Ning Wang

Effect concentrations of ammonia, nickel, sodium chloride, and potassium chloride from short-term 7-day tests were compared to those from standard chronic 28-day toxicity tests with juvenile mussels (fatmucket, Lampsilis siliquoidea) to evaluate the sensitivities of the 7-day tests. The effect concentrations for nickel (59 µg Ni/L), chloride (316–519 mg Cl/L, a range from multiple tests), and potassium (15 mg K/L) obtained from the 7-day tests were within a range of effect concentrations for each corresponding chemical in the 28-day tests (41–91 µg Ni/L, 251–>676 mg Cl/L, 15–23 mg K/L), whereas the 7-day ammonia effect concentration (0.40 mg/L total ammonia nitrogen; TAN) was up to 3.3-fold greater than the 28-day effect concentrations (0.12–0.36 mg TAN/L) but with overlapped 95% confidence limits. These results indicate that the 7-day tests produced similar estimates compared to the 28-day tests. Further studies are needed to evaluate the 7-day test sensitivity using additional chemicals with different modes of toxic action. Environ Toxicol Chem 2024;43:2020–2025. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

The ASTM International standard test method for freshwater mussels (E2455‐13) recommends 4‐week toxicity testing with juveniles to evaluate chronic effects on survival and growth. However, concerns remain that the method may not adequately address the sensitivity of mussels to longer term exposures (>4 weeks), particularly in relation to potential reproductive impairments. No standard method directly evaluates toxicant effects on mussel reproduction. The objectives of the present study were to (1) evaluate toxicity endpoints related to reproduction in fatmucket (Lampsilis siliquoidea) using two common reference toxicants, potassium chloride (KCl) and nickel (Ni); (2) evaluate the survival and growth of juvenile fatmucket in standard 4‐week and longer term (12‐week) KCl and Ni tests following a method refined from the standard method; and (3) compare the sensitivity of the reproductive endpoints with the endpoints obtained from the juvenile mussel tests. Reproductive toxicity tests were conducted by first exposing female fatmucket brooding mature larvae (glochidia) to five test concentrations of KCl and Ni for 6 weeks. Subsamples of the glochidia were then removed from the adults to determine three reproductive endpoints: (1) the viability of brooded glochidia; (2) the viability of free glochidia in a 24‐h exposure to the same toxicant concentrations as their mother; and (3) the success of glochidia parasitism on host fish. Mean viability of brooded glochidia was significantly reduced in the high KCl concentration (26 mg K/L) relative to the control, with a 20% effect concentration (EC20) of 14 mg K/L, but there were no significant differences between the control and any Ni treatment (EC20 > 95 µg Ni/L). The EC20s for viability of free glochidia after the additional 24‐h exposure and parasitism success were similar to the EC20s of brooded glochidia. The EC20s based on the most sensitive biomass endpoint in the 4‐week juvenile tests were 15 mg K/L and 91 µg Ni/L, similar to or greater than the EC20s from the reproductive KCl and Ni tests, respectively. When exposure duration in the juvenile tests was extended from 4 to 12 weeks, the EC20s decreased by more than 50% in the KCl test but by only 8% in the Ni test. Overall, these results indicate that a standard 4‐week test with juvenile mussels can prove effective for estimating effects in chronic exposures with different life stages although a longer term 12‐week exposure with juvenile mussels may reveal higher sensitivity of mussels to some toxicants, such as KCl. Environ Toxicol Chem 2024;43:1097–1111. © 2024 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Elevated concentrations of potassium (K) often occur in effluents from wastewater treatment plants, oil and gas production operations, mineral extraction processes, and other anthropogenic sources. Previous studies have demonstrated that freshwater mussels are highly sensitive to K in acute and chronic exposures, and that acute toxicity of K decreases with increasing water hardness. However, little is known about the influence of hardness on the chronic toxicity of K. The objective of our study was to evaluate the chronic toxicity of K (tested as KCl) to a commonly tested unionid mussel (fatmucket, Lampsilis siliquoidea) at five hardness levels (25, 50, 100, 200, and 300 mg/L as CaCO3) representing most surface waters in the United States. Chronic 28-day K toxicity tests were conducted with 3-week-old juvenile fatmucket in the five hardness waters using an ASTM International standard method. The maximum acceptable toxicant concentrations (geometric mean of the no-observed-effect concentration and the lowest-observed-effect concentration) increased from 15.1 to 69.3 mg K/L for survival and from 15.1 to 35.8 mg K/L for growth (length and dry wt) and biomass when water hardness was increased from 25 mg/L (soft) to 300 mg/L (very hard). These results provide evidence to support water hardness influence on chronic K toxicity to juvenile fatmucket. However, the chronic effect concentrations based on the more sensitive endpoint (growth or biomass) increased only 2.4-fold from the soft water to the very hard water, indicating that water hardness had a limited influence on the chronic toxicity of K to the mussels. These results can be used to establish chronic toxicity thresholds for K across a broad range of water hardness and to derive environmental guideline values for K to protect freshwater mussels and other organisms. Environ Toxicol Chem 2023;42:1085–1093. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

