Simulated Pond Research Articles

Effect of ozone on Vibrio removal in a simulated earthen shrimp pond

ABSTRACT This study investigated the efficacy of ozone treatment on Vibrio pathogen removal within a simulated earthen shrimp pond, conducted in three phases. First, physical and chemical properties of the soil, alongside the Vibrio pathogen, were assessed. Results indicated neutral pH levels, high organic matter, and organic carbon content, with a Vibrio pathogen load of 1.0 ± 0.0 × 103 CFU/mg. Second, ozone treatment was applied, comparing its effectiveness in Vibrio pathogen control between treated and untreated soil sets. The treated set exhibited a significantly lower Vibrio pathogen load (6.00 ± 1.41 × 103 CFU/mg) compared to the untreated control (2.00 ± 2.12 × 105 CFU/mg), resulting in a 97.23% eradication efficiency. Concurrently, ammonia rates decreased with ozone, indicating potential benefits for shrimp aquaculture. Finally, ozone application in a simulated earthen pond over 45 days effectively controlled Vibrio pathogens. In the untreated soil set, Vibrio pathogen levels rose to 9.48 ± 1.73 × 105 CFU/mg, while in the ozone-treated, they ranged from 6.5 ± 2.12 × 103 to 1.25 ± 0.29 × 105 CFU/mg. Shrimp growth parameters, including average daily gain, survival rates, and feed conversion ratio, were compared between groups, suggesting ozone treatment's feasibility without adverse effects on shrimp growth. Water quality parameters remained within suitable ranges for shrimp cultivation. These findings highlight ozone's potential as an effective method for Vibrio pathogen control in shrimp aquaculture, with implications for industry sustainability and productivity.

A comparative analysis of growth and nutritional quality of the hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) in a simulated pond system and a recirculating aquaculture system

Groupers, as a popular economic fish species, are now more frequently cultured in land-based facilities, however, traditional pond-farming methods are plagued by frequent disease outbreaks, unstable economic benefits, and environmental pollution. To explore a new farming mode for a grouper, an 80-day cultivation experiment was conducted using both a simulated pond system (SPS) and a recirculating aquaculture system (RAS). The research aims to evaluate the growth performance, health (pathogenic bacteria, intestinal microbiota), off-flavor compounds (geosmin, 2-methylisoborneol), and nutritional component (amino acids, fatty acid composition and content) of a hybrid grouper (Pinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) under different aquaculture systems. The results showed that the hybrid grouper in a RAS exhibited better growth performance; the concentration of Vibrio in the fish tissue in the RAS was significantly lower than that in the SPS. Moreover, the content of fresh amino acids in the RAS was significantly higher, and the levels of saturated fatty acids (SFAs) and ω-6 polyunsaturated fatty acids (ω-6PUFAs) were significantly higher in the RAS. This finding indicates the superior flavor and nutritional value of the grouper. These results prove that the RAS is suitable for the widespread cultivation of grouper.

Hypothalamic transcriptome response to simulated diel earthen pond hypoxia cycles in channel catfish (Ictalurus punctatus).

Commercial culture of channel catfish (Ictalurus punctatus) occurs in earthen ponds that are characterized by diel swings in dissolved oxygen concentration that can fall to severe levels of hypoxia, which can suppress appetite and lead to suboptimal growth. Given the significance of the hypothalamus in regulating these processes in other fishes, an investigation into the hypothalamus transcriptome was conducted to identify specific genes and expression patterns responding to hypoxia. Channel catfish in normoxic water were compared with catfish subjected to 12 h of hypoxia (20% oxygen saturation; 1.8 mg O2/L; 27°C) followed by 12 h of recovery in normoxia to mimic 24 h in a catfish aquaculture pond. Fish were sampled at 0-, 6-, 12-, 18-, and 24-h timepoints, with the 6- and 12-h samplings occurring during hypoxia. A total of 190 genes were differentially expressed during the experiment, with most occurring during hypoxia and returning to baseline values within 6 h of normoxia. Differentially expressed genes were sorted by function into Gene Ontology biological processes and revealed that most were categorized as "response to hypoxia," "sprouting angiogenesis," and "cellular response to xenobiotic stimulus." The patterns of gene expression reported here suggest that transcriptome responses to hypoxia are broad and quickly reversibly with the onset of normoxia. Although no genes commonly reported to modulate appetite were found to be differentially expressed in this experiment, several candidates were identified for future studies investigating the interplay between hypoxia and appetite in channel catfish, including adm, igfbp1a, igfbp7, and stc2b.NEW & NOTEWORTHY Channel catfish are an economically important species that experience diel episodic periods of hypoxia that can reduce appetite. This is the first study to investigate their transcriptome from the hypothalamus in a simulated 24-h span in a commercial catfish pond, with 12 h of hypoxia and 12 h of normoxia. The research revealed functional groups of genes relating to hypoxia, angiogenesis, and glycolysis as well as individual target genes possibly involved in appetite regulation.

