Metabolic utilization of body stores during the early life of whitefish, Coregonus lavaretus L.

Patterns of oxygen consumption, ammonia and urea excretion were monitored during late embryogenesis, i.e. 5 days before mass hatching and 12 days during the free-swimming stage of whitefish larvae, Coregonus lavaretus. Oxygen consumption increased from 1.31 to 2.53 mgO₂ h⁻¹× 10³ eggs⁻¹ at hatching. Fasted, free-swimming larvae showed increasing oxygen consumption to the tenth day after hatching when it reached 5.52 mgO₂h⁻¹× 10³ larvae⁻¹. Ammonia and urea excretion increased during pre-hatching period from 52.1 to 163.2 and 26.8 to 51.4 μgh⁻¹× 10³ eggs⁻¹, respectively. The nitrogen excretion rate increased between the sixth and tenth day of fasting, i.e. for ammonia from 117.7 to 160.9 and for urea from 35.8 to 52.5 μg h⁻¹× 10³ larvae⁻¹. Cumulative data on nitrogen and energy metabolism indicated that during late embryogenesis, and up to the fifth day after hatching, protein dominated in the energy expenditure. During the free swimming stage, the ratio of fat to protein in energy expenditure rose from 0.86 to 1.99. Combined data for several fish species indicated high dependance of oxygen uptake during the hatching period on egg size and temperature.     

Chronic toxicity of ammonia to juvenile gilthead seabream Sparus aurata and related histopathological effects

Effect of 20 days exposure of juvenile gilthead seabream ( Sparus aurata ) to elevated levels of ammonia on growth and survival was examined in a continuous flow system. Suppressed growth and reduced survival were observed at concentrations of 8.2 and 13 mg l⁻¹ total ammonia-N (0.5 and 0.7 mg l⁻¹ un-ionized ammonia-N, respectively) and higher. The maximum acceptable toxic concentration (MATC) for growth was between 4.8 to 8.2 mg l⁻¹ total ammonia-N (0.3 and 0.5 mg l⁻¹ un-ionized ammonia-N, respectively). Fish exposed to high ammonia levels (13 mg l⁻¹ total ammonia-N, 0.7 mg l⁻¹ un-ionized ammonia-N) displayed clear signs of liver pathology. Existing evidence suggests that S. aurata is less sensitive to ammonia than other reported marine and freshwater fish.
Under certain conditions ammonia concentration in the intensive fish ponds in Eilat may exceed the no observed effect concentration for S. aurata .     

The respiration of young coho Oncorhynchus kisutch at gradually declining oxygen levels and during recovery from oxygen deprivation

The respiration of coho salmon, Oncorhynchus kisutch , weighing between 15 and 50 g was measured at gradually declining oxygen levels and at temperatures ranging between 14 and 17°C. The maximum and minimum oxygen concentrations tested were 250 and 40 μmol L⁻¹, respectively. Respiration rates were measured for 1 h periods before oxygen concentration was lowered by 12.5 or 25.0 μmol oxygen L⁻¹. At the end of these endurance tests the oxygen level was returned to normoxic conditions and respiration rates were determined for the recovery period. Under normoxic conditions (> 200 μmol L⁻¹) the respiration of coho levelled around 5.1 μmol g⁻¹ wet weight h⁻¹. At intermediate levels between 150 and 200 μmol oxygen L⁻¹, the average rate increased to 5.8 μmol g⁻¹ h⁻¹, which could be attributed to higher spontaneous activity of the test animals. At low oxygen levels (< 150 μmol⁻¹) average respiration rates dropped to values between 5.5 and 5.7 μmol g⁻¹ h⁻¹, reaching a minimum of 3.8 μmol g⁻¹ h⁻¹ at oxygen levels below 50 μmol L^μ. First mortality was observed in this range. After exposure to reduced oxygen levels the fish maintained a higher respiration rate when again exposed to normoxic oxygen levels above 200 μmol L⁻¹. Increased respiration rates were observed for a recovery period of 6 h.     

