Toxicity of ammonia to three marine fish and three marine invertebrates

Determination of ammonia nitrogen by surface-enhanced Raman spectroscopy and DFT studies

Ammonia nitrogen is one of the most important indicators for evaluating the quality of water bodies. It is very difficult to determine ammonia nitrogen directly by Surface-enhanced Raman spectroscopy (SERS) in practice. In order to realize SERS determination of ammonia nitrogen, in this paper, SERS combined with density functional theory (DFT) was used to investigate why ammonia nitrogen needs to be derivatized to hexamethylenetetramine (HMTA) and why HMTA can be determined using SERS. The molecular electrostatic potential (MEP) results exhibit that there was no adsorption site on the surface of ammonia nitrogen, whereas its derivate HMTA had four available adsorption sites. This provides a basic guarantee for the SERS detection of HMTA. The molecular adsorption state of HMTA on the gold nanoparticles surface was concluded from the binding energies, the bond length, and the Raman activity spectra. Among them, the HMTA-Au4 complex has the lowest bond energy (-586.873 Kcal/mol) and the shortest bond length (2.161 Å), which is the most stable state and its Raman activity spectrum is the closest to the experimental data. Calculations results of frontier molecular orbital (FMO) demonstrate that the energy gap of HMTA and HMTA-Au4 complex are 0.30258 eV and 0.10947 eV, respectively, with a really obvious difference between them, which indicates that the HMAT-Au4 complex possessed higher chemical reactivity. In addition, charge transfer phenomenon on the MEP of HMTA-Au4 complex was deduced due to the change in the symmetry of its charge distribution, which can be explained the mechanism of chemical enhancement in the detection of HMTA by SERS. The selective enhancement at 1048 cm-1 peaks in theoretical spectrum and at 1044 peaks cm-1 in experimental spectrum provided theoretical and practical basis for indirect determination of ammonia nitrogen by SERS. The obtained results will help to better understand the reasons why some components are difficult to be directly determined by SERS, and why these components need to be derivatized. It provides a new method for components that are difficult to detect by SERS.

Investigating the Effect of Bacilli and Lactic Acid Bacteria on Water Quality, Growth, Survival, Immune Response, and Intestinal Microbiota of Cultured Litopenaeus vannamei

Shrimp is one of the most important aquaculture industries. Therefore, we determined the effect of nitrifying-probiotic bacteria on water quality, growth, survival, immune response, and intestinal microbiota of Litopenaeus vannamei cultured without water exchange. In vitro, only Bacillus licheniformis used total ammonia nitrogen (TAN), nitrites, and nitrates since nitrogen bubbles were produced. TAN decreased significantly in the treatments with B. licheniformis and Pediococcus pentosaceus and Leuconostoc mesenteroides, but no differences were observed in nitrites. Nitrates were significantly higher in the treatments with bacteria. The final weight was higher only with bacilli and bacilli and LAB treatments. The survival of shrimp in the bacterial treatments increased significantly, and superoxide anion increased significantly only in lactic acid bacteria (LAB) treatment. The activity of phenoloxidase decreased significantly in the treatments with bacteria compared to the control. Shrimp treated with bacilli in the water showed lower species richness. The gut bacterial community after treatments was significantly different from that of the control. Linoleic acid metabolism was positively correlated with final weight and superoxide anion, whereas quorum sensing was correlated with survival. Thus, bacilli and LAB in the water of hyperintensive culture systems act as heterotrophic nitrifers, modulate the intestinal microbiota and immune response, and improve the growth and survival of shrimp. This is the first report on P. pentosaceus and L. mesenteroides identified as nitrifying bacteria.

Ammonium halide selective ion pair recognition and extraction with a chalcogen bonding heteroditopic receptor

The first example of a heteroditopic receptor capable of cooperative recognition and extraction of ammonium salt (NH4X) ion-pairs is described. Consisting of a bidentate 3,5-bis-tellurotriazole chalcogen bond donor binding cleft, the appendage of benzo-15-crown-5 (B15C5) substituents to the tellurium centres facilitates binding of the ammonium cation via a co-facial bis-B15C5 sandwich complex, which serves to switch on chalcogen bonding-mediated anion binding potency. Extensive quantitative ion-pair recognition 1H NMR titration studies in CD3CN/CDCl3 (1 : 1, v/v) solvent media reveal impressive ion-pair binding affinities towards a variety of ammonium halide, nitrate and thiocyanate salts, with the heteroditopic receptor displaying notable ammonium halide salt selectivity. The prodigious solution phase NH4X recognition also translates to efficient solid-liquid and liquid-liquid extraction capabilities.