Submerged plant-biochar composite system exhibits effective control over residual organic pollutants in the benthic organisms of aquaculture ponds

As of now, submerged plants and biochar have demonstrated significant benefits in aquaculture pond sediment remediation. However, there is limited research on the synergistic effects of biochar and submerged plants in mitigating hydrophobic organic contaminant (HOC) accumulation in aquaculture benthic organisms and in controlling the nutrient (nitrogen and phosphorus) levels in aquaculture water. This study assesses a submerged plant-biochar system's efficacy in removing HOCs from simulated freshwater aquaculture ponds. Vallisneria natans was planted in sediment with varying levels of wheat straw biochar, while Corbicula fluminea served as the targeted benthic organism. The bioaccumulation experiment identified the optimal biochar ratio for the Vallisneria natans-biochar system in controlling HOCs in aquaculture products. Analyses included final accumulation concentrations in benthic organisms, changes in freely-dissolved concentrations in aquaculture sediment, and a mass balance calculation to explore key factors in their removal from the system. Results indicated that the Vallisneria natans-1.5% biochar composite system achieved optimal control of HOCs in sediment and aquaculture products. Biochar addition to the sediment in the composite system demonstrated a “promotion with low addition, inhibition with high addition” effect on Vallisneria natans growth. Notably, the addition of 1.5% biochar (VN1.5 group) significantly promoted the growth of Vallisneria natans leaves and roots. Comparing the final pollutant proportions in different environmental media, concentrations in water (0.20%–1.8%), clam accumulation (0.032%–0.11%), and plant absorption (0.10%–0.44%) constituted a minimal portion of the overall pollutant load in the system. The majority of pollutants (24%–65%) were degraded in the aquaculture environment, with microbial degradation likely playing a predominant role. Bacterial phyla, particularly Proteobacteria and Firmicutes, were identified as potential direct contributors to pollutant degradation in the Vallisneria natans-biochar system.

EXPERIMENTATION OF EVAPORATION REDUCTION BY A USE OF PLASTIC BOTTLES COVERING

Evaporation significantly affects the loss of water in reservoir. The effective use of water-surface covering materials for evaporation reduction purpose is commercially performed including plastic spherical and circular shapes. This study initiates to reuse very common Polyethylene Terephthalate (PET) drinking-water bottles to cover water surface instead. The bottle shape could have a covering percentage ratio as much as 91% equal to a commercial ball or circular disk. The experiment was designed and conducted to prove the reduction of water evaporation rate using eight simulated ponds. The testing aspects are the opacity of the floating bottles, the coverage area, and the floating pattern. Based on environmental impact concern, the deterioration of PET bottles due to hydrolysis reaction and ultraviolet rays in natural conditions is also investigated. The water samples from the testing ponds are collected and analyzed to be compared with the water quality standard. Initial result from the experiment showed that PET bottles containing laminated-aluminum-foiled (LAF) plastic bags have the greatest reduction in evaporation among different opaque materials. Cover flotation percentages of 75% and 100% were able to reduce evaporation the most and with little difference. The raft-floating pattern has a slightly lower evaporation rate compared to the free-floating. All this has the potential to reduce evaporation which are a very cost-effective alternative to the existing commercial materials and help support the reuse of plastic waste.

Developmental environment has lasting effects on amphibian post-metamorphic behavior and thermal physiology.