The rapid development of marine fish farming provides high quality protein for human society. The design, construction and performance calculation of large-scale aquaculture equipment provide convenience and safety. Based on CFD and diffraction theory, the motion and load response of the mooring system of the aquaculture vessel under full load in four different sea areas were studied in this paper. The calculation results in frequency domain and time domain show that: The mooring system can meet the environmental load and specification requirements of level 4 sea state; In the frequency range of 0.2rad/s ~ 0.8rad/s, the hydrodynamic response of the mooring system is large.

US Environmental Protection Agency's short-term freshwater effluent test methods include a fish (Pimephales promelas), a cladoceran (Ceriodaphnia dubia), and a green alga (Raphidocelis subcapitata). There is a recognized need for additional taxa to accompany the 3 standard species for effluent testing. An appropriate additional taxon is unionid mussels because mussels are widely distributed, live burrowed in sediment and filter particles from the water column for food, and exhibit high sensitivity to a variety of contaminants. Multiple studies were conducted to develop a relevant and robust short-term test method for mussels. We first evaluated the comparative sensitivity of 2 mussel species (Villosa constricta and Lampsilis siliquoidea) and 2 standard species (P. promelas and C. dubia) using 2 mock effluents prepared by mixing ammonia and 5 metals (cadmium, copper, nickel, lead, and zinc) or a field-collected effluent in 7-d exposures. Both mussel species were equally or more sensitive (>2 fold) to effluents compared to the standard species. Next, we refined the mussel test method by first determining the best feeding rate of a commercial algal mixture for 3 age groups (1-, 2-, and 3-wk old) of L. siliquoidea in a 7-d feeding experiment, and then used the derived optimal feeding rates to assess the sensitivity of the 3 ages of juveniles in a 7-d reference toxicant (NaCl) test. Juvenile mussels grew substantially (30 to 52% length increase) when the 1- or 2-wk-old mussels were fed 2 mL twice daily and the 3-wk-old mussels were fed 3 mL twice daily. 25% inhibition concentrations (IC25s) for NaCl were similar (314 to 520 mg Cl/L) among the 3 age groups, indicating that an age range of 1- to 3-wk-old mussels can be used for a 7-d test. Finally, using the refined test method, we conducted an interlaboratory study among 13 laboratories to evaluate the performance of a 7-d NaCl test with L. siliquoidea. Eleven laboratories successfully completed the test, with >80% control survival and reliable growth data. IC25s ranged from 296 to 1,076 mg Cl/L, with a low (34%) coefficient of variation, indicating that the proposed method for L. siliquoidea has acceptable precision.