Exploring Alternatives for Marine Toxicity Testing: Initial Evaluation of Fish Embryo and Mysid Tests

Current regulations require that toxicity assessments be performed using standardized toxicity testing methods, often using fish. Recent legislation in both the European Union and United States has mandated that toxicity testing alternatives implement the 3Rs of animal research (replacement, reduction, and refinement) whenever possible. There have been advances in the development of alternatives for freshwater assessments, but there is a lack of analogous developments for marine assessments. One potential alternative testing method is the fish embryo toxicity (FET) test, which uses fish embryos rather than older fish. In the present study, FET methods were applied to two marine model organisms, the sheepshead minnow and the inland silverside. Another potential alternative is the mysid shrimp survival and growth test, which uses an invertebrate model. The primary objective of the present study was to compare the sensitivity of these three potential alternative testing methods to two standardized fish-based tests using 3,4-dichloroaniline (DCA), a common reference toxicant. A secondary objective was to characterize the ontogeny of sheepshead minnows and inland silversides. This provided a temporal and visual guide that can be used to identify appropriately staged embryos for inclusion in FET tests and delineate key developmental events (e.g., somite development, eyespot formation, etc.). Comparison of the testing strategies for assessing DCA indicated that: (1) the standardized fish tests possessed comparable sensitivity to each other; (2) the mysid shrimp tests possessed comparable sensitivity to the standardized fish tests; (3) the sheepshead minnow and inland silverside FET tests were the least sensitive testing strategies employed; and (4) inclusion of sublethal endpoints (i.e., hatchability and pericardial edema) in the marine FETs increased their sensitivity. Environ Toxicol Chem 2024;43:1285-1299. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Did you consider ammonium? A possible confounding factor in evaluating the toxicity of marine sediments

Bioassays are a crucial tool for assessing environmental quality, but they face inherent variability due to unexplored confounding factors in marine ecosystems. Ammonium (NH4+) is a vital form of nitrogen in aquatic environments, but it is also a significant focus due to its toxic effects, particularly on marine invertebrates. This study examines the impact of ammonium toxicity on Paracentrotus lividus embryo-development bioassays, which are widely used to evaluate the environmental quality of dredged sediment. The aim is to establish threshold values (EC01, EC05, EC20, and EC50 values) for the correct application of the P. lividus bioassay. The research reveals that ammonium has a significant impact on larval development (EC50 for NH4+ equivalent to 0.81 mg/L). The results emphasize the ecological implications of elevated NH4+ levels in dredged material and highlight the need for precise assessments in environmental management. This study provides essential data for refining guidelines and understanding the complex interactions of this compound in marine ecosystems, ensuring accurate evaluations of environmental quality.

Sensitive Electrochemical Detection of Ammonia Nitrogen via a Platinum-Zinc Alloy Nanoflower-Modified Carbon Cloth Electrode

As a common water pollutant, ammonia nitrogen poses a serious risk to human health and the ecological environment. Therefore, it is important to develop a simple and efficient sensing scheme to achieve accurate detection of ammonia nitrogen. Here, we report a simple fabrication electrode for the electrochemical synthesis of platinum-zinc alloy nanoflowers (PtZn NFs) on the surface of carbon cloth. The obtained PtZn NFs/CC electrode was applied to the electrochemical detection of ammonia nitrogen by differential pulse voltammetry (DPV). The enhanced electrocatalytic activity of PtZn NFs and the larger electrochemical active area of the self-supported PtZn NFs/CC electrode are conducive to improving the ammonia nitrogen detection performance of the sensitive electrode. Under optimized conditions, the PtZn NFs/CC electrode exhibits excellent electrochemical performance with a wide linear range from 1 to 1000 µM, a sensitivity of 21.5 μA μM-1 (from 1 μM to 100 μM) and a lower detection limit of 27.81 nM, respectively. PtZn NFs/CC electrodes show excellent stability and anti-interference. In addition, the fabricated electrochemical sensor can be used to detect ammonia nitrogen in tap water and lake water samples.

