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Changes in environmental factors may deeply affect the energy budget of Antarctic organisms as many of them are stenothermal and/or stenohaline ectotherms. In this context, the aim of this study is to contribute to knowledge on variations in the energy demand of the Antarctic amphipod, Gondogeneia antarctica as a function of temperature and salinity. Experiments were held at the Brazilian Antarctic Station "Comandante Ferraz", under controlled conditions. Animals collected at Admiralty Bay were acclimated to temperatures of 0ºC; 2.5ºC and 5ºC and to salinities of 35, 30 and 25. Thirty measurements were made for each of the nine combinations of the three temperatures and three salinities, totalling 270 measurements. Metabolic rates were assessed by oxygen consumption and total nitrogenous ammonia excretion, in sealed respirometers. When acclimated to salinities 30 or 35, metabolic rates at 0ºC and 2.5ºC were very similar indicating a possible mechanism of metabolic compensation for temperature. At 5.0ºC, however, metabolic rates were always higher. Lower salinities enhanced the effects of temperature on metabolism and ammonia excretion rates. The physiological adaptations of individuals of G. antarctica suggest adaptive mechanisms for energy saving, adjusted to an environment with stable conditions of temperature and salinity. Little is known about the joint effects of salinity and temperature and this study is an important contribution to the understanding of the mechanism of polar organisms in their adaptation to both factors. Alterações ambientais podem modificar a alocação de energia dos organismos, principalmente dos ectotermos estenotérmicos e/ou estenohalinos. Nesse contexto, este trabalho contribui com o conhecimento da demanda de energia do anfípode antártico Gondogeneia antarctica em função da temperatura e da salinidade. Experimentos foram realizados na Estação Antártica Brasileira "Comandante Ferraz", em condições laboratoriais controladas. Animais coletados na Baía do Almirantado foram aclimatados a temperaturas de 0ºC; 2.5ºC e 5ºC e salinidades de 35, 30 and 25. Foram realizadas trinta medições para cada uma das nove combinações das três temperaturas com as três salinidades, totalizando 270 medições. As taxas metabólicas foram estimadas por meio do consumo de oxigênio e excreção de amônia, em câmaras respirométricas seladas. Quando aclimatados a salinidades 30 ou 35, as taxas metabólicas a 0ºC e 2.5ºC foram semelhantes indicando possível mecanismo de compensação térmica, nessa faixa de variação dos fatores. A 5.0ºC, no entanto, as taxas metabólicas foram sempre mais elevadas. Baixas salinidades potencializaram os efeitos da temperatura no consumo de oxigênio e na excreção de produtos nitrogenados. Os resultados estão relacionados a mecanismos adaptativos para economia de energia em indivíduos G. antarctica, ajustados a um ambiente que tem condições estáveis de temperatura e de salinidade. Pouco se sabe sobre os efeitos conjugados da salinidade e temperatura nos organismos e este trabalho é uma importante contribuição para esse conhecimento.

Polystyrene multiwell plates with integrated optodes act as multiple closed-system respirometers that enable the simultaneous measurement of oxygen consumption in small animals. However, the diffusion of oxygen through polystyrene needs to be taken into consideration. Here we provide an equation that accounts for the empirically determined rate of oxygen through a polystyrene well when calculating the instantaneous rate of oxygen consumption. Furthermore, we describe a novel method of calibrating a small respirometer for accuracy using micro-osmotic pumps containing an oxygen scavenger, which is delivered at a constant rate and therefore yields a constant rate of oxygen consumption in an airtight system.

In this study we describe a novel flow-through respirometer with automated and semi-continuous detection of key water variables. The recirculating aquaculture system was designed to house aquatic organisms in culture-like conditions and allow long-term, high-precision measurements. Nine respirometry tanks (250 L in volume each) housed animals, and a tenth (without animals) acted as a reference tank. A single measurement unit made sequential measurements of each tank to eliminate the problem of sensor variation associated with multi-probe setups. The accuracy of the analyzers in relation to measurement range was: O-2 = 1%; CO2 < 1%; NH3 = 2%; temperature

In this study, activated sludge from two experimental full-scale membrane bioreactor (MBR) systems (microfiltration and ultrafiltration) working in parallel has been used to determine YH and bH in a batch respirometer. Both systems were equipped with a pre-denitrification stage and followed the same configuration: anoxic bioreactor, aerobic bioreactor and MBR. Nowadays, describing a conventional or MBR biological process cannot be understood without determining the values of several bio-kinetic parameters describing biomass growth and decay. The aim of this study is to evaluate the influence of several operational parameters related to MBR systems such as sludge retention time (SRT), hydraulic retention time, organic load, sludge temperature and aerobic bioreactor height over the heterotrophic decay coefficient (bH ) and the heterotrophic yield (YH ), whose values ranged from 0.0088 to 0.31 d−1 and from 0.40 to 0.88 mgCOD/mgCOD, respectively. Average sludge temperature and SRT have statistically ...

The potential of microalgae for wastewater treatment has recently led to significant surge in research towards economically more viable and technologically optimised systems. In this context, mathematical modelling has not been used to its full capacity. In this work, a combined respirometric–titrimetric unit for determination of microalgae kinetics and an experimental protocol is proposed. It was found that overall oxygen production was lower than stoichiometrically expected, which could be attributed to CO 2 -transfer to the gas phase. A basic model for microalgae growth on inorganic carbon and oxygen production is proposed and was successfully calibrated using several respirometric–titrimetric datasets. The model structure was based on the activated sludge models (ASMs) and can now be extended with impact of additional degrees of freedom. To our knowledge it is the first time that a respirometric–titrimetric approach is applied to microalgae and used to calibrate an ASM based kinetic model.

Although dietary exposure of adult fish to organoselenium in contaminated aquatic ecosystems has been reported to bioaccumulate and cause larval deformities in offspring, subtle physiological effects produced through low level waterborne selenium exposure in fish such as swim performance and aerobic capacity have not been investigated. To evaluate potential effects of selenite on these responses, adult zebrafish (Danio rerio) were exposed to nominal aqueous concentrations of 0, 10 or 100 μg/L sodium selenite for 14 days. Upon completion of the exposure period, fish underwent two successive swim trials in a swim tunnel respirometer to determine critical swim speed (Ucrit), oxygen consumption (MO2), standard and active metabolic rates, aerobic scope (AS) and cost of transport (COT) followed by analysis of whole body triglyceride and glycogen concentrations. Selenite exposure had a significant negative effect on Ucrit and aerobic capacity. Active metabolic rates and AS significantly decreased in both selenite exposure groups after the second swim trial. No significant effect was observed in MO2, standard metabolic rate, COT, triglyceride and glycogen levels, or condition factor between groups. These results suggest that aqueous selenite exposure at environmentally relevant concentrations produces adverse effects on aerobic capacity that can diminish endurance and maximum swim speeds, which may lower fish survivability.

The determination of microbial activity is important for assessing soil fertility or indicating soil contamination. There exist several well established methods like calorimetry or respirometry. With these methods large samples campaigns are relatively elaborate and they do not allow a detection of spatial patterns of microbial activity. In this paper we present a new method to study microbial activity using infrared thermography (IRT). This method is based on the fact that microbial activity produces heat due to respiration. The main advantages of this method are: (i) spatial patterns of microbial activity can be determined, (ii) measurements are easy to conduct, (iii) both sample volume and sample number can be large, and (iv) measurements can potentially be conducted in situ without soil disturbance. Two laboratory experiments were conducted. 8 samples of a Cambisol A horizon were treated with a glucose mixture while 8 were used as reference. Surface temperature distributions on the samples were measured using an IR camera. The microbial activity of glucose treated samples was also determined by CO2 and heat production measurements using respirometry and calorimetry, respectively. In the second experiment a glass container was filled with the same soil treated with glucose. Half of the soil in the container was additionally contaminated with copper. Differences between surface temperatures between treated and untreated samples measured with the IR camera corresponded well with respirometer and calorimeter measurements. The predefined pattern of soil contamination in the second experiment could be well detected using the IR camera. The new method is a useful tool to easily and rapidly determine microbial activity on large numbers of samples simultaneously. Furthermore, spatial distributions of soil contamination are detectable. If more precise information about microbial activity in soil samples is required, the classically used methods are favorable.

