The Challenges of Characterizing the Zooplankton Community Response Following Simulated Spills of Diluted Bitumen into Boreal Lake Limnocorrals.

We attempted to characterize zooplankton community response following spills of the unconventional crude oil, diluted bitumen (dilbit), into 10-m diameter, ~ 100 m3, ~ 1.5-m deep boreal lake limnocorrals, including two controls and seven dilbit treatments ranging from 1.5 to 180 L (1:100,000 to 1:1,000 v/v, dilbit:water). Community composition and abundances were monitored weekly to bi-weekly over three months. Total zooplankton biomass and abundance seemingly collapsed in all limnocorrals, regardless of treatment, though some rotifer species persisted. As a result, it was not possible to determine the impacts of dilbit. We theorize several potential non-oil-related reasons for the sudden community collapse - including elevated zinc levels, fish grazing pressures, and sampling biases - and provide guidance for future work using in-lake enclosures.

Surface oil is the primary driver of macroinvertebrate impacts following spills of diluted bitumen in freshwater.

The response of freshwater invertebrates following accidental releases of oil is not well understood. This knowledge gap is more substantial for unconventional oils such as diluted bitumen (dilbit). We evaluated the effects of dilbit on insect emergence and benthic invertebrates by conducting experimental spills in limnocorrals (10-m diameter; ~100-m3) deployed in a boreal lake at the IISD-Experimental Lakes Area, Canada. The study included seven dilbit treatments (spill volumes ranged from 1.5 L [1:66,000, oil:water, v/v] to 180 L [1:590, oil:water, v/v]), two controls, and additional lake reference sites, monitored for 11 weeks. Invertebrate emergence declined at the community level following oil addition in a significantly volume-dependent manner, and by 93-100 % over the 11 weeks following the spill in the highest treatment. Dilbit altered community structure of benthic invertebrates, but not abundance. One-year post-spill and following oil removal using traditional skimming and absorption techniques, benthic richness and abundance were greater among all treatments than the previous year. These results indicate that recovery in community composition is possible following oil removal from a lake ecosystem. Research is needed concerning the mechanisms by which surface oil directly affect adult invertebrates, whether through limiting oviposition, limiting emergence, or both. The response of benthic communities to sediment tar mats is also warranted.

Simulating diluted bitumen spills in boreal lake limnocorrals - part 2: Factors affecting the physical characteristics and submergence of diluted bitumen.

We examined the fate and behaviour of diluted bitumen (dilbit) as it weathered for 70 days in freshwater limnocorrals (10 m diameter × 1.5 m depth) installed in a boreal lake to simulate dilbit spills in a natural aquatic environment. We added seven different dilbit spill volumes, ranging from 1.5 to 180 L, resulting in oil-to-water ratios between 1:71,000 (v/v, %) and 1:500 (v/v, %). Volatile hydrocarbons in the dilbit slick decreased rapidly after the dilbit was spilled on the water's surface, and dilbit density and viscosity significantly increased (>1 g mL-1 and >5,000,000 mPa s, respectively). Dilbit sank to the bottom sediments in all treatments, and the time to sinking was positively correlated with spill volume. The lowest dilbit treatment began to sink on day 12, whereas the highest dilbit treatment sank on day 31. Dilbit submerged when its density surpassed the density of freshwater (>0.999 g mL-1), with wind, rain, and other factors contributing to dilbit sinking by promoting the break-up of the surface slick. This experiment improves our ability to predict dilbit's aquatic fate and behaviour, and its tendency to sink in a boreal lake. Our findings should be considered in future pipeline risk assessments to ensure the protection of these important aquatic systems.

Neonicotinoids in the Canadian aquatic environment: a literature review on current use products with a focus on fate, exposure, and biological effects.