Enhanced Sensitivity of Electrochemical Sensors for Ammonia-Nitrogen via In-Situ Synthesis PtNi Nanoleaves on Carbon Cloth

Pt-based electrochemical ammonia-nitrogen sensors played a significance role in real-time monitoring the ammonia-nitrogen concentration. The alloying of Pt and transition metals was one of the effective ways to increase the detectability of the sensitive electrode. In this paper, a self-supported electrochemical electrode for the detection of ammonia nitrogen was obtained by the electrodeposition of PtNi alloy nanoleaves on a carbon cloth (PtNi-CC). Experimental results showed that the PtNi-CC electrode exhibited enhanced detection performance with a wide linear range from 0.5 to 500 µM, high sensitivity (7.83 µA µM-1 cm-2 from 0.5 to 150 μM and 0.945 µA µM-1 cm-2 from 150 to 500 μM) and lower detection limit (24 nM). The synergistic effect between Pt and Ni and the smaller lattice spacing of the PtNi alloy were the main reasons for the excellent performance of the electrode. This work showed the great potential of Pt-based alloy electrodes for the detection of ammonia-nitrogen.

Adverse effects of chronic ammonia stress on juvenile oriental river prawn (Macrobrachium nipponense) and alteration of glucose and ammonia metabolism

Ammonia is one of the common stress factors in aquaculture. However, the effect of chronic ammonia exposure in juvenile oriental river prawn (Macrobrachium nipponense) is currently unexplored. This study explored the effects of chronic ammonia on juvenile healthy oriental river prawns. Fifty prawns (0.123 ± 0.003 g) were exposed to 0, 5, and 15 mg/L total ammonia nitrogen (TAN) in triplicates for 28 days. The effects of chronic ammonia challenge were evaluated on growth, antioxidant capacity, hepatopancreas and gill morphology, and glucose and ammonia metabolism. The results showed that, the chronic ammonia exposure reduced significantly survival rate and weight gain of prawns. The prawns exposed to 15 mg/L ammonia had induced oxidative stress. However, the prawn exposed to 15 mg/L ammonia had significantly lower aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and acid phosphatase activities in the serum. Furthermore, exposure of prawns to 15 mg/L ammonia increased the activities of hexokinase, pyruvate kinase, pyruvate and lactic acid content, and glutamine synthase activity. However, the prawns exposed to 15 mg/L ammonia, reduced succinic dehydrogenase, 6-phosphogluconic dehydrogenase, phosphoenolpyruvate carboxykinase, glutamate synthase, and glutamate dehydrogenase activities but increased ammonia content in serum. The exposure of ammonia deformed lumen, damaged basement membrane and decreased secretory cells in the hepatopancreas, disordered gill epithelial and pillar cells, and caused gill filament base vacuolation. Our study indicates that chronic ammonia stress impairs growth performance, tissue morphology, induces oxidative stress, and alters glucose and ammonia metabolism in juvenile oriental river prawns.

Metabolomics analysis reveals the response mechanism to carbonate alkalinity toxicity in the gills of Eriocheir sinensis

Aquatic water with carbonate alkalinity presents a survival challenge to aquatic animals. As an economically important crab, large quantities of Eriocheir sinensis are cultured in carbonate-type saline-alkali ponds, while the toxic effect on E. sinensis from carbonate alkalinity is still unclear. In this study, untargeted liquid chromatography-mass spectrometry metabolomics was performed to investigate the metabolic change caused by culture alkalinity, and confirmed distinct physiological response under gradient alkalinities. There were 39 differential metabolites obtained in the low-alkalinity group (4.35 mmol/L) versus control group, and "arachidonic acid metabolism" was enriched as a core response pathway. 93 differential metabolites were identified in the high-alkalinity group (17.43 mmol/L) versus control group, and a complex response net was manifested through integrated analysis, building by "steroid hormone biosynthesis", "phenylalanine, tyrosine and tryptophan biosynthesis", "phosphonate and phosphinate metabolism", "phenylalanine metabolism", "mineral absorption", "purine metabolism" and "carbon metabolism". This indicated the mobilization of energy reserves and the suppression of protein and amino acid catabolism were manifested in E. sinensis gills to defense high alkalinity stress. In addition, the persistently regulation of key metabolites under various alkalinity, including diuretic compound "spironolactone" and the antiphlogistic compound "LXB₄", suggested anti-inflammatory action and excretion regulation were initiated to defend the stress.