Availability, uptake and turnover of glycerol in hypersaline environments

Abstract A sensitive assay for glycerol and other polyols was developed, based on periodate oxidation to formaldehyde, followed by a colorimetric assay with 3-methyl-2-benzothiazolone hydrazone. Apparent glycerol concentrations thus measured in saltern crystallizer ponds were around 20–36 μM, while in the Dead Sea, during a Dunaliella bloom, values were up to 27 μM. However, these values probably overestimate the glycerol concentrations present, as shown by labeled glycerol uptake experiments. Values of [K + S_n] (natural concentration + affinity constant) in saltern ponds were as low as 0.76–1.4 μM, with V_max values of 193–303 nmol 1⁻¹h⁻¹, and turnover times between 2.6–7.2 h at 35°C. Similar measurements in the Dead Sea were: [K + S_n] 0.07–1.41 μM, V_max values 160–426 nmol 1⁻¹h⁻¹, and turnover times in the range of 0.45–3.3 h.     

Comparison of epilithic and epixylic biofilm development in a boreal river

SUMMARY. 1. We assessed substratum effects on lotic biofilm development by placing glass and white pine sampling units in a fourth-order boreal river, and analysing, at 6-week intervals, upper-surface biofilms for ATP, chlorophyll, ergosterol, and the activities of nine exoenzymes.
2. All parameters, except chlorophyll standing stock (range 80–320 μg dm⁻²) and β-xylosidase activity (range 0.4–4.8 μmol h⁻¹ dm⁻²), were significantly greater for epixylic biofilms than for epilithic ones, but the magnitude of the increases varied from 2 to 5 fold, showing that, even under similar hydrodynamic conditions, epilithic and epixylic biofilms are structurally and functionally distinct. For example, ergosterol concentrations ranged from undetectable to 0.93 μg dm⁻² for epilithon and from 11–49 μg dm⁻² for epixylon; corresponding ranges for ATP were 1.6–3.7 (epilithon) and 4.2–7.7 μg dm⁻² (epixylon), for acid phosphatase activity: 2.3–4.9 and 20–41 μmolh⁻¹dm⁻², and for alkaline phosphatase activity: 1.9–8.1 and 29–150 μmol h⁻¹dm⁻², respectively.
3. The more extensive epixylic development was attributed to utilization of the wood substratum as a supplemental carbon source and to a higher density of microbial attachment sites.     

The cytotoxic and photodynamic inactivation of micro-organisms by Rose Bengal

Rose Bengal was cytotoxic to the following bacteria at the concentrations given in parentheses (highest concentrations of dye in mol/1 at which growth occurred on nutrient medium): Brochothrix thermosphacta and Deinococcus radiodurans (1 times 10^-6 or less); Streptococcus, Micrococcus, Staphylococcus, Bacillus, Arthrobacter and Kurthia spp. (1 times 10^-5–1 x 10^-4), and Pseudomonas spp. and Enterobacteriaceae (5 times 10^-3–1 x 10^-2 or greater). These organisms were killed rapidly when suspended in illuminated (170 μE/m²/s) solutions of Rose Bengal (1 times 10^-4 mol/1) providing oxygen was present. Singlet oxygen was identified as the lethal agent, because the rate of killing was increased by dissolving the dye in deuterium oxide while the organisms were protected against photoinactivation by L-histidine or crocetin. Yeasts from chilled foods were killed in illuminated solutions of Rose Bengal but a light intensity of 315 μE/m²/s was needed for a death rate comparable with that of bacteria. The yeasts present in a range of chilled meat and dairy products failed to form colonies on Rose Bengal (5 times 10^-5 mol/1) media exposed continuously to modest illumination (55–80 μE/m²/s).     

