Un-ionized Ammonia Concentrations Research Articles

Implications of ammonia stress for the pathogenicity of Shewanella spp. in Oreochromis niloticus: effects on hematological, biochemical, immunological, and histopathological parameters

Environmental stressors (such as ammonia) in aquaculture could increase the risk of pathogenicity, posing a more severe threat to farmed fish. The aim of this study was to investigate the effects of ammonia stress on the pathogenicity of Shewanella spp. in Oreochromis niloticus. First, a 96-hour static test was used to determine the median lethal concentration (LC50) of unionized ammonia to Nile tilapia. After 96 h of exposure, the Un-ionized ammonia (UIA) LC50 was estimated to be 4.26 mg/L. Second, an experiment was conducted to test the effect of unionized ammonia stress on the pathogenicity of Shewanella spp. in O. niloticus for 30 days. A study involved 180 fish divided into six groups, with the first group serving as a control. The second group (AMN1/10) and the third group (AMN1/20) were not challenged and were exposed to 1/10 (0.42 mg/L) and 1/20 (0.21 mg/L) of the 96-hour LC50 of UIA, respectively. Then 0.2 mL (0.14 × 105) of Shewanella spp. was intraperitoneally injected into the fourth (SH), fifth (SH + AMN1/10), and sixth (SH + AMN1/20) groups, which were subjected to 0, 1/10 (0.42 mg/L), and 1/20 (0.21 mg/L) of the 96-hour LC50 of UIA, respectively. The survival rate, hematological indices, immunological parameters, and antioxidant activity of the fish significantly decreased when they were exposed to ammonia and Shewanella infection separately or together. Histopathological changes were also observed in the kidney and liver. Furthermore, both individual and combined exposures significantly altered renal and hepatic function, with notable increases in glucose and cortisol levels, as well as in the expression of proinflammatory cytokine genes (TNF-α and IL-1ß). However, the detrimental effects of co-exposure to ammonia stress and Shewanella infection were greater than those of separate exposures. As a result, we may say that increased ammonia concentrations enhance the infection of Shewanella spp. These findings could contribute to a better understanding of Shewanella infection in Nile tilapia.

The Ability of the Red Tilapia (Oreochromis sp.) to Tolerate Different Concentrations of Unionized Ammonia and Water Salinity Levels

The Ability of the Red Tilapia (Oreochromis sp.) to Tolerate Different Concentrations of Unionized Ammonia and Water Salinity Levels

Nile tilapia (Oreochromis niloticus) show high tolerance to acute ammonia exposure but lose metabolic scope during prolonged exposure at low concentration

Ammonia is a respiratory gas that is produced during the process of protein deamination. In the unionised form (NH3), it readily crosses biological membranes and is highly toxic to fish. In the present study we examined the effects of unionized ammonia (UIA), on the resting oxygen consumption (MO2), ventilation frequency (fV), heart rate (HR) and heart rate variability (HRV) in Nile tilapia (Oreochromis niloticus). Fish were either exposed to progressively increasing UIA concentrations, up to 97 µM over a 5 h period, or to a constant UIA level of 7 µM over a 24 h period. For both treatment groups resting MO2, HR and fV were recorded as physiological variables. Relative to the control group, the fish groups exposed to the incremental UIA levels did not exhibit significant changes in their MO2, HR and fV at UIA concentrations of 4, 10, 35, or 61 µM compared to control fish. Exposure to 97 µM UIA, however, elicited abrupt and significant downregulations (p < 0.05) in all three responses, as MO2, HR and fv decreased by 25, 54 and 76 % respectively, compared to control measurements. Heart rate became increasingly irregular with increasing UIA concentrations, and heart rate variability was significantly increased at 61 and 97 µM UIA. Prolonged exposure elicited significant changes at exposure 7 µM UIA. Standard (SMR) and maximum metabolic rate (MMR) were significantly reduced, as was the corresponding fV and HR. It is evident from this study that Nile tilapia is tolerant to short term exposure to UIA up to 61 µM but experience a significant metabolic change under conditions of prolonged UIA exposures even at low concentrations.

