Determination of wastewater LC50 of the different process stages of the textile industry

Textile plants are very important sources of toxic discharges. The purpose of the research described in this paper was to use bioassays with daphnids to determine the LC50 values of textile wastewater samples taken from different stages of the finishing textile industry. Toxicity due to dyeing, chlorination, and the absence of adequate physicochemical conditions for daphnid survival were considered. Wastewater samples corresponding to each process stage were collected at five finishing textile industries and assayed according to previously published procedures. The sensitivity of daphnids to chemicals was assayed using sodium dodecyl sulfate and was similar to other reports (14.6+/-6.8 vs 14.5+/-2.3 mg/L). All effluents from the five company samples were toxic in terms of LC50 and exhibited very high toxicity with acute toxicity unit (ATU) levels between 2.2 and 960, indicating that the five textile industries produced toxic water. The sensory characteristics indicated that the dyes contributed to overall sample toxicity at all process stages. The most toxic contaminant seemed to be ClO- at levels between 0.2 and 6.8 mg/L, suggesting that further research is needed on the economic costs of stage-by-stage and total effluent treatments.     

Coagulant toxicity and effectiveness in a slaughterhouse wastewater treatment plant

Attempts were made in this study to examine the toxicity of polymer/alum addition to the aeration tank effluent prior to sludge flotation as practiced in a slaughterhouse wastewater treatment plant. Based on the Microtox toxicity assay, alum at concentrations 100-200 mg/L was found to slightly increase the toxicity level of slaughterhouse wastewater effluent. However, at higher concentrations (300-1000 mg/L), significant residual chronic toxicity remained in all slaughterhouse wastewater effluents, independent of the treatment process. Polymer, on the other hand, removed organics and solids, but polymer effluents are more toxic than alum at extremely low concentration. Results indicated that alum and polymer caused inhibitory effects to the system at soluble concentrations of approximately 400 and 60 mg/L and above, respectively. The data also indicated that the solids collected in both tests (polymer/alum) were much more toxic than those from the effluents. Sediment samples from the polymer tests were the most toxic. Furthermore, the effluent toxicity of the coagulants was dramatically more significant when used after the settlement of solids than when used in mixed liquor. In addition, strong correlations were observed between the observed toxicity for a series of supernatants and the coagulant concentrations of alum/polymer processes, and between supernatants and solids collected in both tests.     

Effects of Tetrachloroethylene on the Viability and Development of Embryos of the Japanese Medaka, Oryzias latipes

We evaluated the acute toxicity of Tetrachloroethylene (C₂Cl₄), and investigated its sub-chronic effects on the embryonic development of Japanese medaka (Oryzias latipes). One-day-old eggs/embryos of this fish species were exposed, under static renewal conditions, to serial concentrations (0, 20, 40, 60, and 80 mg/L) of C₂Cl₄ for 96 h (acute) and 10 days (sub-chronic) time periods. The toxic endpoints evaluated included: egg/embryo viability, hatchability, and morphological/developmental abnormalities. The acute toxicity test resulted in a 96 h-LC₅₀ of 27.0 (19.5–32.9) mg/L for egg viability. Exposure of eggs to sub-chronic concentrations (0, 1.5, 3, 6, 12, and 25 mg/L) of C₂Cl₄ significantly reduced hatchability and larval survival, in a concentration dependent manner. At the highest tested concentration (25 mg/L) of the sub-lethal exposure, larval survival was greatly reduced to within three days post-hatch. The lowest tested concentration (1.5 mg/L) produced a significant number of developmental effects to the Japanese medaka, including abnormal development of the circulatory system, yolk-sac edema, pericardial edema, scoliosis, hemorrhaging, blood pooling, and defects in heart morphology. The severity of these abnormalities was concentration-dependent. It can be concluded from these results that tetrachloroethylene is teratogenic to the Japanese medaka. Received: 20 February 2001/Accepted: 21 December 2001     

Influence of Dissolved Organic Matter on Acute Toxicity of Zinc to Larval Fathead Minnows (Pimephales promelas)

