The effects of acute exposure to the water soluble fraction of diesel fuel oil on survival and metabolic rate of an antarctic fish (Pagothenia borchgrevinki)

Diluted bitumen-induced alterations in aerobic capacity, swimming performance, and post-exercise recovery in juvenile sockeye salmon (Oncorhynchus nerka)

The transportation of heavy crudes such as diluted bitumen (dilbit) sourced from Canadian oil sands through freshwater habitat requires the generation of information that will contribute to risk assessments, spill modelling, management, and remediation for the protection of aquatic organisms. Juvenile sockeye salmon (Oncorhynchus nerka) were exposed acutely (96 h) or subchronically (28 d) to the water-soluble fraction (WSFd) of Cold Lake Blend dilbit at initial total polycyclic aromatic compound (TPAC) concentrations of 0, 13.7, 34.7, and 124.5 µg/L. A significant induction (>3-fold) of hepatic liver ethoxyresorufin-O-deethylase (EROD) activity was induced by 96 h in fish exposed to [TPAC] ≥ 34.7 µg/L and at ≥13.7 µg/L for a 28 d exposure. Exposure resulted in a typical physiological stress response and disturbance of ion homeostasis; this included elevations in plasma [cortisol], [lactate], [Na⁺], and [Cl^-], and significant reductions in muscle [glycogen]. Critical swimming speed (U_crit) was significantly reduced (28.4%) in the acute exposure at [TPAC] 124.5 µg/L; reductions of 14.2% and 35.4% were seen in fish subchronically exposed at the two highest concentrations. Reductions in U_crit were related to significant reductions in aerobic scope (24.3-46.6%) at [TPAC]s of 34.7 and 124.5 µg/L, respectively. Exposure did not impair the ability to mount a secondary stress response following burst exercise, however, the time required for biochemical parameters to return to baseline values was prolonged. Alterations in critical systems supporting swimming, exercise recovery and the physiological stress response could result in decreased salmonid fitness and contribute to population declines if a dilbit spill occurs.

Effects of suspended coal particles on gill structure and oxygen consumption rates in a coral reef fish

Large quantities of coal are transported through tropical regions; however, little is known about the sub-lethal effects of coal contamination on tropical marine organisms, including fish. Here, we measured aerobic metabolism and gill morphology in a planktivorous coral reef damselfish, Acanthochromis polyacanthus to elucidate the sub-lethal effects of suspended coal particles over a range of coal concentrations and exposure durations. Differences in the standard oxygen consumption rates (M_O2) between control fish and fish exposed to coal particles (38 and 73 mg L^-1) were minimal and generally not dose dependent; however, the M_O2 of fish exposed to 38 mg coal L^-1 (21 days) and 73 mg coal L^-1 (31 days) were both significantly higher than the M_O2 of control fish. Chronic coal exposure (31 days) altered gill structure in the higher coal treatments (73 and 275 mg L^-1), with fish exposed to 275 mg L^-1 exhibiting significant reductions in gill mucous and thinning of lamellar and filament epithelium. These findings contribute to our limited understanding of the potential impacts of coal on tropical reef species; however, most of the observed effects occurred at high coal concentrations that are unlikely under most coal spill scenarios. Future studies should investigate other contamination scenarios such as the impacts of chronic exposures to lower concentrations of coal.

Environmental modulators of diluted bitumen effects in juvenile pink salmon (Oncorhynchus gorbuscha)

Recent and potential expansions in the transportation of diluted bitumen (dilbit) through marine terminals in coastal regions of British Columbia require the examination of potential risks to estuarine species such as Pacific salmon. The estuarine habitat of out-migrated pink salmon (Oncorhynchus gorbuscha) exhibits dynamic temperature and salinity regimes, possibly modifying dilbit exposure, bioavailability and/or its effects. To examine dilbit toxicity and its modification by environmental stressors, juvenile pinks were subchronically exposed for 3 months to the water-accommodated fraction (WAF) of Cold Lake Blend dilbit (winter) in seawater at three salinities (7, 14, and 28‰ [temperature 12.5 °C]) and three temperatures (8.5, 12.5, and 16.5 °C [salinity of 28‰]). Temperature and salinity alone did not affect any measured endpoints in control fish. Dilbit exposure induced higher mortality at high (16.5 °C) and low temperatures (8.5 °C) as well as at higher salinity (28‰) in fish exposed to the highest dilution of WAF [total polycyclic aromatic compounds (TPAC) = 128.9 μg/L]. A concentration-dependent reduction of growth was evident in fish exposed to the medium (TPAC = 97.3 μg/L) and high dilution of WAF at higher temperatures (12.5 and 16.5 °C) and high salinity (28‰). At 28‰, swimming performance (U_burst) was decreased in fish exposed to the highest concentration of dilbit at all 3 temperatures. Gill Na⁺-K⁺-ATPase activity, white muscle lactate, glycogen, and triglyceride concentrations were altered by dilbit exposure and modified by temperature and salinity. In addition, gene expression associated with phase I biotransformation, energy metabolism, mitochondrial activity, and inflammation showed significant upregulation with exposure and temperature stress. Dilbit exposure at PAC concentrations in the ppb range, affected pink salmon at the molecular, biochemical, and whole organism level; effects that were exacerbated by environmental temperature and salinity.