Acipenser schrenckii, the Amur Sturgeon, was a commercially valuable fish species inhabiting the Amur (Heilongjiang) River but populations have rapidly declined in recent years. Dams impede A. schrenckii spawning migration and wild populations were critically endangered. Building fishways helped maintain fish populations but data on swimming performance and behavior was crucial for fishway design. To obtain such data on A. schrenckii, a laboratory study of juvenile A. schrenckii (n = 18, body mass = 32.7 ± 1.2 g, body length = 18.8 ± 0.3 cm) was conducted using a stepped velocity test carried out in a fish respirometer equipped with a high-speed video camera at 20°C. Results indicate: (1) The counter-current swimming capability of A. schrenckii was low with critical swimming speed of 1.96 ± 0.10 BL/sec. (2) When a linear function was fitted to the data, oxygen consumption, as a function of swimming speed, was determined to be MO2 = 337.29 + 128.10U (R(2) = 0.971, P

Oxygen uptake (VO 2 ) through the gills of a hill-stream fish Glyptothorax telchitta from the Saptakoshi river (Nepal) has been studied in relation to different body weights. The oxygen uptake was determined at 24.0±1°C using a cylindrical glass respirometer with continuous water flow system. The aquatic oxygen uptake through the gills increased from 1.048 to 8.115 mlO 2 kg -1 .h -1 within the body weight range of 3.215 to 31.355 g. A fish of 17.052 g average body weight consumes 4.461 mlO 2 -1 .h -1 . The relation between oxygen uptake (VO 2 ) and body weight was determined by performing regression analysis using logarithmic transformation. It has been found that with a unit increase in body weight, the oxygen uptake per unit time (mlO 2 h -1 ) increases by a power of 0.930 showing significant positive correlation whereas, the weight specific oxygen uptake decreases by a power of 0.070 showing significant but negative correlation. DOI: http://dx.doi.org/10.3126/njbs.v1i0.7464 Nepalese Journal of Biosciences 1: 11-18 (2011)

Methylene blue (MB), a tricyclic phenothiazine drug, has been reported to enhance mitochondrial functions including mitochondrial respiration. By comparison, stress associated with abrupt ethanol withdrawal (EW) impedes mitochondrial functions. We investigated whether MB protects mitochondrial respiration and cell survival from EW stress through a key mitochondrial enzyme, cytochrome c oxidase (COX). We also investigated whether the MB’s protection involves the inhibition of an excitatory neurotransmitter, glutamate. Male rats were exposed to and withdrawn from ethanol-diet (7.5%, 5 weeks). MB (0.5 mg/kg, intraperitoneal) was injected for the last 5 days of ethanol-diet and on the first day of EW. Cerebellum was then harvested to measure mitochondrial respiration and COX expression using real-time XF respirometer and immunohistochemistry, respectively. Separately, HT22 cells (a murine hippocampal cell line) were exposed to and abruptly withdrawn for 4 hours from chronic ethanol (100 mM, 3 days). MB was administered during EW with or without a COX inhibitor (NaN3) or glutamate. Mitochondrial respiration, COX content, and cell viability were then assessed using real-time XF respirometer, an immunoblot method, and Calcein assay, respectively. MB attenuated the suppressing effects of EW on mitochondrial respiration, COX content, and cell survival. This protection was reduced after NaN3 or glutamate cotreatment. These results suggest that MB treatment help maintain mitochondrial respiratory and cellular integrity through COX-upregulation and glutamateinhibition upon EW stress. MB treatment may help identify mitochondrial mechanisms underlying hyperexcitatory CNS disorders.

Temperature is one of the most important abiotic factors in the habitats of ectothermic animals and has been called the 'ecological master factor′ for organisms.As ectotherms in bodies of water,fish are often subjected to large diurnal or seasonal changes in temperature,and,thus,they must adapt physiologically to the environmental temperature variation that occur over the course of their life histories.To examine the responses of cutaneous respiration in juvenile southern catfish(Silurus meridionalis Chen)(body mass:(29.15±0.51) g;body length:(15.63±0.08) cm) to chronic temperature acclimation and acute temperature change(increase and decrease temperature) and to test whether the contribution of cutaneous respiration to whole organism routine metabolism varies with chronic and acute thermal changes,the oxygen(O2) uptake across the skin(MO2skin) and gills(MO2gill) of anaesthetized individuals acclimated under three different temperature(10,20 and 30℃ for 2 weeks) were measured under 10,20 and 30℃ by self-designed fish MO2skin respirometer(patent number: 200920127987.7).The total O2 uptake rate(MO2total) was calculated accordingly as the sum of MO2skin and MO2gill.The cutaneous O2 uptake,i.e.MO2skin were(12.83±0.70),(18.20±0.97) and(22.65±2.07) mgO2 · h-1 · kg-1,respectively,at 10,20 and 30℃ temperature acclimation groups,which made up 16.4%—19.0% those of total O2 uptake.The MO2skin increased more slowly than the MO2total with the increase of acclimation temperature(P0.05) thus let to a smaller MO2skin: MO2total ratio at higher temperatures.There were significant differences in the MO2total among all three temperature acclimation groups while only the MO2skin of 10℃ temperature acclimation group was significantly different from the other two temperature acclimation groups(P0.05).The MO2skin of acute temperature rise groups were significantly higher than those of temperature acclimation groups with the same temperature before the acute temperature change(P0.05),but they were not significantly different from those of temperature acclimation groups with the same temperature after acute temperature change(P0.05).On the contrary,the MO2skin of acute temperature fall groups was significantly lower than those of acclimation temperature groups with the same temperature before acute temperature change(P0.05),they were also not significantly different from those of acclimation temperature groups with the same temperature after acute temperature change(P0.05).The average Q10 value of MO2skin was significantly lower than that of MO2total(P0.05).The respiratory sensitivity of juvenile southern catfish to acute thermal change as suggested by the average Q10 value of MO2total was higher than that of chronic temperature acclimation which suggested a metabolic compensation during chronic temperature acclimation.However,there were no significant differences in the average values of Q10 for MO2skin between acute temperature change groups and temperature acclimation groups(P0.05).The level of MO2skin: MO2total ratio in southern catfish was relatively high compared to many others fish species.It suggested that southern catfish adopted either metabolic compensation or acute stress responses to chronic temperature acclimation or acute temperature change.The cutaneous O2 uptake was neither a chemical reaction process nor a biological response,but appeared to be a process related to physical perfusion.

Chinese sturgeon (Acipenser sinensis) is a critically endangered species. A flume-type respirometer, with video, was used to conduct two consecutive stepped velocity tests at 10, 15, 20, and 25 °C. Extent of recovery was measured after the 60-min recovery period between trials, and the recovery ratio for critical swimming speed (U crit) averaged 91.88% across temperatures. Temperature (T) effects were determined by comparing U crit, oxygen consumption rate (MO 2), and tail beat frequency (TBF) for each temperature. Results from the two trials were compared to determine the effect of exercise. The U crit occurring at 15 °C in both trials was significantly higher than that at 10 and 25 °C (p

The objective of this research was to estimate short-term biochemical oxygen demand (BOD st ) using an oxygen uptake rate (OUR) measurement method. Activated sludge samples were taken from a return sludge pipe in an oxidation ditch at Maharaj Hospital, Nakhon Ratchasima Province, Thailand. Sludge samples were filtered and aerated overnight in the preparing chamber until reaching the endogenous respiration phase, which provided the initial sludge concentration of 5,489 mg/L. Sludge sample concentrations were diluted to 880, 2,160, and 5,297 mg/L. Sodium acetate of 20 mg/mL (13 mg COD/mL) was used as a readily biodegradable COD substrate (rbCOD) and dosed to the sludge sample. Final COD concentration was varied into 4 dilutions; 7.21, 14.40, 28.71 and 57.70 mg/L. Temperature, pH and dissolved oxygen (DO) were controlled throughout the experiment at 28±0.5 °C, 7.8±0.1 and 6–7 mg/L, respectively. DO and OUR values were collected using an ultimate hybrid respirometer, which was developed by Saensing and Kanchanatawee [1]. The results showed that the linear relationship between BODst and COD substrate in all sludge dilutions were high and similar (R2 = 0.9891−0.9957). The area under the OUR curve can be used to easily estimate the BOD st and linearly related with biodegradable organic substances. Average R2 throughout the experiment was 0.9940. The results were consistent with the studies of Gernaey et al. [2], Saensing and Kanchanatawee [1] and Premanoch [3] which had average R2 values of 0.9990, 0.9952 and 0.9964, respectively. Estimation of BODst from an OUR respirogram can provide rapid results and also give a linear relationship for the amount of organic matter concentration. It was apparent that the OUR measurement method using an ultimate hybrid respirometer was effective for determination of BODst with less chemical and time consumption.