Locomotory behaviour of euryhaline rotifer Brachionus rotundiformis: The potential influence of probiotics on swimming pattern and speed

AbstractWe evaluated the effect of probiotics on the growth and culture condition of rotifer in medium‐sized culture tanks. The influence of probiotics on the changes in swimming patterns, velocity and sinuosity indices of rotifer was also examined. The rotifers (Brachionus rotundiformis) were cultured for 14 days in nine polycarbonate tanks containing seawater which were divided into three groups: a control group (Chlorella product) and two treatment groups: Chlorella + Probiotic I and Chlorella + Probiotic II. The rotifer population and the water quality parameters were monitored daily. To evaluate the locomotory behaviour of the rotifer, a sub‐sample containing rotifers was obtained from each treatment and placed on a glass‐bottomed dish. A high‐speed camera mounted on a stereo microscope was used to record the rotifer movement. The footage was then analysed using motion analysis software to establish the swimming velocity, swimming pattern and sinuosity indices of the rotifers. Co‐feeding rotifer on microalgae and probiotics resulted in a higher rotifer growth rate (0.51 ± 0.03) and decreased concentration of unionized ammonia (0.14 ± 0.02 mg L−1). In addition, the probiotic‐fed rotifers had 1.59 times higher average swimming velocity (0.97 ± 0.11 mm s−1) and more straight swimming pattern compared to rotifers that fed on microalgae alone whose velocity was slow (0.61 ± 0.14 mm s−1) and more sinuous. From these data, we can postulate that probiotics have the potential to attenuate rotifer culture conditions by decreasing ammonia concentration as well as influence rotifer swimming behaviour which could affect rotifer reproduction and the quality of fish larvae in aquaculture systems.

Determination of acute toxicity of unionized ammonia in juvenile longfin yellowtail (Seriola rivoliana)

AbstractThe median lethal concentration (LC50) of unionized ammonia (NH3‐N) in longfin yellowtail, Seriola rivoliana juveniles was assessed after 96 h of exposure using a semistatic water system. Experimental fish were exposed in triplicate to different ammonia concentrations: 0.55 ± 0.00; 0.94 ± 0.02; 1.18 ± 0.00; 1.72 ± 0.02, and 1.97 ± 0.09 NH3‐N mg/L. Additionally, a control group (0.00 ± 0.00 NH3‐N mg/L) was included. The 96 h LC50 of unionized ammonia in S. rivoliana was 0.58 mg/L. Fish exposed to different ammonia concentrations for 96 h displayed several lesions on gill tissues, that is, hyperplasia, epithelial lifting, fusion of the secondary lamellae, and some irreversible damage. Erratic behavior, such as swimming in circles and hyperventilation was observed before the fish died. The safe concentration of unionized ammonia in this study was estimated at 0.06 and 1.68 mg/L of total ammonia nitrogen (TAN). The outcomes observed in this study provide valuable insights into unionized ammonia effects for better water quality management in semi‐intensive and intensive systems for S. rivoliana culture.

Behavioral Variables to Assess the Toxicity of Unionized Ammonia in Aquatic Snails: Integrating Movement and Feeding Parameters

Behavioral endpoints are important parameters to assess the effects of toxicants on aquatic animals. These endpoints are useful in ecotoxicology because several toxicants modify the animal behavior, which may cause adverse effects at higher levels of ecological organization. However, for the development of new bioassays and for including the behavior in ecotoxicological risk assessment, the comparison of sensitivity between different behavioral endpoints is necessary. Additionally, some toxicants remain in aquatic environments for a few hours or days, which may lead to animal recovery after toxicant exposure. Our study aimed to assess the effect of unionized ammonia on the movement and feeding behaviors of the aquatic gastropod Potamopyrgus antipodarum (Tateidae, Mollusca) and its recovery after exposure. Four treatments were used: a control and three nominal concentrations of unionized ammonia (0.25, 0.5 and 1 mg N-NH3/L). Each treatment was replicated eight times, with six animals in each replicate. Animals were exposed to unionized ammonia for 48 h (exposure period) and, subsequently, to control water for 144 h (post-exposure period). Two movement variables were monitored without food and five feeding behavioral variables were monitored in the presence of food. Some of the feeding behavioral variables showed higher sensitivity (LOEC = 0.25–0.5 mg N-NH3/L) than the movement behavior variables monitored without food (LOEC = 1 mg N-NH3/L). After exposure to unionized ammonia, animals showed a recovery of most behavioral endpoints. The inclusion of post-exposure period and feeding behaviors in bioassays may make studies more realistic, which is crucial for a proper ecotoxicological risk assessment.

