Modeling the pH-ammonia toxicity relationship for Hydra viridissima in soft waters with low ionic concentrations

α-lipoic acid ameliorates hepatotoxicity induced by chronic ammonia toxicity in crucian carp (Carassius auratus gibelio) by alleviating oxidative stress, inflammation and inhibiting ERS pathway

High environment ammonia (HEA) poses a deadly threat to aquatic animals and indirectly impacts human healthy life, while nutritional regulation can alleviate chronic ammonia toxicity. α-lipoic acid exhibits antioxidative effects in both aqueous and lipid environments, mitigating cellular and tissue damage caused by oxidative stress by aiding in the neutralization of free radicals (reactive oxygen species). Hence, investigating its potential as an effective antioxidant and its protective mechanisms against chronic ammonia stress in crucian carp is highly valuable. Experimental fish (initial weight 20.47 ± 1.68 g) were fed diets supplemented with or without 0.1% α-lipoic acid followed by a chronic ammonia exposure (10 mg/L) for 42 days. The results revealed that chronic ammonia stress affected growth (weight gain rate, specific growth rate, and feed conversion rate), leading to oxidative stress (decreased the activities of antioxidant enzymes catalase, superoxide dismutase, glutathione peroxidase; decreased total antioxidant capacity), increased lipid peroxidation (accumulation of malondialdehyde), immune suppression (decreased contents of nonspecific immune enzymes AKP and ACP, 50% hemolytic complement, and decrease of immunoglobulin M), impaired ammonia metabolism (reduced contents of Glu, GS, GSH, and Gln), imbalance of expression of induced antioxidant-related genes (downregulation of Cu/Zu SOD, CAT, Nrf2, and HO-1; upregulation of GST and Keap1), induction of pro-apoptotic molecules (transcription of BAX, Caspase3, and Caspase9), downregulation of anti-apoptotic gene Bcl-2 expression, and induction of endoplasmic reticulum stress (upregulation of IRE1, PERK, and ATF6 expression). The results suggested that the supplementation of α-lipoic acid could effectively induce humoral immunity, alleviate oxidative stress injury and endoplasmic reticulum stress, and ultimately alleviate liver injury induced by ammonia poisoning (50-60% reduction). This provides theoretical basis for revealing the toxicity of long-term ammonia stress and provides new insights into the anti-ammonia toxicity mechanism of α-lipoic acid.

Responses of Micropterus salmoides under Ammonia Stress and the Effects of a Potential Ammonia Antidote

Ammonia is a common environmental limiting factor in aquaculture. To investigate the effects of ammonia stress and explore the protective effect of N-carbamylglutamate (NCG) on Micropterus salmoides (M. salmoides), tissue sections and parameters related to oxidative stress and the inflammatory response in M. salmoides were carried out during the ammonia stress test and feeding test. The results demonstrated that the LC50 for 24 h, 48 h, 72 h, and 96 h under ammonia stress in M. salmoides were 25.78 mg/L, 24.40 mg/L, 21.90 mg/L, and 19.61 mg/L, respectively. Under ammonia stress, the structures of the tissues were damaged, and the GSH content decreased, while the MDA content increased with the increase in stress time and ammonia concentration. The NO content fluctuated significantly after the ammonia nitrogen stress. In the 15-day feeding test, with the increased NCG addition amount and feeding time, the GSH content increased while the MDA and NO contents decreased gradually in the NCG addition groups (NL group: 150 mg/kg; NM group: 450 mg/kg; NH group: 750 mg/kg) when compared with their control group (CK group: 0 mg/kg). In the ammonia toxicology test after feeding, the damage to each tissue was alleviated in the NL, NM, and NH groups, and the contents of GSH, MDA, and NO in most tissues of the NH group were significantly different from those in the CK group. The results suggested that ammonia stress caused tissue damage in M. salmoides, provoking oxidative stress and inflammatory response. The addition of NCG to the feed enhances the anti-ammonia ability of M. salmoides. Moreover, the gill and liver might be the target organs of ammonia toxicity, and the brain and kidney might be the primary sites where NCG exerts its effects. Our findings could help us to find feasible ways to solve the existing problem of environmental stress in M. salmoides culture.

