Application of a Unique Test Design to Determine the Chronic Toxicity of Boron to the Aquatic Worm Lumbriculus variegatus and Fatmucket Mussel Lampsilis siliquoidea

The chronic (21- and 28-day) toxicity of boron was determined for two freshwater benthic macroinvertebrates: the fatmucket mussel Lampsilis siliquoidea and the aquatic worm Lumbriculus variegatus. The rapid depletion of boric acid from spiked sediments in tests using flow-through overlying waters was addressed by constant addition of boric acid to overlying water at concentrations matching those of the targeted porewater exposures. This proved highly successful in maintaining constant whole-sediment and sediment porewater boron concentrations. Boron sublethal 25 % inhibition concentration values based on porewater concentrations were 25.9 mg B/L (L. variegatus) and 38.5 mg B/L (L. siliquoidea), indicating similar test organism sensitivity. Expressed as dry whole-sediment values, the respective L. variegatus and L. siliquoidea sublethal (growth) IC₂₅ values for whole-sediment exposures were 235.5 mg B/kg sediment dry weight (dw) and 310.6 mg B/kg dw. The worm lethality-based end points indicated greater sensitivity than the sublethal end points, bringing into question the validity of a “lethality” end point for L. variegatus given its fragmentation mode of reproduction. For comparison, water-only mussel exposures were tested resulting in an IC₂₅ value of 34.6 mg B/L, which was within 20 % of the porewater value. This suggests that the primary route of boron exposure was through the aqueous phase. The results of this study indicated that for test materials that are readily water soluble, standard sediment test designs may be unsuitable, but water-only exposures can provide toxicological data representative of sediment tests.     

Toxicity of Nickel on the Selected Species of Marine Diatoms and Copepods

Toxicity values for nickel on marine diatoms and copepods were derived based on bioassay tests. The 96 h IC₅₀ of nickel on diatoms, Odontella mobiliensis and Coscinodiscus centralis were 0.31?±?0.01 and 0.62?±?0.02 mg/L and LC₅₀ values on copepods, Oithona similis and Acartia danae were 2.78?±?0.14 and 2.34?±?0.32 mg/L, respectively. The species mean chronic values of nickel were 0.016, 0.17, 0.57 and 0.42 mg/L for O. mobiliensis, C. centralis, O. similis and A. danae, respectively. A hazardous concentration was derived and evaluated using the species sensitivity distribution (SSD) method. SSD indicated that 13 µg Ni/L is the maximum allowable concentration for protection of 95% plankton species in coastal and marine ecosystem of India. Diatoms are more sensitive to nickel than copepods by almost an order of magnitude. The toxicity values derived in the present study may be useful to calculate ambient water quality criteria/standard for nickel.     

Toxicity of Silver and Titanium Dioxide Nanoparticle Suspensions to the Aquatic Invertebrate, Daphnia magna

The purpose of this study was to investigate the 48 h acute toxicity of capped silver nanoparticles (AgNPs), and capped and uncapped titanium dioxide (nTiO₂) to Daphnia magna neonates. In addition, a 24 days chronic toxicity study was performed for D. magna exposed to uncapped nTiO₂ to evaluate effects on growth, reproduction and survival. The 48 h median lethal concentrations (LC₅₀) for carboxy-functionalized capped AgNPs and uncapped nTiO₂ were 2.75 μg/L and 7.75 mg/L, respectively. In contrast, no mortalities were observed for Daphnia exposed to carboxy-functionalized capped nTiO₂ at concentrations up to 30 mg/L. In the chronic toxicity experiment with uncapped nTiO₂, the growth, reproduction and survival of D. magna were significantly (p < 0.05) reduced at concentrations ranging from 4.5 to 7.5 mg/L. Growth and reproduction were reduced by 35 % and 93 %, respectively in the treatments at the highest uncapped nTiO₂ concentration (7.5 mg/L). Time to first reproduction was delayed by 2–3 days in D. magna and the test organisms produced only 1–2 broods over 24 days exposure to the highest concentration of uncapped nTiO₂. Overall, the results from the present study indicate that exposures of aquatic invertebrates to nanoparticles could have important ecological effects on lower trophic levels in aquatic ecosystems.     

