Ammonia Efflux Rates Research Articles

Nitrogen budget for a low-salinity, zero-water exchange culture system: II. Evaluation of isonitrogenous feeding of various dietary protein levels to Litopenaeus vannamei (Boone)

This study evaluated the effects of isonitrogenous feeding (60 g dietary protein per kilogram of body weight per day) using experimental feeds with 25%, 30%, 35% and 40% protein on the nitrogen budget, ammonia efflux rate, growth and survival of juvenile Litopenaeus vannamei raised in a low-salinity (4 g L−1) zero-water exchange culture system for 4 weeks. No significant differences in weight gain or instantaneous growth rate were observed between the dietary treatments with 35% and 40% protein after 3 weeks of study, or between treatments with 25% and 30% protein after 4 weeks of study. High mortality rates were observed for the 35% and 40% protein treatments, probably associated with high nitrite levels (4.80 and 7.36 mg NO2-NL−1 respectively) in water. Among the various dietary treatments, 39–46.3% of feed nitrogen was converted to shrimp biomass, 32.8–38.0% and 14.4–39.9% remained within the system as organic and inorganic nitrogen, respectively, and 32.5–39.3% was unaccounted for. The results of the present study showed high nitrogen utilization efficiencies. However, as the nitrogen loading of the zero-water exchange system increased, so did the nitrogen excretion of shrimp, causing a deteriorated general condition of the shrimp, demonstrated by the low ammonia efflux rates recorded at the end of the trial. This study confirms that low-salinity closed systems are particularly susceptible to nitrogen loading. Thus, in these culture systems, low-protein feeds may perform better as they provide more carbon for heterotrophic bacteria and less nitrogen to be degraded and transformed into nitrogenous wastes.

Nitrogen budget for a low salinity, zero-water exchange culture system: I. Effect of dietary protein level on the performance of Litopenaeus vannamei (Boone)

A 4-week study was conducted to evaluate the effects of different dietary protein levels (25%, 30%, 35% and 40%) on the growth and survival of juvenile Litopenaeus vannamei raised in a low salinity (4.6 g L⁻¹), zero-water exchange culture system, as well as on the nitrogen budget and ammonia efflux rate. No significant differences were observed among the dietary treatments for final weight, weight gain or survival of shrimp, although the best performance was observed in the 25% protein treatment group. Both weight and survival decreased as the dietary protein increased. Significant differences (P<0.05) were observed in the ammonia concentration among dietary treatments during the first 2 weeks of the experiment. The highest concentration was measured in the 40% dietary protein treatment (5.88 mg NH4-N L⁻¹). The nitrogen budget showed that the nitrogen loss increased as the dietary protein increased under the experimental conditions; the largest amount of nitrogen recovered as shrimp biomass (42.9%) was in the 25% protein treatment group, and the largest amount of unaccounted nitrogen (39.5%) was in the 40% protein treatment. Under these conditions, utilization of low-protein diets resulted in better performance, presumably because they provided more carbon for heterotrophic bacteria and reduced the nitrogen loading of the system.

Postprandial acid–base balance and ion regulation in freshwater and seawater-acclimated European flounder, Platichthys flesus

The effects of feeding on both acid-base and ion exchange with the environment, and internal acid-base and ion balance, in freshwater and seawater-acclimated flounder were investigated. Following voluntary feeding on a meal of 2.5-5% body mass and subsequent gastric acid secretion, no systemic alkaline tide or respiratory compensation was observed in either group. Ammonia efflux rates more than doubled from 489 +/- 35 and 555 +/- 64 mumol kg(-1) h(-1) under control conditions to 1,228 +/- 127 and 1,300 +/- 154 mumol kg(-1) h(-1) post-feeding in freshwater and seawater-acclimated fish, respectively. Based on predictions of gastric acid secreted during digestion, we calculated net postprandial internal base gains (i.e., HCO (3) (-) secreted from gastric parietal cells into the blood) of 3.4 mmol kg(-1) in seawater and 9.1 mmol kg(-1 )in freshwater-acclimated flounder. However, net fluxes of ammonia, titratable alkalinity, Na(+) and Cl(-) indicated that branchial Cl(-)/HCO (3) (-) and Na(+)/H(+) exchange played minimal roles in counteracting these predicted base gains and cannot explain the absence of alkaline tide. Instead, intestinal Cl(-)/HCO (3) (-) exchange appears to be enhanced after feeding in both freshwater and seawater flounder. This implicates the intestine rather than the gills as a potential route of postprandial base excretion in fish, to compensate for gastric acid secretion.