Freshwater mussels are one of the most imperiled groups of animals in the world and are among the most sensitive species to a variety of chemicals. However, little is known about the sensitivity of freshwater mussels to wastewater effluents. The objectives of the present study were to (1) assess the toxicity of a permitted effluent, which entered the Deep Fork River (DFR), Oklahoma, USA, to a unionid mussel (Lampsilis siliquoidea) and to 2 standard test species (cladoceran Ceriodaphnia dubia; and fathead minnow Pimephales promelas) in short-term 7-d effluent tests; (2) evaluate the relative sensitivities of the 3 species to potassium (K), an elevated major ion in the effluent, using 7-d toxicity tests with KCl spiked into a DFR upstream reference water; (3) determine the potential influences of background water characteristics on the acute K toxicity to the mussel (96-h exposures) and cladoceran (48-h exposure) in 4 reconstituted waters that mimicked the hardness and ionic composition ranges of the DFR; and (4) determine the potential influence of temperature on acute K toxicity to the mussel. The effluent was found to be toxic to mussels and cladocerans; and it contained elevated concentrations of major cations and anions relative to the upstream DFR reference water. The K concentration in the effluent was 48-fold greater than in the upstream water. Compared to the standard species, the mussel was >4-fold more sensitive to the effluent in the 7-d effluent tests and >8-fold more sensitive to K in the 7-d K toxicity tests. The acute K toxicity to the mussel decreased by a factor of 2 when the water hardness was increased from soft (42 mg/L as CaCO₃) to very hard (314 mg/L as CaCO₃) whereas the acute K toxicity to the cladoceran remained almost the same as hardness increased from 84 to 307 mg/L as CaCO₃. Acute K toxicity to the mussel at 23°C was similar to the toxicity at an elevated temperature of 28°C. The overall results indicate that the 2 standard test species may not represent the sensitivity of the tested mussel to both the effluent and K; and the toxicity of K was influenced by the hardness in test waters, but by a limited magnitude.

The potential for delayed mortality following short-term episodic pollution events was evaluated by exposing cladocerans (Ceriodaphnia dubia) and rainbow trout (Oncorhynchus mykiss) to zinc (Zn) in various 1- to 48-h and 1- to 96-h exposures, respectively, followed by transferring the exposed organisms to clean water for up to 47 h for C. dubia and up to 95 h for trout for additional observation. For C. dubia, 1-h exposures of up to 3790 µg Zn/L never resulted in mortality during the actual Zn exposures, but by 48 h, a 1-h exposure to 114 µg/L, a concentration similar to the present US national water quality acute criterion for the test water conditions, ultimately killed 70% of C. dubia. With C. dubia, the speed of action of Zn toxicity was faster for intermediate concentrations than for the highest concentrations tested. For rainbow trout, pronounced delayed mortalities by 96 h only occurred following ≥8-h exposures. For both species, ultimate mortalities from Zn exposures ≤8 h mostly presented as delayed mortalities, whereas for exposures ≥24 h, almost all ultimate mortalities presented during the actual exposure periods. With Zn, risks of delayed mortality following exposures to all concentrations tested were much greater for the more sensitive, small-bodied invertebrate (C. dubia) than for the less sensitive, larger-bodied fish (rainbow trout). These results, along with previous studies, show that delayed mortality is an important consideration in evaluating risks to aquatic organisms from brief, episodic exposures to some substances. Environ Toxicol Chem 2021;40:2484–2498. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA. Abstract Rainbow trout could withstand extreme Zn pulses of 1 to 3 h, with few subsequent deaths. Few Ceriodaphnia dubia died during 1- to 3-h Zn pulses, but after 48 h, most were dead. Time to effects decreased as expected as rainbow trout were exposed to increasing Zn concentrations. Not so with C. dubia: time to effects was fastest in intermediate Zn exposures, with longer survivals in higher Zn exposures.