Environmental challenges early in development can result in complex phenotypic trade-offs and long-term effects on individual physiology, performance and behavior, with implications for disease and predation risk. We examined the effects of simulated pond drying and elevated water temperatures on development, growth, thermal physiology and behavior in a North American amphibian, Rana sphenocephala. Tadpoles were raised in outdoor mesocosms under warming and drying regimes based on projected climatic conditions in 2070. We predicted that amphibians experiencing the rapid pond drying and elevated pond temperatures associated with climate change would accelerate development, be smaller at metamorphosis and demonstrate long-term differences in physiology and exploratory behavior post-metamorphosis. Although both drying and warming accelerated development and reduced survival to metamorphosis, only drying resulted in smaller animals at metamorphosis. Around 1month post-metamorphosis, animals from the control treatment jumped relatively farther at high temperatures in jumping trials. In addition, across all treatments, frogs with shorter larval periods had lower critical thermal minima and maxima. We also found that developing under warming and drying resulted in a less exploratory behavioral phenotype, and that drying resulted in higher selected temperatures in a thermal gradient. Furthermore, behavior predicted thermal preference, with less exploratory animals selecting higher temperatures. Our results underscore the multi-faceted effects of early developmental environments on behavioral and physiological phenotypes later in life. Thermal preference can influence disease risk through behavioral thermoregulation, and exploratory behavior may increase risk of predation or pathogen encounter. Thus, climatic stressors during development may mediate amphibian exposure and susceptibility to predators and pathogens into later life stages.

Sediment remediation using submerged plants mitigated the bioaccumulation of organic contaminants in benthic organisms in simulated freshwater aquaculture ponds

Few studies have investigated whether growing submerged plants can provide significant mitigation of both polycyclic aromatic hydrocarbons (PAHs) and antibiotics (ATBs) in sediments and cultured aquaculture products. In this study, Corbicula fluminea was selected as the indicator organism in the laboratory simulation experiment, and four remediation systems using Vallisneria natans L. (VN), Hydrilla verticillate L. (HV), Elodea nuttallii P. (EL) and Control Check (CK) were constructed individually. The accumulated concentrations (Cb) and changes in both bioavailability (Cfree) and bulk burden (Cs) of 16 PAHs and four ATBs were analyzed before, during, and after the experiment. Compared with the CK group, the introduction of VN, HV, and EL reduced: Cb of ΣPAHs by 43%, 32%, and 27%, respectively; ΣATBs by 68%, 49%, and 39%, respectively, in Corbicula fluminea; the corresponding cancer risk of ΣPAHs by 19%, 8.9%, and 13%, respectively; and the target hazard quotients of ΣATBs by 73%, 48%, and 41%, respectively. The freely dissolved concentrations of ΣPAHs and ΣATBs (Cfree) in the experimental groups decreased by 38%− 58% and 37%− 70%, respectively. More ATBs than PAHs were reduced in biota, with VN showing the highest efficiency. Reduction in Cfree was more related to reduction in Cb than reduction in Cs. In terms of Cb reduction, Cfree was more indicative for ATBs than PAHs. Analyses of the bacterial community revealed that the introduction of submerged plants significantly increased the abundance of Sphingomonas and Mycobacterium, with specific degradation effects observed for high molecular weight PAHs in the sediment.

Experimentation of Evaporation Suppression by Various Plastic Bottles Coverage Area

Evaporation significantly affects the loss of water in reservoir. The effective use of water-surface covering materials for evaporation reduction purpose is commercially performed including plastic spherical and circular shapes. This study initiates to reuse very common polyethylene terephthalate (PET) drinking-water bottles to cover water surface instead. The bottle shape could have a covering percentage ratio as much as 91% equal to a commercial ball or circular disk. The experiment was designed and conducted to prove the reduction of water evaporation rate using five simulated ponds. The testing aspect is the percentage of the coverage area over the water surface. Based on environmental impact concern, the deterioration of PET bottles due to hydrolysis reaction and ultraviolet rays in natural conditions is also investigated. The initial result from the experiment shows that PET bottles have a potential for the evaporation reduction which are a very cost-effective alternative to the existing commercial materials and help support the reuse of plastic waste.

