Ingestion of crude oil: sublethal effects in herring gull chicks

Sublethal effects of early-life exposure to common and emerging contaminants in birds

The plight of wild birds is becoming critical due to exposure to environmental contaminants. Although laboratory studies have provided insights into the developmental effects of chemical exposures, less is known about the adverse effects of environmental chemicals in developing wild birds. Early life stages are critical windows during which long-term organization of physiological, behavioral, and neurological systems can occur. Thus, contaminant exposure at early life stages can directly influence survival and reproductive success, with consequences for population stability and resilience in wild species. This review synthesizes existing knowledge regarding both short- and long-term effects of early-life exposure to widespread contaminants in birds. We focus especially on wild birds and on contaminants of concern within the Gulf of Mexico as an example of a habitat under anthropogenic stress from exposure to a complex mixture of chemicals and changing land uses that exacerbate existing vulnerabilities of wildlife in this region. Chemical contaminants for discussion in this review are based on avian mortality records from the Wildlife Health Information Sharing Partnership (WHISPers) database and on additional review of the literature regarding avian contaminants of concern for the northern Gulf of Mexico, and include oil and associated polycyclic aromatic hydrocarbons, dioxin and dioxin-like compounds, flame retardants, pesticides, heavy metals, and plastics. We provide an overview of effects in bird species at both the pre-hatching and post-hatching early life stages, discuss differences in sensitivities by route of exposure, life stage, and life history, and provide recommendations for future research. We find that additional research is needed on altricial species, post-hatching early-life exposure, long-term effects, and on ecologically relevant contaminant concentrations and routes of exposure. Given the increasing frequency and intensity of anthropogenic stressors encountered by wild animals, understanding both lethal and sublethal impacts of contaminants on the health of individuals and populations will be critical to inform restoration, management, and mitigation efforts.

Review of contaminant levels and effects in shorebirds: Knowledge gaps and conservation priorities

Environmental pollution has emerged as a major threat to bird populations. Many shorebird populations are declining, although contamination has been documented in some shorebirds, evidence of negative impacts is sparse and this important topic remains understudied. To guide future research and develop effective conservation strategies, we carried out a comprehensive review of environmental pollutants and their consequences on shorebirds. In total, we found 93 relevant articles which examined pollutant contamination in ~37% (79 of 215) of all shorebird species, mostly from the Charadriidae and Scolopacidae families. Studies were geographically biased: the majority were conducted in American flyways, while only 1 was found from Australasia and few were conducted in Asian flyways. The main geographic gap for research includes East Africa, South Asia and Siberian Arctic. The most well-documented pollutants included mercury (Hg, 37 studies), cadmium (33), and lead (Pb, 28); less well studied pollutants were barium (1), calcium (1), strontium (1), dicofols (1), and other newly emerging contaminants, such as plastic debris/microplastics (4) and antibiotics resistance (2). Several pollutants have caused considerable concerns in shorebirds, including embryotoxicity caused by PCBs at non-optimum temperature (laboratory experiments); reduced reproduction performance linked to maternal Hg and paternal Pb (field evidence); and reduced refueling and flight performance related to oil contamination (both field and laboratory evidence). Our results confirm that an in-depth understanding of the local, regional and global factors that influence population trends of shorebirds in light of increasing pollution threats is essential for accurate and effective management and conservation strategies.

Effects of diluted bitumen exposure on the survival, physiology, and behaviour of zebra finches (Taeniopygia guttata)