Effects of ammonia nitrogen on early growth and survival of the ‘Zebra 2’ strain of the manila clam ( Ruditapes philippinarum )

The ‘Zebra 2’ strain of the Manila clam (Ruditapes philippinarum) is a newly bred for aquaculture in the low temperature Bohai and Yellow seas in northern China. The goal of this study was to determine the tolerance of ‘Zebra 2’ clams at early developmental stages to total ammonia nitrogen (TAN) under acute stress and continuous subacute stress levels. ‘Zebra 2’ were cultured under TAN stress at water salinity of 27–28, temperature of 21–28°C and pH of 8.0–8.2. Survival rate and production of clams from the fertilized egg to juvenile stages were measured. The acute stress test revealed that the median effective concentrations of TAN for hatchability and deformity of fertilized eggs at 24 h were 7.08 and 15.12 mg/L, with the unionized ammonia (UIA) at 0.22 and 0.36 mg/L respectively. The 50% lethal concentrations for D-shaped larvae (shell length 101.50 μm), umbo larvae (179.67 μm) and juveniles (610.50 μm) at 96 h were 3.28, 48.90 and 57.57 mg/L, with UIA at 0.10, 2.08 and 2.99 mg/L respectively. These results suggested that the ‘Zebra 2’ clams hatching and D-shaped larvae stages were most sensitive to TAN and that the tolerance significantly increased after the umbo larval stage. In the continuous subacute stress test, ‘Zebra 2’ juveniles were observed under all the treatments after 53 days of exposure to TAN stress at 5.45 mg/L (0.23 mg/L UIA). The maximal acceptable toxicant concentration of UIA used to determine the mortality rate, yield and relative yield was ranged from 0.12 to 0.23 mg/L. These findings suggested that maintaining TAN <0.22 mg/L and UIA ≤0.021 mg/L at seawater pH ≤8.5, salinity ≥25 and water temperature ≤25°C would improve larval rearing of ‘Zebra 2’ clams.

The effects of acute and chronic exposure of ammonia on juvenile burbot (Lota lota) growth and survival

Burbot, Lota lota are a candidate species for commercial aquaculture because of their palatability and optimal growth at temperatures similar to those used in freshwater trout aquaculture. However, data on burbot environmental tolerances and requirements are sparse, especially with reference to water quality parameters relevant to aquaculture, such as un-ionized ammonia (UIA) concentration. We used a two-phased approach to evaluate the effects of un-ionized ammonia on the growth and survival of burbot. First, we measured the acute toxicity of ammonia to juvenile burbot (mean SL: 144 ± 6 mm; mean wet weight: 27.3 ± 3.4 g) and calculated a 96-h LC50 of 0.58 mg·L−1 UIA. We then measured the 60-d growth, food consumption rate, and performance of burbot (mean initial SL: 190 ± 6.9 mm; mean initial weight: 67.0 ± 4.5 g) reared in 0.00, 0.03, 0.06, 0.12, or 0.19 mg·L−1 UIA using a 20-tank flow-through system under optimal temperature (14.7 °C) and dissolved oxygen (DO >80% saturation) conditions. Elevated ammonia concentration significantly reduced daily food consumption and subsequent growth. Fish exposed to 0.03 and 0.06 mg·L−1 UIA showed temporal acclimation to UIA, achieving food consumption and growth rates on par with control fish after 30 days of exposure. The estimated effective UIA concentrations for 10 and 20% reductions in growth (EC10 and EC20) based on our data are: EC10 = 0.03 ± 0.006 mg·L−1 and EC20 = 0.050 ± 0.004 mg·L−1. We recommend rearing burbot under conditions that keep UIA levels ≤0.03 mg·L−1 based on our finding that above 0.03 mg·L−1 cause measurable reductions in growth rate.