Developed to replace organophosphate and carbamate insecticides, neonicotinoids are structurally similar to nicotine. The three main neonicotinoid insecticides, imidacloprid, clothianidin, and thiamethoxam, are being re-evaluated by Health Canada's Pest Management Regulatory Agency (PMRA). An important aspect of the re-evaluation is the potential for effects in non-target organisms, including aquatic organisms. Leaching into surface waters is one of the major concerns surrounding extensive use of neonicotinoids, especially in close proximity to water bodies. The PMRA has classified IMI as 'persistent' with a 'high' leaching potential. Globally, neonicotinoids have been detected in a variety of water bodies, typically at concentrations in the low µg/L range. While IMI has been included in some monitoring exercises, there are currently very few published data for the presence of CLO and THM in Canadian water bodies. The majority of neonicotinoid toxicity studies have been conducted with IMI due to its longer presence on the market and high prevalence of use. Aquatic insects are particularly vulnerable to neonicotinoids and chronic toxicity has been observed at concentrations of IMI below 1 µg/L. Acute toxicity has been reported at concentrations below 20 µg/L for the most sensitive species, including Hyalella azteca, ostracods, and Chironomus riparius. Fish, algae, amphibians, and molluscs are relatively insensitive to IMI. However, the biological effects of THM and CLO have not been as well explored. The Canadian interim water quality guideline for IMI is 0.23 µg/L, but there is currently insufficient use, fate, and toxicological information available to establish guidelines for CLO and THM. Based on concentrations of neonicotinoids reported in surface waters in Canada and globally, there is potential for aquatic invertebrates to be negatively impacted by neonicotinoids. Therefore, it is necessary to address knowledge gaps to inform decisions around guidelines and registration status for neonicotinoid insecticides in Canada to protect our aquatic ecosystems.

Selenium bioaccumulation in stocked fish as an indicator of fishery potential in pit lakes on reclaimed coal mines in Alberta, Canada.

Pit lakes are a common reclamation strategy for open pit mines; however, there is a concern about their water quality and suitability as fish habitat because they are often contaminated by metals or metalloids. This study assessed the exposure of fish and invertebrates to selenium (Se) and other metals and metalloids in pit lakes formed by open pit coal mining in Tertiary (thermal coal) and in Cretaceous (metallurgical coal) bedrock. Juvenile hatchery rainbow trout, Oncorhynchus mykiss, and brook trout, Salvelinus fontinalis, were stocked into two thermal coal pit lakes (water Se < 2 µg/L, low water Se) and two metallurgical coal pit lakes (water Se > 15 µg/L, high water Se). Se accumulation in stocked fish and concentrations in invertebrates were characterized over a period of 2 years. In the metallurgical pits, invertebrates had higher Se concentrations and fish accumulated Se to higher levels (exceeding USEPA tissue Se guidelines) than biota in the thermal pits. Rainbow and brook trout accumulated similar concentrations of Se in their muscle and exhibited a similar relationship between whole-body and muscle Se concentrations. These results may be used by resource managers to assess compliance with whole-body tissue Se guidelines and to determine if pit lakes in coal mining areas pose a significant Se risk to wildlife or human health. The high Se exposure in metallurgical coal pits indicates that under the current mining and reclamation strategy, these lakes are not suitable for management as recreational "put and take" fisheries.

The physiological stress response and oxidative stress biomarkers in rainbow trout and brook trout from selenium-impacted streams in a coal mining region.

Selenium (Se) is an essential element that can be toxic at concentrations slightly greater than those required for homeostasis. The main chronic toxic effects of Se in fish are teratogenic deformities, but Se can also activate the physiological stress response and redox cycle with reduced glutathione causing oxidative damage. Rainbow trout, Oncorhynchus mykiss, appear to be more sensitive to Se than brook trout, Salvelinus fontinalis. The objective of this study was to compare the physiological stress response (plasma cortisol, glucose, triiodothyronine, thyroxine, gill Na+/K+ ATPase, cortisol secretory capacity, K and liver somatic index) and oxidative stress biomarkers (liver GSH, GPx, lipid peroxidation, vitamin A and vitamin E) in rainbow trout (RNTR) and brook trout (BKTR) collected from reference and Se-exposed streams. The physiological stress response was not impaired (cortisol secretory capacity unchanged); although there were species differences in plasma cortisol and plasma glucose levels. Liver GSH, GPx and vitamin levels were higher in RNTR than BKTR, but lipid peroxidation levels were not different. The elevated GSH reserves may make RNTR more sensitive to Se-induced lipid peroxidation, but this may be offset by the RNTR's higher antioxidant (GPx and vitamin) levels. Species-specific biochemical differences may mediate differences in Se sensitivity and be used in aquatic Se risk assessments.