Exposure to low concentrations of dissolved ammonia promotes growth rate in walleye Sander vitreus

The objective of the current study was to examine whether sublethal (moderate) levels of dissolved ammonia may be beneficial to growth in juvenile walleye Sander vitreus (recent evidence in juvenile rainbow trout Oncorhynchus mykiss has shown significant increases in protein synthesis in the presence of moderately elevated concentrations of dissolved ammonia). Moderately elevated dissolved ammonia concentrations between 100 and 300 μmol l⁻¹ suppressed routine aerobic metabolic activity by 20% during acute trials (2 h), while promoting specific growth rate (>50%) and elevating whole body soluble protein content by 20% in the early stages (14–42 days) in chronic ammonia exposure experiments. Juvenile S. vitreus held at ammonia concentrations between 107·6 ± 5·5 and 225·5 ± 4·7 μmol l⁻¹ (mean ± s . e .) grew significantly faster than control fish and significantly reduced plasma cortisol levels (<3 μg dl⁻¹). Results from this study suggest that chronic exposure to moderate amounts of dissolved ammonia significantly increase growth rates in juvenile S. vitreus by increasing nitrogen accessible for supplementary protein deposition leading to somatic development.     

Ammonium and phosphate regenerationby the zooplankton of an Amazon floodplain lake

SUMMARY. 1. Regeneration of ammonium and phosphate by macro-zooplankton (Cladocera. adult copepods. and copepodites) was measured in Lake Calado. an Amazon floodplain lake, Macrozooplanktonabundances ranged between 1×10⁴ and 3×10⁵ individuals m⁻².
2. Phosphate regeneration ranged from 0.2 to 1.3 μ mol PO₄ m⁻² b⁻¹at station 1. located 2 km from the Solimoes River, and from 1.6 to8.3 μ mol PO₄ m⁻² h ⁻¹ at station 3, located 7 km from the SolimoesRiver. Ammonium regeneration at stations 1 and 3 ranged from 1.7 to11.9 and from 13.4 to 77.2 μ mol NH₄ m⁻² h⁻¹. respectively.
3. Zooplankton regenerated ammonium and phosphate at similarrates during rising and falling waier. Regeneration by macrozooplankton was low compared to other tropical lakes and compared to microbesand microzooplankton in Lake Calado.     

Oxygen consumption by eggs and larvae of striped mullet, Mugil cephalus, in relation to development, salinity and temperature

Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk-sac, preflexion, flexion and post-flexion larval stages.
Oxygen uptake rates of eggs increased linearly from 0.024 μl O₂ per egg h^-1 (0·323 μl O₂ mg^-1 dry wt h^-1) by blastulae to 0·177 μlO₂ per egg h^-1 (2·516 μlO₂mg ¹dry wth^-1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%₀).
Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O₂ per larva h^-1 shortly after hatching to 18·880 μl O₂ per larva h^-1 on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass-specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O₂ mg ¹dry wt h^-1).
Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk-sac larvae ( Q₁₀ = 2·75) than in postflexion larvae ( Q₁₀ = 1·40).     

Minimum inhibitory concentrations of intestinal Escherichia coli from broiler chickens after oral administration of apramycin

This study describes the influence of apramycin on minimum inhibitory concentrations (MIC) of intestinal Escherichia coli in young broiler chickens, after oral administration of the antibiotic at a dosage equivalent to a prophylactic course of treatment for 10 d. The bacteria were isolated from cloacal swabs and caecal contents. MICs were determined by agar dilution procedures. MIC of apramycin for the investigated strains ranged from 1 μg ml^-1 to 16 μg ml^-1. Strains obtained from undosed birds mainly had MIC values of 1 μg ml^-1. MIC values of 8 μg ml^-1 or more were recorded only among isolates obtained from chickens which had received apramycin. Administration of apramycin resulted in a slight but statistically significant increase in the average MIC. Statistically higher average MICs were recorded among isolates from cloacal swabs 10 d after withdrawal until the end of the experiment. For strains from caecal contents, this was demonstrated only on one sampling occasion, 15 d after withdrawal.     