Physiological disturbances in juvenile sockeye salmon (Oncorhynchus nerka) exposed to the water-soluble fraction of diluted bitumen

Current and proposed transcontinental pipelines for the transport of diluted bitumen (dilbit) from the Canadian oil sands traverse the coastal watersheds of British Columbia, habitat essential to Pacific salmonids. To determine the potential risks posed to these keystone species, juvenile sockeye (Oncorhynchus nerka; 1+ parr) were acutely (24-96 h) or subchronically (21-42 d) exposed to 4 concentrations of the water-soluble fraction (WSF) of unweathered Cold Lake Blend dilbit (initial total PAC concentrations: 0, 13.7, 34.7 and 124.5 μg/L) in a flow-through system. Dilbit effects on iono-osmoregulation, the physiological stress response, and the immune system were assessed by both biochemical and functional assays. Hydrocarbon bioavailability was evidenced by a significant induction of liver ethoxyresorufin-O-deethylase (EROD) activity in exposed fish. Acute and subchronic exposure significantly reduced gill Na⁺-K⁺-ATPase activity and resulted in lower plasma osmolality, Cl^-, and Na⁺ concentrations. Acute exposure to dilbit resulted in a classic physiological stress response, however at 21 d of exposure, plasma cortisol remained elevated while other measured parameters had returned to baseline values. A compromised immune system was demonstrated by a 29.5 % higher mortality in fish challenged with Vibrio (Listonella) anguillarum following dilbit exposure compared to unexposed controls. Exposure of juvenile salmonids to the WSF of dilbit (at TPAC concentrations at the ppb level) resulted in sublethal effects that included a classic physiological stress response, and alterations in iono-osmoregulatory homeostasis and immunological performance.

The effect of temperature and meal size on the aerobic scope and specific dynamic action of two temperate New Zealand finfish Chrysophrys auratus and Aldrichetta forsteri

Shallow coastal and estuarine habitats function as nurseries for many juvenile fish. In this comparative study, metabolic profiles of two New Zealand finfish, snapper (Chrysophrys auratus) and yellow-eyed mullet-YEM (Aldrichetta forsteri) that as juveniles share the same temperate coastal environments, were examined. Metabolic parameters (routine and maximum metabolic rates, and specific dynamic action-SDA) were investigated at a set of temperatures (13, 17, 21 °C) within the range juveniles both species experience annually. SDA was also determined for a range of different feed rations to investigate the effects of meal size on postprandial metabolic response. Temperature was a strong modulator of snapper and YEM metabolic profile (routine and maximum metabolic rates, and absolute and factorial aerobic scope). Metabolic rates increased with temperature in both species as did absolute scope in YEM, though for snapper, it was only greater at the highest temperature. Factorial scope behaved in the same fashion for the two species, being greatest at 13 °C. Both absolute and factorial scope were ~ twofold greater in YEM than in snapper across the entire temperature range. Temperature also affected SDA response in snapper, while in YEM, SDA parameters were largely unaffected when temperature increased from 17 to 21 °C. Snapper were able to consume a large range of meal sizes (0.5-3.0% body mass-BM) with meal sizes > 1% BM having a pronounced effect on numerous SDA parameters, whereas mullet appeared to consume more limited ration sizes (≤ 1.0% BM). In both species, rations ≤ 1% BM produced similar changes in SDA parameters identifying comparable digestive bio-energetics. Overall, our metabolic characterisations demonstrate that both species can adjust to the variable temperate environmental temperatures and manage the energetic costs of digestion and feed assimilation. Yet, despite these general similarities, YEM's greater aerobic scope may point to better physiological adaptation to the highly variable temperate coastal environment than were observed in snapper.

Species-specific impacts of suspended sediments on gill structure and function in coral reef fishes

Reduced water quality, in particular increases in suspended sediments, has been linked to declines in fish abundance on coral reefs. Changes in gill structure induced by suspended sediments have been hypothesized to impair gill function and may provide a mechanistic basis for the observed declines; yet, evidence for this is lacking. We exposed juveniles of three reef fish species (Amphiprion melanopus, Amphiprion percula and Acanthochromis polyacanthus) to suspended sediments (0-180 mg l^-1) for 7 days and examined changes in gill structure and metabolic performance (i.e. oxygen consumption). Exposure to suspended sediments led to shorter gill lamellae in A. melanopus and A. polyacanthus and reduced oxygen diffusion distances in all three species. While A. melanopus exhibited impaired oxygen uptake after suspended sediment exposure, i.e. decreased maximum and increased resting oxygen consumption rates resulting in decreased aerobic scope, the oxygen consumption rates of the other two species remained unaffected. These findings imply that species sensitive to changes in gill structure such as A. melanopus may decline in abundance as reefs become more turbid, whereas species that are able to maintain metabolic performance despite suspended sediment exposure, such as A. polyacanthus or A. percula, may be able to persist or gain a competitive advantage.