Vanadium Pentoxide Phytotoxicity: Effects of Species Selection and Nutrient Concentration

Vanadium concentrations in soil can be increased through anthropogenic inputs and can be harmful to plants. A Petri dish experiment was conducted to assess the effect of vanadium toxicity on the germination and survival of the garden lettuce, Lactuca sativa. A second study was conducted in a greenhouse to investigate the influence of species selection and nutrient concentration on the toxicity of vanadium pentoxide to plants. L. sativa and four non-crop native plant species, two grasses (Elymus virginicus and Panicum virgatum) and two broad-leaved species (Lycopus americanus and Prunella vulgaris) were selected. Artificial soil was used in both experiments, and a geometric progression of five vanadium concentrations plus controls was selected for the soil treatments. Results of the Petri dish experiment showed that seedling survival is a less sensitive end point than above-ground dry weight (DW) as measured in the greenhouse experiment. Nutrient level (100, 10, and 1 kg/ha) was found to strongly influence vanadium toxicity in the greenhouse study. At 100 kg/ha, plant tolerance to vanadium was greatest, as indicated by higher no-observed, lowest-observed, and percentage effect concentration values. Results showed that forbs (L. americanus and P. vulgaris) tended to be more sensitive than both the crop (L. sativa) and grasses (E. virginicus and P. virgatum) at high concentrations of vanadium. Soil concentrations resulting in a 25 % decrease in shoot DW were generally less than the Canadian soil quality guideline for vanadium, suggesting that 130 mg/kg may not be protective of the Canadian native plant species used in this study.     

Effects of Sublethal Copper Concentrations on Gills of White Shrimp (Litopenaeus vannamei, Boone 1931)

The objective of this study was to measure the copper (Cu) concentration in gills of juveniles Litopenaeus vannamei after exposure to Cu at sublethal concentrations, and to evaluate its effect upon the structure of gill tissue. The Cu concentration in gills of control shrimp was 0.075 mg/kg. Copper concentrations increased significantly by 147 %, 180 % and 205 % in gills of shrimp exposed to 0.675, 1.325 and 2.010 mg Cu/L, respectively. After exposure to 0.675 mg Cu/L for 15 days, gill tissue hyperplasia was observed, with a narrowing of the hemolymphatic lacunae. Necrosis and loss of hemolymphatic lacunae were observed at exposures of 1.325 and 2.010 mg Cu/L.     

In vitro activity of ceftobiprole on 440 Staphylococcus aureus strains isolated from bronchopulmonary infections

Objective

We assessed the in vitro activity of ceftobiprole on 440 Staphylococcus aureus clinical strains isolated from bronchopulmonary infections (2010–2014).

Cerium Oxide Nanoparticles are More Toxic than Equimolar Bulk Cerium Oxide in Caenorhabditis elegans

Engineered cerium oxide nanoparticles (CeO₂ NPs) are widely used in biomedical and engineering manufacturing industries. Previous research has shown the ability of CeO₂ NPs to act as a redox catalyst, suggesting potential to both induce and alleviate oxidative stress in organisms. In this study, Caenorhabditis elegans and zebrafish (Danio rerio) were dosed with commercially available CeO₂ NPs. Non-nano cerium oxide powder (CeO₂) was used as a positive control for cerium toxicity. CeO₂ NPs suspended in standard United States Environmental Protection Agency reconstituted moderately hard water, used to culture the C. elegans, quickly formed large polydisperse aggregates. Dosing solutions were renewed daily for 3 days. Exposure of wild-type nematodes resulted in dose-dependent growth inhibition detected for all 3 days (p < 0.0001). Non-nano CeO₂ also caused significant growth inhibition (p < 0.0001), but the scale of inhibition was less at equivalent mass exposures compared with CeO₂ NP exposure. Some metal and oxidative stress-sensitive mutant nematode strains showed mildly altered growth relative to the wild-type when dosed with 5 mg/L CeO₂ NPs on days 2 and 3, thus providing weak evidence for a role for oxidative stress or metal sensitivity in CeO₂ NP toxicity. Zebrafish microinjected with CeO₂ NPs or CeO₂ did not exhibit increased gross developmental defects compared with controls. Hyperspectral imaging showed that CeO₂ NPs were ingested but not detectable inside the cells of C. elegans. Growth inhibition observed in C. elegans may be explained at least in part by a non-specific inhibition of feeding caused by CeO₂ NPs aggregating around bacterial food and/or inside the gut tract.     

