Impact of triphenyltin acetate in microcosms simulating floodplain lakes. II. Comparison of species sensitivity distributions between laboratory and semi-field

Physiological and ultrastructural responses of the brown seaweed Undaria pinnatifida to triphenyltin chloride (TPTCL) stress

Triphenyltin chloride (TPTCL) is a well-known marine pollutant that may constitute major environmental threats to seaweed mariculture. In the present study, the toxic effects of TPTCL on physiology and ultrastructure of cultivated sporophytes of Undaria pinnatifida were investigated under different TPTCL concentrations ranging from 0 to 100 μg L-1. Significant negative effects of increased TPTCL concentration were detected in the relative growth rates, survival percentages and chlorophyll a contents of young and adult sporophytes. Low TPTCL concentrations could significantly stimulate the activities of enzymes related to nitrogen metabolism. The chloroplast, mitochondria and nucleus inside cells were greatly damaged by TPTCL. Meanwhile, significant increases of electron dense deposits and physodes were found. Additionally, young sporophytes exhibited greater tolerance to TPTCL stress than adult sporophytes. The results of this study indicate that coastal TPTCL pollution could reduce the productivity and quality of cultivated U. pinnatifida.

Herbicide Exposure and Toxicity to Aquatic Primary Producers

The aim of the present review was to give an overview of the current state of science concerning herbicide exposure and toxicity to aquatic primary producers. To this end we assessed the open literature, revealing the widespread presence of (mixtures of) herbicides, inevitably leading to the exposure of non-target primary producers. Yet, herbicide concentrations show strong temporal and spatial variations. Concerning herbicide toxicity, it was concluded that the most sensitive as well as the least sensitive species differed per herbicide and that the observed effect concentrations for some herbicides were rather independent from the exposure time. More extensive ecotoxicity testing is required, especially considering macrophytes and marine herbicide toxicity. Hence, it was concluded that the largest knowledge gap concerns the effects of sediment-associated herbicides on primary producers in the marine/estuarine environment. Generally, there is no actual risk of waterborne herbicides to aquatic primary producers. Still, median concentrations of atrazine and especially of diuron measured in China, the USA and Europe represented moderate risks for primary producers. Maximum concentrations due to misuse and accidents may even cause the exceedance of almost 60% of the effect concentrations plotted in SSDs. Using bioassays to determine the effect of contaminated water and sediment and to identify the herbicides of concern is a promising addition to chemical analysis, especially for the photosynthesis-inhibiting herbicides using photosynthesis as endpoint in the bioassays. This review concluded that to come to a reliable herbicide hazard and risk assessment, an extensive catch-up must be made concerning macrophytes, the marine environment and especially sediment as overlooked and understudied environmental compartments.

Is the Effect Assessment Approach for Fungicides as Laid Down in the European Food Safety Authority Aquatic Guidance Document Sufficiently Protective for Freshwater Ecosystems?

In Europe, the European Food Safety Authority aquatic guidance document describes the procedures for the derivation of regulatory acceptable concentrations (RACs) for pesticides in edge-of-field surface waters on the basis of tier-1 (standard test species), tier-2 (geometric mean and species sensitivity distributions [SSDs]), and tier-3 (model ecosystem studies) approaches. In the present study, the protectiveness of such a tiered approach was evaluated for fungicides. Acute and chronic RACs for tier-1 and tier-2B (SSDs) were calculated using toxicity data for standard and additional test species, respectively. Tier-3 RACs based on ecological thresholds (not considering recovery) could be derived for 18 fungicides. We show that tier-1 RACs, in the majority of cases, are more conservative than RACs calculated based on model ecosystem experiments. However, acute tier-2B RACs do not show a sufficient protection level compared with tier-3 RACs from cosm studies that tested a repeated pulsed exposure regime or when relatively persistent compounds were tested. Chronic tier-2B RACs showed a sufficient protection level, although they could only be evaluated for 6 compounds. Finally, we evaluated the suitability of the calculated RACs for 8 compounds with toxicity data for fungi. The comparison shows that the current RACs for individual fungicides, with a few exceptions (e.g., tebuconazole), show a sufficient protection level for structural and functional fungal endpoints. However, more data are needed to extend this comparison to other fungicides with different modes of action. Environ Toxicol Chem 2019;38:2279-2293. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Water quality criteria derivation and ecological risk assessment for triphenyltin in China