Diluted bitumen (dilbit) is an unconventional crude petroleum increasingly being extracted and transported to market by pipeline and tanker. Despite the transport of dilbit through terrestrial, aquatic, and coastal habitat important to diverse bird fauna, toxicity data are currently only available for fish and invertebrates. We used the zebra finch (Taeniopygia guttata) as a tractable, avian model system to investigate exposure effects of lightly weathered Cold Lake blend dilbit on survival, tissue residue, and a range of physiological and behavioural endpoints. Birds were exposed via oral gavage over 14-days with dosages of 0, 2, 4, 6, 8, 10, or 12 mL dilbit/kg bw/day. We identified an LD₅₀ of 9.4 mL/kg/d dilbit, with complete mortality at 12 mL/kg/d. Mortality was associated with mass loss, external oiling, decreased pectoral and heart mass, and increased liver mass. Hepatic ethoxyresorufin-O-deethylase activity (EROD) was elevated in all dilbit-dosed birds compared with controls but there was limited evidence of sublethal effects of dilbit on physiological endpoints at doses < 10 mL/kg/d (hematocrit, hemoglobin, total antioxidants, and reactive oxygen metabolites). Dilbit exposure affected behavior, with more dilbit-treated birds foraging away from the feeder, more birds sleeping or idle at low dilbit doses, and fewer birds huddling together at high dilbit doses. Naphthalene, dibenzothiophene, and their alkylated congeners in particular (e.g. C2-napthalene and C2-dibenzothiophene) accumulated in the liver at greater concentrations in dilbit-treated birds compared to controls. Although directly comparable studies in the zebra finch are limited, our mortality data suggest that dilbit is more toxic than the well-studied MC252 conventional light crude oil with this exposure regime. A lack of overt sublethal effects at lower doses, but effects on body mass and composition, behaviour, high mortality, and elevated PAC residue at doses ≥ 10 mL/kg/d suggest a threshold effect.

A review of the toxicology of oil in vertebrates: what we have learned following the Deepwater Horizon oil spill

In the wake of the Deepwater Horizon (DWH) oil spill, a number of government agencies, academic institutions, consultants, and nonprofit organizations conducted lab- and field-based research to understand the toxic effects of the oil. Lab testing was performed with a variety of fish, birds, turtles, and vertebrate cell lines (as well as invertebrates); field biologists conducted observations on fish, birds, turtles, and marine mammals; and epidemiologists carried out observational studies in humans. Eight years after the spill, scientists and resource managers held a workshop to summarize the similarities and differences in the effects of DWH oil on vertebrate taxa and to identify remaining gaps in our understanding of oil toxicity in wildlife and humans, building upon the cross-taxonomic synthesis initiated during the Natural Resource Damage Assessment. Across the studies, consistency was found in the types of toxic response observed in the different organisms. Impairment of stress responses and adrenal gland function, cardiotoxicity, immune system dysfunction, disruption of blood cells and their function, effects on locomotion, and oxidative damage were observed across taxa. This consistency suggests conservation in the mechanisms of action and disease pathogenesis. From a toxicological perspective, a logical progression of impacts was noted: from molecular and cellular effects that manifest as organ dysfunction, to systemic effects that compromise fitness, growth, reproductive potential, and survival. From a clinical perspective, adverse health effects from DWH oil spill exposure formed a suite of signs/symptomatic responses that at the highest doses/concentrations resulted in multi-organ system failure.

Weathered Mississippi Canyon 252 crude oil ingestion alters cytokine signaling, lowers heterophil:lymphocyte ratio, and induces sickness behavior in zebra finches (Taeniopygia guttata)

The Deepwater Horizon (DWH) oil spill caused an estimated 100,000 bird mortalities. However, mortality estimates are often based on the number of visibly oiled birds and likely underestimate the true damage to avian populations as they do not include toxic effects from crude oil ingestion. Elevated susceptibility to disease has been postulated to be a significant barrier to recovery for birds that have ingested crude oil. Effective defense against pathogens involves integration of physiological and behavioral traits, which are regulated in-part by cytokine signaling pathways. In this study, we tested whether crude oil ingestion altered behavioral and physiological aspects of disease defense in birds. To do so, we used artificially weathered Mississippi Canyon 242 crude oil to orally dose zebra finches (Taeniopygia guttata) with 3.3 mL/kg or 10 mL/kg of crude oil or a control (peanut oil) for 14 days. We measured expression of cytokines (interleukin [IL]-1β, IL-6, IL-10) and proinflammatory pathways (NF-κB, COX-2) in the intestine, liver, and spleen (tissues that exhibit pathology in oil-exposed birds). We also measured heterophil:lymphocyte (H:L) ratio and complement system activity, and video-recorded birds to analyze sickness behavior. Finches that ingested crude oil exhibited tissue-specific changes in cytokine mRNA expression. Proinflammatory cytokine expression decreased in the intestine but increased in the liver and spleen. Birds exposed to crude oil had lower H:L ratios compared to the control on day 14, but there were no differences in complement activity among treatments. Additionally, birds exposed to 10 mL/kg crude oil had reduced activity, indicative of sickness behavior. Our results suggest cytokines play a role in mediating physiological and behavioral responses to crude oil ingestion. Although most avian population damage assessments focus on mortality caused by external oiling, crude oil ingestion may also indirectly affect survival by altering physiological and behavioral traits important for disease defense.