Expert systems and the prospects of artificial intelligence for the automatic supervisory control of salinity gradient solar ponds

Salt Gradient Solar Ponds (SGSPs) are conventionally operated wholly manually. They hence suffer from a loss of efficiency for substantial durations when disturbed by natural diffusion and environmental elements such as temperature variation, solar radiation, and wind. They also impose considerable operational costs and time when a repair is unavoidable. Here, a Zero-Discharge Closed Cycle (ZDClC) is proposed for sustainable implementation of control architectures. We then define the SGSP as a control system and propose an automatic approach that uses Artificial Intelligence (AI) to mimic experts’ actions during repair operations. More specifically, an Automatic Supervisory Controller (ASC-SGSP) is proposed that decomposes the pond into several uniform sublayers according to their thicknesses and salt concentrations. The automated supervisor then uses a decision tree analysis of pond stability to determine the sequences of injection/suction actions to guarantee the pond stability and prevent layer overturning. An on–off subcontroller then directs the chosen sublayer’s salt density to its desired value. The supervisory structure is general and can operate with either the proposed open-loop or closed-loop configurations. Results indicate the potential utility of AI and expert systems as a successful paradigm for SGSP control. Specifically, the proposed approach is examined in a simulated pond under several scenarios challenging its efficiency, adaptivity, robustness, and constraint handling properties. The ASC-SGSP fulfills the automatic control requirements during either open/closed-loop configurations and regulates the desired salinity levels under parameter constraints and uncertainties, even when the SGSP parameters are perturbed by as much as 50%.

Modeling and optimization of phycoremediation of heavy metals from simulated ash pond water through robust hybrid artificial intelligence approach

AbstractIn thermal power plants, ash pond water is being polluted with heavy metals such as Lead (II), Nickel (II), Manganese (II), Cadmium (II), Chromium (VI), and so on, through leaching from coal ash and this can eventually contaminate the groundwater. In the present study, a consortium consisting of a cyanobacterium Synechococcus sp. and green algae Chlorella sp. was used for phycoremediation of such heavy metals from simulated ash pond water. The concentrations of metals, pH and days were varied during experimentation. An accurate data‐driven artificial neural network (ANN) model was developed with the experimental data to find a relation between the input variables of the phycoremediation process with the percentage removal of the pollutants and amount of biomass produced. The optimum ANN design and ANN algorithm were evaluated using an automatic exhaustive search technique. To maximize metal removal and biomass production, a hybrid artificial neural network‐simulated annealing (ANN‐SA) optimization technique was applied to determine optimal values of input parameters. The established modeling and optimization technique is generic and can be applied to any other experimental study.

EXPERIMENTAL AND 3D NUMERICAL SIMULATION OF THREE SOLAR PONDS WITH DIFFERENT LEVEL OF TURBIDITY: DOUGLAS-GUNN ADI APPROACH

In most previous works dealing with the modelling and numerical simulation of salinity gradient solar ponds, the heat diffusion is 1D or 2D, the diffusion of salt is very slow and that there are small convection movements, which obviously supposes that the wind speed is negligible. The studies are often limited to sodium chloride-based ponds where only relatively clear water is considered. The present work comes to fulfil the lack of 3D thermal behaviour prediction where, in one hand, we simulated solar ponds by a mixture of three different techniques, which are stable and well adapted to this type of problem using the method of finite differences in conjunction with the schemes of ADI-Gunn, Adams-Bashford and Schneider and al, which finds its first application in this type of problems. On the other hand, in order to validate our numerical results, we conducted an experiment on three identical parallelepiped ponds with {2.3040}$\,\text{m}^2$ of area and {1.200}$\,\text{m}$ depth; each one containing the same fungicide salt namely \ce{KH2PO4}, that has never been used before.

Balancing the health effect between risks of methylmercury and benefits of nutrients in consumption of Chinese mitten crab (Eriocheir sinensis) in China.

Aquatic products contain both beneficial substances such as polyunsaturated fatty acids and harmful compounds such as methylmercury, and their combined health effects should be assessed at a common end point for a rational analysis. We used a risk-benefit model to assess net IQ point gain from consumption of Chinese mitten crabs (Eriocheir sinensis) from Jiangsu Province. Levels of methylmercury in the edible parts of the crabs ranged from 0.79 to 69.47μg/kg (mean: 26.88 ± 15.09μg/kg). Levels of methylmercury did not differ by sampling location. In aquaculture experiments, we simulated artificial pond farming using either iced trash fish or formulated feed. Crabs fed iced trash fish contained 28.72 ± 2.30mg/g of eicosapentaenoic acid and docosahexaenoic acid and crabs fed formulated feed contained 19.64 ± 3.62mg/g of eicosapentaenoic acid and docosahexaenoic acid. Model calculations estimated a gain of 7.52 IQ points from consumption of crabs fed formulated feed and 11.00 IQ points from consumption of crabs fed iced trash fish. They are all above the maximum theoretical IQ point gain value. Chinese mitten crab is a kind of high-quality food which is beneficial to the neural development of infants. Our findings may assist in improving crab farming methods and consumption patterns, accelerating the sustainable development of the Chinese mitten crab industry.