Triphenyltin (TPT) is one of the most toxic chemicals artificially discharged into aquatic environment with human activities. Due to its intensive use in antifouling paints and adverse effects on non-target species, TPT has aroused wide concern in both saltwater and freshwater environment. Nevertheless, the water quality criteria (WQC) are not available in China, which impedes the risk assessment for this emerging pollutant. This study aims to establish the WQC of TPT for both freshwater and saltwater ecosystems. With the derived WQC, a four-level tiered ecological risk assessment (ERA) approach was employed to assess the ecological risks of this emerging pollutant in Chinese waters. Through the species sensitivity distribution (SSD) methodology, the freshwater criterion maximum concentration (CMC) and criterion continuous concentration (CCC) were derived as 396 ng Sn L^-1 and 5.60 ng Sn L^-1, respectively, whereas the saltwater CMC and CCC were 66.5 ng Sn L^-1 and 4.11 ng Sn L^-1, respectively. The ecological risk assessment for TPT demonstrated that the acute risk was negligible whereas the chronic risk was significant with HQ (Hazard Quotient) values of up to 5.669 and 57.1% of coastal waters in China facing clear risk. TPT contamination in coastal environment, therefore, warrants further concern.

The Consequences of Nonrandomness in Species-Sensitivity in Relation to Functional Traits for Ecosystem-Level Effects of Chemicals

Estimating ecosystem-level effects from single-species bioassays is a major challenge in environmental risk assessment. Most extrapolation procedures are based on the implicit assumption that species sensitivities are random with regard to their functional traits. Here, we explore how nonrandomness in species sensitivities affects how species-level and ecosystem level effects of chemical exposure correspond. The effect of a correlation between the trait value under control conditions and the sensitivity of the trait to chemical stress is studied for two traits (per capita growth rate and monoculture yield) under constant and temporary exposure. Theoretical model predictions are thereby validated against a 3-week microcosm experiment, in which eight marine diatoms systems with different correlations between trait values and sensitivities were temporary (1 week) or constantly (3 weeks) exposed to two concentrations of the herbicide atrazine (100 and 250 μg L^-1). Negative correlations increased the reduction in ecosystem functioning (productivity) by atrazine for both traits. However, correlations in the per capita growth rate affected productivity only shortly following changes in environmental conditions, whereas correlations in the monoculture yield affected productivity throughout exposure. Correlations between species sensitivities and functional trait values can thus help to identify when ecosystem-level effects are likely to exceed species-level effects.

Development and application of the SSD approach in scientific case studies for ecological risk assessment

Species sensitivity distributions (SSDs) are used in ecological risk assessment for extrapolation of the results of toxicity tests with single species to a toxicity threshold considered protective of ecosystem structure and functioning. The attention to and importance of the SSD approach has increased in scientific and regulatory communities since the 1990s. Discussion and criticism have been triggered on the concept of the approach as well as its technical aspects (e.g., distribution type, number of toxicity endpoints). Various questions remain unanswered, especially with regard to different endpoints, statistical methods, and protectiveness of threshold levels, for example. In the present literature review (covering the period 2002-2013), case studies are explored in which the SSD approach was applied, as well as how endpoint types, species choice, and data availability affect SSDs. How statistical methods may be used to construct reliable SSDs and whether the lower 5th percentile hazard concentrations (HC5s) from a generic SSD can be protective for a specific local community are also investigated. It is shown that estimated protective concentrations were determined by taxonomic groups rather than the statistical method used to construct the distribution. Based on comparisons between semifield and laboratory-based SSDs, the output from a laboratory SSD was protective of semifield communities in the majority of studies. Environ Toxicol Chem 2016;35:2149-2161. © 2016 SETAC.