Data were compiled from the literature on the critical oxygen level (Pcrit), a hypoxia-tolerance trait, comprising 96 studies covering 151 fish species from 58 families. Salinity, temperature, body mass, and routine metabolic rate were highly correlated with Pcrit. The effects of temperature, CO2, acidification, metals and feeding are also assessed., Hypoxia is a common occurrence in aquatic habitats, and it is becoming an increasingly frequent and widespread environmental perturbation, primarily as the result of anthropogenic nutrient enrichment and climate change. An in-depth understanding of the hypoxia tolerance of fishes, and how this varies among individuals and species, is required to make accurate predictions of future ecological impacts and to provide better information for conservation and fisheries management. The critical oxygen level (Pcrit) has been widely used as a quantifiable trait of hypoxia tolerance. It is defined as the oxygen level below which the animal can no longer maintain a stable rate of oxygen uptake (oxyregulate) and uptake becomes dependent on ambient oxygen availability (the animal transitions to oxyconforming). A comprehensive database of Pcrit values, comprising 331 measurements from 96 published studies, covering 151 fish species from 58 families, provides the most extensive and up-to-date analysis of hypoxia tolerance in teleosts. Methodologies for determining Pcrit are critically examined to evaluate its usefulness as an indicator of hypoxia tolerance in fishes. Various abiotic and biotic factors that interact with hypoxia are analysed for their effect on Pcrit, including temperature, CO2, acidification, toxic metals and feeding. Salinity, temperature, body mass and routine metabolic rate were strongly correlated with Pcrit; 20% of variation in the Pcrit data set was explained by these four variables. An important methodological issue not previously considered is the inconsistent increase in partial pressure of CO2 within a closed respirometer during the measurement of Pcrit. Modelling suggests that the final partial pressure of CO2 reached can vary from 650 to 3500 µatm depending on the ambient pH and salinity, with potentially major effects on blood acid–base balance and Pcrit itself. This database will form part of a widely accessible repository of physiological trait data that will serve as a resource to facilitate future studies of fish ecology, conservation and management.

In this research study, the co-composting process of a waste mixture containing strawberry extrudate, fish waste, sewage sludge and bulking agent (SEFW, 190:1:22:90 ratio) was carried out in a dynamic-solid respirometer at pilot scale. The aerobic biodegradability of the mixture was previously ensured in a static-liquid respirometer. The advantages and drawbacks of the SEFW co-composting process were subsequently identified through the determination of respirometric activity and the physical-chemical characterization of the waste, as well as the monitoring of odor emissions. The evolution of the physical-chemical variables showed that pH increased slightly and that the organic matter concentration, expressed as volatile solids (VS, %) or oxidable organic carbon (COXC, %), decreased by around 15% in both cases and by approximately 56% in its biodegradable form (total organic carbon, TOC, %). The low odor emission rate (OER) in the least favorable scenario (the maximum odor generation) during SEFW composting was 1.59 ouE/s, whereas this figure reached 3.52 ouE/s when only the organic fraction of municipal solid waste (OFMSW) was composted. Consequently, the co-composting of SEFW is more favorable in terms of odor emission and permits the simultaneous treatment of different types of waste.

This article presents a comprehensive overview on the functional role of respiration in horticultural crops pre- and postharvest. The various factors affecting respiration of horticultural commodities postharvest and the role of respiratory quotient in designing efficient packaging and storage systems.

The objective of this study was to provide information on the toxicity of lead to the pink shrimp (Farfantepeneaus paulensis)based on oxygen consumption and the excretion of ammonia at different salinity levels. Organisms were collected andanalyzed in the Cananeia region, Sao Paulo, Brazil. The study of lead toxicity is very relevant for the history of the region,due to the high economic value of shrimps and the estimated future environmental impacts. 45 organisms were collectedand acclimated with constant aeration. Five replicates were used for routine measurement of metabolism in salinities 10,20 and 30 and temperature of 27 °C. Four different lead concentrations were tested: 0.04, 0.4, 0.08 and 2.12 mg/L, beyondcontrol. Respirometers chambers were used for 60 minutes. Dissolved oxygen was determined by the method of Winklerand ammonia based on phenol spectrophotometric method. The average oxygen consumption and ammonia excretionwere evaluated using analysis of variance (p

This study aimed to verify the biological anaerobic treatability of tebuconazole effluent manufacturing. For this purpose, two preliminary batch tests were performed using an ‘anaerobic respirometer’ adjusting the initial pH of the effluent at 7.0 and 8.0, respectively (first phase). In addition, two tests (second phase) were run using sequential batch anaerobic fermenters, the first operated at different hydraulic detention times (10 and 16.7 days) and the second with different initial dilutions of the effluent (5 and 20%). The chemical oxygen demand (COD) removal observed on the anaerobic respirometer tests was in the range of 66–81%. According to the preliminary batch tests an optimal value of initial COD concentration and amount of biomass was identified, which was considered for the fermenters start up. However, it was observed that the optimal relation provided by the respirometer test was not a good parameter of operational control for the fermenters due to the accumulation of inhibitory substances, which affected the microbial activity and took the system to collapse. The initial dilution of the effluent (5 and 20%) was essential for the stability of the anaerobic system, allowing COD removals above 74% during this study.

Quantifying oxygen demand and nitrifier yield are important in the design and operation of advanced wastewater treatment systems. However, the accurate stoichiometry of the autotrophic nitrification process has not been fully developed. In this research, stoichiometric links between nitrifier yield, ammonia and nitrite oxidization, ammonia assimilation, and oxygen uptake for each step of the nitrification process were determined. A pulse-flow respirometer was used to measure the oxygen uptake for complete nitrification and nitrite oxidation reactions. Results indicated that the specific oxygen uptake was 4.23 mg-O 2 /mg-N oxidized for complete nitrification, with 3.17 mg-O 2 /mg-N oxidized for ammonia oxidation (first step nitrification) and 1.06 mg-O 2 /mg-N oxidized for nitrite oxidation (second step nitrification). For the complete nitrification, fractions of ammonia used for electron donation, synthesis of ammonia oxidizers, and synthesis of nitrite oxidizers were 97.1%, 2.2%, and 0.7%, respectively. The fractions of electrons transferred into cell synthesis were approximately 7.5% for ammonia oxidation and 7.3% for nitrite oxidation. Biomass yield coefficients for ammonia oxidizers and nitrite oxidizers were 0.18 and 0.06 g-VSS/g-N oxidized, respectively. These parameters are critical when calculating oxygen needs and nitrifier biomass concentrations during the design of advanced wastewater treatment processes.