Sensitivity of Arctic sea ice to melt pond processes and atmospheric forcing: A model study

Melt ponds are pools of meltwater forming principally on Arctic sea ice during the melt season. The albedo of melt ponds is a key component of the surface energy balance. For this reason, various melt pond schemes have been developed for climate models. These schemes require assumptions on the physical processes governing melt ponds as well as a knowledge of the atmospheric state, which are not perfectly known. In this study, we investigate the effects of the sources of uncertainty from the prescribed atmospheric surface state, the melt pond scheme definition and the refreezing formulation of melt ponds on the simulated Arctic sea ice and melt pond properties with the NEMO-LIM3 ocean–sea ice general circulation model. We find that the simulated melt pond state is largely controlled by the freezing point of melt ponds. The representation of melt ponds is in better agreement with observations when using the freezing point of −0.15°C compared to the value of −2.00°C, in our model set-up. All the simulations feature positive trends in melt pond area fraction over the past decades. However, only 3 out of 8 simulations have significant positive trends in melt pond volume per sea ice area. This suggests an influence of the sea ice state for melt ponds over the last 30 years. Overall, we find that the simulated sea ice state, and in particular sea ice volume, is more affected by changes in the prescribed atmospheric forcing than by changes in the prescribed melt pond scheme or refreezing formulation. Including explicit melt pond schemes in large-scale sea-ice models offer the possibility to improve the representation of the surface energy balance in climate general circulation models. Our results underline that, in parallel to these efforts in model developments, improved estimates of surface atmospheric conditions will be required to achieve more realistic sea ice states.

Molybdate effectively controls sulphide production in a shrimp pond model

The production of shrimp is often performed in earthen outdoor ponds in which the high input of feed and faeces on the bottom can result in deterioration of the water quality, which negatively impacts the animals and the environment. Here, we investigate the potential of sodium molybdate (Na₂MoO₄·2H₂O), sodium nitrate (NaNO3) and sodium percarbonate (Na2CO3·1.5H2O2) to control sulphide production in a simulated shrimp pond bottom system that included the sediment, overlaying artificial seawater and organic matter input in the form of shrimp feed and shrimp faeces. Sediment depth gradient measurements of oxygen, H2S and pH were obtained during 7 days of incubation using microelectrodes. The most significant impact in terms of H2S, was observed for 50 mg/L sodium molybdate. At the water-sediment interface, there was up to 73% less H2S detected for this treatment in comparison to a control treatment, while in the deeper layers of the sediment it was up to 47% less H2S. The residual sulphate concentrations in the molybdate treated samples were 16 ± 4% higher than the control, indicating an inhibition in sulphate reduction. Nitrate and sodium percarbonate treatments also showed a limited capacity to decrease H2S entering in the water column, yet no clear difference in H2S concentrations in the sediment compared to the control were observed. Molybdate treatment appears to work through the inhibition of sulphate reducing bacteria in situ for the control of H2S production better than the chemical oxygen boosters or nitrate treatment.

A submerged duckweed mutant with abundant starch accumulation for bioethanol production

AbstractDuckweed is one kind of promising bioenergy plant with prominent advantages such as fast growth rate and high starch content. However, almost all previous studies focused on the natural duckweed germplasms. In this study, heavy‐ion irradiation was used to establish a mutant library of Lemna aequinoctialis 6002, and one mutant named submarine‐1 (sub‐1) was screened, which could accumulate more starch but with smaller granules. Unexpectedly, under proper external growth conditions such as poor nutritional status and insufficient growth space, sub‐1 mutant would sink underwater due to formation of dense tissue structure and large amount of fine starch particles with the extension of cultivation time. The starch content in the sinking sub‐1 increased to over 45% (dry weight) and was 12% higher than the floating sub‐1, highlighting that submergence can be considered as a spontaneous and efficient indicator for screening of high‐starch duckweed. Additionally, the saccharification efficiency of starch and ethanol yield had increased in sub‐1 mutant compared to the wild type. Based on the unique characteristics of sub‐1 mutant, a cultivation model of submerged duckweed in a simulated aquaculture pond was designed to get more starch‐rich biomass, enabling effective production of renewable bioenergy.