Hemato-biochemical responses and histopathological alterations in the gill and kidney tissues of Osteobrama belangeri (Valenciennes, 1844) exposed to different sub-lethal unionized ammonia

Ammonia is a factor restricting production in aquaculture systems, hindering fish production adversely. A detailed study was planned and conducted using a static water system to scrutinize the toxic effects of unionized ammonia (UIA) on patho-physiological responses of O. belangeri, an important aquaculture candidate for diversification of freshwater aquaculture and endangered species, when exposed to different sub-lethal concentrations of UIA. The 96-h LC50 value of UIA on O. belangeri was found to be 1.36 mg l−1. The sub-lethal toxicity test with three UIA concentrations, i.e., 0.27, 0.68, and 0.80 mg l−1 at different exposure period of 24, 48, 72, and 96-h revealed that exposure to UIA induced a significant reduction in hematological parameters, such as total erythrocyte count (TEC), total leukocyte count (TLC), hemoglobin (Hb), and hematocrit (Hct). Mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) also substantially declined due to UIA exposure. Among biochemical parameters, blood glucose, serum glutamate pyruvate transaminase (SGPT), serum glutamate oxaloacetate transaminase (SGOT) and Na+ and K+ ion increased significantly. In contrast, serum protein, alkaline phosphatase (ALP) and serum albumin notably decreased due to ammonia exposure. Fish exposed to different UIA concentrations for 96-h displayed several histopathologic alterations in the gill and kidney tissues. Gill tissues showed several lamellar deformations, while kidney tissues showed significant changes at the level of the glomerulus and tubular epithelium. The NOEL or safe concentration of UIA for this particular fish species was found to be 0.07 mg l−1. The observed patho-physiological alterations in the present study establish the most detail insights of UIA stress in O. belangeri and will enhance the international literature on UIA toxicity.

Comparison of Surface- and Pore-Water Quality Between Two Maryland Streams with the Endangered Dwarf Wedgemussel (Alasmidonta heterodon)

Degraded water quality, particularly elevated concentrations of ammonia, chloride, and toxic metals, can be harmful to freshwater mussels. We investigated whether the contraction in Dwarf Wedgemussel (Alasmidonta heterodon) distribution that occurred between 2002 and 2012 within Browns Branch (BB), a stream within a predominantly agricultural watershed on the Coastal Plain of Maryland, was associated with these and other water-quality factors. We measured surface- and pore-water concentrations of different forms of nitrogen, orthophosphate, anions, and dissolved metals at two sites in BB for 7 mo in 2014. The upstream site (BBUP) represented the lower extent of the current Dwarf Wedgemussel population, and the downstream site (BBDO) represented the lower extent of the species' distribution observed in a 2002 survey. As a comparison, we also sampled one site in Nanjemoy Creek (NANJ), a largely forested Coastal Plain watershed where Dwarf Wedgemussel distribution exhibited no change over the same 10-yr period. We tested the hypothesis that concentrations of potentially toxic analytes were significantly higher at BBDO than at BBUP and NANJ. Total ammonia nitrogen (TAN) was the only analyte consistent with this hypothesis in both surface and pore water. Concentrations of pore-water un-ionized ammonia (UIA-N) at BBDO were below the U.S. Environmental Protection Agency's Ambient Water Quality Criterion, but they frequently exceeded 0.2 µg/L, a concentration previously associated with a lack of mussel recruitment. We recommend conducting a new mussel survey of BB to assess current condition. If range contraction is still evident, more frequent and extended sampling should be performed, including capturing high-flow events to determine if pulses of ammonia and other pollutants occur.