The effect of the water soluble fraction of crude oil on survival, physiology and behaviour of Caspian roach, Rutilus caspicus (Yakovlev, 1870)

The water soluble fraction (WSF) of crude oil is a complex and toxic mixture of hydrocarbons that aquatic organisms directly encounter in oil spills. WSF plays an important role in the toxicity of crude oil to aquatic organisms. In the present study, the effects of WSF on juvenile Caspian roach, Rutilus caspicus, at lethal and sub-lethal level was investigated. The lethality of WSF on R. caspicus was studied by conducting 96h LC50 tests with semi-static exposure methods with 6 and 24h solution renewals. The 96h LC50 of WSF was estimated at 62.5% and 35.9% WSF concentrations for 24h and 6h renewal methods, respectively. To investigate the sub-lethal effect of WSF on R. caspicus, fish were exposed to 62.5, 31.3, and 6.3% concentrations of WSF for 24h and changes in their respiration rate and swimming activity was monitored during the exposure. At the end of the exposure period, four hematologic parameters [O2 and CO2 pressures (pO2 and pCO2), hematocrit, and hemoglobin content] of the fish were measured. The result of the behavioural experiment revealed that all three studied concentrations of WSF elevated the respiration rate and reduced the swimming activity of R. caspicus. No significant changes were detected in the hematocrit and hemoglobin content of the fish blood, but the blood pO2 of the fish exposed to 62.5% WSF decreased while the blood pCO2 increased. The results of this study suggest that the egression of the volatile components in hydrocarbon mixtures during conventional semi-static toxicity tests may lead to underestimating the toxicity of the hydrocarbons. The results of the sub-lethal experiments propose that failure of the respiratory system that leads to asphyxia may be a major mechanism that results in lethal effect of WSF in high concentrations.

Trophic contamination by pyrolytic polycyclic aromatic hydrocarbons does not affect aerobic metabolic scope in zebrafish Danio rerio

The effect of trophic exposure to pyrolitic polycyclic aromatic hydrocarbons (PAH) on aerobic metabolism of zebrafish Danio rerio was investigated. There were no significant differences in standard metabolic rate (SMR), active metabolic rate (AMR) or aerobic metabolic scope (AS) at any sublethal concentration of PAH in the diet of adult or juvenile fish. This suggests that under these experimental conditions, exposure to PAH in food did not influence aerobic metabolism of this species.

Effects of HMX exposure upon metabolic rate of northern bobwhite quail (Colinus virginianus) in ovo

We evaluated the use of the gas exchange rate as an ecologically relevant indicator of chemical stress in avian embryos/eggs. Northern bobwhite quail (Colinus virginianus) were exposed to octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) via feed containing nominal concentrations of 0, 12.5, 50.0, and 125.0 mg kg(-1). Metabolic rates (oxygen consumption) of developing quail eggs were then measured via respirometry to examine potential effects of HMX exposure. Metabolic rates were examined on 5, 9, and 21 d of incubation. Next, concentrations of HMX in embryos/eggs were determined by liquid chromatography-mass spectrometry. Mean (+/-SE) concentrations of HMX in eggs were 21.0+/-5.9, 1113+/-79.0, 3864+/-154.0, and 7426+/-301.1 ng g(-1) in control, low, medium and high dose groups, respectively. There were significant differences in oxygen consumption among the three embryo ages, however differences among the ages were not consistent among dose groups (age x dose group interaction p<0.0001). Oxygen consumption rates did not vary as a function of HMX in embryos (p=0.18). No evidence was observed for alterations of in ovo metabolic rates associated with HMX exposure.

Naphthalene treatment alters liver intermediary metabolism and levels of steroid hormones in plasma of rainbow trout (Oncorhynchus mykiss)

To assess the effects of naphthalene on liver intermediary metabolism and plasma steroid hormones, immature female rainbow trout (Oncorhynchus mykiss), in a first experiment, were intraperitoneally injected (2 microLg(-1)) with vegetable oil alone (control) or containing naphthalene (10 and 50 mgkg(-1)) and returned to their tanks. At 1, 3, and 6h after injection, eight fish were sampled from each group. A second experiment was similarly designed but used fish intraperitoneally implanted (10 microLg(-1)) with slow-release coconut oil implants alone (control) or containing naphthalene at doses of 10 and 50 mgkg(-1) body weight that were sampled 1, 3, and 5 days after injection. At each sampling time, plasma hormone levels (cortisol and 17beta-estradiol) and metabolic parameters in plasma (glucose and lactate) and liver (glucose, lactate, and glycogen levels and HK, GK, GPase, GDH, FBPase, and PK activities) were assessed. Changes described for both hormonal systems resulted in a decrease in plasma levels of cortisol and 17beta-estradiol. Changes observed in intermediary metabolism described effects in several pathways of liver energy metabolism due to naphthalene. These changes can be summarized as increased glycogenolysis, use of exogenous glucose, and glycolysis and decreased gluconeogenesis. The increased energy production in liver suggested by these changes can be related to the increased detoxification activity known to occur in liver after PAH exposure, and can be also related directly or indirectly to the changes observed in the levels of plasma steroids.