Ecological interactions affecting population-level responses to chemical stress in Mesocyclops leuckarti

Higher tiers of ecological risk assessment (ERA) consider population and community-level endpoints. At the population level, the phenomenon of density dependence is one of the most important ecological processes that influence population dynamics. In this study, we investigated how different mechanisms of density dependence would influence population-level ERA of the cyclopoid copepod Mesocyclops leuckarti under toxicant exposure. We used a combined approach of laboratory experiments and individual-based modelling. An individual-based model was developed for M. leuckarti to simulate population dynamics under triphenyltin exposure based on individual-level ecological and toxicological data from laboratory experiments. The study primarily aimed to-(1) determine which life-cycle processes, based on feeding strategies, are most significant in determining density dependence (2) explore how these mechanisms of density dependence affect extrapolation from individual-level effects to the population level under toxicant exposure. Model simulations showed that cannibalism of nauplii that were already stressed by TPT exposure contributed to synergistic effects of biotic and abiotic factors and led to a twofold stress being exerted on the nauplii, thereby resulting in a higher population vulnerability compared to the scenario without cannibalism. Our results suggest that in population-level risk assessment, it is easy to underestimate toxicity unless underlying ecological interactions including mechanisms of population-level density regulation are considered. This study is an example of how a combined approach of experiments and mechanistic modelling can lead to a thorough understanding of ecological processes in ecotoxicology and enable a more realistic ERA.

Photosynthetic and molecular responses of the marine diatom Thalassiosira pseudonana to triphenyltin exposure

This study aimed to investigate the responses of the marine diatom Thalassiosira pseudonana upon waterborne exposure to triphenyltin chloride (TPTCl) through determining their photosynthetic response, growth performance, and expressions of genes and proteins. Based on the growth inhibition test, the 96-h IC50 (i.e., median inhibition concentration) was found to be 1.09 μg/L (95% confidence interval (CI): 0.89-1.34 μg/L). According to photosynthetic parameters, the 96-h EC50s (i.e., median effect concentrations) were estimated at 1.54 μg/L (95% CI: 1.40-1.69 μg/L) and 1.51 μg/L (95% CI: 1.44-1.58 μg/L) for the maximum quantum yield of photosystem II (PSII) photochemistry (ΦPo) and the effective quantum yield of photochemical energy conversion in PSII (Φ2), respectively. Non-photochemical quenching in the algae was increased at low concentrations of TPTCl (0.5-1.0 μg/L) but it decreased gradually when the TPTCl concentration further increased from 1.0 to 2.5 μg/L. Results of gene expressions showed that lipid metabolism related genes were not influenced by TPTCl at 0.5 or 1.0 μg/L, while silica shell formation genes were down-regulated at 0.5 μg/L. Photosynthesis related genes were up-regulated at 0.5 μg/L TPTCl but were down-regulated at 1.0 μg/L TPTCl. Proteomics analysis revealed that relatively less proteins could be detected after exposure to 1.0 μg/L TPTCl (only about 50-60 spots) compared with that observed in the 0.5μg/L TPTCl treatment and two control groups (each with about 290-300 protein spots). At 0.5 μg/L TPTCl, five proteins were differentially expressed when compared with the seawater control and solvent control, and most of these proteins are involved in defence function to protect the biological systems from reactive oxygen species that generated by TPTCl. These proteins include oxygen-evolving enhancer protein 1 precursor, fucoxanthin chlorophyll a/c protein - LI818 clade, and mitochondrial manganese superoxide dismutase, which can function to maintain the capacity of PSII and stabilize the photosynthesis efficiency as reflected by the unchanged ΦPo and Φ2 values at 0.5 μg/L TPTCl. In contrast, the excess toxicity that caused by TPTCl at the high concentration (1.0 μg/L TPTCl) might directly damage the proteins, inhibit their expression, and/or cause the suppression of metabolism as indicated by the down-regulation of most studied proteins and genes, which could ultimately inhibit the photosynthesis and growth of the algae. Overall, this study comprehensively elucidated the toxicity effects of TPT on T. pseudonana, and partially revealed the molecular toxic mechanisms and corresponding defence responses in this model algal species.

Comparative chemical sensitivity between marine Australian and Northern Hemisphere ecosystems: is an uncertainty factor warranted for water-quality-guideline setting?