Exploring bacterioplankton communities and their temporal dynamics in the rearing water of a biofloc-based shrimp (Litopenaeus vannamei) aquaculture system

Biofloc technology (BFT) has recently gained considerable attention as a sustainable method in shrimp aquaculture. In a successful BFT system, microbial communities are considered a crucial component in their ability to both improve water quality and control microbial pathogens. Yet, bacterioplankton diversity in rearing water and how bacterioplankton community composition changes with shrimp growth are rarely documented. In this study, the Pacific white shrimp, Litopenaeus vannamei was cultivated in a greenhouse-enclosed BFT system. Rearing water samples were collected on a weekly basis for 5 months (152 days) and water quality variables such as physicochemical parameters and inorganic nutrients were monitored. In parallel, 16S rRNA gene pyrosequencing was employed to investigate the temporal patterns of rearing-water microbiota. The productivity, survival rate, and feed conversion ratio were 3.2-4.4 kg/m3, 74%-89%, and 1.2-1.3, respectively, representing successful super-intensive cultures. The metataxonomic results indicated a highly dynamic bacterioplankton community, with two major shifts over the culture. Members of the phylum Planctomycetes dominated in rearing water during the early stages, while Actinobacteria dominated during the middle stages, and Chloroflexi and TM7 dominated during the late stages of culture. The bacterioplankton community fluctuated more in the beginning but stabilized as the culture progressed. Intriguingly, we observed that certain bacterioplankton groups dominated in a culture-stage-specific manner; these groups include Rhodobacteraceae, Flavobacteriaceae, Actinobacteria, and Chloroflexi, which either contribute to water quality regulation or possess probiotic potential. Altogether, our results indicate that an operationally successful BFT-based aquaculture system favors the growth and dynamics of specific microbial communities in rearing water. Our study expands the scientific understanding of the practical utilization of microbes in sustainable aquaculture. A thorough understanding of rearing-water microbiota and factors influencing their dynamics will help to establish effective management strategies.

Transcriptome analysis reveals the mechanism of alkalinity exposure on spleen oxidative stress, inflammation and immune function of Luciobarbus capito

Saline-alkali land is distributed all over the world, and it affects the economic development of fisheries. The alkalinity in water is related to the accumulation of carbonate, so the is generally higher. To understand how alkalinity impacts the immune response in Luciobarbus capito, we performed transcriptomic profiles for spleen, the immune organ of Luciobarbus capito which were underwent alkalinity exposure. Totally there are 47,727,954, 53,987,820 and 51,398,546 high quality clean reads obtained from the control groups, and 46,996,982, 49,650,460 and 45,964,986 clean reads from the alkalinity exposure groups. Among them, 611 genes were differently expressed, including 534 upregulated and 77 down-regulated genes. The identified genes were enriched using databases of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). It was found that differentially expressed genes in Luciobarbus capito spleen tissue were enriched into 14 GO pathways, and differentially expressed genes in Luciobarbus capito spleen were enriched into 25 corresponding KEGG pathways under alkalinity stress. Inflammation and immune function genes and pathways were identified and validated by quantitative real-time RT-PCR. Our results showed that alkalinity exposure leads to inflammation and immunoregulation in spleen of Luciobarbus capito. These results provide new insights for unveiling the biological effects of alkalinity in Luciobarbus capito.

Progress on Noble Metal-Based Catalysts Dedicated to the Selective Catalytic Ammonia Oxidation into Nitrogen and Water Vapor (NH3-SCO)

A recent development for selective ammonia oxidation into nitrogen and water vapor (NH3-SCO) over noble metal-based catalysts is covered in the mini-review. As ammonia (NH3) can harm human health and the environment, it led to stringent regulations by environmental agencies around the world. With the enforcement of the Euro VI emission standards, in which a limitation for NH3 emissions is proposed, NH3 emissions are becoming more and more of a concern. Noble metal-based catalysts (i.e., in the metallic form, noble metals supported on metal oxides or ion-exchanged zeolites, etc.) were rapidly found to possess high catalytic activity for NH3 oxidation at low temperatures. Thus, a comprehensive discussion of property-activity correlations of the noble-based catalysts, including Pt-, Pd-, Ag- and Au-, Ru-based catalysts is given. Furthermore, due to the relatively narrow operating temperature window of full NH3 conversion, high selectivity to N2O and NOx as well as high costs of noble metal-based catalysts, recent developments are aimed at combining the advantages of noble metals and transition metals. Thus, also a brief overview is provided about the design of the bifunctional catalysts (i.e., as dual-layer catalysts, mixed form (mechanical mixture), hybrid catalysts having dual-layer and mixed catalysts, core-shell structure, etc.). Finally, the general conclusions together with a discussion of promising research directions are provided.