Effect of dietary protein level on growth, survival and ammonia efflux rate of Litopenaeus vannamei (Boone) raised in a zero water exchange culture system

Litopenaeus vannamei postlarvae (1.96±0.07 g) were reared in a zero water exchange system for 25 days at 28°C. They were fed four commercial diets containing 25%, 30%, 35% or 40% crude protein in three replicate aquaria per dietary treatment. Total ammonia, nitrite, nitrate and pH were monitored weekly and total ammonia levels were additionally measured every 3 days using the flow injection analysis method. Total ammonia efflux rates were measured at days 0, 14 and 21, and survival and growth rates were recorded at the end of the experiment. No significant differences between water quality parameters such as temperature, salinity, dissolved oxygen and pH were found. Nitrite concentration remained low in all dietary treatments up to the second week increasing considerably from day 14 onwards suggesting the initiation of the nitrification process. Water total ammonia of all experimental groups exhibited a gradual increase up to day 13; however, following this time ammonia levels of all experimental groups decreased, probably due to either the action of bacterial nitrification or ammonia-N uptake by the animals. High ammonia efflux rates were recorded at day 14, especially after the first hour of immersion in the 25% protein group, but no significant changes occurred in any experimental group after 3 h. No significant differences in weight gain, final weight or survival of shrimp were observed under these experimental conditions. The importance of zero water exchange systems and their effects on the nitrogen metabolism of crustaceans are discussed.

Ammonia efflux rates and free amino acid levels in Litopenaeus vannamei postlarvae during sudden salinity changes

A laboratory simulation of a salinity test on Litopenaeus vannamei postlarvae was performed [a 30-min exposure to bottled freshwater (1.5 ppt) followed by an abrupt return to seawater (37 ppt) for another 30 min] in order to evaluate physiological responses such as ammonia efflux rates and free amino acid levels. Ammonia efflux rate in the control group (37 ppt; 28 °C) was 4.55±0.25 μmol g −1 h −1. Postlarvae exposed to freshwater media had a significantly higher ammonia efflux rate during the first 5 min post-transfer which reduced after 30 min, but was still higher than in the control group. A return to seawater (37 ppt) induced the highest ammonia efflux rate of 82.04±7.79 μmol g −1 h −1 and higher rates persisted throughout the exposure period. Total free amino acids (TFAAs) in whole PL were 2.96 μmol gfw −1 (gfw −1=gram fresh weight), but increased after exposure to both salinity changes, with methionine, serine, valine, phenylalanine, isoleucine, glutamic, lysine, and arginine being several-fold higher after the sudden return to seawater. In the control group, glycine and alanine were the most abundant free amino acids (FAA) with the essential amino acid (EAA) arginine also present in significant amounts. Postlarvae of the white shrimp L. vannamei may be able to resist sudden salinity changes by manipulation of nitrogen metabolism and rapidly increase ammonia efflux rates and increase organic osmolytes such as certain amino acids for osmotic regulation.