Sensitivity of the Endogeic Tropical Earthworm <Emphasis Type="Italic">Pontoscolex corethrurus</Emphasis> to the Presence of Heavy Crude Oil

Contamination of soil with petroleum is common in oil-producing areas across the tropical regions of the world. There is limited knowledge on the sensitivity of endogeic tropical earthworms to the contamination of soil with total petroleum hydrocarbons (TPH) present in crude oil. Pontoscolex corethrurus is a dominant species in tropical agroecosystems around oil-processing facilities. The sensitivity of P. corethrurus to soil artificially contaminated with “Maya” Mexican heavy crude oil was investigated through avoidance and acute ecotoxicity tests, using the following measured concentrations: 0 (reference soil), 551, 969, 4845, 9991 and 14,869 mg/kg. The avoidance test showed that P. corethrurus displayed a significant avoidance behavior to heavy crude oil at a concentration of 9991 mg/kg or higher. In contrast, acute toxicity tests indicate that the median lethal concentration (LC₅₀) was 3067.32 mg/kg; however, growth (weight loss) was more sensitive than mortality. Our study revealed that P. corethrurus is sensitive to TPH, thus highlighting the importance of P. corethrurus for petroleum ecotoxicological tests.     

Toxicopathic Branchial Lesions in Grass Carp (<Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>) Exposed to Chlorpyrifos

Present investigation aimed to assess the alterations in branchial architecture of Ctenopharyngodon idellus exposed to chlorpyrifos. 96 h LC50 of chlorpyrifos to C. idellus was found to be 7.24 µg/L. Fish were exposed chronically to 2.41 and 1.44 µg/L sublethal concentrations (ecologically relevant concentrations) of chlorpyrifos for 15, 30 and 60 days. The gills of the CPF exposed fish showed partially affected secondary lamellae with shortening and curling, increased inter-lamellar space, sloughed off epithelium, hyperplasia and necrosis of pavement cells. On 60 days exposure, more pronounced degenerative changes, including severe necrosis, hyperplasia and hypertrophy of pavement cells, eroded and uplifted lamellar epithelium were noticed. Ultrastructural alterations include distorted nucleus and mitochondria in pavement cells, marked contraction in cisternae of golgi complex. Particularly in chloride cells, abundant mitochondria with distorted shape and size, dilation in between their cristae and tubular network were observed. The severity of damage was more profound at 60 days exposure. Thus, the observed cytopathological lesions of fish gills can be used as sensitive biomarkers for pesticide contamination.     

Effects of Fertilizer-Urea on Growth,Photosynthetic Activity and Microcystins Production of Microcystis aeruginosa Isolated from Dianchi Lake

Urea is the most frequently applied nitrogen (N) fertilizer in agriculture, while its loss is assumed triggering algal blooms in adjacent water bodies. In this context the present study assessed the growth, photosynthetic activity as well as toxin production of Microcystis aeruginosa at different urea concentrations (0.125, 1.25, 12.5, 250 and 2,500 mg/L) using BG11 (containing 250 mg/L NO₃ ^?-N) as control. The results showed for all endpoints that M. aeruginosa is capable of using urea as N source: the two highest urea treatments delivered comparable values like the control. Low urea concentrations (0.125 and 1.25 mg/L), which were comparable to environmental urea levels, did not sustainably promote the growth, photosynthesis and toxin production of the test species. While, in certain microenvironments urea might potentially reach the concentrations that may affect M. aeruginosa.     