A new type of metabolism chamber for the determination of active and postprandial metabolism offish, and consideration of results for coregonid and salmon juveniles

The optomotor reaction of juvenile Coregonus schinzipalea Val. et Cuv. and Salmo salar L. was utilized to develop a circular tube metabolism chamber to measure oxygen consumption and ammonia excretion as a function of swimming speed. The metabolism chamber with a constant water flow assured the maintenance of stable conditions. The unidirectional movement of fish was measured in a circular tube with a single narrowing. The relationships between the swimming speed and oxygen consumption or ammonia excretion described by exponential equations allowed the extrapolation towards the standard metabolism, i.e., zero swimming speed. For a juvenile coregonid (0.1–0.15 g individual weight, 2.6–2.8 cm total length) standard metabolism at 14° C was estimated as 0.65 mg0₂ g⁻¹ h⁻¹ and 17.3 μg N(NH₃)g⁻¹ h⁻¹, whereas for juvenile salmon (136mg individual weight) respective values at 22° C were 0.047mg0₂g⁻¹h⁻¹ and 0.61 μg N(NH₃)g⁻¹ h⁻¹. The feeding test with juvenile salmon was also performed in this circular chamber, and in both energy and nitrogen budgets after a meal the partitioning could be precisely attributed to standard metabolism, active metabolism and specific dynamic action (in the case of oxygen consumption) or postprandial nitrogen increase.
The new metabolism chamber allowed the relationship between metabolism and swimming velocity of juvenile fish with developed rheotactic response. It could be used with adult fish for similar purposes.     

Poor water quality suppresses the cortisol response of salmonid fish to handling and confinement

Confinement of brown trout in small troughs of static water for 1 h at a density of six fish 251⁻¹ stimulated the hypothalamic-pituitary-interrenal axis and resulted in an elevation of plasma cortisol from basal levels (less than 2 ng m1⁻¹) to about 100 ng m1⁻¹, the degree of stimulation being dependent upon water temperature. Confinement at a density of 30 fish 251⁻¹ resulted in a 50% suppression of this response. It is demonstrated that this effect is mediated by changes in water chemistry and not by crowding per se . Experimental manipulation of the water chemistry showed that reduced pH (7.1 → 6.3), elevated free CO₂ (63 → 520 μmoll⁻¹) or elevated ammonia (8 → 1300 μg 1⁻¹ as total ammonia nitrogen) had no individual effects on the interrenal response to acute confinement. Elevated ammonia in combination with reduced pH significantly increased the plasma cortisol levels in response to acute confinement, whereas a combination of reduced oxygen (100 → 20% saturation), elevated free CO₂ and elevated ammonia markedly suppressed (∼ 50%) the cortisol response of both brown trout and rainbow trout to acute confinement in a manner similar to that observed with trout at high densities. A compensatory increase in plasma cortisol levels was observed during the subsequent recovery of fish which had been confined for 1 h in water of poor quality. These findings are discussed in relation to the exposure of fish to multiple stresses and to the role of corticosteroids in the stress response.     

A method for long-term measurement of respiration in intertidal fishes during simulated intertidal conditions

Aquatic and aerial respiration of the amphibious fishes Lipophrys pholis and Periophthalmus barbarus were examined using a newly designed flow-through respirometer system. The system allowed long-term measurements of oxygen consumption and carbon dioxide release during periods of aquatic and aerial respiration. The M o ₂ of L. pholis , measured at 15° C, was 2·1 μmol O₂ g^–1 h^–1 during aquatic and 1·99 μmol O₂ g^–1 h^–1 during aerial exposure. The corresponding values of the M co₂ were 1.67 and 1.59 μmol O₂ g^–1 h^–1 respectively, giving an aquatic respiratory exchange ratio (RER) of 0·80 and an aerial RER of 0·79. The M o₂ of P. barbarus , measured at 28°C, was 4·05 μmol O₂ g^–1 h^–1 during aquatic and 3·44 μmol O₂ g^–1 h^–1 during aerial exposure. The corresponding values of the Mco₂ were 3·29 μmol CO₂ g^–1 h^–1 and 2·63 μmol CO₂ g^–1 h^–1 respectively, giving an aquatic RER of 0·81 and an aerial RER of 0·77. While exposed to air for at least 10 h, both species showed no decrease in metabolic rate or carbon dioxide release. The RER of these fishes equalled their respiratory quotient. After re-immersion an increased oxygen consumption, due to the payment of an oxygen debt, could not be detected.     