Some aspects of nitrogen metabolism in Mytilus edulis : effects of aerial exposure

The effects of starvation and emersion on the ammonia effluxes of Mytilus edulis L. were studied. Both fed and starved groups showed similar patterns of efflux during re-immersion, indicating no compensation for starvation during anaerobic catabolism; this is taken as evidence that carbohydrate or lipid is the predominant energy source at the outset of anaerobiosis. Instead of an overshoot of ammonia excreted during the 4 h following re-immersion, all groups showed significantly reduced efflux rates independent of emersion duration. Such results suggest some conversion of ammonia during the recovery period, as no significant drop in haemolymph ammonia occurred at this time. The level of ammonia accumulation in haemolymph and mantle cavity fluid decreased exponentially with emersion duration, implying the stabilisation, at a low rate, of ammonia production after a relatively long period of emersion (16 to 24 h). Oxygen levels of the mantle cavity fluid dropped rapidly during emersion but never attained anoxia over 24 h of emersion, which may indicate some oxygen uptake by emersed mussels. It has been concluded that the behaviour and physiological responses shown by M. edulis to emersion appear to reflect a need for respiratory gas exchange more than a response to desiccation – presumably in the interest of energy-conservation. The reductions in ammonia efflux rate during emersion and, to a certain extent, immediately after re-immersion have also been considered here to be energy-saving strategies that illustrate the importance of ammonia in restoring normal levels of some amino acids following re-immersion.

Metabolic responses of Nephrops norvegicus to progressive hypoxia

This work studied some of the metabolic responses of Nephrops norvegicus to a progressive reduction in water oxygen tension (PwO 2) at 12 °C. Experiments were designed to simulate water quality conditions that may occur during the trade of live crustaceans. Oxygen consumption rates and ammonia efflux rates were found to be constant over a wide range of PwO 2 values (20.4–5.9 kPa). A similar result was found for the difference between post-branchial and pre-branchial oxygen concentrations (20.4–2.6 kPa), obtained from a separate experiment. Anaerobic pathways, however, were activated after PwO 2 reached 6.3 kPa, as blood lactate and glucose concentrations increased from 1.24 ± 0.08 and 1.17 ± 0.19 (T 0 values) to 10.55 ± 8.99 and 3.63 ± 0.89 mg · 100 mL −1 respectively. N. norvegicus was able to maintain blood pH levels at relatively constant values despite a drop in water pH levels and the accumulation of lactate observed at low PwO 2. Heart rates also remained stable during PwO 2 reductions, but scaphognathite beat rate increased considerably, probably as an attempt to maintain steady weight-specific oxygen consumption rates. N. norvegicus appeared to be well adapted to cope with progressive hypoxia as may occur during holding and transportation procedures.

Haemolymph and mantle fluid ammonia and ninhydrin positive substances variations in salinity-challenged mussels ( Mytilus edulis L.)

Ambient salinity change-induced variability of ammonia efflux rates, concentrations of ninhydrin positive substances (NPS) and dissolved ammonia (DA) in the haemolymph and mantle cavity fluid of Mytilus edulis were examined. Hypo-osmotic challenges evoked rapid (< 1 h) increases of DA efflux rates, to levels which persisted for the 4 h exposure period, and concomitant increases in haemolymph and mantle fluid NPS and DA levels. Exposure to hyper-osmotic media induced decreased DA efflux rates (cf. normal seawater levels in all cases). Such results suggest that intertidal M. edulis, which may normally experience rapid salinity changes, can make rapid adjustments to such osmotic stresses. Haemolymph hypoglycaemia (cf. control group) accompanied all salinity changes which suggests increased glucose utilisation occurs during the initial adjustments to external media salinity changes.