Assessing Caffeine as an Emerging Environmental Concern Using Conventional Approaches

Organic wastewater contaminants, including pharmaceuticals, caffeine, and nicotine, have received increased scrutiny because of their detection in water bodies receiving wastewater discharge. Despite recent measurement in United States streams, caffeine’s effect on freshwater organisms is not well documented. The present study measured caffeine’s lethal and sublethal effects on the freshwater species, Ceriodaphnia dubia, Pimephales promelas, and Chironomus dilutus. These organisms, which are used in standard testing or effluent monitoring, were exposed to aqueous caffeine solutions under static exposure for 48 hours and daily renewed static exposure for 7 days. Averaged responses of 48-hour acute end points indicated that C. dubia was more sensitive to caffeine exposures (LC₅₀ = 60 mg/L) than either P. promelas (LC₅₀ = 100 mg/L) or C. dilutus (LC₅₀ = 1,230 mg/L). Exposure-response slopes confirmed these findings (3% mortality/mg/L for C. dubia; 0.5% mortality/mg/L for P. promelas; and 0.07% mortality/mg/L for C. dilutus). Comparative 7-day responses between C. dubia and P. promelas (LC₅₀ = 46 and 55 mg/L, respectively) were more similar than the broad range of acute values. Sublethal effects measured for caffeine exposure included impaired C. dubia reproduction (IC₅₀ = 44 mg/L) and inhibited P. promelas growth (IC₅₀ = 71 mg/L). According to the results of this study, combined with earlier studies reporting environmental concentrations and product half-lives, caffeine should pose negligible risk for most aquatic vertebrate and invertebrate organisms.     

The toxicity of waterborne boron toDaphnia magna andChironomus decorus and the effects of water hardness and sulfate on boron toxicity

The concentrations of many elements, including boron, are increasing in aquatic ecosystems due to anthropogenic activities. Laboratory studies were undertaken to evaluate the toxicity of waterborne boron to two key fresh water macroinvertebrates and to evaluate the effects of water hardness and sulfate on boron toxicity. Acute toxicity evaluations of waterborne sodium tetraborate resulted in 48 h. LC₅₀ values of 141 and 1376 mg B/L for neonateDaphnia magna and fourth instarChironomus decorus, respectively. Chronic sublethal studies demonstrated a significant decrease inC. decorus growth rate at 20 mg B/L. Further studies showed that increasing water hardness (10.6 to 170 mg/L as CaCO₃) and sulfate (10.2 to 325.4 mg SO₄ ^–1/L) concentrations did not affect boron toxicity toD. magna. These results, in conjunction with a review of the literature, suggest that aquatic macrophytes may be more sensitive to boron than macroinvertebrates and thus would be better choices for aquatic risk assessment evaluations for this element.     

Acute Toxicity of Copper,Zinc, and Ammonia to Larvae (Glochidia) of a Native Freshwater Mussel Echyridella menziesii in New Zealand

Adult New Zealand freshwater mussel Echyridella menziesii were collected from three locations in the North Island of New Zealand. In a series of tests that followed standard test guidance, glochidia were exposed to either dissolved copper (Cu), zinc (Zn), or total ammonia nitrogen (TAN) for 6, 24, or 48 h (20 °C, pH 7.8, water hardness 30 mg L^?1 as CaCO₃, dissolved organic carbon [DOC] 2.0–2.9 mg L^?1). Of the three contaminants and tests that met control survival criteria, mussel larvae (glochidia) were most sensitive to Cu exposure (48-h EC₅₀ = 1.7–3.4 μg L^?1, 48-h no observed effect concentrations (NOEC) of 1.3–2.6 μg L^?1). The Zn 48-h EC₅₀ concentrations were 229–337 μg L^?1 and the 48-h NOEC values were 128–240 μg L^?1. Compared with other native New Zealand species, glochidia were also relatively sensitive to TAN exposure (48-h EC₅₀ 12–15 mg TAN L^?1 [pH 7.8], 48-h NOEC 8–10 mg TAN L^?1). Comparison of our data with those of previous studies on North American freshwater mussels indicates that (1) E. menziesii are among those aquatic species most sensitive to acute Cu or TAN exposure; and (2) E. menziesii juveniles would not be adequately protected by current ANZECC water quality guidelines for TAN or Cu. Inclusion of North American juvenile mussel data in a revision of the current ANZECC water-quality guideline (95th percentile) for chronic ammonia exposure results in a decrease from 0.9 mg to 0.2 mg TAN L^?1 (pH 8).     