Physiological stress response in white suckers from agricultural drain waters containing pesticides and selenium.

To assess the effect of agriculture drain water, a complex mixture containing pesticides and selenium (Se), on the physiological stress response, white suckers were collected from irrigation return flows in the summer and the fall and subjected to a stress challenge. Water (0.40-26.71microg/L) and muscle Se (0.37-1.52microg/g ww) levels were elevated at two sites and plasma acetylcholinesterase (AChE) activity (a marker of pesticide exposure) was lower in the fall (5.97+/-0.45micromol/min/mL) than the summer (10.73+/-0.73micromol/min/mL). Fish raised plasma cortisol levels in response to the stress challenge 11.8 times above basal levels (12.8+/-4.9ng/mL). Multivariate statistics linked Se exposure to elevated plasma glucose levels, and pesticide exposure to elevated liver glycogen levels generating hypotheses for further testing. This study showed that white suckers accumulated Se from agricultural drain water and the complex mixtures present in the drain water influenced the physiological stress response.

Effects of acute and subchronic exposures to waterborne selenite on the physiological stress response and oxidative stress indicators in juvenile rainbow trout.

Selenium (Se) is an essential element that may bioaccumulate to toxic levels. In fish, the major toxicity symptom is larval teratogenic deformities, but little is known about the effect of Se on other systems such as the physiological stress response and oxidative stress. To test the hypothesis that Se is a chemical stressor that causes toxicity through oxidative stress, juvenile rainbow trout were exposed to waterborne sodium selenite, and physiological stress response and stress-related parameters (plasma cortisol, glucose, T3 and T4, gill Na+/K+-ATPase, the ability of the head kidney to secrete cortisol, and condition factor) and hepatic oxidative stress indicators (reduced glutathione, glutathione peroxidase, and lipid peroxidation) were measured after 96 h (acute exposure to 0-2.67 mg/L Se) and 30 days (sub-chronic exposure to 0-0.16 mg/L). Acute exposure to waterborne sodium selenite significantly increased plasma cortisol levels (control=0.01+/-0.0 ng/mL, and 2.52 mg/L Se=73.5+/-22 ng/mL) and plasma glucose levels (control=0.75+/-0.1 mg/mL, and 3.60 mg/L Se=1.64+/-0.2 mg/mL), but gill Na+/K+-ATPase activities, plasma T3 and T4 levels, and condition factor were unchanged. The 96 h acute selenite exposure decreased hepatic reduced glutathione levels (control=18.4+/-1.5 micromol/mg protein, and 3.60 mg/L Se=12.4+/-1.1 micromol/mg protein). Lipid peroxidation levels (0.03-0.08 U/mg protein) and glutathione peroxidase (3.7-6.0 mU/mg protein) activities significantly varied with treatment. The 30 days sub-chronic exposure increased plasma cortisol, T3, and T4, but there was no effect on plasma glucose levels, gill Na+/K+-ATPase activity, the ability to secrete cortisol, and condition factor. The 30 days sub-chronic exposure to selenite did not alter antioxidant activities or lipid peroxidation levels. These experiments show, for the first time, that exposure to waterborne selenite up to 0.1mg/L, activates the physiological stress response in fish but does not impair cortisol secretion after 30 days. The decrease in reduced glutathione in juvenile rainbow trout subjected to the acute sodium selenite exposure suggests that oxidative stress may play an important role in the effects of Se in fish.

Altered distribution of lipid-soluble antioxidant vitamins in juvenile sturgeon exposed to waterborne ethynylestradiol.