David S. Miller: Scientist, Mentor, Friend-a tribute and thank you

David S. Miller was Acting Scientific Director of the Division of Intramural Research at the National Institute of Environmental Health Sciences, National Institutes of Health, and Head of the Intracellular Regulation Group in the Laboratory of Toxicology and Pharmacology before he retired in 2016. David received his Ph.D. in biochemistry from the University of Maine in 1973. David was a Group Leader at the Michigan Cancer Foundation before joining the NIEHS in 1985. His research covered a wide range from renal excretory transport mechanisms to regulation of transporters at the blood–CSF and blood–brain barriers, from fish, amphibians and birds to mammals. David was an outstanding scientist with irresistible enthusiasm for science and an incredible ability to think outside the box while being an exceptional mentor and friend.

Transcriptome analysis indicates a broad range of toxic effects of Deepwater Horizon oil on Seaside Sparrows

In marine species, the transcriptomic response to Deepwater Horizon (DWH) oil implicated many biochemical pathways, with corresponding adverse outcomes on organ development and physiological performance. Terrestrial organisms differ in their mechanisms of exposure to polycyclic aromatic hydrocarbons (PAHs) and their physiological challenges, and may reveal either distinct effects of oil on biochemical pathways or the generality of the responses to oil shown in marine species. Using a cross-species hybridization microarray approach, we investigated the transcriptomic response in the liver of Seaside Sparrows (Ammospiza maritima) exposed to DWH oil compared with birds from a control site. Our analysis identified 295 genes differentially expressed between birds exposed to oil and controls. Gene ontology (GO) and canonical pathway analysis suggested that the identified genes were involved in a coordinated response that promoted hepatocellular proliferation and liver regeneration while inhibiting apoptosis, necrosis, and liver steatosis. Exposure to oil also altered the expression of genes regulating energy homeostasis, including carbohydrate metabolism and gluconeogenesis, and the biosynthesis, transport and metabolism of lipids. These results provide a molecular mechanism for the long-standing observation of hepatic hypertrophy and altered lipid biosynthesis and transport in birds exposed to crude oil. Several of the activated pathways and pathological outcomes shown here overlap with the ones altered in fish species upon exposure to oil. Overall, our study shows that the path of oil contamination from the marine system into salt marshes can lead to similar responses in terrestrial birds to those described in marine organisms, suggesting similar adverse outcomes and shared machinery for detoxification.

Post-release breeding success of oil-rehabilitated and non-rehabilitated little blue penguins, Eudyptula minor, following the M/V Rena oil spill, New Zealand

During the 2011 M/V Rena oil spill in Tauranga, New Zealand, 383 little blue penguins (LBP, Eudyptula minor) were oiled, rescued and rehabilitated, with 90.6% surviving to be released back to the wild. We monitored the post-release breeding success of rehabilitated LBPs to assess the effectiveness of the rehabilitation process. Breeding success was monitored during the first breeding season post-release (2012-13) to assess productivity for both rehabilitated and control penguins (breeding pairs of rehabilitated or non-oiled (control) birds). Egg laying, hatching and fledging success rates for pairs of rehabilitated and control penguins were both within ranges reported for other LBP colonies in Australia and New Zealand. The only significant difference between rehabilitated and control pairs was that hatching success was reduced in the first season after release for rehabilitated pairs. Overall, rehabilitation appeared to reverse most potential negative effects of oiling on the post-release breeding success of rehabilitated LBP.