EFEK SUB LETHAL AMONIA AMBIEN TERHADAP HISTOPATOLOGIS IKAN NILA (Oreochromis niloticus) YANG DIPELIHARA DALAM SISTEM BIOFLOK

The purpose of this research were to measure the increasing of unionized ammonia during start-up period of biofloc system for growing Nile Tilapia and to figure out its effect on histopathological changes. There was only one treatment that designed with three replication, which was 40 liters of water that contained eight fishes of each weighed 22.. The biofloc system was treated with C/N ration 12:1. Total Ammonia Nitrogen, pH and temperature were measured daily as long as 14 days. the tissue of gill, liver and kidney were cut off at the end of the experiment for histopathological examination. The result of the experiment showed that the peak of unionized ammonia concentration achieved 0.34±0.05 mg/l at 10th day. Then, decreased rapidly to 0.003±0.0009 mg/l at 14th day. The gill, liver, and kidney had regressive changes as physiologic sub lethal response of unionized ammonia expose. Keywords : Biofloc, unionized ammonia, Nile Tilapia, histopatholocal

Acute toxicity of non-ionized ammonia on tambacu (Colossoma macropomum x Piaractus mesopotamicus)

Ammonia is a toxic compound to aquatic organisms and at high concentrations in water, it can cause various changes in the animal. Therefore, it becomes important to determine the tolerance of farmed aquatic animals for that substance. Thus, the aim of this study was to determine the mean lethal concentration (LC50-96 h) of un-ionized ammonia (NH3) in tambacu fingerlings (Colossoma macropomum x Piaractus mesopotamicus) in acute toxicity test. The fingerlings were exposed to ammonia at concentrations of: 0.09 (control); 0.54; 1.23; 2.52; 3.44 and 3.66 mg L-1 NH3, which were obtained from the application of NH4Cl. The test lasted 96 hours and mortalities were recorded over that period. The LC50 was determined by the Trimmed Spearman Karber statistical method. The LC50-96 h of non-ionized ammonia (NH3) for fingerlings of the tambacu hybrid was 1.63 mg L-1.

Acute and chronic toxicity of ammonia in Persian sturgeon, Acipenser persicus, fingerlings

In the present study, susceptibility of Persian sturgeon, Acipenser persicus, to un-ionized ammonia (UIA) was studied. Fish with an average weight of 5.52±0.45 g were exposed to different concentrations of un-ionized ammonia (UIA) to determine median lethal concentration (96-h-LC 50 ). The fish were exposed to six different concentrations of UIA (control, 0.16, 0.31, 0.62, 0.94 and 1.25 mg/l UIA). The control group was not challenged with ammonia (0.0008 mg/l UIA). The results showed that the 96-h-LC 50 of UIA in Persian sturgeon was 0.46 mg/l. According to 96-h-LC 50 ,mid-term exposure to sub-lethal UIA was examined. In the chronic examination, the fish were exposed to different levels of sub-lethal ammonia; control (0.0008 mg/l UIA), 10% of LC 50 (0.05 mg/l UIA), 5% of LC 50 (0.025 mg/l UIA) and 1% of LC 50 (0.005 mg/l UIA) for 30 days. Final length, final weight, weight gain, specific growth rate, daily weight gain and body weigh index decreased significantly in the fish exposed to 0.05 and 0.025 mg/l UIA. According to the results, conversion ratio and condition factor indices were higher in the fish exposed to 0.005 mg/l UIA and control group compared with the fish exposed to 0.05 and 0.025 mg/l UIA.

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 135.4mgL-1, the corresponding unionized ammonia (NH3) concentration was 1.5mgL-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 11.3mgL-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.