Studies in mammals have shown that exposure to estrogenic compounds can affect lipid metabolism and plasma concentrations of lipid-soluble vitamins. However, the potential for estrogenic contaminants to induce these effects in fish has not yet been examined. The ability of the estrogen analog ethynylestradiol (EE2) to alter concentrations of the lipid-soluble vitamins A and E in plasma, liver, and kidney was investigated in juvenile lake sturgeon (430 +/- 20 g). The EE2 was delivered to the sturgeon in the tank water at nominal concentrations of 0 (control), 15, 60, or 125 ng EE2/L for a period of 25 d. Concentrations of the egg yolk precursor, vitellogenin, increased dose dependently in plasma. Plasma vitamin E (tocopherol), A1 (retinol), and A2 (dehydroretinol) were elevated by the two highest EE2 treatments compared with the controls. Esterified storage forms of vitamin A were marginally lower in the livers of fish from the highest EE2 dose group, but vitamin E levels in the liver were not significantly affected. Concentrations of vitamin E and vitamin A were significantly depleted in the kidney of fish from the two highest EE2 dose groups. Total lipid content was elevated in the gonad of fish treated with the highest dose of EE2 compared with the controls. Altered lipid and vitamin distribution may be induced by estrogen to facilitate gonadal maturation in sturgeon. Results from these studies indicate that an examination of the implications for vitamin depletion by estrogenic contaminants in juvenile fish is warranted.

Vitamin and thyroid status in arctic grayling (Thymallus arcticus) exposed to doses of 3,3',4,4'-tetrachlorobiphenyl that induce the phase I enzyme system.

Induction of phase I biotransformation enzymes is recognized as a hallmark response in fish exposed to coplanar PCBs. Depletions of vitamins A and E and disrupted thyroid hormone and glandular structure secondary to this induction have not yet been examined in an arctic fish species. Arctic grayling were exposed to a single oral dose of 0 (control), 10, 100 or 1000 ng 3,3',4,4'-tetrachlorobiphenyl (TCB) g(-1) bodyweight, a contaminant found in most arctic fish. After 30 and 90 days of exposure, TCB concentrations in tissues, hepatic phase I activity (as ethoxyresorufin-O-deethylase (EROD)), plasma and tissue vitamin A and E concentrations, plasma thyroid hormone levels and thyroid glandular structure were examined. Total plasma osmolality, as an indicator of overall fish health was also monitored. TCB recovery in tissues was low and extremely variable, making comparisons between intended dose groups inappropriate. Therefore, correlation analysis between actual recovered TCB concentrations and biochemical responses was employed. Hepatic EROD activity correlated strongly with liver TCB concentrations. Liver concentrations of vitamin A were altered as a function of TCB concentrations and EROD activity, but plasma vitamin A status was not affected. Vitamin E was depleted by TCB accumulation in blood and EROD induction in liver of males only at 90 days postexposure. Thyroid hormones status and glandular structure were not affected by the short duration TCB exposures used in this experiment. TCB concentrations were correlated with an elevation in plasma osmolality. Results from this experiment indicate that the vitamin status and osmoregulation of arctic grayling exposed to TCB can be compromised. Further studies of field populations exposed to this type of contaminant are warranted.

Assessment of selenium effects in lotic ecosystems.

The selenium literature has grown substantially in recent years to encompass new information in a variety of areas. Correspondingly, several different approaches to establishing a new water quality criterion for selenium have been proposed since establishment of the national water quality criterion in 1987. Diverging viewpoints and interpretations of the selenium literature have lead to opposing perspectives on issues such as establishing a national criterion based on a sediment-based model, using hydrologic units to set criteria for stream reaches, and applying lentic-derived effects to lotic environments. This Commentary presents information on the lotic verse lentic controversy. Recently, an article was published that concluded that no adverse effects were occurring in a cutthroat trout population in a coldwater river with elevated selenium concentrations (C. J. Kennedy, L. E. McDonald, R. Loveridge, and M. M. Strosher, 2000, Arch. Environ. Contam. Toxicol. 39, 46-52). This article has added to the controversy rather than provided further insight into selenium toxicology. Information, or rather missing information, in the article has been critically reviewed and problems in the interpretations are discussed.

Metabolism of vitamin A in the heart increases after a myocardial infarction.