Differential effect of natural and pigment‐supplemented diets on larval development and phenotype of anurans

AbstractDiet has major effects on development, growth, health, and performance of animals. Photosynthetic pigments, in particular, are key components of the diet of many organisms that can play important roles in their development and performance. Compared to other taxa, we know relatively little about how these pigments impact amphibian larval development. We conducted diet supplementation experiments on tadpoles of two amphibian species, in which we offered various naturally co‐occurring aquatic macrophytes or diet enriched or not with supplement pigments. We evaluated the effect of these diets on developmental period, size, mass, color, and jumping performance of metamorphs exposed or not to risk of simulated pond drying during the larval period. Diet based on Myriophyllum alterniflorum resulted in high mortality rates of Mediterranean tree frog larvae (Hyla meridionalis), this macrophyte did not affect survival of Western spadefoot toads (Pelobates cultripes), but individuals took longer to reach metamorphosis. Regardless of the macrophyte consumed, spadefoot toad tadpoles speeded up metamorphosis when exposed to reduced water volume, whereas tree frog tadpoles did not show significant responses to simulated pond drying. The three supplemented diets tested—β‐carotene, lutein, and chlorophyll—had positive effects on size and mass of tree frogs; supplemented diet based on β‐carotene improved dorsal coloration of tree frogs and had positive effects on size and mass at metamorphosis of spadefoot toads. Tadpoles fed with supplements did not exhibit significant response to water reduction. Our study highlights the importance of larval diet on phenotypically plastic responses and post‐metamorphic traits in anurans.

Spread of resistance genes from duck manure to fish intestine in simulated fish-duck pond and the promotion of cefotaxime and As

Integrated culture is a widespread culture mode in South China, in which resistance genes (RGs) also spread in the circulation system with nutrients. Accordingly, the aim of the present study was to investigate the spread of RGs in a fish-duck pond and the RGs and bacterial community of fish intestines. Five fish tanks, including a control tank and four experimental tanks (duck manure, duck manure + cefotaxime, duck manure + As, and duck manure + cefotaxime + As), were tested for 100 days. The results showed that duck manure increased both the diversity and relative abundance of RGs in fish intestines, and the addition of stress factors (cefotaxime, As) increased the relative abundance of RGs by one to two orders of magnitude. The stress-inducing effect of cefotaxime was greater than that of As. Tetracycline resistance genes were more sensitive to stress factors and were the predominant RGs in fish intestines. RGs in duck manure preferentially spread from the water to biofilm and then to fish intestines, whereas co-stress of cefotaxime and As obviously promoted the spread of RGs to fish intestines. In comparison to the control tank, duck manure and stress factors significantly changed the bacterial community of fish intestines. Correlation analysis also revealed that arsB, MOX, tetA and sul1 were significantly correlated with intI1 (P < 0.01), which hinted a potentially dissemination risk of RGs in fish intestines. These findings provide a theoretical basis for further investigating the dissemination of RGs in integrated culture systems and for evaluating the ecological risk of antibiotic and As use in aquaculture.

Vermicompost for Mitigation of Surfactant Contamination in Surface Water

Surfactants are the most important pollutants of surface water which should be removed for the safety of aquatic life. The potentiality of vermicompost for the removal of surfactant contamination in surface water was studied by measuring surfactant concentration, pH and conductivity for nine days in six trials with different proportions of soil, vermicompost and phosphate keeping the surfactant concentration constant. The trials T1, T2, T3, T4 and T5 were considered as simulated ponds and T0 as control. The surfactant concentration, electrical conductivity and pH were found to change upon the application of vermicompost. The surfactant degradation rate of vermicompost amended systems was significantly higher than the control system. Surfactant was almost completely depleted in vermicompost amended systems within the monitoring period. The presence of phosphate increases the surfactant removal efficacy of vermicompost. The pH values for vermicompost amended systems were almost constant near 7. The electrical conductivity of vermicompost amended systems was found to increase with time whereas that for the control systems was almost constant. Therefore, vermicompost can be considered as an excellent amendment as they have the ability to remove surfactant in surface water correcting the pH and increasing the availability of nutrients of the systems.