Productivity of waterbirds in potentially impacted areas of Louisiana in 2011 following the Deepwater Horizon oil spill

The Deepwater Horizon oil spill (2010) could have affected the behavior and productivity of birds nesting along the Gulf of Mexico. This research examined the productivity of several species of colonial waterbirds in 2011 in LA colonies that were classified according to the M252 peak SCAT shoreline map oiling designations (as of April 6 2011) within 2 km of each colony. Colonies were classified as no oil, little oil, or medium to heavy oil. Because of the uneven distribution of oil and variation in bird composition within colonies, not all species occurred in each of the three oiling classes in the LA colonies studied. I tested the following hypotheses: (1) there were no interspecific differences in nesting phenology, (2) there were no differences in the number of species per colony as a function of oiling, and (3) there were no differences in reproductive measures as a function of oiling. Nesting phenology differed among species, with brown pelicans (Pelecanus occidentalis), great egrets (Ardea alba), and tri-colored herons (Egretta tricolor) nesting earlier than the other species. There were no significant differences in the number of species nesting in colonies as a function of oiling category. Along LA's shoreline, nests in colonies with a "no oil" category within 2 km of the colony had similar or lower maximum number of chicks/nest, than those from birds in colonies designated as light or moderate/heavy oiling. Average maximum chick sizes in nests in colonies designated as no oil were either similar to or smaller than chicks in nests in colonies designated as either category of oiled. The data suggest that in the year following the oil spill, there were no differences in reproductive success. Although long-term studies are essential to determine effects on population dynamics, the continued exposure of birds nesting along the Gulf of Mexico to acute and chronic oil sources make this a nearly impossible task.

Toxicological and thermoregulatory effects of feather contamination with artificially weathered MC 252 oil in western sandpipers (Calidris mauri)

The external contamination of bird feathers with crude oil might have effects on feather structure and thus on thermoregulation. We tested the thermoregulatory ability of western sandpipers (Calidris mauri) in a respirometry chamber with oil applied either immediately prior, or three days before the experiment. The birds were then exposed to a sliding cold temperature challenge between 27°C and -3°C to calculate thermal conductance. After the experiment, a large blood sample was taken and the liver extracted to measure a range of parameters linked to toxicology and oxidative stress. No differences in thermal conductance were observed among groups, but birds exposed to oil for three days had reduced body temperatures and lost more body mass during that period. At necropsy, oiled birds showed a decrease in plasma albumin and sodium, and an increase in urea. This is reflective of dysfunction in the kidney at the loop of Henle. Birds, especially when exposed to the oil for three days, showed signs of oxidative stress and oxidative damage. These results show that the ingestion of externally applied oil through preening or drinking can cause toxic effects even in low doses, while we did not detect a direct effect of the external oil on thermoregulation over the temperature range tested.

Organ weights and histopathology of double-crested cormorants (Phalacrocorax auritus) dosed orally or dermally with artificially weathered Mississippi Canyon 252 crude oil

A series of toxicity tests were conducted to assess the effects of low to moderate exposure to artificially weathered Deepwater Horizon Mississippi Canyon 252 crude oil on representative avian species as part of the Natural Resource Damage Assessment. The present report summarizes effects of oral exposure (n=26) of double-crested cormorants (DCCO; Phalacrocorax auritus) to 5 or 10ml oil kg^-1 day^-1 for up to 21 days or dermal application (n=25) of 13ml oil to breast and back feathers every three days totaling 6 applications in 21 days on organ weights and histopathology. Absolute and relative kidney and liver weights were increased in birds exposed to oil. Additionally, gross and/or histopathologic lesions occurred in the kidney, heart, pancreas and thyroid. Clinically significant renal lesions in the orally dosed birds included squamous metaplasia and increased epithelial hypertrophy of the collecting ducts and renal tubules and mineralization in comparison to controls. Gross cardiac lesions including thin walls and flaccid musculature were documented in both orally and dermally dosed birds and myocardial fibrosis was found in low numbers of dermally dosed birds only. Cytoplasmic vacuolation of the exocrine pancreas was noted in orally dosed birds only. Thyroid follicular hyperplasia was increased in dermally dosed birds only possibly due to increased metabolism required to compensate damaged feather integrity and thermoregulate. Gastrointestinal ulceration was found in orally dosed birds only. There were no significant hepatic histopathologic lesions induced by either exposure route. Therefore, hepatic histopathology is likely not a good representation of oil-induced damage. Taken together, the results suggest that oral or dermal exposure of DCCOs to artificially weathered MC252 crude oil induced organ damage that could potentially affect survivability.