Molecular Characterization of Vibrio Harveyi and Vibrio alginolyticus with the Impact of Stressful Environment on Some Naturally Infected Marine Fish

Cultured seabass (Dicentrarchus labrax L.) and seabream (Sparus aurata L.) are marine species of high economic important especially in Mediterranean aquaculture. Among bacterial diseases of marine cultured and wild fish, vibriosis caused by Vibrio species is one of the most prevalent diseases. In the present work, we report the isolation and identification of the V. harveyi and V. alginolyticus, based on biochemical and molecular characterization, from cultured seabass and seabream native to private fish farms at Mathalath-El Diba region, Domitte City at Domitte Governorate, Egypt during summer season. The most prominent clinical signs of diseased fish were hemorrhagic ulceration on the dorsal musculature and caudal peduncle area as well as sever protrusion of the eye outside the orbital cavity. Histological examination of seabass revealed haemorrhage on the liver and nodular formation on different organs especially in kidney and liver. While, diseased seabream showed marbling appearance of gill with nodular formation and necrotic area distributed over the liver. Physico-chemical characteristics of water samples collected parallel to fish samples indicated that pH and organic matter of the water sample was within the permissible limits. However, the unionized ammonia, nitrate, and hydrogen sulphate concentrations were higher than the acceptable limits. Moreover, the heavy metals (copper, zinc, cadmium, lead, mercury, nickel, and iron) contained of water samples were higher than permissible limits. In regards to the haematological parameters associated with diseased and apparently healthy seabream and seabass. The total protein, albumin, and globulin were lower in diseased seabass and seabream than apparently healthy fish. Serum lysozyme and bactericidal activity was lower in the diseased fish than apparently healthy seabass and seabream. Levels of aspartate amino-transferase (S.AST) and alanine amino transferase (S.ALT) in plasma of diseased seabass and seabream were higher than apparent healthy seabass and seabream. Altogether, higher level of heavy metal concentrations in water samples than the permissible limits act as chemical stressors that help in increase the prevalence of V. harveyi and V. alginolyticus species in seabass and seabream.

Effect of two commercial probiotic products on population growth of rotifer Brachionus rotundiformis Tschugunoff

The application of probiotics has varying effects on rotifer culture. These effects can either be directly on their growth and reproduction or indirectly by affecting the culture environment. The role played by specific probiotic candidates is still indistinct and further research is required to ascertain their significance in rotifer culture. In this study, euryhaline rotifer Brachionus rotundiformis (SS-type) was used to evaluate the effect of two commercial probiotic products on rotifer density, reproductive parameters and unionized ammonia concentration for a twelve-day culture period. To estimate these parameters, rotifers were cultured in glass bottles containing dilute sterilized sea water with the following five diet treatments: Nannochloropsis oculata (control), Igsign (PB1), Toaraze Aqua (PB2) or the combination of N. oculata with either PB1 or PB2. The rotifer density was significantly affected by the addition of probiotic. N. oculata + PB2 treatment resulted in higher rotifer density and specific growth rate compared to the control treatment. Mixis induction was unaffected by N. oculata + PB2 while it was repressed by N. oculata + PB1. Ammonia concentration was not significantly affected with the addition of probiotics. These results indicate that probiotics have synergetic effects with microalgae diet that resulted in the highest rotifer densities.

Simultaneous nutrient removal and biomass/lipid production by Chlorella sp. in seafood processing wastewater

Microalgae cultivation in wastewater has received increasing attention in recent years due to its many advantages. In this work, microalgae were cultured in seafood processing wastewater (SPW) for algal biomass and lipid production as well as nutrient removal. The biomass yield of Chlorella sp. achieved in the batch cultivation was 896 mg L−1, indicating that SPW contains a certain amount of nutrients which can be used for the growth of microalgae. However, the maximum specific growth rate of Chlorella sp. cultured in SPW throughout the whole cultivation period was only 0.040 d−1, suggesting that the growth of algal cells was inhibited during the culture process. High concentration of unionized ammonia in the SPW was found to be a factor inhibiting the growth of Chlorella sp. Aerated SPW (ASPW) and diluted SPW (DSPW) proved to be better culture media than SPW without pretreatment. The maximum specific growth rates of Chlorella sp. cultured in ASPW and DSPW during the culture interval were 0.156 and 0.091 d−1, respectively. Aeration pretreatment of SPW reduced the amount of toxic unionized ammonia, while most of the nutrients were retained in the wastewater. Therefore, higher biomass productivity (77.7 mg L−1 d−1) and higher lipid productivity (20.4 mg L−1 d−1) of microalgae were achieved in ASPW. Additionally, improved nutrient removal rates from ASPW were also achieved due to the faster growth of microalgae. The average nutrient removal rates in ASPW during the whole cultivation period were 4.98 and 1.91 mg L−1 d−1 for nitrogen and phosphorus, respectively.