We conducted laboratory toxicity tests in support of the development of a biotic ligand model (BLM) to predict acute toxicity of zinc (Zn) to fathead minnows (Pimephales promelas). To test the effect of dissolved organic matter (DOM) on Zn toxicity, we exposed larval fathead minnows to Zn in water containing elevated concentrations of dissolved organic carbon (DOC) in 96-h static-renewal toxicity tests. We tested DOM isolated from four surface waters: Cypress Swamp, Delaware; Edisto River, South Carolina; Suwannee River, Georgia; and Wilmington, Delaware, wastewater treatment effluent. The DOM isolates from the Edisto River and Wilmington wastewater treatment effluent contained elevated concentrations of NaCl (20–110× control NaCl) due to the use of a Na⁺-exchange resin to remove Ca²⁺ and Mg²⁺ during the DOM isolation process. Therefore, we also performed Zn toxicity tests in which we added up to 20 mM NaCl to exposure solutions containing Cypress Swamp and Suwannee River DOM. A threshold concentration of 11 mg DOC/L was needed to decrease Zn toxicity, after which the 96 h Zn LC50 was positively correlated with DOC concentration. Elevated NaCl concentrations did not alter Zn toxicity in the presence of DOM. In conjunction with data from other studies with fish and invertebrates, results of this study were used to calibrate Version 2.1.1 of the Zn BLM. BLM-predicted LC50s for our exposure waters containing elevated DOM concentrations were within the range of acceptable deviation relative to the observed LC50s (i.e., 0.5–2× observed LC50s); however, BLM-predicted LC50s for our exposure waters containing < 1 mg DOC/L were 2–3× lower than the observed LC50s (i.e., the BLM over-predicted the toxicity). Therefore, the current composite-species BLM for Zn could be improved for fathead minnows if that species were modeled separately from the other species used to calibrate Version 2.1.1.     

Toxicity of Select Beta Adrenergic Receptor-Blocking Pharmaceuticals (B-Blockers) on Aquatic Organisms

One class of pharmaceutical compounds identified in U.S. and European waters are the B-adrenergic receptor blocking compounds (B-blockers). However, little information is available on the potential aquatic toxicity of these compounds. Therefore, Hyalella azteca, Daphnia magna, Ceriodaphnia dubia, and Oryias latipes (Japanese medaka) were exposed to metoprolol, nadolol, and propranolol to determine potential toxicity. Average 48-h LC₅₀ for propranolol to H. azteca was 29.8 mg/L. The no-observed-effects concentration (NOEC) and lowest-observed-effects concentration (LOEC) for propranolol affecting reproduction of H. azteca were 0.001 and 0.1 mg/L, respectively. The average propranolol and metoprolol 48-h LC₅₀s for D. magna were 1.6 and 63.9 mg/L, respectively. C. dubia 48-h LC₅₀s were 0.85 and 8.8 mg/L for propranolol and metoprolol, respectively. The NOEC and LOEC of propranolol affecting reproduction in C. dubia were 0.125 and 0.25 mg/L, respectively. In O. latipes, the propranolol 48-h LC₅₀ was 24.3 mg/L. Medaka growth was decreased at 0.5 mg/L propranolol. A 2-week medaka reproductive study indicated significant changes in plasma steroid levels; however, no changes in the average number of eggs produced or number of viable eggs which hatched was observed. In a 4-week follow-up propranolol exposure, the total number of eggs produced by medaka and the number of viable eggs that hatched were decreased at concentrations as low as 0.5 μg/L. Based on this study and the expected aqueous environmental exposure levels, adverse effects of propranolol to invertebrate populations is unlikely; however, further reproductive studies are need to elucidate the risk to teleosts. Received: 14 August 2001/Accepted: 4 March 2002     

Wastewater treatment polymers identified as the toxic component of a diamond mine effluent