The lack of Australian species data has pragmatically led to the use of toxicological data from the Northern Hemisphere to develop water-quality guidelines. However, it is unknown whether Australian species and ecosystems are equally as sensitive and if an uncertainty factor is warranted for Australian guideline setting. In the present study, it is hypothesized that an uncertainty factor is not required. This was tested by generating species sensitivity distributions by 2 parametric methods using marine Northern Hemisphere and Australian/New Zealand data. Sufficient acute data were found for only 3 compounds: 4-chlorophenol, phenol, and ammonia. For ammonia and 4-chlorophenol, the 95% species protection levels generated with Australian and Northern Hemisphere data were essentially the same. For phenol, protection levels derived from Australian data were approximately 10-fold higher. Therefore, the derived benchmark concentration from Northern Hemisphere data should be protective. It is tentatively concluded that there is no need for an uncertainty factor when deriving water-quality guidelines for marine Australian ecosystems using Northern Hemisphere data. It is, however, noted that this is based on only 3 compounds.

Sensitivity of hypogean and epigean freshwater copepods to agricultural pollutants

Widespread pollution from agriculture is one of the major causes of the poor freshwater quality currently observed across Europe. Several studies have addressed the direct impact of agricultural pollutants on freshwater biota by means of laboratory bioassays; however, as far as copepod crustaceans are concerned, the ecotoxicological research is scarce for freshwater species and almost nonexistent for the hypogean ones. In this study, we conducted a comparative analysis of the available literature data on the sensitivity of freshwater copepods to agricultural pollutants. We also assessed the acute and chronic sensitivity of a hypogean and an epigean species, both belonging to the Crustacea Copepoda Cyclopoida Cyclopidae, to two N-fertilizers (urea and ammonium nitrate) and two herbicides (ARIANE(TM) II from Dow AgroSciences LLC, and Imazamox), widely used for cereal agriculture in Europe. According to the literature review, freshwater copepods are sensitive to a range of pesticides and N-fertilizers. Ecotoxicological studies on hypogean species of copepods account only one study. There are no standardized protocols available for acute and chronic toxicity tests for freshwater copepods, making comparisons about sensitivity difficult. From our experiments, ionized ammonia proved to be more toxic than the herbicide Imazamox, in both short and chronic bioassays. Urea was the less toxic chemical for both species. The hypogean species was more sensitive than the epigean one to all chemicals. For both species and for all tested chemicals, acute lethality and chronic lethality were induced at concentrations higher than the law limits of good water body quality in Europe, except for ionized ammonia, which provoked the chronic lethality of the hypogean species at a lower concentration. The hazardous concentration (HC) of un-ionized ammonia for 5 % of freshwater copepods, obtained by a species sensitivity distribution, was 92 μg l(-1), significantly lower than the HC computed for traditional test species from freshwater environments.

Life-stage-dependent sensitivity of the cyclopoid copepod Mesocyclops leuckarti to triphenyltin

The effects of triphenyltin (TPT) on non-target aquatic groups like copepods have not yet been studied in detail. Recently, Mesocyclops leuckarti was suggested as a representative species for freshwater cyclopoid copepods to study the effects of plant protection products. We conducted 96h acute toxicity tests in the laboratory to study the effects of TPT on the different life stages of M. leuckarti. We used the recently proposed General Unified Threshold model of Survival (GUTS) to mechanistically describe the underlying toxicokinetic and toxicodynamic process for the nauplii, copepodites and adults (males and females) of M. leuckarti. Experimental results showed that nauplii were significantly more sensitive to TPT compared to the other stages. Also, the 96h LC50 values were much lower than the 48h LC50 values, suggesting that standard acute toxicity test durations for aquatic invertebrates may underestimate toxic effects with respect to compounds like TPT which have a slow mechanism of action. The GUTS analysis, which mechanistically described the toxicity of TPT to the different life stages of M. leuckarti, suggested that the differences in sensitivity were a consequence of a lower threshold of effects in the nauplii compared to a higher threshold in the later stages. This study shows the potential of using the GUTS to understand how toxic compounds interact with different life-stages. Further experiments to provide a more detailed understanding of toxicokinetics of TPT in copepods could be useful.