Reprint of: Overview of avian toxicity studies for the Deepwater Horizon Natural Resource Damage Assessment

The Oil Pollution Act of 1990 establishes liability for injuries to natural resources because of the release or threat of release of oil. Assessment of injury to natural resources resulting from an oil spill and development and implementation of a plan for the restoration, rehabilitation, replacement or acquisition of natural resources to compensate for those injuries is accomplished through the Natural Resource Damage Assessment (NRDA) process. The NRDA process began within a week of the Deepwater Horizon oil spill, which occurred on April 20, 2010. During the spill, more than 8500 dead and impaired birds representing at least 93 avian species were collected. In addition, there were more than 3500 birds observed to be visibly oiled. While information in the literature at the time helped to identify some of the effects of oil on birds, it was not sufficient to fully characterize the nature and extent of the injuries to the thousands of live oiled birds, or to quantify those injuries in terms of effects on bird viability. As a result, the US Fish and Wildlife Service proposed various assessment activities to inform NRDA injury determination and quantification analyses associated with the Deepwater Horizon oil spill, including avian toxicity studies. The goal of these studies was to evaluate the effects of oral exposure to 1-20ml of artificially weathered Mississippi Canyon 252 oil kg bw^-1 day^-1 from one to 28 days or one to five applications of oil to 20% of the bird's surface area. It was thought that these exposure levels would not result in immediate or short-term mortality but might result in physiological effects that ultimately could affect avian survival, reproduction and health. These studies included oral dosing studies, an external dosing study, metabolic and flight performance studies and field-based flight studies. Results of these studies indicated changes in hematologic endpoints including formation of Heinz bodies and changes in cell counts. There were also effects on multiple organ systems, cardiac function and oxidative status. External oiling affected flight patterns and time spent during flight tasks indicating that migration may be affected by short-term repeated exposure to oil. Feather damage also resulted in increased heat loss and energetic demands. The papers in this special issue indicate that the combined effects of oil toxicity and feather effects in avian species, even in the case of relatively light oiling, can significantly affect the overall health of birds.

Toxic effects of orally ingested oil from the Deepwater Horizon spill on laughing gulls

The explosion of the Deepwater Horizon oil rig released, millions of gallons of oil into the environment, subsequently exposing wildlife, including numerous bird species. To determine the effects of MC252 oil to species relevant to the Gulf of Mexico, studies were done examining multiple exposure scenarios and doses. In this study, laughing gulls (Leucophaeus atricilla, LAGU) were offered fish injected with MC252 oil at target doses of 5 or 10mL/kg bw per day. Dosing continued for 27 days. Of the adult, mixed-sex LAGUs used in the present study, ten of 20 oil exposed LAGUs survived to the end of the study; a total of 10 of the oil exposed LAGUs died or were euthanized within 20 days of initiation of the study. Endpoints associated with oxidative stress, hepatic total glutathione (tGSH), oxidized glutathione (GSSG) and reduced glutathione (rGSH) significantly increased as mean dose of oil increased, while the rGSH:GSSG ratio showed a non-significant negative trend with oil dose. A significant increase in 3-methyl histidine was found in oil exposed birds when compared to controls indicative of muscle wastage and may have been associated with the gross observation of diminished structural integrity in cardiac tissue. Consistent with previous oil dosing studies in birds, significant changes in liver, spleen, and kidney weight when normalized to body weight were observed. These studies indicate that mortality in response to oil dosing is relatively common and the mortality exhibited by the gulls is consistent with previous studies examining oil toxicity. Whether survival effects in the gull study were associated with weight loss, physiologic effects of oil toxicity, or a behavioral response that led the birds to reject the dosed fish is unknown.