The supply of vitamin A to the myocardium by storage organs during increased oxidative stress subsequent to myocardial infarction (MI) was examined in hemodynamically assessed rats using compartment analysis of a radio-labeled vitamin A. 3H-Vitamin A was injected into two groups of rats: an MI group and a control group. There were no differences in the plasma or myocardial content of total vitamin A (unlabeled + labeled) between the two groups. However, the proportion of 3H-vitamin A was greater in the myocardium as well as plasma of MI rats. Rats with MI also had significantly lower 3H-vitamin A levels in liver and kidney than sham controls. The greatest difference in vitamin A content was in the concentrations of 3H-labeled storage forms of vitamin A in the liver of MI animals. Activity of bile salt-dependent retinyl ester hydrolase, an enzyme responsible for hydrolyzing vitamin A storage forms, was significantly increased in the liver of MI animals. These data indicate that analysis of plasma concentrations of vitamin A to ascertain links to cardiac conditions may be inappropriate. Specifically, during MI, increased amounts of vitamin A are mobilized from the liver to the heart without changing plasma concentrations. This is facilitated by an increase in the activity of an enzyme that hydrolyzes vitamin A storage forms.

Antioxidant potentials of vitamin A and carotenoids and their relevance to heart disease.

Despite being one of the first vitamins to be discovered, the full range of biological activities for vitamin A remains to be defined. Structurally similar to vitamin A, carotenoids are a group of nearly 600 compounds. Only about 50 of these have provitamin A activity. Recent evidence has shown vitamin A, carotenoids and provitamin A carotenoids can be effective antioxidants for inhibiting the development of heart disease. Vitamin A must be obtained from the diet: green and yellow vegetables, dairy products, fruits and organ meats are some of the richest sources. Within the body, vitamin A can be found as retinol, retinal and retinoic acid. Because all of these forms are toxic at high concentrations, they are bound to proteins in the extracellular fluids and inside cells. Vitamin A is stored primarily as long chain fatty esters and as provitamin carotenoids in the liver, kidney and adipose tissue. The antioxidant activity of vitamin A and carotenoids is conferred by the hydrophobic chain of polyene units that can quench singlet oxygen , neutralize thiyl radicals and combine with and stabilize peroxyl radicals. In general, the longer the polyene chain, the greater the peroxyl radical stabilizing ability. Because of their structures, vitamin A and carotenoids can autoxidize when O2 tension increases, and thus are most effective antioxidants at low oxygen tensions that are typical of physiological levels found in tissues. Overall, the epidemiological evidence suggests that vitamin A and carotenoids are important dietary factors for reducing the incidence of heart disease. Although there is considerable discrepancy in the results from studies in humans regarding this relationship, carefully controlled experimental studies continue to indicate that these compounds are effective for mitigating and defending against many forms of cardiovascular disease. More work, especially concerning the relevance of how tissue concentrations, rather than plasma levels, relate to the progression of tissue damage in heart disease is required. This review assembles information regarding the basic structure and metabolism of vitamin A and carotenoids as related to their antioxidant activities. Epidemiological, intervention trials and experimental evidence about the effectiveness of vitamin A and carotenoids for reducing cardiovascular disease is also reviewed.

Mobilization of antioxidant vitamin pools and hemodynamic function after myocardial infarction.

BACKGROUND: Although most previous studies have attempted to correlate plasma concentrations of vitamins with specific cardiovascular end points, metabolic considerations suggest that changes in myocardial tissue and storage organs may be better indicators of myocardial oxidative stress. METHODS AND RESULTS: Rats fed commercial chow or a diet enriched with vitamin E for 2 weeks were subjected to either a surgical myocardial infarction (MI) or a sham procedure. Rats were hemodynamically assessed 16 weeks after surgery, and their heart, liver, kidney, and plasma were analyzed for antioxidant vitamins E (tocopherol) and A (retinol and total retinyl esters). At 16 weeks, MI rats on a control diet showed depressed peak systolic and elevated diastolic pressures in both right and left ventricles compared with their sham controls. Plasma concentrations of vitamins E and A in MI rats were not different from sham controls fed the same diet. However, concentrations of vitamin E in left ventricle and liver and of vitamin A in liver (retinol) and kidney (retinyl esters) were decreased in rats with MI compared with the sham controls. Vitamin E supplementation improved hemodynamic function in rats with MI and increased plasma, myocardial, liver, and kidney concentrations of vitamin E. The vitamin E diet also prevented the loss of total retinyl esters from the kidney but not of retinol from the liver in MI rats. CONCLUSIONS: Dietary supplements of vitamin E can sustain better cardiac function subsequent to MI. Antioxidant vitamin levels in the myocardium or in storage organs and not in plasma may be better indicators of myocardial oxidative stress.