An "on-off" fluorescent probe based on cucurbit[7]uril for highly sensitive determination of ammonia nitrogen in aquaculture water

A novel "on-off" fluorescent probe was synthesized for highly sensitive and ultra-trace determination of ammonia nitrogen in aquaculture water. Ammonium can react with formaldehyde and sodium hydroxide to form a ring substance (urotropine), which shows no fluorescence signal. Palmatine hydrochloride (PAL) can enter the hydrophobic cavity of cucurbit[7]uril (CB[7]), eventually forming a 1 : 1 host guest complex called PAL@CB[7] under neutral or acidic conditions, which has strong green fluorescence with the maximum excitation (λ_ex) wavelength at 343 nm, and the maximum emission (λ_em) wavelength at 500 nm, while urotropine has a fluorescence quenching effect on the fluorescence enhancement system of PAL@CB[7]. Therefore, a fluorescent chemosensor based on PAL@CB[7] and the reaction of ammonia nitrogen with formaldehyde was developed. The results indicate that the linearity range and the limit of detection of the proposed method are 1-300 μg L^-1 with a good correlation coefficient (r² = 0.9966) and 1.8 × 10^-2 μg L^-1, respectively. Under the optimal conditions, the method was employed for the detection of ammonia nitrogen in real aquaculture water samples, revealing high selectivity and sensitivity. In the future, the combination of the "on-off" fluorescence method, a portable hardware system and intelligent algorithms will provide technology support for the design of on-line sensors for measuring ammonia nitrogen in aquaculture water.

An Electrochemical Enzyme Biosensor for Ammonium Detection in Aquaculture Using Screen-Printed Electrode Modified by Gold Nanoparticle/Polymethylene Blue

A SPEC/AuNPs/PMB modified electrode was prepared by electrodeposition and electro-polymerization. The electrochemical behavior of reduced nicotinamide adenine dinucleotide (NADH) on the surface of the modified electrode was studied by cyclic voltammetry. A certain amount of substrate and glutamate dehydrogenase (GLDH) were coated on the modified electrode to form a functional enzyme membrane. The ammonia nitrogen in the water sample could be calculated indirectly by measuring the consumption of NADH in the reaction. The results showed that the strength of electro-catalytic current signal was increased by two times; the catalytic oxidation potential was shifted to the left by 0.5 V, and the anti-interference ability of the sensor was enhanced. The optimum substrate concentration and enzyme loading were determined as 1.3 mM NADH, 28 mM α-Ketoglutarate and 2.0 U GLDH, respectively. The homemade ceramic heating plate controlled the working electrode to work at 37 °C. A pH compensation algorithm based on piecewise linear interpolation could reduce the measurement error to less than 3.29 μM. The biosensor exhibited good linearity in the range of 0~300 μM with a detection limit of 0.65 μM NH₄⁺. Compared with standard Nessler's method, the recoveries were 93.71~105.92%. The biosensor was found to be stable for at least 14 days when refrigerated and sealed at 4 °C.

Assessment of the environmental carrying capacity of pollutants in Tam Giang-Cau Hai Lagoon (Viet Nam) and solutions for the environment protection of the lagoon

Tam Giang-Cau Hai lagoon is the largest lagoon in Viet Nam. It has two inlets that exchange water with the sea: Thuan An inlet in the north and Tu Hien inlet in the south. Every year, Tam Giang-Cau Hai lagoon receives a large amount of wastewater from five coastal districts with various waste sources such as residences, aquaculture, livestock and industry among others. Due to the low water exchange through the two inlets, wastewater is discharged into the lagoon and pollutants accumulate in the water. This results in pollution concentrations in the water exceeding the environmental limits and causing adverse effects on aquatic life. This paper presents the environmental carrying capacity (ECC) of the lagoon based on calculations from the Delft-3D model using three scenarios: 1) ECC following Vietnamese regulations; 2) maximum ECC or dangerous scenario (which the water body can no longer purify itself or becomes a dead water body); 3) proposed ECC for the protection of aquatic life. Based on the study results, some solutions have been proposed to protect the lagoon with the construction of wastewater treatment plants being the most important action to reduce pollution load in the lagoon.