Effect of oral exposure to artificially weathered Deepwater Horizon crude oil on blood chemistries, hepatic antioxidant enzyme activities, organ weights and histopathology in western sandpipers (Calidris mauri)

Shorebirds were among birds exposed to Mississippi Canyon 252 (MC252) crude oil during the 2010 Deep Water Horizon (DWH) oil spill in the Gulf of Mexico. The western sandpiper (Calidris mauri) was chosen as one of four species for initial oral dosing studies conducted under Phase 2 of the avian toxicity studies for the DWH Natural Resource Damage Assessment (NRDA). Thirty western sandpipers were assigned to one of three treatment groups, 10 birds per group. The control group was sham gavaged and the treatment groups were gavaged with 1 or 5mL oil kg bw^-1 daily for 20 days. Periodic blood samples for hemoglobin measurements were collected during the trial. A final blood sample used to determine hemoglobin concentration in addition to complete blood counts, plasma clinical chemistries, haptoglobin concentration and plasma electrophoresis was collected when birds were euthanized and necropsied on day 21. Tissues were removed, weighed and processed for subsequent histopathological evaluation. There were numerical decreases in hemoglobin concentrations in oil-dosed birds over the 21-day trial, but values were not significantly different compared to controls on day 21. There were no significant differences between controls and oiled birds in complete blood counts, plasma chemistries, haptoglobin concentration, and plasma electrophoresis endpoints. Of the hepatic oxidative stress endpoints assessed, the total antioxidant capacity assessment (Trolox equivalents) for the control group was lower compared to the 1mL oil kg bw^-1 group. Absolute liver weights in the 5mL oil kg bw^-1 group were significantly greater compared to controls. While not conclusive, the numerical decrease in hemoglobin concentration and significant increase in absolute liver weight are consistent with exposure to oil. Histological changes in the adrenal gland could be considered a non-specific indicator of stress resulting from exposure to oil. It is possible that the quantity of oil absorbed was not sufficient to induce clearly evident hemolytic anemia or that the western sandpiper is relatively insensitive to ingested oil.

Mercury correlates with altered corticosterone but not testosterone or estradiol concentrations in common loons

We investigated the relation between environmental mercury exposure and corticosterone concentrations in free-living adult common loons (Gavia immer). We determined blood and feather mercury concentrations and compared them to testosterone, estradiol, and stress-induced plasma corticosterone concentrations. Although neither testosterone nor estradiol correlated with Hg levels, there was a robust positive relation between blood Hg and stress-induced corticosterone concentrations in males, but not in females. The lack of an effect in females may have been due to overall less contamination in females. There were no significant correlations between feather Hg and stress-induced corticosterone in either sex. To help determine whether Hg had a causal effect on corticosterone, we investigated the impact of experimental Hg intake on the corticosterone stress response in captive juvenile loons. Juveniles were subjected to three different feeding regimes: 0, 0.4 and 1.2μg Hg (as MeHgCL)/g wet weight (ww) fish. We then measured baseline and 30min post-solitary confinement stressor corticosterone concentrations. The Hg fed chicks exhibited a decreased ability to mount a stress response. From these data, we conclude that Hg contamination does appear to alter the corticosterone response to stress, but not in a consistent predictable pattern. Regardless of the direction of change, however, exposure to mercury contamination and the resulting impact on the corticosterone stress response in common loons may substantially impact health, fitness and survival.

Overview of avian toxicity studies for the Deepwater Horizon Natural Resource Damage Assessment

The Oil Pollution Act of 1990 establishes liability for injuries to natural resources because of the release or threat of release of oil. Assessment of injury to natural resources resulting from an oil spill and development and implementation of a plan for the restoration, rehabilitation, replacement or acquisition of natural resources to compensate for those injuries is accomplished through the Natural Resource Damage Assessment (NRDA) process. The NRDA process began within a week of the Deepwater Horizon oil spill, which occurred on April 20, 2010. During the spill, more than 8500 dead and impaired birds representing at least 93 avian species were collected. In addition, there were more than 3500 birds observed to be visibly oiled. While information in the literature at the time helped to identify some of the effects of oil on birds, it was not sufficient to fully characterize the nature and extent of the injuries to the thousands of live oiled birds, or to quantify those injuries in terms of effects on bird viability. As a result, the US Fish and Wildlife Service proposed various assessment activities to inform NRDA injury determination and quantification analyses associated with the Deepwater Horizon oil spill, including avian toxicity studies. The goal of these studies was to evaluate the effects of oral exposure to 1-20ml of artificially weathered Mississippi Canyon 252 oil kg bw^-1 day^-1 from one to 28 days or one to five applications of oil to 20% of the bird's surface area. It was thought that these exposure levels would not result in immediate or short-term mortality but might result in physiological effects that ultimately could affect avian survival, reproduction and health. These studies included oral dosing studies, an external dosing study, metabolic and flight performance studies and field-based flight studies. Results of these studies indicated changes in hematologic endpoints including formation of Heinz bodies and changes in cell counts. There were also effects on multiple organ systems, cardiac function and oxidative status. External oiling affected flight patterns and time spent during flight tasks indicating that migration may be affected by short-term repeated exposure to oil. Feather damage also resulted in increased heat loss and energetic demands. The papers in this special issue indicate that the combined effects of oil toxicity and feather effects in avian species, even in the case of relatively light oiling, can significantly affect the overall health of birds.