Mercury Toxicity to Freshwater Organisms: Extrapolation Using Species Sensitivity Distribution

Mercury toxicity to aquatic organisms was evaluated in different taxonomic groups showing the following species sensitivity gradient: Daphnia magna > Daphnia longispina > Pseudokirchneriella subcapitata > Chlorella vulgaris > Lemna minor > Chironomus riparius. Toxicity values ranged from 3.49 μg/L (48 h-EC₅₀ of D. magna) to 1.58 mg/L (48 h-EC₅₀ of C. riparius). A species sensitivity distribution was used to estimate hazardous mercury concentration at 5 % level (HC5) and the predicted no effect concentration (PNEC). The HC5 was 3.18 μg Hg/L and the PNEC varied between 0.636 and 3.18 μg Hg/L, suggesting no risk of acute toxicity to algae, plants, crustaceans and insects in most freshwaters.     

Sublethal Zinc and Copper Exposure Affect Acetylcholinesterase Activity and Accumulation in Different Tissues of Leporinus obtusidens

In this study, we investigated zinc and copper effects on acetylcholinesterase (AChE, EC. 3.1.1.7) activity and metal accumulation in tissues of native fish Leporinus obtusidens (piava). Fish were exposed to 10 and 20 % of the LC₅₀ that corresponded at 2.28 and 4.57 mg/L (zinc) and 0.018 and 0.038 mg/L (copper) for 30 and 45 days. The AChE activity was evaluated in brain and white muscle of fish and metals accumulation was measured in kidney, liver, muscle and brain. Exposure to zinc and copper significantly increased AChE activity in both tissues and times tested, except for brain AChE activity at 2.28 mg/L of Zn (II) after 45 days where a reduction of 52.5 % was observed. Fish exposed to zinc showed accumulation of this metal in liver and kidney in both concentrations and times tested. A different result was obtained for copper: significant copper accumulation was obtained only in brain at both concentrations tested after 45 days of exposure. These results suggest that piavas exposed to zinc and copper showed changes in AChE activity and also demonstrate accumulation in some tissues. These results demonstrate that L. obtusidens could be a good bioindicator to evaluate water containing metals. The metal accumulation absence in muscle tissue is an indicative of low potential contamination by metals in this fish species.     

Endosulfan Effects on Rana dalmatina Tadpoles: Quantitative Developmental and Behavioural Analysis

Endosulfan is an organochlorine pesticide that was recently labeled as a persistent organic pollutant, but it is still widely employed, particularly in developing countries. The goal of this study is to evaluate the acute (LC₅₀) and chronic effects (developmental and behavioural traits) of this insecticide on Rana dalmatina tadpoles after exposure to ecologically relevant concentrations (0.005, 0.01, and 0.05 mg/L) by applying video-tracking techniques to evaluate the quantitative effect of endosulfan on amphibian behavioural patterns. The 96 h LC₅₀ value was 0.074 mg endosulfan/L. Tadpoles chronically exposed to 0.01 and 0.05 mg endosulfan/L underwent high mortality rate, decreased larval growth, delayed development, and increased incidence of malformations, and they did not reach metamorphosis by the end of the experiment. Moreover, tadpoles exposed to these concentrations exhibited several abnormalities in swimming patterns, such as shorter distance moved, swirling, resting, and unusual use of space. The exposure to 0.005 mg endosulfan/L did not cause any significant effects on behaviour, larval growth, or development, but we observed a significant decrease in both survival and time to metamorphosis. We showed that developmental abnormalities are dose-dependent and that the pesticide effects could differ depending on the endosulfan concentration and the species tested. We also validated the hypothesis that behavioural analysis, along with the use of new analytical methods, could be a useful tool in amphibian ecotoxicological studies.     

