonstrated or were minor. There was no evidence that metiram affected the biomass, abundance or functioning of aquatic hyphomycetes on decomposing alder leaves. The most sensitive populations in the microcosms comprised representatives of Rotifera with a NOEC of 12 μg a.i./L on isolated sampling days and a NOEC of 36 μg a.i./L on consecutive samplings. At the highest treatment-level populations of Copepoda (zooplankton) and the blue-green alga Anabaena (phytoplankton) also showed a short-term decline on consecutive sampling days (NOEC = 108 μg a.i./L). Indirect effects in the form of short-term increases in the abundance of a few macroinvertebrate and several phytoplankton taxa were also observed. The overall community and population level no-observed-effect concentration (NOECmicrocosm) was 12–36 μg a.i./L. At higher treatment levels, including the test systems that received the highest dose, ecological recovery of affected measurement endpoints was fast (effect period

Ecosystems today increasingly suffer invasions by multiple invasive species. Complex interactions between invasive species can have different fitness implications for each invader, which can in turn determine the future progression of their invasions and result in differential impacts on native species and ecosystems. To this end, through pair-wise and group scale experiments, we examined possible interaction outcomes, competition effects and their potential fitness implications for two widespread invasive species of crayfish that increasingly co-occur in freshwater ecosystems of Europe (Pacifastacus leniusulus and Orconectes limosus). In all trials, P. leniusculus demonstrated the potential to outcompete O. limosus in both staged encounters and direct resource competition, being more likely to win heterospecific agonistic encounters and to acquire shelters at a higher rate. Observed dyadic dominance was translated to a broader social context of group-scale experiments, in which dominance of P. leniusculus was further strengthened by size differential between species. O. limosus was not able to compensate for competitive pressure by the dominant P. leniusculus and suffered wet weight loss and more frequent injuries in the presence of P. leniusculus. While both species are detrimental to native ecosystems, the ability of P. leniusculus to withstand competition pressure from another successful invasive species underscores its potential to establish dominant populations. Our results highlight the importance of understanding interspecies competition in prioritizing potential management activities or control efforts in contact zones.

The present study compared the effects of different time-variable exposure regimes having the same time-weighted average (TWA) concentration of the organophosphate insecticide chlorpyrifos on freshwater invertebrate communities to enable extrapolation of effects across exposure regimes. The experiment was performed in outdoor microcosms by introducing three different regimes: a single application of 0.9 µg active ingredients (a.i.)/L; three applications of 0.3 µg a.i./L, with a time interval of 7 d; and continuous exposure to 0.1 µg a.i./L for 21 d. Measurements showed that the TWA21d concentration in the continuous-exposure treatment (0.098 µg/L) was slightly lower than in the three-application (0.116 µg/L) and single-application (0.126 µg/L) treatments. The application of chlorpyrifos resulted in decreased abundances in the arthropod community, with the largest adverse effects reported for the mayfly Cloeon dipterum and cladocerans Daphnia gr. longispina and Alona sp., while smaller effects were observed for other insects, copepods, and amphipods. At the population level, however, the mayfly C. dipterum only responded to the single-application treatment, which could be explained by the toxicokinetics of chlorpyrifos in this species. At the end of the experimental period the invertebrate community showed approximately the same effect magnitude for all treatment regimes. These results suggest that for this combination of concentrations and duration of the TWA, the TWA concentration is more important for most species than the peak concentration for the assessment of long-term risks of chlorpyrifos. Environ. Toxicol. Chem. 2011; 30:1383–1394. © 2011 SETAC

The predictive power of bioaccumulation models may be limited when they do not accountfor strong sorption of organic contaminants to carbonaceous materials (CM) such as black carbon, and when they do not include metabolic transformation. We tested a food web accumulation model, including sorption to CM, on data from a model ecosystem experiment with historically contaminated sediment. In combination with measured CM contents of the sediment, the model gave good fits for the biota that are known not to metabolize PAHs (macrophytes, periphyton, floating algal biomass). The same model was applied to invertebrates and fish but now with optimization of their metabolic transformation rates (k(m)). For fish, these rates correlated empirically with log K(OW): Log k(m) = -0.8 log K(OW) + 4.5 (r2 adj = 0.73). For invertebrates, log k(m) did not correlate with logK(OW). Sensitivity analysis revealed that the model output is highly sensitive to sediment CM content and sorption parameters, moderately sensitive to metabolic transformation rates, and slightly sensitive to lipid fraction of the organism and diet-related parameters. It is concluded that CM-inclusive models yield a better assessment of accumulation than models without sorption to CM. Furthermore, inclusion of CM in a model enables metabolic transformation rates to be calculated from the remaining overestimation in the model results when compared to measured data.