To address the question about costs of living in polluted areas, biomarkers linked to metabolism were measured in Pterostichus oblongopunctatus (Coleoptera: Carabidae) collected along two metal-pollution gradients in the vicinity of the two largest Polish zinc smelters: 'Bolesław' and 'Miasteczko Śląskie' in southern Poland. Both gradients covered a broad range of Zn and Cd concentrations in the humus layer (109-6151 and 1.48-71.4 mg kg(-1), respectively) and body metal concentrations increased with increasing soil metal concentrations. The whole-organism respiration rate was measured as oxygen consumption with Micro-Oxymax respirometer, and cellular energy consumption-as the activity of electron transport system, which is linked to cellular respiration rate. The significant increase in the whole-organism respiration rate with the body metal concentration was found when taking into account other factors such as body mass, gradient (or year of sampling as the beetles were collected on the gradients in different years) and the interactions: body metal concentrations × collection date, body metal concentrations × body mass, and body mass × gradient/sampling year. However, no relationships between metal concentrations in soil or body metal concentrations and the whole-organism or cellular respiration rate could be detected when using mean values per site, underlining the crucial importance of incorporating individual variability in such analyses. The observed increase of the whole-organism respiration rate with increasing body contamination with metals suggests that P. oblongopunctatus incurs energetic expenditures resulting from the necessity to facilitate metal elimination or repair of toxicant-induced damage.

The swimming ability of neotropical fish species is an important aspect for fish ladder designs. Especially in Latin America, where fish ladders are highly selective, fish strategies to negotiate the passage should be studied focusing on target species. This paper shows the swimming ability of three neotropical species (Leporinus reinhardti, Pimelodus maculatus and Prochilodus costatus), from São Francisco river basin. Respirometer was employed for data collection. Regarding the critical and prolonged speeds, L. reinhardti was the fastest among the three neotropical species in relative values (body length/second). The performance of neotropical species was better when compared to critical and maximum prolonged speeds of fish species from temperate areas. Finally, regarding the experimental procedures, the optimization of swimming speed in respirometer is lower than the optimal processes obtained with free swimming in open channels. A capacidade natatória das espécies neotropicais de peixes é um importante aspecto a ser considerado em projetos de passagem para peixes. Especialmente na América Latina, aonde as passagens para peixes apresentam alta seletividade, estratégias para vencer barreiras de velocidade devem ser estudadas para espécies alvo. Este trabalho levantou a capacidade natatória de três espécies de peixes neotropicais (Leporinus reinhardti, Pimelodus maculatus e Prochilodus costatus) da bacia do rio São Francisco. Foi empregado o método forçado com uso de um em respirômetro. A comparação da velocidade entre as três espécies permitiu concluir que o L. reinhardti foi a espécie com maior velocidade crítica e velocidade prolongada em termos relativos (comprimentos/segundo). As espécies neotropicais foram mais rápidas, em termos relativos, do que as espécies de regiões temperadas, considerando velocidade crítica e máxima velocidade prolongada. Com relação aos procedimentos para determinação da capacidade natatória, verificou-se que a otimização da velocidade pelos peixes em respirômetro é inferior a desenvolvida em testes voluntários em canais abertos.

In this study the oxygen consumption rate in four groups of Oplegnathus insignis was examined under three different water temperatures 13, 18 and 23oC. Average weight of each group of fish was 9.5, 198, 333 and 525 g respectively. Oxygen consumption was measured in a respirometer of 18.8 L capacity and results show that at the same water temperature occurs an inverse relationship between body weight and oxygen consumption whereas for same body weight (W in kg) the respiration rate varies proportionally with temperature rise (T in oC). The generalized equation of oxygen consumption (Ro) in routine metabolism was determined as: Ro (mg O2 kg -1 h -1 ) = [85.229 + (10.03 T)]-(221.344 W). The information it is analized with regard to establishing quantitative relationships that allow a more precise specification of the water flow requirements and renewal rates in open flow systems without oxygenation, considering aspects such as body weight, respiratory rate, temperature and stocking density.

This paper presents the design of a miniaturized electrochemical respirometer to monitor organic content in water samples semi-continuously, in contrast to current biochemical oxygen demand, BOD, methods. We demonstrate the use of finite element method simulations as design tool for a novel concept microfluidic respirometer. The device is based on a flow cell separated by a thin membrane from a bioreactor. Simulations show that once membrane material and thickness are chosen, oxygen supply rate still provides sufficient flexibility to allow the measurement of samples spanning a very wide range of organic matter concentrations. The design presented here uses an electrochemical oxygen sensor, and the whole system is amenable to fabrication using standard microfabrication and rapid prototyping techniques.

Oxygen consumption rates (mg O 2 /kg fish/min; OC) of juvenile palm fish (average weight 420 g) were determined for temperatures of 14 and 18 °C. Three replicates of two tanks rearing fish at a density of 24 kg/m 3 were used to measure OC at 34 ppt working as open respirometers in a recirculating system under farm-like conditions. The fish were fed commercial dry pelleted feeds at a ratio of 1% of total biomass. Oxygen consumption rates were determined by mass balance calculations. The OC increased from 1.6 to 2.4 g O 2 /kg fish/day as temperature increased from 14 to 18 °C. The determination of oxygen consumption by palm fish in farm-like conditions provides valuable information on the oxygen requirement of these fish in an aquacultural setting. This bioengineering information can be used for designing and sizing a rearing facility for the intensive culture of palm fish.

We describe a computer-operated recirculating respirometer system (ca. 140 L water) with six respirometer chambers and a reference chamber (L × W × H: 26 cm × 12 cm × 20 cm; volume 6.24 L) that simulates diurnal dissolved oxygen (DO) fluctuations normally occur in aquaculture ponds. A gas-mixing device, “Digamat” proportionately dissolves gaseous nitrogen and oxygen (and if desired, carbon dioxide) in water to achieve DO levels from 1.0 to 40.0 kPa (0.3–14.0 mg L−1) at different temperatures. A series of computer-operated valves sequentially allow water from respirometer chambers to a single oxygen probe to measure DO concentration. Oxygen consumptions of fish as the differences in DO concentrations between respirometer and reference chamber are used to calculate different metabolic rates (standard, routine, and active), and critical (Pc) and recovery (Pr) oxygen tensions of individually reared unfed and fed fish. An experiment was conducted to evaluate the ability of the system to measure metabolic parameters for individually reared Nile tilapia (Oreochromis niloticus L.) at three temperatures (low: 22.5, optimum: 27.5 and high: 33.5 °C). The fed fish had significantly higher Pc and Pr values at optimum and high temperatures than unfed fish. At low and high temperatures, both fed and unfed fish had higher Pc and Pr than at optimum temperature. The standard metabolic rate was significantly higher at higher temperatures (44.9, 51.7, and 77.7 mg O2 kg−0.8 h−1 at 22.5, 27.5, and 33.5 °C, respectively).

Largemouth bronze gudgeon (Coreius guichenoti), a fish species once abundant in the Yangtze River, has been rapidly declining in recent years. One important factor, among many, is the interruption of the free-flowing rivers by dams. To obtain data that can be applied to the design of an effective fishway for C. guichenoti and other species in the fish community, a laboratory study of juvenile C. guichenoti's swimming ability and energetics was conducted in a flume-type respirometer equipped with a high-speed video camera system to record swimming behavior. The critical swimming speed (Ucrit), standard metabolic rate (SMR), and maximum metabolic rate (MO2,max) were determined during steady swimming at four water temperatures (10, 15, 20, and 25°C). A power function accurately describes the relationship between oxygen consumption rate (MO2) and swimming speed (U) at the four temperatures. The Ucrit, SMR, MO2,max, and metabolic scope increased with increasing temperature. The relationship between cost of transport (COT) and U was characteristically inverse bell-shaped, with minimum COT at Uopt = 4.5–5.0 body lengths per second (bl sec−1). This investigation provides data on the swimming ability of C. guichenoti that will add to the basic science required for fishway design. J. Exp. Zool.317:294–302, 2012. © 2012 Wiley Periodicals, Inc.