Toxic Effects on Bioaccumulation, Hematological Parameters, Oxidative Stress, Immune Responses and Tissue Structure in Fish Exposed to Ammonia Nitrogen: A Review

Simple Summary

Ammonia nitrogen is a common environmental limiting factor in aquaculture, which can accumulate rapidly in water and reach toxic concentrations. In most aquatic environments, fish are vulnerable to the toxic effects of high levels of ammonia nitrogen exposure. It has been found that the toxic effects of ammonia nitrogen on fish are multi-mechanistic. Therefore, the purpose of this review is to explore the various toxic effects of ammonia nitrogen on fish, including oxidative stress, neurotoxicity, tissue damage and immune response.

Abstract

Ammonia nitrogen is the major oxygen-consuming pollutant in aquatic environments. Exposure to ammonia nitrogen in the aquatic environment can lead to bioaccumulation in fish, and the ammonia nitrogen concentration is the main determinant of accumulation. In most aquatic environments, fish are at the top of the food chain and are most vulnerable to the toxic effects of high levels of ammonia nitrogen exposure. In fish exposed to toxicants, ammonia-induced toxicity is mainly caused by bioaccumulation in certain tissues. Ammonia nitrogen absorbed in the fish enters the circulatory system and affects hematological properties. Ammonia nitrogen also breaks balance in antioxidant capacity and causes oxidative damage. In addition, ammonia nitrogen affects the immune response and causes neurotoxicity because of the physical and chemical toxicity. Thence, the purpose of this review was to investigate various toxic effects of ammonia nitrogen, including oxidative stress, neurotoxicity and immune response.

Assessing the Toxicity of Mine-Water Mixtures and the Effectiveness of Water Quality Guideline Values in Protecting Local Aquatic Species

Six tropical freshwater species were used to assess the toxicity of mine waters from a uranium mine adjacent to a World Heritage area in northern Australia. Key contaminants of potential concern for the mine were U, Mg, Mn, and total ammonia nitrogen (TAN). Direct toxicity assessments were carried out to assess whether the established site-specific guideline values for individual contaminants would be protective with the contaminants occurring as mixtures. Metal speciation was calculated for contaminants to determine which were the major contributors of toxicity, with 84 to 96% of Mg predicted in the free-ion form as Mg²⁺ , and 76 to 92% of Mn predicted as Mn²⁺ . Uranium, Al, and Cu were predicted to be strongly bound to fulvic acid. Uranium, Mg, Mn, and Cu were incorporated into concentration addition or independent action mixture toxicity models to compare the observed toxicity in each of the waters with predicted toxicity. For >90% of the data, mine-water toxicity was less than predicted by the concentration addition model. Instances where toxicity was greater than predicted were accompanied by exceedances of individual metal guideline values in all but one case (i.e., a Mg concentration within 10% of the guideline value). This indicates that existing individual water quality guideline values for U, Mg, Mn, and TAN would adequately protect ecosystems downstream of the mine. Environ Toxicol Chem 2021;40:2334-2346. © 2021 Commonwealth of Australia. Environmental Toxicology and Chemistry © 2021 SETAC.

Toxicological Assessment of Ammonia Exposure on Carassius auratus red var. Living in Landscape Waters

To understand the toxic mechanism of ammonia and identify effective biomarkers on the oxidative stress for the fish Carassius auratus red var., acute and chronic toxicity tests were conducted. The 96-h LC₅₀ of total ammonia nitrogen (TAN) for C. auratus was 135.4 mg L^-1, the corresponding unionized ammonia (NH₃) concentration was 1.5 mg L^-1. The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione-peroxidase (GSH-Px) and glutathione (GSH) showed an increase with a subsequent falling, while the malondialdehyde (MDA) increased during the chronic test. The SOD, MDA, and GSH could be effective biomarkers to evaluate the TAN oxidative stress, the maximum acceptable toxicant concentration (MATC) was 11.3 mg L^-1 for TAN. To our knowledge, this is the first study to propose biomarkers to evaluate potential environmental risk and establish a risk threshold for TAN in C. auratus.