Decomposition of 8 mol·L−1 Urea Solution at 298.15 K

Degradation of urea in 8 mol·L−1 aqueous solution (20% w/w N) has been studied at 298.15 ± 0.01 K over a time period of 150 days. The data were obtained by periodicaly measuring the electric conductivity, acidity, and concentrations of the main species of the solution, such as cyanate, ammonim carbonate and ammonium hydrogencarbonate. The concentration of un-ionized ammonia was calculated on the basis of the data for the total ammonia content in the solution.

Mortality, hematology, and histopathology of common snook Centropomus undecimalis (Perciformes: Centropomidae) exposed to acute toxicity of ammonia

ABSTRACTThis study aimed to evaluate the tolerance of common snook Centropomus undecimalis larvae and juveniles exposed to acute concentrations of un-ionized ammonia for 96 h at 35g L−1 salinity, after 24 h starvation. For that, 10 larvae (20.85 ± 1.46 mm) of 47 days post hatch (DPH) per experimental unit (1.5 L) were exposed to 0.00 ± 0.00, 0.65 ± 0.04, 1.29 ± 0.09, 2.59 ± 0.18, 3.88 ± 0.27, 5.17 ± 0.34, and 6.47 ± 0.43 mg L−1 NH3, in triplicates, at 26.72 ± 0.08°C, dissolved oxygen at 5.72 ± 0.10 mg L−1 and pH 8.45 ± 0.06. During this period, no mortalities were observed. Another trial was performed with five juveniles (20.35 ± 6.10 g, 13.90 ± 1.75 cm) per experimental unit (60 L) exposed to 0.00 ± 0.00, 2.26 ± 0.07, 2.68 ± 0.11, 3.20 ± 0.13, 3.68 ± 0.17, and 4.27 ± 0.16 mg L−1 NH3, in triplicates, at 21.90 ± 0.76°C, dissolved oxygen at 6.27 ± 0.21 mg L−1 and pH at 8.38 ± 0.04. Fish mortality increased as ammonia concentrations increased at each day, and LC50 96 h was 3.52 mg L−1 NH3. Larvae were less sensitive than juveniles, demonstrating that the environmental toxicity of ammonia to common snook is influenced by age. Sublethal exposition to ammonia caused histological damages in gills of common snook juveniles and variation on glucose levels, hematocrit, and red blood cells number, showing negative effects on fish homeostasis. Moreover, compared to other species, the common snook has great resistance to ammonia.

Biomarkers as tools to assess the chronic toxicity of ammonia in the juvenile Mugil cephalus

ABSTRACTWith juvenile fish as the subject, the effects of low concentration ammonia on antioxidant system were studied using Mugil cephalus. Samples of gill and liver tissue were obtained from 0.35, 0.70, 1.5 and 3 mg/L ammonia groups at 0, 5, 10, 15 and 20 days of exposure, at which times the biomarkers were measured. Results showed that gill malondialdehyde (MDA) content exhibited an initial significant increase (p ≤ 0.05) at unionised ammonia concentrations of 0.70, 1.5 and 3.0 mg/L on day 5, followed by subsequent declines, while liver MDA levels exhibited significant increases (p ≤ 0.05) at unionised ammonia concentrations of 1.5 mg/L starting on day 10 and at 3.0 mg/L starting on day 5. With exposure to ammonia at different concentrations, Na+-K+-ATPase activity in liver and gill decreased over time. The Na+-K+-ATPase activity was negatively related to ammonia concentration from 0.70 to 3.0 mg/L. Overall, our results show that MDA and Na+-K+-ATPase, evaluated here as potential biomarkers of ammonia exposure, exhibited responses to sublethal concentrations of ammonia that were concentration dependent.