Kinetics of Deposition,Acute Toxicity and Bioaccumulation of Copper in some Freshwater Organisms

Experiments with environmentally relevant concentrations of Cu in glass aquaria revealed that Cu was quickly removed from water. Cubic regression of Cu concentration against time showed that maximum rate of removal was around 69.34–72.11 h irrespective of treatment. The 96 h LC₅₀ value of Cu was respectively 0.18, 0.19 and 0.35 mg/L for fish Cyprinus carpio, crustacean Diaptomus forbesi and worm Branchiura sowerbyi. Normalizing the lethal values and plotting them against time it was observed that there was sharp differences in mortality over time between the organisms and 96 h lethal values could misrepresent susceptibility of the organisms to Cu. Treatment of 0.1 mg/L of Cu in water resulted in accumulation of 10.57, 4.38, 1.46 and 2.44 µg/g of Cu, respectively in sediment, worm, crustacean zooplankton and whole body of fish. But, Cu deposited in high concentrations in gut and liver of fish indicating that Cu was principally accumulated through food.     

Toxicity of Diclofenac in the Fern <Emphasis Type="Italic">Azolla filiculoides</Emphasis> and the Lichen <Emphasis Type="Italic">Xanthoria parietina</Emphasis>

This study investigated the occurrence of toxicity, expressed as damage to the photosynthetic apparatus, in the aquatic fern Azolla filiculoides and the lichen Xanthoria parietina following treatments with diclofenac at different concentrations (0.1, 1, 10 and 100 mg/L) and different exposure times (24, 48, 72 and 240 h). Measurements of photosynthetic efficiency, chlorophyll content and chlorophyll degradation indicated dose- and time-dependent toxicity, since significant differences with control samples as well as among treatments, emerged mainly for the highest concentration (100 mg/L) and the longest time (240 h). In addition, also the mycobiont of the lichen X. parietina showed similar toxic effects, expressed as ergosterol content. The absence of relevant alterations at the lowest concentration (0.1 mg/L) suggested a very limited susceptibility of these species to environmentally relevant levels of this pharmaceutical.     

A Pilot Evaluation of the Toxicity of EarthTec® QZ on Invasive (<Emphasis Type="Italic">Bithynia tentaculata</Emphasis>) and Native (<Emphasis Type="Italic">Physa gyrina</Emphasis>) Snail Species from the Upper Mississippi River

We used a comparative approach to investigate the effects of a copper-based pesticide (EarthTec® QZ) on embryos of an invasive snail (Bithynia tentaculata) and a native snail (Physa gyrina). Embryos were exposed to one of three treatments: control (0 mg/L Cu²⁺), low-dose (0.1 mg/L Cu²⁺), or high-dose (0.6 mg/L Cu²⁺), which reflect manufacturer-recommended low and medium 4-day molluscicide treatment concentrations. Exposure to 0.6 mg/L Cu²⁺ over 4 days generated 100% mortality in both invasive and native snail embryos; however, reducing the exposure time from 4 to 1 day resulted in 100% mortality in B. tentaculata but some hatching (7%) in P. gyrina. In contrast, embryos of both species exposed to 0.1 mg/L Cu²⁺ treatment for 4 days showed almost 100% survivorship. Further manipulations of Cu²⁺ concentrations and exposure times may yield regimes that maximize mortality in B. tentaculata while minimizing negative impacts on native species.     

Effects of Exposure to Cadmium on Some Endocrine Parameters in Tilapia, Oreochromis niloticus

The cadmium impact on interrenal and thyroid functions was assessed in tilapia, Oreochromis niloticus. Fish were exposed to 25 mg L^?1 of CdCl₂ during 24, 48, and 96 h. Exposure to 24 and 48 h induced a significant increase in plasma cortisol levels, whereas at 96 h no differences were found. A significant and sustained decrease in plasma T3 concentrations, and an over time increase in plasma glucose, was also found in exposed fish. The results of the current study show that acute exposures to sublethal cadmium concentrations induce changes in endocrine status and carbohydrate metabolism in O. niloticus.