Toxicity of pentachlorophenol to native aquatic species in the Yangtze River

INTRODUCTION

While the literature is replete with studies of the toxic potency of pentachlorophenol (PCP), site-specific criteria for native aquatic species that can be used in ecological risk assessments has been lacking and application of toxicity information for non-native species is controversial.

MATERIALS AND METHODS

In the present study, acute and chronic toxicities of PCP to six aquatic species native to the Yangtze River were determined. The HC₅ and HC₅₀ (hazardous concentration for 5% and 50% of species) were derived from dose-response curves for these native aquatic species and were then compared with those derived for non-native species.

RESULTS

The acute toxicity values for the native species ranged from 8.8 × 10⁻² mg l⁻¹ (Plagiognathops microlepis) to 1.1 mg l⁻¹ (Soirodela polyrhiza), while chronic toxicity values based on no observed effect concentrations (NOECs) ranged from 0.01 mg l⁻¹ (Macrobrachium superbum) to 0.25 mg l⁻¹ (Soirodela polyrhiza). Native aquatic benthos was more sensitive to acute PCP exposure than non-native species. There was no significant difference in NOECs derived from native fish species and those based on non-native fish species. The median acute HC₅ and HC₅₀ derived from the toxicity data of native taxa were both less than those derived from non-native taxa. There was no significant difference between chronic HC₅s derived from the two sets of taxa. However, the median chronic HC₅₀ derived from native taxa was less than that derived from non-native taxa.

CONCLUSION

The study upon which we report here provides site-specific toxicity information developed for native species which can be used for the protection of local aquatic life from a common contaminant, PCP.

Effects of four fungicides on nine non-target submersed macrophytes

We tested the sensitivity of nine submersed macrophyte species to the fungicides chlorothalonil, pentachlorophenol, fluazinam, and carbendazim. Endpoints determined 3 weeks after the start of the treatment were based on shoot and root growth in water. Carbendazim proved not or only moderately toxic to these macrophytes. Pentachlorophenol and chlorothalonil were more toxic than fluazinam. Taking all endpoints into consideration, toxicity levels differed very substantially. Although root endpoints reflecting root growth were in some cases more sensitive than shoot endpoints, shoot growth endpoints like relative growth turned out to be more reliable than the root growth endpoints. Due to the large differences in the type of mode of action between fungicides, it is very difficult to predict their potential effect in the environment or even to predict whether non-target organisms like macrophytes are likely to be sensitive. Ideally, therefore, the registration of fungicides requires an extensive risk-assessment procedure, which also covers non-target groups like macrophytes.

Interactions between nutrients and organic micro-pollutants in shallow freshwater model ecosystems

Effects of nutrients and toxicants in aquatic ecosystems may interact in several ways. Here, we (a) present an overview of reported mechanisms that may play a role in these interactions, and (b) compare these reported mechanisms against the results of a suite of experiments performed with organic micro-pollutants in outdoor and indoor microcosms representing shallow lakes dominated either by phytoplankton or by macrophytes. The presence of macrophytes affected the fate of the persistent hydrophobic organic chemicals (triphenyltin, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls) in particular. Differences in community structure affected indirect treatment-related effects and recoverability of affected populations in the lambda-cyhalothrin and TPT experiments high nutrient status. Four major interaction categories reported in the literature are I) dilution of pollutants by biomass, II) impact on transport and cycling of pollutants, III) direct toxicant-food interactions, and IV) indirect toxicant-food interactions. Results of our experiments showed interactions in all four categories (I, II, III, and IV). However, it is concluded that risks of organic micro-pollutants cannot be adapted to (or compensated for?) these four mechanism because of time and space dependent feedback in shallow water communities.

Ecological risk assessment of organic waste amendments using the species sensitivity distribution from a soil organisms test battery

Safe amendment rates (the predicted no-effect concentration or PNEC) of seven organic wastes were estimated from the species sensitivity distribution of a battery of soil biota tests and compared with different realistic amendment scenarios (different predicted environmental concentrations or PEC). None of the wastes was expected to exert noxious effects on soil biota if applied according either to the usual maximum amendment rates in Europe or phosphorus demands of crops (below 2 tonnes DM ha(-1)). However, some of the wastes might be problematic if applied according to nitrogen demands of crops (above 2 tonnes DM ha(-1)). Ammonium content and organic matter stability of the studied wastes are the most influential determinants of the maximum amendment rates derived in this study, but not pollutant burden. This finding indicates the need to stabilize wastes prior to their reuse in soils in order to avoid short-term impacts on soil communities.