Characterization of a thaumarchaeal symbiont that drives incomplete nitrification in the tropical sponge Ianthella basta

Marine sponges represent one of the few eukaryotic groups that frequently harbour symbiotic members of the Thaumarchaeota, which are important chemoautotrophic ammonia-oxidizers in many environments. However, in most studies, direct demonstration of ammonia-oxidation by these archaea within sponges is lacking, and little is known about sponge-specific adaptations of ammonia-oxidizing archaea (AOA). Here, we characterized the thaumarchaeal symbiont of the marine sponge Ianthella basta using metaproteogenomics, fluorescence in situ hybridization, qPCR and isotope-based functional assays. 'Candidatus Nitrosospongia ianthellae' is only distantly related to cultured AOA. It is an abundant symbiont that is solely responsible for nitrite formation from ammonia in I. basta that surprisingly does not harbour nitrite-oxidizing microbes. Furthermore, this AOA is equipped with an expanded set of extracellular subtilisin-like proteases, a metalloprotease unique among archaea, as well as a putative branched-chain amino acid ABC transporter. This repertoire is strongly indicative of a mixotrophic lifestyle and is (with slight variations) also found in other sponge-associated, but not in free-living AOA. We predict that this feature as well as an expanded and unique set of secreted serpins (protease inhibitors), a unique array of eukaryotic-like proteins, and a DNA-phosporothioation system, represent important adaptations of AOA to life within these ancient filter-feeding animals.

Integrating multiple lines of evidence of sediment quality in a tropical bay (Guanabara Bay, Brazil)

The present study evaluated the ecological risk of metal contamination in sediments of Guanabara Bay (GB) by combining multiple lines of evidence (LOEs). Chemical analysis and a set of whole-sediment toxicity assays were conducted with Tiburonella viscana, Kalliapseudes schubartii, Anomalocardia flexuosa, and Nitocra sp. Results were integrated by multivariate analysis and qualitative methods. Additionally, a whole-sediment Toxicity Identification Evaluation technique (TIE) was applied to identify the chemical groups responsible for the effects. Sediments from harbor and industrial areas exhibited toxicity linked to moderate to high concentrations of Zn, Pb, Cu and Cr. The TIE technique confirmed such effects, but it also indicates the contribution of ammonia and organic compounds to the observed toxicity. Our results demonstrate that the combination of multiple LOEs improves the effectiveness of environmental risk assessment of chemical stressors and management of coastal ecosystems in tropical regions.

Sensitivity of the Marine Calanoid Copepod Pseudodiaptomus pelagicus to Copper, Phenanthrene, and Ammonia

There are limited acute toxicity test methods for native North American marine species that are considered zooplankton for their entire life cycle. Examples of standardized marine zooplankton methods include mussel, bivalve, and echinoderm development tests that use a relatively short-lived planktonic larval stage, chronic life-cycle toxicity tests using epibenthic copepods, and a 24-h Acartia tonsa copepod test method. The objectives of the present study were to: 1) develop and evaluate a novel, 48-h acute toxicity test method using the marine North American copepod Pseudodiaptomus pelagicus that is planktonic for its entire life cycle, and 2) determine the sensitivity of P. pelagicus relative to commonly tested marine toxicity test species. The average (±1 standard deviation) median lethal concentrations (LC50s) for copper (Cu), phenanthrene, and un-ionized ammonia were 32 ± 15 µg/L, 161 ± 51 µg/L, and 1.08 ± 0.30 mg NH₃ /L, respectively. These results placed P. pelagicus on the more sensitive end of Cu and phenanthrene species sensitivity distributions. The copepod was less sensitive to un-ionized ammonia than commonly tested marine species. This finding suggests that the acute P. pelagicus test method will allow a focus on assessing the impacts of persistent contaminants of concern with less confounding impact from naturally occurring ammonia released to the water from sources such as suspended sediments. Environ Toxicol Chem 2019;38:1221-1230. Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Life stage sensitivity of the marine mussel Mytilus edulis to ammonia

Ammonia is an important contaminant to consider in all toxicity tests. It is especially important to consider the impacts of ammonia in test methods that use sensitive water column organisms exposed to sediments or sediment extracts, such as porewater and elutriate toxicity tests. Embryo-larval development toxicity tests, such as the 48-h method using Mytilus mussel species, are particularly sensitive to ammonia. To better understand the effect thresholds across different life stages of these mussels, 6 short-term (48-h) development toxicity tests and 3 21-d toxicity tests with different-sized juvenile mussels were conducted. Two of the juvenile mussel tests involved 21-d continuous chronic exposure to ammonia, whereas the third involved an acute 2-d ammonia exposure, followed by a 19-d recovery period. The embryo-larval development test method (50% effect concentration [EC50] = 0.14-0.18 mg/L un-ionized ammonia) was 2.5 times more sensitive than the juvenile mussel 21-d survival endpoint (50% lethal concentration = 0.39 mg/L un-ionized ammonia) and 2 times more sensitive than the most sensitive sublethal juvenile mussel endpoint (EC50 = 0.26 mg/L un-ionized ammonia). Further, it was found that the juveniles recovered from a 48-h exposure to un-ionized ammonia of up to 1.1 mg/L. The data generated suggest that the embryo development endpoint was sufficiently sensitive to un-ionized ammonia to protect the chronically exposed (21 d) juvenile mussels. Environ Toxicol Chem 2017;36:89-95. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Responses of growth and hemolymph quality in juvenile Chinese horseshoe crab Tachypleus tridentatus (Xiphosura) to sublethal tributyltin and cadmium