The effect of water temperature and body weight on oxygen consumption by the fasted olive flounder Paralichthys olivaceus was investigated in order to assess the metabolic rate of this species under different conditions. The oxygen consumption rate (OCR) was measured at three different water temperatures (15, 20 and 25℃) and two different body weights [9.1±1.2 g (mean±SD) for the juvenile group and 266.4±29.3 g for the immature group] at an interval of 5 minutes for 24 hours using a closed flow-through respirometer. For each treatment condition, three replicates were set up and 135 fish in the juvenile group and 18 fish in the immature group were used. The OCRs exhibited a linear increase described by OCR=?82.06+28.30T (r²=0.96, p＜0.001) in the juvenile group and OCR=?52.52+14.73T (r²=0.97, p＜0.001) in the immature group. The OCRs decreased with increasing body weights at a given water temperature (p＜0.001). The metabolic rate was related to the body weight of the fish as a power function with a weight exponent of between 0.77 and 0.82. Q 10 values ranged 1.67~2.28 when the temperature was between 15 and 20℃, 1.57~1.93 when the temperature was between 20 and 25℃, and 1.79~1.89 when the temperature was between 15 and 25℃. The energy expenditure by respiration increased with increasing water temperature and decreasing body weight (p＜0.001). The mean energy loss rates at 15, 20 and 25℃ were 115.9, 149.8 and 208.2 kJ ㎏ ?1 d ?1 in the juvenile groups and 53.8, 81.2 and 101.9 kJ ㎏ ?1 d ?1 in the immature groups.

Two stocking densities, “low” (L, between ~ 19 and ~ 25 kg m − 3 ) and “high” (H, between ~ 75 and ~ 100 kg m − 3 ) were compared for effects on specific growth rate (SGR), feed conversion, energetics and welfare of rainbow trout reared at 14 °C either in static water (S) or swimming in a gentle current of ~ 0.9 bodylengths s − 1 (C). Trout (initial mass ~ 110 g) were reared for 9 weeks in circular tanks (volume 0.6 m 3 ), in triplicate of four conditions (LS, LC, HS, HC). Fish were fed ad-libitum daily; waste pellets were swirl-collected at the outflow to calculate feed intake. SGR was measured each three weeks for the last six weeks of the trial. The tanks functioned as intermittent-stopped flow respirometers, to permit metabolic rate to be measured as instantaneous oxygen uptake once per hour. Mean (± SD) SGR was significantly lower at H than L (1.51 ± 0.03 vs 1.44 ± 0.04% day − 1 , respectively, n = 6) and lowest in HC. When compared over a similar interval of mass gain, H groups had approximately 25% higher metabolic rates than L, with the highest rates in the HC condition. As a result, fish in the H groups dissipated a greater amount of feed energy as metabolism and, across all groups, there was a direct negative relationship between the quantity of energy dissipated and their SGR. There was no evidence of a neuroendocrine stress response, plasma cortisol was around 1 ng ml − 1 in all conditions. An acute crowding stress increased plasma cortisol to above 120 ng ml − 1 in all groups, but C groups recovered to control levels within 8 h whereas S groups required 20 h. Respirometry on individuals revealed that H fish had approximately 14% higher metabolic rates than L fish, indicating that increased metabolic rate in rearing tanks was in part physiological. The H groups had approximately 15% lower critical swimming speeds than the L groups which, together with their raised metabolic rate, indicated a physiological impairment. Thus, high density reduced SGR by raising energy dissipation, at least partially as a physiological response by the fish, although there was no evidence of an endocrine stress response. The only beneficial effect of C was in recovery from acute stress.

Disolved oxygen plays an important role for fish living in its life environment. Information on the ammount of oxygen consumption of a fish in certain volume of water is needed in order to give balancing between the ammount of disolved oxygen and fish in it. The objective of this research is obtaining oxygen consumption level of a juvenile of humpback grouper (Cromileptes altivelis) of 5-7 cm body length. Oxygen consumption of fish was measured using a tube that equiped with DO tool (dissolved oxygent, DO), and the tube was filled by sea water. Measurement of oxygen con-sumption of juvenil was done by measuring the concentration of dissolved oxygen from sea water in the respirometer tube, began when fish had entered into the respirometer tube up to two hours observation. The result showed that oxygen consumption rate of a juvenile of humpback grouper (Cromileptes altivelis) of 5-7 cm length, is ranging between 0.816 and 1.734 mg/hour.

A respirometric approach has been developed to determine heterotrophic biofilm kinetics using fluidized bioparticles--particles with attached biomass. Lava rock particles of 600 microm were used as a biomass carrier medium. The modified respirometer successfully estimates in situ biofilm kinetics of the bioparticles collected from a pilot-scale liquid-solid circulating fluidized bed (LSCFB) bioreactor. The observed maximum specific growth rates (micro(max)) of 3.69 +/- 0.44 d(-1) and biomass yields (Y(H)) of 0.36 +/- 0.03 g COD/g COD in the fluidized bed respirometers were significantly different from the micro(max) of 5.57-5.72 d(-1) and Y(H) of 0.54-0.59 g COD/g COD observed in the conventional respirometric tests for bioparticles and detached biomass. The higher Monod half-saturation coefficient (K(S)) of 186-219mg COD/L observed in the fluidized bed respirometers relative to the 49-58 mg COD/L in the conventional respirometers reveals the presence of mass transfer resistance in the LSCFB despite fluidization. Significantly reduced yields in the fluidized bed respirometers and the estimated maintenance coefficient of 1.16 d(-1) for the particulate biofilm in the LSCFB clearly emphasize that a substantial amount of substrate was utilized for cell maintenance at the low food to microorganism (S/X) ratio of 0.5 g COD/g VSS.

The lack of data on the metabolism of deep-sea demersal fishes is a major gap in our ecological knowledge of the deep ocean. Metabolism influences individual rate processes such as resource utilization, growth, and reproduction. It also correlates with an animal's ability to accommodate ocean acidification. Here we describe an autonomous in situ respirometry system that is deployed autonomously from a ship to capture fishes attracted to bait, and measure their rate of oxygen consumption. This instrument is multi-chambered and relies on the fish to actuate the capture mechanism and start the experiments. Although capture rates were low, data on five fishes were obtained including Eptatretus deani , two Coryphaenoides acrolepis , Antimora microlepis , and Pachycara gymninium . The metabolisms of the latter two species were measured for the first time. The metabolic rates were low (0.09–0.40 μmols O 2 g −1 h −1 at temperatures of 1.8–4.0 °C) in comparison to shallow water species. After taking temperature differences into account only the metabolic rates of benthopelagic species, C. acrolepis and A. microlepis , were substantially lower, by an order of magnitude, than shallow water relatives such as cod and pollock. The metabolic rate of the deep-sea fishes varied considerably clearly warranting further experiments to ascertain which factors are likely to explain the differences.

Nitrogenous compounds can be toxic to aquatic animals, especially when they are reared for production purposes at high stocking densities. Seriolella violacea is a pelagic fish, native from the easterly South Pacific Ocean. This species has shown desirable behavioral and metabolic characteristics under captivity conditions, which leaded the Marine Fish Laboratory from the UCN to increase its efforts on the research and development to validate S. violacea as a new aquaculture option. Therefore, the objective of this study is to determine the excretion rates of palm fish juveniles weighing 300–500 g at two different temperatures: 14 °C and 18 °C. Total ammonia as nitrogen (TAN) excreted was 4.4 ± 0.9 and 7.1 ± 1.9 mg TAN/kg fish/h for 14 °C and 18 °C respectively. The experiments were carried out in a recirculating system operating as a farm-like situation. Tests were performed in 1000 L rearing tanks operating as open respirometers. The results of the present study indicate that TAN excretion rates on S. violacea juveniles, is temperature dependent. Data obtained in these experiments are valuable information for the engineering design of land based aquaculture systems for palm fish.

Standard and active metabolisms determine the key aspects of the development and survival of fish species. We describe the first bioenergetic model for the standard metabolic rate (SMR) and active metabolic rate (AMR) of the Chilean native darter Percilia irwini. Adult individuals (5.5 ± 1.2 cm, 2.1 ± 0.9 g) were tested in a Blaska-type respirometer at 19.5 ± 0.5°C. Fish held a position by resting at the bottom at low velocities (5 and 15 cm s−1) and by swimming at higher velocities (25 and 35 cm s−1). SMR = 0.166 M 1.39 with an average of 220 mg O2 h−1 kg−1. Two bioenergetic models for AMR were adjusted. AMR = 0.16 M 1.16 U 0.23 at low velocities and AMR = 0.026 M 0.77 U 0.97 at higher velocities. Therefore, low velocities have little effect on the active metabolism of this species, but it is the main factor at higher velocities. Metabolic scope per unit weight was larger for smaller individuals, which is consistent with the faster growth of younger individuals.