The Ekati Diamond Mine, located approximately 300 km northeast of Yellowknife in Canada's Northwest Territories, uses mechanical crushing and washing processes to extract diamonds from kimberlite ore. The processing plant's effluent contains kimberlite ore particles (< or =0.5 mm), wastewater, and two wastewater treatment polymers, a cationic polydiallydimethylammonium chloride (DADMAC) polymer and an anionic sodium acrylate polyacrylamide (PAM) polymer. A series of acute (48-h) and chronic (7-d) toxicity tests determined the processed kimberlite effluent (PKE) was chronically, but not acutely, toxic to Ceriodaphnia dubia. Reproduction of C. dubia was inhibited significantly at concentrations as low as 12.5% PKE. Toxicity identification evaluations (TIE) were initiated to identify the toxic component of PKE. Ethylenediaminetetraacetic acid (EDTA), sodium thiosulfate, aeration, and solid phase extraction with C-18 manipulations failed to reduce PKE toxicity. Toxicity was reduced significantly by pH adjustments to pH 3 or 11 followed by filtration. Toxicity testing with C. dubia determined that the cationic DADMAC polymer had a 48-h median lethal concentration (LC50) of 0.32 mg/L and 7-d median effective concentration (EC50) of 0.014 mg/L. The anionic PAM polymer had a 48-h LC50 of 218 mg/L. A weight-of-evidence approach, using the data obtained from the TIE, the polymer toxicity experiments, the estimated concentration of the cationic polymer in the kimberlite effluent, and the behavior of kimberlite minerals in pH-adjusted solutions provided sufficient evidence to identify the cationic DADMAC polymer as the toxic component of the diamond mine PKE.     

Stage-dependent differences in effects of carbaryl on population growth rate in Japanese medaka (Oryzias latipes)

Fish embryo toxicology is important because embryos are considered more susceptible than adult fish to the effects of toxic chemicals. Recently, fish embryo bioassay was proposed to replace the conventional fish acute toxicity chemical test of the Organization for Economic Cooperation and Development guidelines because it offers the advantages of fewer reagents, easy handling, and efficient data production. To accelerate the establishment of a chemical toxicity database for the protection of environmental and human health, we need to determine whether the conventional toxicity test can safely be replaced by such fish embryo toxicity tests. For instance, it is unclear how the presence of the chorion moderates the toxic effects of some chemicals. If such chemical toxicities do differ between embryos and, for example, the larval stage, then different toxic effects should appear in later life. We tested the later-life effects of the neurotoxic insecticide carbaryl at sublethal concentrations (0 [control] and 5 and 10 mg/L) in embryos and posthatch larvae of the freshwater fish medaka, Oryzias latipes. Although embryos exposed until hatching showed multiple developmental malformations and reductions in subsequent survival rates over three months, no significant reduction was observed in tolerance to starvation for 7 d and in intrinsic population growth rate (r). Exposure of larvae for 96 h resulted in dose-responsive vertebral fracture, significant reduction in tolerance to starvation for 7 d, and reduced three-month survival rate; r was reduced significantly and consistently. These results suggested that posthatch larvae were more susceptible than embryos to carbaryl exposure and that the toxic cascades may differ between larvae and embryos. The influences of carbaryl exposure on population growth rate differed significantly with developmental stage.     

Toxicity of laundry detergent components to a freshwater cladoceran and their contribution to detergent toxicity

The toxicity of 39 laundry detergent components including surfactants, enzymes, builders, fabric brighteners, fillers, and coloring agents to the cladoceran Ceriodaphnia cf. dubia was determined. The difference between the most and the least toxic components was approximately 17,000-fold and 1,000,000-fold for the mg/L and mmol/L EC50 data, respectively. Two of the components had high toxicity (EC50 values < 1 mg/L), 11 moderate toxicity (EC50 values between 1 and 10 mg/L), and the remaining 26 components had low toxicity (EC50 values > 10 mg/L). Analysis revealed that mixtures of the components interacted antagonistically, additively, and synergistically. On a molarity basis the most toxic group of compounds was the surfactants followed by the brighteners. The most toxic individual components included sodium carboxymethyl cellulose, sodium silicate solution, four brighteners, sodium perborate tetrahydrate, and the surfactants. Many of the most toxic components, however, contributed very little to the toxicity of the detergents due to being present in the detergents at low concentrations. The main contributors to the toxicity of detergents were the sodium silicate solution and the surfactants-with the remainder of the components contributing very little to detergent toxicity. The potential for acute aquatic toxic effects due to the release of secondary or tertiary sewage effluents containing the breakdown products of laundry detergents may frequently be low. However, untreated or primary treated effluents containing detergents may pose a problem. Chronic and/or other sublethal effects that were not examined in this study may also pose a problem.     