Responses of growth endpoints and hemolymph constituents in juvenile Chinese horseshoe crab Tachypleus tridentatus under treatments of 0.01 and 0.1 mg/l tributyltin (TBT) and 0.1 and 1 mg/l cadmium (Cd) were examined in a 12-week experiment. A significant decline in final body weight, final prosomal width, percentage of individuals molted and mean molting time was detected under TBT exposures. While morphological abnormalities of the juveniles between TBT treatments and the control were statistically indistinguishable, significantly higher occurrences of carapace erosion and appendage loss were noted under 0.1 and 1 mg/l Cd exposures. Various hemolymph quality indicators, including hemolymph plasma protein level, amebocyte viability and percentage of granular-spherical state of amebocytes of the juveniles exposed to TBT or Cd were significantly lower than the control. Such a decrease in hemolymph quality suggested deleterious effects of metal contaminant-induced stressors on the health status of the juveniles even at low exposure levels (i.e., 0.01 mg/l TBT and 0.1 mg/l Cd). Changes of hemolymph parameters in juvenile horseshoe crabs were more sensitive than growth performance as well as morphological abnormalities in response to metal stressors, and can be used as an indicator to reflect habitat conditions and contaminant levels.

Responses of Takifugu obscurus fertilized eggs and larvae to increased ammonia exposure

Ammonia is a common toxicant in aquatic systems; this substance has become a critical threat to fish, especially in early life stages. This study aimed to evaluate the effects of unionized ammonia (NH3-N: 0, 0.068, 0.138, 0.206, 0.275, 0.343, 0.412, and 0.481 mg L(-1)) on fertilized eggs and larvae of obscure puffer Takifugu obscurus, a fish species with potential economic value. Results showed that hatch time was significantly retarded and hatch rate was significantly decreased as NH3-N concentrations increased; newly hatched larvae exhibited high rate of abnormalities and low viability. The survival rate of larvae also decreased significantly as NH3-N concentrations increased; larvae could tolerate NH3-N to a less extent than embryos. NH3-N also caused a significant decrease in superoxide dismutase (SOD) and Na(+)/K(+) ATPase activities but not in malondialdehyde (MDA) levels of larvae. Two-way ANOVA indicated that there was a statistically significant interaction between NH3-N concentrations and exposure times on SOD activity but not on Na(+)/K(+) ATPase activity. Such responses indicated that an increase in ammonia concentration in surface water may negatively affect the early development of T. obscurus and thus likely impair population recruitment and persistence of this fish species.

Air-breathing fishes in aquaculture. What can we learn from physiology?

During the past decade, the culture of air-breathing fish species has increased dramatically and is now a significant global source of protein for human consumption. This development has generated a need for specific information on how to maximize growth and minimize the environmental effect of culture systems. Here, the existing data on metabolism in air-breathing fishes are reviewed, with the aim of shedding new light on the oxygen requirements of air-breathing fishes in aquaculture, reaching the conclusion that aquatic oxygenation is much more important than previously assumed. In addition, the possible effects on growth of the recurrent exposure to deep hypoxia and associated elevated concentrations of carbon dioxide, ammonia and nitrite, that occurs in the culture ponds used for air-breathing fishes, are discussed. Where data on air-breathing fishes are simply lacking, data for a few water-breathing species will be reviewed, to put the physiological effects into a growth perspective. It is argued that an understanding of air-breathing fishes' respiratory physiology, including metabolic rate, partitioning of oxygen uptake from air and water in facultative air breathers, the critical oxygen tension, can provide important input for the optimization of culture practices. Given the growing importance of air breathers in aquaculture production, there is an urgent need for further data on these issues.