Polycyclic aromatic hydrocarbons in blood related to lower body mass in common loons

We captured 93 wintering adult and subadult Common Loons (Gavia immer) in coastal Louisiana from 2011 to 2015 following the Deepwater Horizon oil spill. We tested blood samples for exposure to polycyclic aromatic hydrocarbons (PAHs) and measured physiological variables including hematocrit, hemoglobin and total blood protein. PAH concentrations in loon blood differed from year to year and by age class. High PAH concentrations were significantly related to lower body masses in both adult and subadult birds and higher serum protein levels in adults only. PAH concentrations had marginal relations with both hematocrit and hemoglobin levels. The types of PAHs detected also underwent a major shift over time. The PAHs detected in 2011, 2012, and 2015 were primarily low molecular weight (three carbon rings); however, in 2013, most detected PAHs were high molecular weight (four carbon rings). It is unclear what events led to the increase in PAH concentrations and the shift in type of PAHs over time.

Embryotoxicity of weathered crude oil from the Gulf of Mexico in mallard ducks (Anas platyrhynchos)

Weathered crude oil in the Gulf of Mexico can result from oil spills such as the Deepwater Horizon incident that occurred on April 20, 2010 or from natural seeps. Adult waterbirds of the Gulf Coast region may become exposed to weathered crude oil while foraging, wading, or resting, and residues can then be transferred to nests, eggs, and hatchlings. Although the toxicity of many types of crude oil to avian embryos has been thoroughly studied, the effects of weathered crude oil on developing avian embryos are not well characterized. The objective of the present study was to examine embryotoxicity of weathered crude oil collected from the Gulf of Mexico in June 2010 using mallard ducks (Anas platyrhynchos) as a model species. Weathered crude oil was applied to fertilized mallard duck eggs by paintbrush in masses ranging from 0.1 to 99.9 mg on day 3 of incubation. Mortality occurred as early as day 7 and the conservatively derived median lethal application of weathered crude oil was 30.8 mg/egg (0.5 mg/g egg) or 30.7 µl/egg (0.5 µl/g egg). Body mass, liver and spleen mass, crown-rump and bill lengths, and frequency of deformities were not significantly different among hatchlings from oiled and control eggs. In comparison to published reports of fresh crude oil embryotoxicity, weathered crude oil was considerably less toxic. We conclude that avian toxicity varies according to the degree of crude oil weathering and the stage of embryonic development at the time of exposure. Results indicate bird eggs exposed to weathered crude oil from the Gulf of Mexico during summer 2010 may have had reduced hatching success.

Cell physiology at the Mount Desert Island Biological Laboratory: a brief look back and forward

The Mount Desert Island Biological Laboratory (MDIBL) has played important roles in the development of modern physiological concepts and tools, particularly in the fields of kidney and epithelial cell physiology. Over the last decade, MDIBL has undergone remarkable growth and evolution. This article will briefly review MDIBL's past and outline its future directions. It is hoped that this overview will renew and stimulate interest in MDIBL and, in particular, will encourage an even wider community of physiologists to participate in its ongoing growth and development.

The corticosterone stress response and mercury contamination in free-living tree swallows, Tachycineta bicolor

We determined mercury concentrations in tree swallows, Tachycineta bicolor, from Massachusetts and Maine with different levels of contamination. Baseline and stress-induced plasma corticosterone concentrations from adults and nestlings (Massachusetts only) were compared with mercury concentrations. In Massachusetts, adult baseline corticosterone was negatively correlated with blood mercury, but showed a nearly-significant positive correlation with feather mercury. There was a negative relationship between baseline corticosterone and blood mercury in nestlings and between baseline corticosterone and egg mercury. There was no relationship between mercury and stress-induced corticosterone in any of the groups, or with baseline corticosterone in Maine sites where mercury levels were lower. The findings suggest blood and egg mercury may be a better indicator of current condition than feather mercury. Further, mercury contamination may not alter stress-induced corticosterone concentrations in tree swallows but appears to have a significant impact on baseline circulating corticosterone.

