Nitrate acute toxicity to post larvae and juveniles of Macrobrachium amazonicum (Heller, 1862)

Differential sensitivity of offspring from four species of goodeine freshwater fish to acute exposure to nitrates

Nitrate-nitrogen (NO3-N) pollution related to anthropogenic activities is increasing in freshwater ecosystems. Knowledge about NO3-N sensitivity in freshwater wild fish is needed to understand the differential tolerance between species. Goodeinae is a subfamily of 41 endemic fishes that inhabit central Mexico, with 33 species in the IUCN red list and three extinct. Distributional patterns suggest tolerant and sensitive goodeines related to the conservation gradient of freshwater ecosystems. Four species with a differential distribution and tolerance were selected to evaluate their physiological responses to NO3-N. Fish were exposed to different NO3-N concentrations for 96 h and the median lethal concentration (LC50) was determined. Swimming disorders plus gill and liver histopathological indexes were estimated and incorporated into an Integrated Biomarker Response (IBR) for each species. Skiffia lermae (LC50 = 474.332 mg/L) and Xenotoca variata (LC50 = 520.273 mg/L) were more sensitive than Goodea atripinnis (LC50 = 953.049 mg/L) and Alloophorus robustus (LC50 = 1537.13 mg/L). The typical histological damage produced by NaNO3-N exposure was fusion of secondary lamellae in gills. This was present in all species and cellular degeneration was observed at the highest concentrations. Secondary lamellae aneurysms were only observed in G. atripinnis. Liver alterations included vascular dilation in hepatic sinusoids, hyperemia and nuclear hypertrophy; higher concentrations produced hepatocyte cytoplasmic vacuolation and reduced frequency of cell nuclei. Behavioral and histopathological alterations could explain the differential species sensitivity. The results suggest that species which preserve gill function and transfer the task of detoxification to the liver might have the best chance of surviving in polluted environments. Moreover, species previously considered as tolerant may be highly susceptible to NaNO3-N exposure. Therefore, it is necessary to closely monitor NaNO3-N concentrations in freshwater ecosystems and, if possible, reduce their levels to avoid the loss of wild populations.

Pseudomonas oligotrophica sp. nov., a Novel Denitrifying Bacterium Possessing Nitrogen Removal Capability Under Low Carbon–Nitrogen Ratio Condition

Pseudomonas is a large and diverse genus within the Gammaproteobacteria known for its important ecological role in the environment. These bacteria exhibit versatile features of which the ability of heterotrophic nitrification and aerobic denitrification can be applied for nitrogen removal from the wastewater. A novel denitrifying bacterium, designated JM10B5a^T, was isolated from the pond water for juvenile Litopenaeus vannamei. The phylogenetic, genomic, physiological, and biochemical analyses illustrated that strain JM10B5a^T represented a novel species of the genus Pseudomonas, for which the name Pseudomonas oligotrophica sp. nov. was proposed. The effects of carbon sources and C/N ratios on denitrification performance of strain JM10B5a^T were investigated. In addition, the results revealed that sodium acetate was selected as the optimum carbon source for denitrification of this strain. Besides, strain JM10B5a^T could exhibit complete nitrate removal at the low C/N ratio of 3. Genomic analyses revealed that JM10B5a^T possessed the functional genes including napA, narG, nirS, norB, and nosZ, which might participate in the complete denitrification process. Comparative genomic analyses indicated that many genes related to aggregation, utilization of alkylphosphonate and tricarballylate, biosynthesis of cofactors, and vitamins were contained in the genome of strain JM10B5a^T. These genomic features were indicative of its adaption to various niches. Moreover, strain JM10B5a^T harbored the complete operons required for the biosynthesis of vibrioferrin, a siderophore, which might be conducive to the high denitrification efficiency of denitrifying bacterium at low C/N ratio. Our findings demonstrated that the strain JM10B5a^T could be a promising candidate for treating wastewater with a low C/N ratio.

Influence of cerium oxide nanoparticles on dairy effluent nitrate and phosphate bioremediation

This study investigated, for the first time, the role of cerium oxide nanoparticles (CeO₂ NPs) on dairy effluent nitrate and phosphate bioremediation using different inoculum sources. Two inoculum sources (wastewater and sludge) were obtained from the dairy wastewater treatment plant unit. A culture was prepared to be tested in the treatment of nitrate and phosphate effluent, and the role of CeO₂ NPs was checked to be completely efficient after 5 days of incubation. The reduction efficiency of nitrate using sludge as inoculum source was improved up to 89.01% and 68.12% for phosphate compared to control. In the case of using wastewater as an inoculum source, the nitrate reduction was improved up to 83.30% and 87.75% for phosphate compared to control. The bacterial richness showed a significant variance (higher richness) between control and other samples. The optimal concentration of CeO₂ NPs for inoculum richness and nitrate and phosphate reduction was (sludge: 1 × 10^-10 ppm) and (wastewater: 1 × 10^-12 ppm). The results revealed that CeO₂ NPs could enhance the microbial growth of different inoculum sources that have a key role in dairy effluent nitrate and phosphate bioremediation.

A state-of-the-art review on producing engineered biochar from shellfish waste and its application in aquaculture wastewater treatment

Global production of shellfish aquaculture is steadily increasing owing to the growing market demands for shellfish. The intensification of shellfish aquaculture to maximize production rate has led to increased generation of aquaculture waste streams, particularly the effluents and shellfish wastes. If not effectively managed, these wastes could pose serious threats to human health and the ecosystem while compromising the overall sustainability of the industry. The present work comprehensively reviews the source, composition, and environmental implications of shellfish wastes and aquaculture wastewater. Moreover, recent advancements in the valorization of shellfish wastes into value-added biochar via emerging thermochemical and modification techniques are scrutinized. The utilization of the produced biochar in removing emerging pollutants from aquaculture wastewater is also discussed. It was revealed that shellfish waste-derived biochar exhibits relatively higher adsorption capacities (300-1500 mg/g) compared to lignocellulose biochar (<200 mg/g). The shellfish waste-derived biochar can be effectively employed for the removal of various contaminants such as antibiotics, heavy metals, and excessive nutrients from aquaculture wastewater. Finally, future research priorities and challenges faced to improve the sustainability of the shellfish aquaculture industry to effectively support global food security are elaborated. This review envisages that future studies should focus on the biorefinery concept to extract more useful compounds (e.g., carotenoid, chitin) from shellfish wastes for promoting environmental-friendly aquaculture.

Analysis of Behavior Trajectory Based on Deep Learning in Ammonia Environment for Fish

Ammonia can be produced by the respiration and excretion of fish during the farming process, which can affect the life of fish. In this paper, to research the behavior of fish under different ammonia concentration and make the corresponding judgment and early warning for the abnormal behavior of fish, the different ammonia environments are simulated by adding the ammonium chloride into the water. Different from the existing methods of directly artificial observation or artificial marking, this paper proposed a recognition and analysis of behavior trajectory approach based on deep learning. Firstly, the three-dimensional spatial trajectories of fish are drawn by three-dimensional reconstruction. Then, the influence of different concentrations of ammonia on fish is analyzed according to the behavior trajectory of fish in different concentrations of ammonia. The results of comparative experiments show that the movement of fish and vitality decrease significantly, and the fish often stagnates in the water of containing ammonium chloride. The proposed approach can provide a new idea for the behavior analysis of animal.