Short-term toxicity of ammonia, sodium hydroxide and a commercial biocide to golden mussel Limnoperna fortunei (Dunker, 1857)

Macrofouling bivalves are considered an ecological and technological problem worldwide. Control measures have been researched with Limnoperna fortunei, but without success. The aim of the manuscript is to test some alternatives to regulate this harmful invasive mollusk. Mortality and behavioral response (shell gaping) of Limnoperna fortunei exposed to three chemical compounds were evaluated. Values for LC50 96h were: 0.25 (0.24-0.27)mg/L NH3-N, 11.10 (7.45-16.55) mg/L MXD-100 and 88.51 (74.61-105.01)mg/L NaOH. Reduced gaping was observed beginning at concentrations of 0.31mg/L (NH3-N), 100mg/L (MXD-100) and 160mg/L (NaOH) and increased above these values. The percentage of individuals gaping after two hours at LC50 96h differed significantly (χ(2)=79.9; DF=3; p<0.001) in MXD-100 (50%), NaOH (0%), NH3-N (96.7%) and the controls (93.3%). This study contributes to the understanding of the relationship between toxicity and behavioral effects of some toxicants in L. fortunei.

Development of guidelines for ammonia in estuarine and marine water systems

The water quality guideline trigger value for ammonia in estuarine and marine waters has been revised with the addition of 38 new results to the data set of 21 used in earlier guideline derivations. Using species sensitivity distributions, a new trigger value of 460 microg total NH(3)-N/L was derived for slightly to moderately disturbed systems (95% protection concentration, PC95), with a value of 160 microg total NH(3)-N/L applying to waters of high conservation value (PC99). For sediment pore waters, a guideline trigger value of 3.9 mg total NH(3)-N/L, derived from the 80th percentile of background data from Sydney Harbour, is recommended. This value is likely to be exceeded in degraded sediments subject to dredging; however, ocean disposal of such sediments results in rapid decreases in porewater ammonia and a guideline trigger value for dissolved ammonia during disposal of dredged sediments of 1550 microg total NH(3)-N/L is proposed.

Acute and chronic aquatic toxicity of ammonium perfluorooctanoate (APFO) to freshwater organisms

Recent concerns have been raised concerning the widespread distribution of perfluorinated compounds in environmental matrices and biota. The compounds of interest include ammonium perfluorooctanoate (APFO, the ammonium salt of perfluorooctanoic acid, PFOA). APFO is used primarily as a processing aid in the production of fluoropolymers and fluoroelastomers. The environmental presence of perfluorooctanoate (PFO(-), the anion of APFO) and its entry into the environment as APFO make quality aquatic toxicity data necessary to assess the aquatic hazard and risk of APFO. We conducted acute and chronic freshwater aquatic toxicity studies with algae, Pseudokirchneriella subcapitata, the water flea, Daphnia magna, and embryo-larval rainbow trout, Oncorhynchus mykiss, using OECD test guidelines and a single, well-characterized sample of APFO. Acute 48-96 h LC/EC(50) values were greater than 400mg/l APFO and the lowest chronic NOEC was 12.5mg/l for inhibition of the growth rate and biomass of the freshwater alga. Un-ionized ammonia was calculated to be a potential significant contributor to the observed toxicity of APFO. Based on environmental concentrations of PFO(-) from various aquatic ecosystems, the PNEC value from this study, and unionized ammonia contributions to observed toxicity, APFO demonstrates little or no risk for acute or chronic toxicity to freshwater and marine aquatic organisms at relevant environmental concentrations.

Design optimization of a self-cleaning moving-bed bioreactor for seawater denitrification

The hydrodynamic behavior and denitrification capacity of a down flow self-cleaning moving bed bioreactor (MBBR) using floating packed-bed carriers were investigated. Water mixing in the MBBR was determined by tracer studies, which showed a completely stirred tank reactor. Eleven different types of patented plastic packed-bed carriers were selected based on their density, shape and specific surface area. Video studies of the carriers were used to determine operating conditions and select the Cascade 1A and Tri-Pack 1 carriers for denitrification experiments. Both carriers showed a similar performance level in terms of the denitrification capacity of the resulting MBBR. The improvement in liquid circulation is thought to explain the high denitrification rates that reached 27 gNm(-2)d(-1) and the maintenance of a thin biofilm. Increasing the overall liquid velocity profile led to an increase of up to 30% in the denitrification rate in conditions with a 1-month-old biofilm. This MBBR design seemed to control biofilm development and could easily be scaled up to denitrify seawater or freshwater systems.