Effects of ambient ammonia levels on blood ammonia, ammonia excretion and heart and scaphognathite rates of Nephrops norvegicus

During commercial handling of Nephropsnorvegicus (L.) there are a number of situations when the prawns may be exposed to very high ambient ammonia levels. These experiments evaluated the effects of increased levels of ambient total ammonia (TA = NH3 + NH4 +) on␣blood ammonia, ammonia efflux rates and on the cardio-ventilatory performance of N. norvegicus. When prawns were taken from <1 to 2000 μmol TA l−1 medium, blood TA concentrations increased rapidly for the first 2 h but tended to drop thereafter. Original blood TA levels were restored 6 h after the prawns were transferred back from seawater containing 2000 to <1 μmol TA l−1. Sudden exposure to 500, 1000, 2000 or 4000 μmol TA l−1 medium induced blood TA concentrations to increase respectively to 50, 30, 33 and 36% of external concentrations (normally, internal TA values are much higher than external levels). Immediately after transfer back to seawater with low ammonia concentration ( <1 μmol TA l−1), excretion rates were higher than those of control prawns, and the absolute amounts of TA excreted were considerably higher than those calculated to have accumulated in the haemolymph. Heart rate (HR) and scaphognathite rate (SR) were not altered when prawns were subjected to sudden alterations in ambient ammonia ( <1 to 2000 to <1 μmol TA l−1). When water ammonia concentrations were altered more gradually, both rates increased, but only at 4000 μmol TA l−1. These results show that N. norvegicus is able to remove ammonia from the haemolymph and/or transform ammonia into some other substance when subjected to increased levels of ambient ammonia. Possible mechanisms involved (e.g. active transport across the gills; storage in some other tissue; glutamate synthe sis) are discussed.

Haemolymph constituent levels and ammonia efflux rates of Nephrops norvegicus during emersion

Nephropsnorvegicus (L.) were subjected to 8 h of emersion, either between layers of seawater-soaked hessian with periodical (20 min) flushes of seawater (high humidity, HH) or to unprotected emersion (low humidity, LH). Blood ammonia levels rose during emersion in both groups but reached higher levels under LH conditions. Ammonia efflux rates after re-immersion were higher than those of control prawns, and amounts of ammonia excreted at such times were considerably higher than those calculated to have accumulated in the blood during emersion. Possible explanations for such differences are discussed. C aO2 and C vO2 decreased rapidly to ca. 10% normoxia values within 2 h of HH and LH emersion and remained low throughout the remaining emersion time. Emersion-induced tissue hypoxia increased blood concentrations of glucose and lactate. Lactate accumulation was higher during LH emersion, compared with HH emersion. Blood pH dropped ca. 0.40 units but increased again after 2 h of re-immersion. Acidosis was probably related more to respiratory difficulties (CO2 accumulation) than to lactate accumulation, as blood lactate values remained high after 2 h of re-immersion. The ability of N. norvegicus to cope with emersion appears to be little influenced by high humidity conditions.

The effect of diet and photoperiod on ammonia efflux rates of the African catfish,Clarias gariepinus(Burchell, 1822)

Total ammonia efflux rates of the African catfish, Clarias gariepinus (Burchell), were measured under different combinations of photoperiod (LD 24:0. LD 0:24, LD 12:12) and feeding regime (50% protein diet, 41% protein diet and zero food). A time-dependent variation of ammonia efflux following feeding was observed, with postprandial excretion rates in the first 12 h being greater than those in the following 12 h. Ammonia efflux rates were directly related to the level of protein in the diet under all photoperiod conditions. Photoperiod had no effect on ammonia efflux rate, except in the LD 24:0-high protein diet group, which may indicate a stress response.

Haemolymph nitrogen compounds and ammonia efflux rates under anoxia in the brackish water isopod Saduria entomon

Haemolymph nitrogen compounds and ammonia efflux rates under anoxia in the brackish water isopod Saduria entomon

Haemolymph nitrogen compounds and ammonia efflux rates under anoxia in the brackish water isopod Saduria entomon

Haemolymph nitrogen compounds and ammonia efflux rates under anoxia in the brackish water isopod Saduria entomon

Moult stage-dependent variability of haemolymph ammonia and total protein levels of Crangon crangon (L.) (Crustacea, Decapoda)