Impact of 17alpha-ethinylestradiol on the plankton in freshwater microcosms--I: response of zooplankton and abiotic variables

We investigated effects of 17alpha-ethinylestradiol (EE) in vertebrate free 230 L still water microcosms. Zooplankton composition and physico-chemical variables were observed during 4 weeks of pre-application, 6 weeks of dosing via controlled release, and a 12 weeks post-treatment period. In the treated microcosms, time-weighted averages of EE concentration ranged between 7 and 220 ng/L during the dosing period, with concentration maxima up to 724 ng/L. EE exposure resulted in a decrease of species numbers and diversity (Shannon-Wiener, Simpson). Abundances of cladocerans, copepods, and, less unambiguously, rotifers declined. Strongest affected groups were the offspring of cladocerans and copepods and, on species level, the cladoceran species Daphnia longispina and Chydorus sphaericus as well as the rotifer species Keratella quadrata and Polyarthra sp. EE apparently affected the phosphate cycle as indicated by increased phosphate concentrations in the water. During post-treatment period, the treated microcosms recovered, but especially the highest treated microcosms did not fully re-approximate to the controls. Whereas EE affected cladocerans and copepods directly, shifts of rotifers may (partly) be caused indirectly, e.g. by competition with crustaceae. Although not providing an absolute proof, the traits of direct and indirect effects on different taxonomic groups and larval stages as well as the time course of the effects indicate that effects primarily resulted from endocrine activity of EE.

Impact of 17alpha-ethinylestradiol on the plankton in freshwater microcosms--II: responses of phytoplankton and the interrelation within the ecosystem

Effects of 17alpha-ethinylestradiol (EE) on phytoplankton were investigated in a lentic freshwater microcosm study. Treatment with EE caused a shift in the species composition as shown by a principle response curve. Whereas densities of Cyanophyceae, Dinophyceae, and Chrysophyceae increased, those of Conjugatophyceae and Cryptophyceae decreased. Furthermore, relative density of Chlorophyceae declined after EE treatment. The changes showed taxa-specific time dependencies. Some species, especially the cyanobacterium Cyanobium parvum, bloomed after the treatment. EE treatment promoted total abundance and biomass of phytoplankton. Although the number of species per microcosm increased, the diversity indices (Shannon-Wiener, Simpson) tended to lower values. The ecosystem only partly recovered during the investigated post-treatment period of 6 weeks. Probably at least the main effects were caused indirectly, i.e. via decrease of grazing zooplankton (crustaceans). The relation of EE to variation of phytoplankton composition was closer than those of other abiotic factors, indicating the relevance of its impact. EE also probably affected nutrients of the phytoplankton.

Impact of triphenyltin acetate in microcosms simulating floodplain lakes. I. Influence of sediment quality

Floodplain lakes in the Rhine-Meuse delta of the Netherlands vary considerably in levels of sediment-bound toxicants. Microcosm experiments were done to compare the ecological impact of the fungicide triphenyltin acetate (TPT) between test systems with clean or polluted sediments (10 microcosms each). Differences in sediment quality affected the structure of the aquatic communities that developed in the microcosms. Initially, a faster growth of the macrophyte Elodea nuttallii was observed on the polluted sediments, which contained not only toxicants but also higher organic matter and nutrient levels. Dynamics of TPT concentrations in the overlying water were very similar between the two types of test system. Higher levels of TPT, however, were found in the sediment compartment of the clean sediment systems containing a smaller macrophyte biomass. TPT was very persistent in the sediments. In both test systems representatives of several taxonomic groups showed clear responses to a single application of TPT, although benthic Nematoda were not affected. Although a few differences in the intensity and/or duration of TPT-related population responses were observed between the two types of test system, the background pollutants in the polluted sediment hardly affected the overall sensitivity of the aquatic community to the additional chemical stressor TPT.