BMR (basal metabolic rate), body mass and organ masses of tree sparrows (Passer montanus) were measured to analyze the correlation between organ masses and BMR in tree sparrows, and to evaluate the underlying physiological causes of difference in BMR. Adult tree sparrows were live-trapped by mist net in Qiqihar City, Heilongjiang Province (47°29′N, 124°02′E). The closed circuit respirometer was used to measure the metabolic rate (MR), and controlled the ambient temperature by using a water bath (±0.5°C). Body masses were measured to the nearest 0.01 g before and after BMR measurements with a Sartorius balance (model BT25S). The mean value was recorded as body mass. Wet and dry masses of several organs were measured, too. BMR was (4.276± 0.385) mL O 2 /(g · h) and mean body mass was (18.522±0.110) g. Since not all the variables were normal distributed, a log 10 -transformation of those variables was employed to linearize them, prior to analyses. Simple regression analyses indicated that most organ masses showed a significant high correlation with body mass. Both the small intestine and rectum masses were notable exception to that trend. The body-mass-adjusted residual analysis showed that only the kidney wet mass, brain mass, stomach mass, small mass and rectum wet mass correlated with BMR. In addition, correlations between several organ masses and BMR were observed. Because of the inter-correlations of organ masses, a principal component analysis (PCA) was performed to redefine the morphological variability. The first four components whose eigenvalues were greater than 1 could explain 75.2% variance of BMR. The first component, whose proportion reached 30.19%, was affected mainly by stomach mass, small intestine mass and rectum mass. Therefore, the results supported the hypothesis that BMR was controlled by some “expensive metabolic” organs.

The effect of cable oil concentration, nutrient amendment and bioaugmentation on cable oil component biodegradation in a pristine agricultural soil was investigated. Biodegradation potential was evaluated over 21 d by measuring cumulative CO(2) respiration on a Micro-Oxymax respirometer and (14)C-phenyldodecane mineralisation using a (14)C-respirometric assay. Cable oil concentration had a significant effect upon oil biodegradation. Microbial respiratory activity increased with increasing cable oil concentration, whereas (14)C-phenydodecane mineralisation decreased. Bioaugmentation achieved the best cable oil biodegradation performance, resulting in increases in cumulative CO(2) respiration, and maximum rates and extents of (14)C-phenyldodecane mineralisation. Generally, nutrient amendment also enhanced cable oil biodegradation, but not to the extent that degrader amendment did. Cable oil biodegradation was a function of (i) cable oil concentration and (ii) catabolic ability of microbial populations. Bioaugmentation may enhance cable oil biodegradation, and is dependent upon composition, cell number and application of catabolic inocula to soil.

We investigated the effects of temperature changes on the oxygen consumption rhythm in Japanese eels, Anguilla japonica, using an automatic intermittent flow respirometer (AIFR). The endogenous rhythm of the oxygen consumption rate (OCR) in the eels (n = 18; 44-74 cm, 145-690 g), freshly collected by bag net from estuaries, was nearly synchronous with the tidal pattern of the estuarine collection site. The magnitude of mean OCR (mOCR) of eels showed variable range of 82.2 - 116.5 ml O2 kg-1 ww h-1 under constant conditions. In case of increasing temperature from 25 to 38℃, the OCR of eels exhibited a gradually increasing trend with a rhythmic pattern until 36℃. Above 36℃, the rhythms of the OCR dampened and the OCR decreased rapidly at around 36 - 37℃. The OCR of the eels exhibited the maximum value at 38℃, and then it sharply decreased. The results suggested that the critical thermal maximum (CTM) regarding the endogenous rhythms of the eels was at around 36 - 37℃ when water temperature increased at 0.5℃/14 h following the acclimation at 25℃. In case of decreasing temperature (0.5℃/14 h) from 25 to 0℃, the OCR of the eels displayed a abrupt decrease up to 23℃, and between at 23 and 20℃, there was an agitation which showed a slight increase in the OCR with a duration of 1-2 days. Below 9℃, the OCR rhythm of the eels showed a constant state regardless of temperature decreasing. These results suggest that the Japanese eel has an upper incipient lethal temperature at 36℃, with a lower thermal limit at 9℃. The biochemical aspects of the eels influenced by water temperature need to be further studied.

An experimental hyperbaric system was designed and built to explore the effect of hyperbaric treatment on the respiration rate (RR) and respiratory quotient (RQ) of tomato. It consists of five containers that can be individually pressurized from 1 to 9 atmabs. The respirometer was equipped with a flow meter, control valve, pressure transducer, CO2 and O2 gas analyzer, and type T thermocouples that are all connected to a data acquisition and control card. A software interface was programmed to allow control of the air flow rate through the proportional valve of the flow meter based on a proportional–integral–derivative algorithm system. Hyperbaric treatments have been performed on tomato fruit, and it was observed that RR was inversely proportional to pressure.

Schizothorax chongi (locally known as Xilian Yu), a fish species commonly found in Yalong River, has been declining quickly in recent years. One of the important factors, among many, is the interruption of the free flowing river by dams. To obtain data that can be applied to the design of a fishway for S. chongi and other species in the community, a laboratory study of juvenile S. chongi’s swimming energetics and kinematics was conducted in a flume-type respirometer equipped with a high speed video camera system to record swimming behavior. The aerobic metabolic rate, tail beat frequency (TBF) and tail beat amplitude (TBA) were measured during steady swimming at varying flow rates for fish of similar mass. A power function accurately describes the relationship between oxygen consumption rate (MO2) and swimming speed (U). The estimated standard metabolic rate (SMR) calculated from the power function was 445.34 mg O2 kg−1 h−1, similar to the experimental result of 431.5 mg O2 kg−1 h−1. The relationship between cost of transport (COT) and U was, characteristically, inverse bell-shaped, with COTmin = 44.6 J kg−1 m−1 at U opt = 5.5 body lengths per second (bl s−1). There was a significant positive linear correlation between TBF and U. The slope of the correlation (0.33) was lower than for many other species, implying that S. chongi swim efficiently. The TBA, ranging from 0.15 to 0.2 bl, was found to be independent of U. Kinematic analyses indicates that S. chongi primarily depends on the caudal fin to generate forward thrust and employs three velocity-dependent swimming gaits. This investigation provides data on the swimming ability of S. chongi that will add to the basic science required for fishway design.

Procedures for the determination of standard metabolic rate (SMR) are variable and subjective in respirometry. We examined the oxygen consumption profile of six fish species (three salmonids and three cyprinids) in respirometry, and analysed the implications for the determination of SMR. In addition, we used data on Arctic charr (Salvelinus alpinus) and bleak (Alburnus alburnus) to define, how the length of a measuring period affects the determination of SMR and to investigate the temporal consistency of SMR. Fish activity in the respirometer differed between the species and there was a family-specific response to change in illumination. In salmonids, switching off the lights resulted in an increased oxygen consumption rate for hours, whereas in cyprinids the response was shorter or totally absent. In Arctic charr and bleak, individual oxygen consumption profiles remained unchanged between the consecutive trials. The results emphasize the importance of taking species-specific responses into account when d...

The purpose of this study was to measure the acute toxicity of zinc (Zn) on Farfantepenaeus paulensis at different salinities and temperatures by monitoring oxygen consumption. This aspect of the effect of zinc has not been studied in this important commercial species before. First, we examined the acute toxicity of zinc in F. paulensis at 24, 48, 72, and 96 h medium lethal concentration (LC50). One hundred and fifty shrimp were employed for the routine metabolism measurement utilizing sealed respirometers. Ten shrimp were subjected to oxygen consumption measurements in one of the four concentrations of zinc (control, 0.5, 1.0, 2.0, and 3.0 mg L−1) at three salinities (36, 20, and 5) and three temperatures (25°C, 20°C, and 15°C). Zinc was significantly more toxic at a salinity of 5 than at 20 or 36. The oxygen consumption was estimated through experiments performed on each of the 12 possible combinations of three temperatures (25°C, 20°C, and 15°C) and three salinities (36, 20, and 5). The shrimp showed a...