The US Environmental Protection Agency (USEPA) is reviewing the protectiveness of the national ambient water quality criteria (WQC) for nickel (Ni) and zinc (Zn) and compiling toxicity databases to update the WQC. An amphipod (Hyalella azteca ) and a unionid mussel (Lampsilis siliquoidea ) have showed high sensitivity to Ni and Zn in previous studies. However, there remained uncertainties regarding the influence of test duration (48 vs 96 h) and the presence and absence of food in acute exposures with the amphipod, and there were also concerns about poor control amphipod growth and reproduction and mussel growth in chronic exposures. We conducted acute 48‐ and 96‐h water‐only toxicity tests to evaluate the influence of feeding and test durations on the toxicity of dissolved Ni and Zn to the amphipod; and we used recently refined test methods to conduct chronic Ni and Zn toxicity tests to evaluate the sensitivity of the amphipod (6‐week exposure) and the mussel (4‐ and 12‐week exposures). The 96‐h 50% effect concentrations (EC50s) of 916 µg Ni/L and 99 µg Zn/L from acute amphipod tests without feeding decreased from the 48‐h EC50s by 62% and 33%, respectively, whereas the 96‐h EC50s of 2732 µg Ni/L and 194 µg Zn/L from the tests with feeding decreased from the 48‐h EC50s by 10% and 26%, indicating that the presence or absence of food had apparent implications for the 96‐h EC50. Our chronic 6‐week EC20s for the amphipod (4.5 µg Ni/L and 35 µg Zn/L) were 50 to 67% lower than the 6‐week EC20s from previous amphipod tests, and our chronic 4‐week EC20s for the mussel (41 µg Ni/L and 66 µg Zn/L) were similar to or up to 42% lower than the 4‐week EC20s from previous mussel tests. The lower EC20s from the present study likely reflect more accurate estimates of inherent sensitivity to Ni and Zn due to the refined test conditions. Finally, increasing the chronic test duration from 4 to 12 weeks substantially increased the toxicity of Zn to the mussel whereas the 4‐ and 12‐week Ni effect needs to be re‐evaluated to understand the large degree of variation in organism responses observed in the present study.

Elevated nitrate (NO₃) and sulfate (SO₄) in surface water are a global concern and studies are needed to generate toxicity data to develop environmental guideline values for NO₃ and SO₄. The present study was designed to fill existing gaps in toxicity databases by determining the acute and/or chronic toxicity of NO₃ (tested as NaNO₃) to a unionid mussel (Lampsilis siliquoidea), a midge (Chironomus dilutus), a fish (rainbow trout Oncorhynchus mykiss), and 2 amphibians (Hyla versicolor, Lithobates sylvaticus), and determine the acute and/or chronic toxicity of SO₄ (tested as Na₂SO₄) to 2 unionid mussels (L. siliquoidea, Villosa iris), an amphipod (Hyalella azteca), and 2 fish species (fathead minnow Pimephales promelas, O. mykiss). Among the different test species, acute NO₃ EC50s ranged from 189 to >883 mg NO₃‐N/L and chronic NO₃ EC20s based on the most sensitive endpoint ranged from 9.6 to 47 mg NO₃‐N/L. The midge was the most sensitive species and the trout was the least sensitive species in both acute and chronic NO₃ exposures. Acute SO₄ EC50s for the 2 mussel species (2071 and 2064 mg SO₄/L) were similar to the EC50 for the amphipod (2689 mg SO₄/L) whereas chronic EC20s for the 2 mussels (438 and 384 mg SO₄/L) were >2‐fold lower than the EC20 of the amphipod (1111 mg SO₄/L), indicating the high sensitivity of mussels in chronic SO₄ exposures. However, the fathead minnow, with an EC20 of 374 mg SO₄/L, was the most sensitive species in chronic SO₄ exposures while the rainbow trout became the least sensitive species (EC20 >3240 mg SO₄/L). The high sensitivity of fathead minnow was consistent with the finding in a previous chronic Na₂SO₄ study. However, the EC20 values from the present study conducted in test water containing a higher potassium concentration (3 mg K/L) were >2‐fold greater than those in the previous study at a lower potassium concentration (1 mg K/L), which confirmed the influence of potassium on chronic Na₂SO₄ toxicity to the minnow.