Abstract Haemolymph ammonia and total protein levels showed similar patterns of quantitative change, and a positive, linear relationship, during the moult cycle of Crangon crangon (L.) (Crustacea, Decapoda), Concentrations were generally lowest after ecdysis (120.5 μmol ammonia l-1; 3.7 g total protein 100 ml-1) and increased through intermoult and early premoult. Premoult (stages D0 ED3) ammonia concentrations were relatively constant (192.1–212.2 μmol ammonia l-1), whereas total protein values were more variable (5.7–7.8 g 100 ml-1). Ecdysis was accompanied by significant (P<0.05), near-identical decreases (34.9% & 35.1% respectively) in haemolymph ammonia and total protein concentrations. Two different mechanisms appear responsible for these changes: a passive drop in protein levels (attributed to haemolymph dilution), and a regulated decrease of ammonia levels. These data show moult stage-dependent ammonia efflux rates to be independent of haemolymph ammonia concentrations.

Effect of angiotensin II on ammonia production and secretion by mouse proximal tubules perfused in vitro.

The effects of angiotensin II on total ammonia (tNH3) production and net secretion were investigated using in vitro microperfused mouse S2 proximal tubule segments incubated in Krebs-Ringer bicarbonate buffer containing 0.5 mM L-glutamine. Basolateral exposure of mouse S2 segments to 10(-11), 10(-10), and 10(-9) M angiotensin II stimulated tNH3 production rates by 23, 52, and 49%, respectively. Addition of 10(-6) M angiotensin II inhibited the tNH3 production rate by 34%. 10(-10) M angiotensin II inhibited net luminal secretion of tNH3 in the presence of enhanced luminal acidification and in the absence of altered luminal tNH3 efflux rates. Measurements of intracellular pH (pHi) and intracellular calcium concentration [( Ca2+]i) suggested that the effects of angiotensin II on tNH3 production were not mediated by changes in pHi but by the stimulatory effect of angiotensin II correlated with increased [Ca2+]i. Inhibition of the calcium-calmodulin-dependent pathway with W-7 blocked the stimulatory effect of 10(-10) M angiotensin II on tNH3 production and luminal acidification. These results indicate that angiotensin II has concentration-dependent effects on tNH3 production; that its action to stimulate tNH3 production may be mediated by rises in [Ca2+]i and the calcium-calmodulin pathway; and that angiotensin II, at concentrations that stimulate tNH3 production, inhibits net luminal ammonia secretion by a mechanism that is not mediated by diminished luminal acidification or by changes in luminal ammonia efflux rates.

Some effects of hypoxia and medium ammonia enrichment on efflux rates and circulating levels of ammonia inNephrops norvegicus

Eutrophication has been reported for autumn months in regions of the Kattegat/Skagerrak, causing stress to bottom-living organisms. The present studies, undertaken in April (1989), investigated the effects of hypoxia and high ammonia levels in the burrowing decapodNephrops norvegicus (L.). The net ammonia efflux rates and circulating ammonia levels at 6 and 12°C, at normoxia [partial pressure of O2 in the water (torr),PwO2 = 155 torr)] and hypoxiaPwO2 = 24 torr) in normal seawater and ammonia-enriched (300µmol ammonia l−1) seawater were examined. The hourly weight-specific efflux rates were very variable and in all groups included some individuals which showed periods of no net efflux, or even a net uptake of ammonia. At each temperature, net efflux-rate differences due to treatments were not significant (P>0.05; ANOVA, in all cases) and only the differences between the net efflux rates of the normoxic groups were significantly affected by temperature (P<0.05; ANOVA). Circulating ammonia levels were also variable, and at 6°C the ammonia-enriched groups had significantly higher weight-specific blood ammonia content values than the normoxic group (P<0.05 in both cases). A net uptake of ammonia occurred in ammoniaenriched conditions — probably along a reversed NH4+ gradient, as downhill pNH3 gradients were maintained in all groups — and may represent the only means by which some branchial efflux of ammonia could proceed.