How Specific Is Site-Specific? A Review and Guidance for Selecting and Evaluating Approaches for Deriving Local Water Quality Benchmarks

Existing prescriptive guidance on the derivation of local water quality benchmarks (WQBs; e.g., guideline values, criteria, standards) for protecting aquatic ecosystems is limited to only 3 to 4 specific approaches. These approaches do not represent the full suite available for deriving local WQBs for multiple types of water quality-related issues. The general lack of guidance is inconsistent with the need for, and benefits of, local WQBs, and can constrain the appropriate selection and subsequent evaluation of derivation approaches. Consequently, the defensibility of local WQBs may not be commensurate with the nature of the issues for which they are derived. Moreover, where local WQBs are incorporated into regulatory requirements, the lack of guidance presents a potential risk to the derivation of appropriate WQBs and the achievement of desired environmental outcomes. This review addresses the deficiency in guidance by 1) defining local WQBs and outlining initial considerations for deciding if one is required; 2) summarizing the existing regulatory context; 3) summarizing existing guidance and identifying gaps; 4) describing strengths, weaknesses, and potential applications of a range of derivation approaches based on laboratory and/or field data; and 5) presenting a conceptual framework for appropriately selecting and evaluating a derivation approach to best suit the need. The guidance incorporates an existing set of guiding principles for deriving local WQBs and reinforces an existing categorization of site-adapted and site-specific WQBs. The conceptual framework recognizes the need to strike an appropriate balance between effort and ecological risk and, thus, embeds the concept of fit-for-purpose by considering both the significance of the issue being assessed and the extent to which the approach provides confidence that the ecosystem will be appropriately protected. The guidance can be used by industry, regulators, and others for both the a priori selection and the post hoc evaluation of appropriate approaches for deriving local WQBs. Integr Environ Assess Manag 2019;15:683-702. © 2019 The Authors.

Chronic ammonia toxicity to juveniles of 2 tropical Australian freshwater mussels (Velesunio spp.): Toxicity test optimization and implications for water quality guideline values

Freshwater mussels play key roles in aquatic ecosystems, but are experiencing a global decline. Although studies have reported high acute sensitivity of mussels to some contaminants, chronic toxicity data are lacking for deriving high-reliability water quality guideline values. Ammonia is a contaminant of potential concern in some catchments of tropical northern Australia, where freshwater mussels are important ecological and cultural components. The extremely soft waters (hardness < 5 mg/L) of these environments can result in increased toxicity of many contaminants including ammonia, and regionally relevant tropical guideline values are needed to adequately protect these unique ecosystems. An optimized 14-d toxicity test protocol was used to assess the chronic toxicity of ammonia for 2 species, the lotic Velesunio sp. and the lentic Velesunio angasi. Ammonia exposures were conducted at pH 6.0 and 27 ± 0.5 °C to represent local environmental conditions, using shell length growth rate as the endpoint. Chronic toxicity estimates indicated high sensitivity to ammonia, with mean median effect concentrations (in total ammonia nitrogen) being 7.0 mg/L for V. angasi from the semi-urbanized Lake Bennett, 9.2 mg/L for V. angasi from Sandy Billabong, and 11.3 mg/L for Velesunio sp. from Gulungul Creek. When the 10% effect concentration values were compared with other chronic ammonia data (normalized to pH 7.0 and 20 °C), Velesunio spp. were found to be more sensitive than 8 of 16 other temperate and 7 of 9 tropical invertebrate and fish species. These chronic toxicity estimates will be used to further inform regionally relevant and site-specific guideline values. Environ Toxicol Chem 2019;38:841-851. © 2019 Commonwealth of Australia. Published by Wiley Periodicals Inc. on behalf of SETAC.