Acute and long-term effects of nine chemicals on the Japanese medaka (Oryzias latipes)

Ninety-six-hour acute and 28-day larval survival and growth tests were conducted with nine organic chemicals, using the Japanese medaka (Oryzias latipes) as the test organism. The nine tested chemicals were allyl isothiocyanate, aniline, benzyl acetate, 4-chloroaniline, 2-chloroethanol, 2,4-diaminotoluene, 1,2-dibromoethane, 2,4-dichlorophenoxyacetic acid (2,4-D), and phenol. The derived 96-h LC50 values for medaka for all chemicals ranged from 0.077 mg/L for allyl isothiocyanate to 2,780 mg/L for 2,4-D. The chronic values for six of the nine chemicals tested ranged from 0.013 mg/L for allyl isothiocyanate to 42.5 mg/L for 2,4-D. Acute-to-chronic ratios for these six chemicals ranged from 1.4 for 2-chloroethanol to 70.9 for 2,4-D. Growth of medaka was significantly reduced in the lowest exposure concentration during 28-day larval tests with aniline, 4-chloroaniline, and 2,4-diaminotoluene. The estimated maximum acceptable toxicant concentration was reported as less than the lowest exposure concentration of 4.6, 2.2 and 40.3 mg/L for tests with aniline, 4-chloroaniline and 2,4-diaminotoluene, respectively. Chronic values for 2-chloroethanol and medaka were 12.6 mg/L during an embryo-larval test and 22.1 mg/L during the 28-day larval test.     

Evaluation of Corophium orientale as bioindicator for Venice Lagoon: sensitivity assessment and toxicity-score proposal

The 96-h water-only exposure and 10-d sediment toxicity tests with the amphipod Corophium orientale were performed in order to enhance the knowledge about its overall sensitivity and its applicability to Venice Lagoon sediments. The values obtained with cadmium as reference toxicant demonstrated a certain variability of the LC(50); the higher value was found in spring and the lower in late summer. Tests with other pure chemicals (Ni, Total Ammonia, Sodium Dodecyl-Sulphate) showed good discriminatory power; the toxicity gradient observed was: Cd (LC(50) of 3.3 mg/L)>SDS (LC(50) of 8.7 mg/L)>total ammonia (LC(50) of 126mg/L)>Ni (LC(50) of 352 mg/L). Sediment toxicity test results were used to obtain information on non-treatment factors (grain-size, TOC content) that could act as confounding factors, and to develop a site-specific toxicity-score based on minimum significant difference approach. Confounding factors seem not to affect test results. The procedure to develop the toxicity score took into account the relatively lower sensitivity of C. orientale with respect to other amphipods commonly used in toxicity tests (Ampelisca abdita and Rhepoxynius abronius).     

Toxicity of Cadmium-Contaminated Clay to the Zebrafish Danio rerio

In this study, the toxicity of cadmium-contaminated clay to the zebrafish Danio rerio was evaluated. Kaolin clay was spiked with CdCl₂ (1.28 mg Cd/g clay) and adult zebrafish were exposed to 0, 500, 1,000, and 2,000 mg/L Cd-contaminated clay in a continuous recirculation system. Cumulative mortality was evaluated as a function of exposure time, and LT50 values were calculated. Results of acute toxicity tests showed that an exposure to 1,000 mg/L Cd-contaminated clay resulted in LT50 values of 12 and 92 h (n = 2 experiments) and in a LT50 value of 22 h in both experiments with 2,000 mg/L Cd-contaminated clay. Positive control experiments with corresponding measured dissolved Cd concentrations were performed to evaluate by comparison the toxicity of the clay-bound Cd. These control experiments gave LT50 values higher than 144 h for both conditions. Moreover, no toxicity (LT50 > 144 h) of 2,000 mg/L uncontaminated clay was observed. This study showed that cadmium present on clay particles can be bioavailable and exert a toxic effect to the zebrafish D. rerio. Received: 26 January 1999/Accepted: 12 July 1999     

The short-term toxicity of some feed additives to different freshwater organisms

Summary The short-term toxicity (EC₅₀ respectively LC₅₀ after 2 or 4 days) of 13 feed additives was determined to 4 freshwater organisms of different trophical levels: Chlorella pyrenoidosa, Daphnia magna, Lebistes reticulatus and Salmo gairdneri. The most toxic (LC(EC)₅₀ < 1 mg/1) were robenidine (to all tested organisms) and stenorol (to Daphnia); moderately toxic (1 < LC(EC)₅₀ < 10 mg/1) was pyrimethamine. Amprolium, ethopabate, furazolidone and zoalene proved to be little toxic (LC (EC)₅₀ > 10 mg/1); whereas buquinolate, carbadox, clopidol, decoquinate, grofas and sulfaquinoxaline were under the experimental conditions not toxic for the tested organisms.     