Kinetics of Pyrite Oxidation in Simulated Mine Tailings Pond Conditions

Pyrite oxidation is the predominant source of acid mine drainage (AMD), which is one of the severe environmental impacts of mining. AMD destroys flora and fauna in the nearby ecosystem, and it causes grave health problems to the people. To further the understanding and help in the mitigation of AMD, this electrochemical study investigates the effect of the type and concentration of oxidant, and the presence of impurity (chalcopyrite) to the rate of pyrite oxidation, while simulating the conditions in tailings ponds. Open Cell Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) analysis were done using a three-electrode cell set-up, which is composed of a pyrite rotating disc electrode (RDE), mercury/mercurous sulfate reference electrode in saturated potassium sulfate, and a platinum counter electrode, with a sulfuric acid working electrolyte. Polarization resistance obtained after fitting an electrical circuit to the EIS data was related to the rate of pyrite oxidation, while OCP was used to describe its oxidation mechanism. It was found out that the oxidation of pyrite by ferric ions preferentially occurred rather than by dissolved oxygen. The parameter setting with the lowest relative oxidation rate were: electrolyte with no ferric addition, and with nitrogen purging; and RDE with 10 % chalcopyrite addition. Reaction orders calculated for the effect of ferric ions and dissolved oxygen were equal to 1; but ferric has a higher slope value in the plot. Presence of chalcopyrite in the RDE caused the preferential oxidation of chalcopyrite instead of the pyrite due to their galvanic interaction. To minimize pyrite oxidation, ferric and dissolved oxygen concentration should be minimized, and chalcopyrite impurities should be increased. Keywords: Electrochemical Impedance Spectroscopy, Acid Mine Drainage, Kinetics, Rotating-Disc Electrode, Pyrite

Dietary administration of Bacillus and yeast probiotics improves the growth, survival, and microbial community of juvenile whiteleg shrimp, Litopenaeus vannamei

ABSTRACT Several microorganisms, including Bacillus and yeasts species, are widely used as aquaculture probiotics. In the present study, a mixed Bacillus sp. contained five species of B. thuringiensis BUU 001, B. megaterium BUU 002, B. polymyxa BUU 003, B. licheniformis BUU 004, and B. subtilis BUU 005, and a mixed yeast probiotics contained Debaryomyces hansenii BUU 01 and Rhodotorula sp. BUU 02. The effects of mixed microbial probiotics as a dietary supplement on growth, survival, and microbiological changes of juvenile whiteleg shrimp (Litopenaeus vannamei) were investigated. Shrimp (~5.7–5.8 g) were fed a commercial diet alone (control) or with one of three probiotic supplements—freeze-dried mixture of Bacillus (FB), freeze-dried mixture of Bacillus and yeast (FBY), and freeze-dried mixture of yeast (FY)—for 90 days in simulated earthen ponds. Growth of FB-fed shrimp was significantly higher (P < 0.05) than those fed with FBY, FY, and control diets. However, survival was not significantly different (P > 0.05) among the three treated groups but was significantly higher (P < 0.05) than that of the control. Numbers of culturable heterotrophic bacteria in intestine were not significantly different (P > 0.05) among the four groups. Bacillus numbers in FB- and FBY-fed shrimp increased significantly (P < 0.05) in intestine. Yeast numbers in intestine of FBY- and FY-treated shrimp were significantly higher (P < 0.05) than those of FB-treated and control shrimp and increased significantly (P < 0.05) during the rearing period, while no yeast was observed in FB-treated and control shrimp. Numbers of Vibrio in intestine were significantly lower (P < 0.05) in the three treated groups than the control. Administration of mixed Bacillus, mixed yeasts, or Bacillus mixture in combination with mixed yeasts resulted in improved (P < 0.05) growth and survival and reduced Vibrio numbers along with an increase in beneficial probiotic abundance and a decrease in the number of potential pathogenic bacteria (V. parahaemolyticus and V. cholerae) in digestive tract of juvenile L. vannamei.