Cauque prawns Macrobrachium americanum of four different weights were tested at different temperatures to determine the differences in their oxygen consumption. The prawns were studied in a closed respirometer system in individual assays of 30 min each. Temperature (18–30°C) had a noticeable effect on oxygen consumption for all weights of prawns; weight had a less significant effect. In all cases, the mass-specific oxygen consumption rate of small prawns was higher than that of large prawns for all of the temperatures studied.

Hyperbaric treatment consists of exposing fruit or vegetable to compressed air in a range lower than 10 atm. Unlike heat or UV processing, where temperature or radiation gradients are established, pressure treatment offers a very rapid establishment of homogeneous conditions as they act instantaneously and uniformly around each single produce or throughout an entire mass of food, independently of its size, shape or composition. A hyperbaric respirometer was designed, built and tested to explore the possibility of using hyperbaric treatment on postharvest commodity. It consisted of an air tight vessel that could be pressurized from 1 to 7 atm and instrumented to automatically monitor gas concentration along time using computer controlled valves, flow meter and CO2 gas analyzer. Calibration of the system and hyperbaric treatments were performed on tomato fruit to evaluate the performance of the respirometer. Results showed that respiration rate was inversely proportional to pressure application.

Off-line analysis of liquid phase samples have traditionally been used for the determination of organics and nitrogen load for process control or optimization in full-scale wastewater treatment plants. However, these sampling and analysis methods are labor-intensive and time-consuming. Besides, the results are not generally available on real-time to the operators who struggle on daily basis to meet the constant discharge license conditions of the effluent while the influent conditions change diurnally with varying loads. Combined respirometric titrimetric sensor is an on-line method that has been developed recently, indicating the oxygen demand exerted by organic and nitrogen loadings. This sensor monitors both the oxygen uptake as well as the proton production/consumption resulting from the biological reactions in activated sludge system. The basic-data can then be interpreted to find out the short-term BOD, which can be used effectively for process control and optimization. Data interpretation and model development are still in progress as researchers keep on unraveling the mystery of how the substrates are biodegraded by activated sludge. Hence, in this study, it is aimed to develop an in-depth understanding about the aerobic biodegradation process using real-time biosensors through addition of different substrates such as acetate, surfactant (SDS) and ammonium to batch cultures of activated sludge by maintaining the pH of 7.8. Basic data interpretation was carried out to calculate oxygen uptake rate (OUR) as well as proton production/consumption rate from the raw data. Besides, the improved bio-kinetic model calibration was presented in this paper explaining the oxidation of different substrates in activated sludge system.

A static electrolytic respirometer was adapted to work under dynamic conditions using an internal airflow recirculation system that passed air through sludge/straw solid mixtures. Airflow reduced oxygen transfer limitations and increased the maximum respiration rate and k L a values, indicating that the observed value may have been close to the actual biodegradation rate. Airflow caused sludge drying, so the sample moisture was controlled by air humidification. To apply the optimised respirometric technique, a pilotscale composting process was developed. Some commonly used respiration indices (RI 24 , AT 4 ) were used to measure the final compost stability. RI 24 indices without airflow were underestimated during the thermophilic composting stage. Once the easily biodegradable carbon was consumed, the static and dynamic RI 24 indices were nearly identical. Because of the dynamic procedure, the respiration rate was likely controlled by the biochemical reaction and not by the mass transfer. The respiration indices indicated that the final compost was unstable.

In this study, the effects of carbon dioxide (CO2) deficiency on the biological growth under respirometric conditions, first- and second-order biological oxygen demand (BOD) progressions using two different BOD measurement techniques and metal toxicity effects on the respirometric BOD are investigated. The effects of CO2 deficiency in the growth of bacteria and related effects on the first- and second-stage BOD progressions are investigated using various media with respirometers in comparison with the BOD dilution method. CO2 deficiency causes significant retardations on the growth of bacteria and the second-stage respirometric BOD values are suppressed. CO2 seems to be an essential nutrient for the growth of microorganisms and for the oxygen uptake progressing rates. HgCl2, HgSO4, CuSO4, K2Cr2O7, ZnSO4 and Al2(SO4)3 inorganic metal compounds cause significant retardations in the respirometric BOD values obtained from a synthetic autotrophic medium. Effects are found to be dependent on the applied concentrations of these chemicals in the medium.

Inference in science depends on us having the right tools to measure with sufficient accuracy and precision the phenomena we are attempting to understand. In this issue of Molecular Metabolism, Burnett and Grobe call into question the accuracy of respirometry, the standard method for measuring energy expenditure in animals and humans [1]. This is an important contribution because in the field of obesity, almost without exception, scientists are agreed that the problem is due to energy imbalance. Energy intake is too high, expenditure is too low, or both. This energy balance framework provides a useful starting point for any discussions about fat storage and obesity [2]. However, the level of energy imbalance that can drive fat storage is rather small. An example is given in Ref. [3] of a typical 45 year old man who might accumulate 0.5 kg of fat over the course of a year, containing around 13.8 MJ of energy, which is only 0.27% of the estimated 5180 MJ of energy expenditure over the same period. Clearly the tools necessary to detect this sort of level of variation in energy expenditure would need to be spectacularly good, and it is widely known that none of the available methods comes close to providing us with this level of accuracy or precision. However, other questions in the field may require less stringent methods. Take for example the characterisation of a mutant mouse, or the impact of a given dietary exposure, or a drug. Here we might expect the impacts on expenditure to be larger, and hence the methodological requirements less taxing. What Burnett and Grobe show is that the techniques we currently have available may not be up to even this less demanding task. Generally, scientists interested in energy expenditure by animals do not measure it directly. They use an indirect approach called respirometry (or indirect calorimetry), in which gaseous O2 consumption and CO2 production are quantified over time. By making several simplifying assumptions the measured O2 consumption can be converted to heat production (energy expenditure) utilising the simultaneous CO2 production to diagnose the metabolic substrate being used, and hence the energy equivalence of the respired oxygen. This is done because accurately and directly measuring the heat produced in small animals is very difficult [see discussion in Ref. [4]]. The quantities are small (mice typically burn energy at a rate of less than 0.2 W), hence a typical 50 W light bulb is pumping out heat equivalent to over 250 mice, so the devices to pick it up have to be supersensitive. But this heat doesn't always immediately leave the body. It can be used to heat up the body, or, alternatively, excess heat can be released if the body cools down during the measurement period. Mice often have very labile body temperatures when placed in a measurement apparatus like a direct or indirect calorimeter (Figure 1). Converting such temperature changes back to the heat that caused them is complex because it depends on the exact body composition of the animal. Changes of up to 2 °C are not uncommon in such measurements requiring about 100 J of energy. If this change happened over say an hour (as in Figure 1) the impact on the direct heat production would be an error of about 16%. Moreover if the animal urinates in the chamber this causes all sorts of issues because the voided urine then cools down to ambient, releasing its stored heat. Half a millilitre of urine cooling down from 37 to 20 °C over 10 min would spuriously increase the measured heat production by 36%. Direct calorimetry is therefore very difficult, and depends on custom built pieces of kit – which is why indirect calorimetry based on gas exchange, utilising the technology developed for gas analysis that is employed in many industrial applications and is extremely accurate, and independent of issues like changes in body temperature has become the standard method. But it is important to recognise that the assumptions on which respirometry are built are also approximations, and dynamics of gas flow and mixing can complicate the inference of the energy expenditure that generated such effects [4]. Figure 1 Simultaneous traces of energy expenditure (kJ/day) measured by indirect calorimetry (thick black line), activity (Counts per 30 s; thin line below thick black line) and body temperature (°C; thin line above thick black line) in four mice ... So we have two imperfect technologies. One might anticipate they wouldn't exactly match up. The key is the size of the discrepancy. Burnett and Grobe examined how resting metabolic rate (RMR) changes when mice are placed on a high fat diet (HFD). They measured the changes in two ways. First, using a custom built direct calorimeter combined with simultaneous radio telemetry of body temperature changes to eliminate that source of error. Second, they used a continuous flow respirometry system based on the applied electrochemistry SA3 analyser. It is important to note here that the respirometry system that they used is superior in most respects to the majority of commercially available respirometry equipment, because the analyser utilises two sensors measuring background and excurrent air from the chamber continuously. In many senses, therefore, this is a best case scenario. The difference between methods at baseline was 6.85%, with respirometry being consistently lower. On high fat feeding RMR by respirometry increased, but that by direct calorimetry didn't, narrowing the difference to almost zero. Subsequently shifting from HFD back to chow caused a decrease in RMR by respirometry of 5.93% (back to baseline levels) and by direct calorimetry down by 8.85%, considerably reduced relative to baseline. In other words, the discrepancies were enormous, relative to the sorts of differences we are interested in measuring. In fact this isn't the first demonstration of such discrepancies. The same authors published a similar paper last year in American Journal of Physiology making comparisons of the methods in a different context [5] and there are some earlier studies within the past decade [6,7]. What does this mean? There is a strong tendency in such papers to assume that the direct calorimetry measure is correct, i.e. measured without error, and hence all the error is due to something wrong with the respirometry. The title of Burnett and Grobes previous paper is ‘Direct calorimetry identifies deficiencies in respirometry…’, Walsberg and Hoffman's paper in 2005 is titled ‘Direct calorimetry reveals large errors in respirometric estimates of energy expenditure’ and while their current paper is thankfully less dogmatic about the source of the discrepancy, some bias in this respect still creeps in. For example there is the inference that respirometry falsely detected an increase in RMR on high fat feeding. Does this study, and the other studies comparing direct and indirect calorimetry, mean we should pack up our respirometers until companies develop direct calorimetry machines for the commercial market? My own view is that the source of the discrepancy between the methods remains unproven, and given the theoretical problems highlighted above, may as much lie in the direct as the indirect calorimetry. The inference that respirometry falsely detected an increase in RMR on HFD could equally be interpreted that direct calorimetry failed to detect the change. Attributing the problem to respirometry alone is therefore unfounded. Moreover, surmounting the technological and practical issues in a 24 h direct calorimetry system would be extremely challenging, and, as mentioned by Burnett and Grobe would require surgical implantation of telemetric monitors into all measured animals. Plus we need to remember why indirect calorimetry came to be the standard method in the first place – because the measurements are more reliable and the technology more accurate. I therefore don't think it is time to pack up the respirometers. Not yet. Perhaps, not ever. Nonetheless, this study does emphasise that errors in our existing technology may compromise our interpretations. If these errors are random then it places more emphasis than ever on making sure that such studies have adequate sample sizes to detect the effect sizes of interest based on an appropriate power analysis [8].