Ecotoxicological characterization of industrial wastewater--sulfite pulp mill with bleaching

Different process wastewaters from a sulfite pulp mill with bleaching were characterized by chemical analysis and toxicity tests. The amount of adsorbable organically bound halogen (AOX) from the bleachery was 3.6 kg per ton pulp. The extractable organically bound chlorine was 15% of AOX. Some identified organochlorine compounds in the effluent could be traced in the receiving water. Effluents from the chlorination and alkaline extraction stages and the condensate were the main contributors to the effluent toxicity. The effluents were particularly toxic to the alga Skeletonema costatum. The EC50 value for growth of the alga was 24-29 ml/liter of the total effluent. The toxicity cannot be ascribed to single chemical components in the effluents. Degradation of toxic components occurs after dilution of the effluents in the receiving water. The toxicity may be reduced to 30-50% of the initial toxicity within 1 week. Predictions of toxic effects in the receiving water, based on results of toxicity tests and estimated dilution, indicate that large areas are affected by the discharges. Som observations of the distribution of organisms in the receiving water indicate that predictions from the toxicity tests may be valid.     

Acute toxicity of ammonia (NH3-N) in sewage effluent to Chironomus riparius: II. Using a generalized linear model

Toxicity of un-ionized ammonia (NH₃-N) to the midge, Chironomus riparius was compared, using laboratory culture (well) water and sewage effluent (0.4 mg/L NH₃-N) in two 96-h, static-renewal toxicity experiments. A generalized linear model was used for data analysis. For the first and second experiments, respectively, LC₅₀ values were 9.4 mg/L (Test 1A) and 6.6 mg/L (Test 2A) for ammonia in well water, and 7.8 mg/L (Test 1B) and 4.1 mg/L (Test 2B) for ammonia in sewage effluent. Slopes of dose-response curves for Tests 1A and 2A were equal, but mortality occurred at lower NH₃-N concentrations in Test 2A (unequal intercepts). Response of C. riparius to NH₃ in effluent was not consistent; dose-response curves for tests 1B and 2B differed in slope and intercept. Nevertheless, C. riparius was more sensitive to ammonia in effluent than in well water in both experiments, indicating a synergistic effect of ammonia in sewage effluent. These results demonstrate the advantages of analyzing the organisms entire range of response, as opposed to generating LC₅₀ values, which represent only one point on the dose-response curve.     

A 48-h larval development toxicity test using the marine polychaete Galeolaria caespitosa Lamarck (Fam. Serpulidae)

Assessing the risk of effluents and other anthropogenic inputs to the receiving environment is ultimately best done on a site-specific basis, which often requires toxicity tests using organisms relevant to that environment. Additionally, the test species or life stage needs to be available for a reasonable portion of the year to allow temporal fluctuations to be assessed. A 48-h larval development toxicity test using the marine polychaete Galeolaria caespitosa was developed. This test was developed as G. caespitosa releases viable gametes year-round, and the test species is environmentally relevant to the marine system receiving the liquid effluent being evaluated. Toxicity tests were conducted using G. caespitosa from different locations and evaluating the gamete response to copper. All population responses were comparable, with EC50 values ranging from 16 to 40 μg/L copper (as CuCl₂· 2H₂O). Toxicity tests were also conducted using G. caespitosa gametes with an effluent produced by a lead smelting operation. The response of the G. caespitosa test with this effluent was compared with three other test methods using two microalgal species, Isochrysis sp. and Nitzschia closterium, and gametes from the mussel Mytilus edulis. The G. caespitosa larval development toxicity test was the most sensitive test to the effluent, with EC50 values ranging from 1–23% effluent, while it ranked second in sensitivity to copper. This test could be applied to other common serpulids worldwide. Received: 31 May 2000/Accepted: 20 November 2000     

Developmental Effects of Urban Storm Water in Medaka (Oryzias latipes) and Inland Silverside (Menidia beryllina)