Freshwater chronic ammonia toxicity: A tropical-to-temperate comparison

The chronic toxicity of ammonia to tropical freshwater species is understudied, and thus data on temperate species have been used to derive water quality guideline values for tropical regions. Such practices may lead to underprotective guideline values due to differences in toxicities observed between tropical and temperate species. In addition, the presence of ammonia in low-ionic-strength waters may also result in higher toxicity, and studies on this factor are limited. The present study assessed the toxicity of ammonia to 6 tropical freshwater species in low-ionic-strength waters. Because ammonia toxicity varies depending on the pH and temperature, test water pH concentrations were maintained at approximately pH 6.0 ± 0.3 at temperatures between 27.5 and 30 °C. Low-effect chronic inhibition concentrations were derived for the following species: Chlorella sp. 66 mg L^-1 ; Lemna aequinoctialis 22 mg L^-1 ; Hydra viridissima 1.8 mg L^-1 ; Moinodaphnia macleayi 27 mg L^-1 ; Amerianna cumingi 17 mg L^-1 ; and Mogurnda mogurnda 5.4 mg L^-1 total ammonia nitrogen. Two of the species tested (a cnidarian and a fish species) were among the most sensitive reported anywhere within their taxonomic group. Chronic ammonia datasets representing toxicity estimates for temperate and tropical species were plotted and compared using species sensitivity distributions. The results indicate that the differences in chronic toxicity observed between tropical and temperate species were likely due to the low ionic strength of the waters to which tropical species were exposed, rather than any inherent physiological differences between species from tropical and temperate regions. This finding suggests that tropical waters of low ionic strength may be at a higher risk from ammonia compared with other freshwater ecosystems. Environ Toxicol Chem 2019;38:177-189. © 2018 Commonwealth of Australia. Published by Wiley Periodicals, Inc. on behalf of SETAC.

Observaciones ecológicas, corológicas y taxonómicas de hídridos dulceacuícolas (Cnidaria, Hydrozoa: Hydridae) en la Cuenca del Duero

Se describe la presencia de cuatro taxones de hidras de agua dulce (Cnidaria, Hydrozoa: Hydridae) en zonas someras epicontinentales de la cuenca del Duero (NO de España). En la subcuenca del Tera se encontraron individuos aislados sobre macrófitos sumergidos de tres taxones: Hydra vulgaris Pallas, 1766, Hydra (Pelmatohydra) oligactis Pallas, 1766 e Hydra (Chlorohydra) viridissima Pallas, 1766, y además en el Carrión grupos coloniales sobre bloques de cuarcita de la forma H. vulgaris var. aurantiaca Ehrenberg, 1838. En todos los casos se corresponde con ecosistemas de media montaña de aguas frías, transparentes y oligotróficas, de pH ligeramente ácido y con escasa mineralización. Todas las especies fueron localizadas en simpatría estricta, aunque en el lago de Sanabria se pudo citar tres taxones en diferentes hábitats. Se documenta la predación en cautividad de H. oligactis sobre gusanos oligoquetos y los periodos de formación de pólipos por gemación.

Acute ammonia toxicity to the larvae (glochidia) of the tropical Australian freshwater mussel Velesunio spp. Using a modified toxicity test protocol

Ammonia is recognized as a major pollutant worldwide, originating from natural and anthropogenic sources. Studies have reported that freshwater mussels are among the most sensitive taxa to ammonia, but few data are available on ammonia toxicity for the early life stages of freshwater mussels from tropical regions. We report on the modification of a 24-h acute toxicity test protocol for tropical freshwater mussels and application of the test using ammonia. Velesunio spp. from 3 different sites were used to assess the toxicity of ammonia at a targeted pH of 6.0 and a water temperature of 27.5 °C, which were the average annual values for some slightly to moderately acidic, soft water (3-6 mg/L as CaCO₃ ) creeks of tropical northern Australia. The valve closure responses of mussel glochidia (larvae) to a sodium chloride solution were used to measure the survival endpoint. Acute toxicity estimates indicate that tropical Velesunio spp. were highly sensitive to ammonia, with 24-h exposures to ammonium sulfate generating median lethal concentration estimates ranging from 6.8 to 14.2 mg/L total ammonia nitrogen, which, when adjusted to pH 7 and 20 °C, were among the highest sensitivities yet reported for any freshwater mussel species, and among the highest in sensitivity for any tropical taxon. These toxicity estimates can contribute to the derivation or refinement of ammonia guideline values for freshwater ecosystems globally. Environ Toxicol Chem 2018;37:2175-2187. © 2018 SETAC.