Significant repeatability of a trait of interest is an essential assumption for undertaking studies of phenotypic variability. It is especially important in studies on highly variable traits, such as metabolic rates. Recent publications suggest that resting/basal metabolic rate of homeotherms is repeatable across wide range of species. In contrast, studies on the consistency of standard metabolic rate (SMR) in ectotherms, particularly fish, are scarce. Here we present a comprehensive analysis of several important technical aspects of body mass-corrected SMR measurements and its repeatability in a small (average weight approximately 3g) fish, the spined loach (Cobitis taenia). First we demonstrated that release of oxygen from the walls of metabolic chambers exposed to hypoxic conditions did not confound SMR measurements. Next, using principle of propagation of measurement uncertainties we demonstrated that in aquatic systems, measurement error is significantly higher in open than closed respirometry setups. The measurement error for SMR of a small fish determined in a closed aquatic system is comparable to that obtainable using top-notch open-flow systems used for air-breathing terrestrial animals. Using a closed respirometer we demonstrated that body mass-corrected SMR in spined loaches was repeatable under both normoxia and hypoxia over a 5-month period (Pearson correlation r=0.68 and r=0.73, respectively) as well as across both conditions (intraclass correlation coefficient tau=0.30). In these analyses we accounted for possible effect of oxygen consumption of the oxygen electrode on repeatability of SMR. Significant SMR consistency was accompanied by significant repeatability of body mass (intraclass correlation coefficient tau=0.86). To our knowledge, this is the first study showing long-term repeatability of body mass and SMR in a small fish, and is consistent with the existence of heritable variation of these two traits.

A study was conducted to investigate the effect of water temperature and photoperiod on the oxygen consumption of the fasting juvenile Pacific cod Gadus macrocephalus (mean body weight 79.9±2.0 g) in order to quantify metabolic response of the species under given conditions. The oxygen consumption rate (OCR) of G. macrorephalus was measured under a combination of four different water temperatures (7, 10, 13 and 16℃) and three different photoperiods (24L:0D, 12L:12D and 0L:24D) with an interval of 5 minutes over a 24-hour period using a closed recirculating respirometer. Three replicates were set up in each treatment. OCRs increased with increased water temperatures under all photoperiod conditions (P＜0.001). Mean OCRs at 7, 10, 13 and 16℃ ranged from 793.7~1108.4, 1145.7~1570.3, 1352.8~1742.5 and 1458.2~1818.6 ㎎ O₂ ㎏?¹ h?¹, respectively. Under all water temperature conditions except 7℃ (P＜0.001), mean OCRs of G. macrorephalus were the highest in continuous light (24L:0D) followed by 12L:12D and 0L:24D photoperiods. Mean OCRs of fish exposed to the 12L:12D photoperiod were significantly higher during the light phase than during the dark phase under all temperature conditions (P＜0.001). Q₁? values ranged from 3.19~5.13 between 7 and 10℃, 1.41~1.74 between 10 and 13℃ and 1.15~1.35 between 13 and 16℃, respectively. Based on overall results, water temperature, photoperiod and their combinations exerted a significant influence on the metabolic rate of juvenile cod. This study provides empirical data for estimating the amount of oxygen demand and managing the culture of cod under the given water temperatures and photoperiods.

Oxygen is a vital parameter in aquaculture activities. The decrease of dissolved oxygen levels in aquaculture media should be highly observed, since very low dissolved oxygen conditions (hypoxia) could negatively affect to the growth and survival of fish. Therefore, research on the condition of hypoxia is very important to be studied. This study was conducted in January-February 2013 at the Laboratorium of Fish Reproductive Physiology, Pukyong National University, South Korea to measure oxygen consumption in tilapia Oreochromis niloticus (total length: 14.2 ± 1.4 cm, weight: 31.3 ± 2.0 g) under normal conditions (normoxia) and hypoxia. Measurement was conducted using respirometer (dimension: 20 × 17,5 × 10 cm; volume: 3,5 L) every 10 minutes during four hours of observation. Experiment was conducted with three replications. The results showed that oxygen consumption of tilapia fingerlings in hypoxia conditions (12.09 ± 3.20 mg O2/kg/h) was lower than normoxia (35.67 ± 4.19 mg O2/kg/h) (P

AlthoughrainbowtroutOncorhynchus mykiss within the American River, California, apparently exhibit minimal upstream or downstream movements in response to hydroelectric-power-generation-related pulsed flows, the associated energetic costs are un- known. We implanted rainbow trout (n=9, ≥30 cm SL) with electromyogram (EMG)-sensor-equipped radio transmitters to assess the swimming behavior and associated energetic costs associated with their responses to pulsed flows. Using laboratory calibrations in a Brett-type swimming respirometer, the trouts' swimming speeds and oxygen consumption rates were estimated for their in-river EMG data, through a complete hydroelectric power-generation river pulsed- flow sequence (pre-pulse, increasing flow, peak, and decreasing flow stages), on several (mean: 3.2) sam- pling dates. Using a mixed-linear model, we found that fish swimming speed estimates increased during the increasing flow stage, while the associated mean oxygen consumption rates also increased at this stage. At river flows near the usual peak (>44 m 3 s −1 ), swimming speeds and movement rates decreased, possibly due to the fish using the river's habitat complexities as hydraulic cover. We conclude that rainbow trout incur increased swimming-related energetic costs during increasing flows and, potentially, decreased foraging opportunities at high flows.