Stormwater runoff in a coastal urban area (San Diego County, CA) produced significant toxicity to early life stages of medaka (Oryzias latipes) and Menidia (M. beryllina). Exposure of embryos to lower concentrations (5 to 25%) increased the incidence of abnormal swim bladder inflation and other teratogenic responses, whereas higher concentrations resulted in mortality or failure to hatch. Comparisons of EC50s for mortality and failure to hatch with concentrations of individual chemical pollutants (including Cd, Cr, Cu, Pb, Ni, and Zn) revealed low correlations; however, the correlation with total metals was high (−0.84) and corresponded with sample exceedences of Water Quality Criteria (WQC) for Cd, Cu, Pb, and Zn. This strong association between developmental toxicity and toxic metal content of storm water compared favorably with developmental anomalies reported in other studies. Analytical chemistry data for pesticides that may have been in these samples were limited to selected pesticides found usually below detection limits. Greater toxicity of the watershed effluents sampled was generally associated with more developed land surface and less open space. Both medaka and Menidia were found to be useful for studying effects of stormwater on embryonic and early larval development. Received: 20 August 1998/Accepted: 14 March 1999     

Acute Toxicity and Risk Assessment of Florfenicol for Nile Tilapia Larvae

The aim of this study was to determine the median lethal concentration (LC_50−96h), effective concentration (EC_50−96h), risk assessment, and development of Nile tilapia Oreochromis niloticus larvae submitted to florfenicol (FF) exposure. Fish (n = 147; 8.6 ± 0.6 mg; 7 fish/aquarium) were randomly distributed in 21 aquaria (1 L) and exposed to five concentrations of FF 58.73; 131.31; 198.96; 241.88 and 381.81 mg L⁻¹ plus one control and a control with solvent, totalizing seven treatments and three replicates. The estimated median LC_50−96h of FF for Nile tilapia larvae was 349.94 mg L⁻¹. The EC_50−96h of FF was 500 mg L⁻¹ for weight reduction and was 1040 mg L⁻¹ for length reduction. After the exposure period, final weight and length differed (p < 0.05) among treatments, showing the lowest biometric values ​​with the highest concentrations of FF. The pH and dissolved oxygen were altered (p < 0.05) during the experimental period. The FF high doses used to determine the LC 50 after 96 h negatively affected the development of the larvae. On the other hand, through risk assessment analysis this antibiotic can be classified as low toxicity to Nile tilapia larvae and show low environmental risk.

     

Distribution of nanoparticles in the see-through medaka (Oryzias latipes)

OBJECTIVE: Because the environmental fate of manufactured nanoparticles is considered an emerging environmental concern, I used water-suspended fluorescent nanoparticles (solid latex solution) to investigate the distribution of nanoparticles in the eggs and bodies of see-through medaka (Oryzias latipes). RESULTS: Particles 39.4-42,000 nm in diameter were adsorbed to the chorion of medaka eggs and accumulated in the oil droplets; 474-nm particles had the highest bioavailability to eggs. Particles 39.4 nm in diameter shifted into the yolk and gallbladder during embryonic development. Adult medaka accumulated 39.4-nm nanoparticles mainly in the gills and intestine when exposed to a 10-mg/L nanoparticle solution. Nanoparticles were also detected in the brain, testis, liver, and blood. Concentrations of nanoparticles in the blood of male and female medaka were 16.5 and 10.5 ng/mg blood protein, respectively. These results suggest that nanoparticles are capable of penetrating the blood-brain barrier and that they eventually reach the brain. Salinity-dependent acute toxicity was observed in medaka eggs exposed for 24 hr to nanoparticles. CONCLUSION: The bioavailability and toxicity of nanoparticles depend on environmental factors and multiple physicochemical properties. Further studies on the toxic effects of nanoparticles used in commercial products and their environmental relevance, are necessary to define the risks and benefit of nanomaterial applications.     

Acute Toxicity of Sodium Metabisulphite in Larvae and Post-Larvae of the Land Crab, <Emphasis Type="Italic">Cardisoma guanhumi</Emphasis>

Sodium metabisulphite (SMB) is used in marine shrimp aquaculture to prevent the occurrence of black spot. The release SMB into the estuarine environment from shrimp farm pond effluents has been reported. This study evaluated the susceptibility of larvae and post-larvae of land crab, Cardisoma guanhumi to this salt. A decrease in dissolved oxygen and pH occurred with increasing concentration of SMB and exposure time. LC₅₀ values after 48 h of exposure were 34 ± 1.1 mg/L, 31.1 ± 1.9 mg/L, and 30.6 ± 0.5 mg/L for I zoea larvae, megalopa larvae and stage I juveniles, respectively.