Oxygen consumption in Oreochromis niloticus (L.) in relation to development, salinity, temperature and time of day

Oxygen consumption of Oreochromis niloticus at different stages of development was studied in relation to salinity, temperature and time of day, using a Warburg apparatus. The oxygen consumption of newly hatched (0–14 h) larvae was 3.40 μl O₂ larva⁻¹ h⁻¹, of older yolk sac larvae 10.09 μl O₂ larva⁻¹ h⁻¹, and of one-month-old fry 32.99 μl O₂ larva⁻¹ h⁻¹. The QO₂ values showed a decrease with development and growth, ranging from 21.2–26.0 μl O₂ mg⁻¹ h⁻¹ in newly hatched larvae to 2.97 μl mg⁻¹ h⁻¹ in one-month-old fry. Changes in oxygen consumption occurred with salinity, the highest being at 17%o. Active larvae (12-24 mm T.L.) showed a doubling of consumption with a 10° C rise in temperature, and their Q₁₀ factor increased from 2.25 to 3.43 with increasing size. Day-old yolk-sac larvae, late yolk-sac larvae (5 days old) and fry of 12 14 mm length all showed a depression in oxygen consumption at midnight followed by a dawn rise.     

The effect of dissolved oxygen and salinity on the toxicity of ammonia to smolts of salmon, Salmo salar L.

The survival of Atlantic salmon smolts on exposure to constant concentrations of ammonia has been measured under laboratory conditions. At concentrations of dissolved oxygen close to the air-saturation value, the 24-h LC50 of un-ionised ammonia is 0.15 mg NH₃1⁻¹ in fresh water (hardness 264 mg 1⁻¹ as CaCO₃) and 0.3 mg NH₃1⁻¹ in 30% sea water; at concentrations of dissolved oxygen of 3.5 mg 1⁻¹ in fresh water and 3.1 mg 1⁻¹ in 30% sea water, the 24-h LC50 is 0.09 mg NH₃ 1⁻¹ and 0.12 mg NH₃ 1⁻¹ respectively; for fish acclimated for 1 day to a concentration of ammonia close to the 24-h median for un-acclimated fish, the median is increased between 38 and 79%, depending on test conditions.     

Activity of methanotrophic bacteria in Green Bay sediments

Abstract Sediment pore water samples obtained from a 19 m station in Green Bay in Lake Michigan were examined for levels of ambient dissolved methane and copper, and for the potential for in situ methane oxidation by methanotrophs found within surface sediments. The in situ methane concentration in the upper oxic sediment layer ranged from 20–150 μmol · 1⁻¹ at this station. The activity of methanotrophs and the kinetics of methane oxidation in these sediments were demonstrated by the uptake of radiolabeled methane. K_s values varied between 4.1–9.6 nmol · cm³ of sediment slurry. High V_max values (12.7–35.2 nmol · cm⁻³ · h⁻¹) suggest a large population of methanotrophs in the sediments. An average methane flux to the oxic sediments of 0.24 mol · m⁻² · year⁻¹ was calculated from the pore water methane gradients. Pore water concentrations of copper in the upper sediment layer ranged from 10–120 nmol · 1⁻¹. Based upon the copper concentration, other measured parameters, and equilibrium conditions defined by WATEQF4, an estimate for dissolved free Cu²⁺ concentration of 5–38 nmol · 1⁻¹ pore water was obtained. Several factors control the rate of methane oxidation, including oxygen, methane, and the bioavailability of free Cu²⁺.     

Photosynthesis and photoassimilation of glucose during photomixotrophic growth of Marchantia polymorpha cells in suspension culture

Even in the presence of glucose the growth of Marchantia polymorpha L. (cell line HYH-2F) requires light, and growth is more sensitive to 10⁻⁶ M 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea than to 10⁻⁴ Antimycin A. The inability of the cells to grow in the dark is due to the low level of respiration. The respiration rate under light increased to four times the dark value. The values of the compensation ratio (the photosyntehtic rate/the respiration rate) for the oxygen exchange were below 1.0 daring the growth period, although oxygen evolution was found. At the early exponential phase, oxygen evolution was 0.373 μmol (mg cell dry weight)⁻¹ h⁻¹ [61.7 μmol (mg chlorophyll)⁻¹ h⁻¹]. M. polymorpha cells are unable to grow anaerobically in the light without a supply of carbon dioxide. When 1% carbon dioxide in nitrogen is supplied, photochemically produced oxygen and energy are sufficient for sustained growth although at significantly reduced yields in both cell dry weight and chlorophyll. Photosyntehtic CO₂ assimilation rate was 0.13 μmol (mg cell dry weight)⁻¹ h⁻¹[11.3 μmol (mg chlorophyll)⁻¹ h⁻¹]. At least one-third of the carbon atoms in cellular constituents seem to be derived from atmospheric carbon dioxide, which indicates that M. polymorpha cells grow photomixotrophicaily.     

The nutrient budget of a small eutrophic loch and the effectiveness of straw bales in controlling algal blooms

1. A 1-year intensive study of nutrient flows in Airthrey Loch, central Scotland, a small eutrophic [mean total phosphorus (TP) = 61.1 μg P l^–1] well-flushed freshwater body (area, 6.9 ha; mean depth, 1.85 m; volume, 1.274 × 10⁵ m³; retention time, 0.44 yr), was undertaken.
2. The nutrient budget was dominated by large allochthonous P inputs, equivalent to an areal load to the loch of 8.56 kg P ha^–1 yr^–1, which occurred predominantly during winter. In the summer, when TP inputs were low, water column levels of TP still increased, as a result of aerobic P release from sediments.
3. Sorption experiments indicated potential for sediment P release at water P concentrations of up to 200 μg P l^–1.
4. Aerobic release rate of P from sediments to the water column of Airthrey Loch was estimated to be of the order of 1 mg P m^–2 day^–1, and occurred during periods of elevated water column pH.
5. Straw bales placed in the loch to retard algal blooms were found not to have any demonstrable impact on algal concentrations observed during the study.     

The nutrient budget of a small eutrophic loch and the effectiveness of straw bales in controlling algal blooms

1. A 1-year intensive study of nutrient flows in Airthrey Loch, central Scotland, a small eutrophic [mean total phosphorus (TP) = 61.1 μg P l^–1] well-flushed freshwater body (area, 6.9 ha; mean depth, 1.85 m; volume, 1.274 × 10⁵ m³; retention time, 0.44 yr), was undertaken.
2. The nutrient budget was dominated by large allochthonous P inputs, equivalent to an areal load to the loch of 8.56 kg P ha^–1 yr^–1, which occurred predominantly during winter. In the summer, when TP inputs were low, water column levels of TP still increased, as a result of aerobic P release from sediments.
3. Sorption experiments indicated potential for sediment P release at water P concentrations of up to 200 μg P l^–1.
4. Aerobic release rate of P from sediments to the water column of Airthrey Loch was estimated to be of the order of 1 mg P m^–2 day^–1, and occurred during periods of elevated water column pH.
5. Straw bales placed in the loch to retard algal blooms were found not to have any demonstrable impact on algal concentrations observed during the study.     

Oxygen uptake in developing eggs and larvae of the cod, Gadus morhua L.

Unfertilised cod eggs showed a mean oxygen uptake rate at 5°C of 0.089 μl O₂, dry wt.⁻¹ h⁻¹; this gradually rose to 0.768 μl O₂ mg dry wt.⁻¹ h⁻¹ in eggs about to hatch. From hatching to complete yolk absorption larvae respired at 1.6 μl O₂, mg dry wt.⁻¹ h⁻¹. During starvation following yolk absorption, uptake fell significantly to 1.1 μl O₂, mg dry ⁻¹ h⁻¹. Much of this decrease in oxygen consumption was shown to be caused by reduction in activity. Loss of weight during the embryo and larval phases could not easily be reconciled with total oxygen consumption; it is suggested that cod embryos and larvae may not rely solely upon endogenous energy reserves during development.