Modulation of steroidogenesis and xenobiotic biotransformation responses in zebrafish (Danio rerio) exposed to water-soluble fraction of crude oil

The induction of CYP enzyme activities, particularly CYP1A1, through the aryl hydrocarbon receptor (AhR) in most vertebrate species is among the most studied biochemical response to planar and aromatic organic contaminant exposure. Since P450 families play central roles in the oxidative metabolism of a wide range of exogenous and endogenous compounds, interactions between the biotransformation processes and reproductive physiological responses are inevitable. Steroidogenesis is the process by which specialized cells in specific tissues, such as the gonad, brain (neurosteroids) and kidney, synthesize steroid hormones. In the present study, we evaluated the effects of water-soluble fraction (WSF) of crude oil on the xenobiotic biotransformation and steroidogenic processes in the head (brain) and whole-body tissue of a model species by transcript analysis using quantitative (real-time) polymerase chain reaction (qPCR), enzyme activities and steroid hormone (testosterone: T and 17beta-estradiol: E2) levels using enzyme immune assay (EIA). Our data showed that exposure of fish to WSF produced an apparent concentration-specific increase of AhR1, CYP1A1 and 3beta-hydroxysteroid dehydrogenase (3beta-HSD) mRNA levels, and decrease of AhR2. On the activity level, WSF produced concentration-specific increase of ethoxyresorufin O-deethylase (EROD), benzyloxyresorufin (BROD) methoxyresorufin (MROD) and pentoxyresorufin (PROD) activities in whole-body tissue. In the steroidogenic pathway, WSF exposure produced apparent concentration-specific decrease of ER* and ERbeta, steroidogenic acute regulatory (StAR) protein, cytochrome P450 side-chain cleavage (P450scc), P450aromA and P450aromB mRNA expression. For steroid hormones, while T levels decreased, E2 levels increased in an apparent WSF concentration-specific manner. In general, the xenobiotic biotransformation and estrogenic responses showed negative relationship after exposure of zebrafish to WSF, suggesting an interaction between these physiological pathways. The relationship between WSF mediated changes in brain StAR, P450scc, 3beta-HSD, ER*alpha, ERbeta, P450aromA, P450aromB and whole-body steroid hormone levels suggests that the experimental animals might be experiencing altered neurosteroidogenesis probably through increased activity level of the biotransformation system. Thus, these responses might represent sensitive diagnostic tools for short-term and acute exposure of fish or other aquatic organisms to WSF.

Polyaromatic hydrocarbon and PAH metabolite burdens in oiled common guillemots (Uria aalge) stranded on the east coast of England (2001 -2002)

Aside from the physical effects of oiling (e.g., hypothermia, dehydration, emaciation), chronic toxicity of polycyclic aromatic hydrocarbons (PAHs) contamination is an important factor influencing long-term recovery of oiled sea birds following an oil spill. Monitoring PAH exposure can help identify populations at risk from toxic effects of PAHs for further study and/or protection. This is the first studyto quantify PAH and metabolite tissue burdens in sea birds directly oiled following oil spills. PAHs and hydroxylated PAHs were quantified in liver samples from oiled Common Guillemots (Uria aalge) stranded along the East Coast of England using gas chromatography-mass spectroscopy (GC-MS). Mean parent and metabolite PAH concentrations were 0.25+/-0.09 (range 0.04-0.97) and 0.52+/-0.14 (range 0.05-1.48) microg/g (wet wt.), respectively. The main source of PAH exposure was via ingestion of crude oil during preening, resulting in PAH uptake and tissue contamination beyond levels expected from exposure via the food chain. PAH composition corresponded with number of benzene rings in each compound and was typical of contamination from petrogenic sources; pentacyclic < tri- and tetracyclic < tricyclic < dicyclic PAHs. The occurrence of PAH metabolites detected in liver samples also provided evidence of the presence and stereoselectivity of hepatic microsomal CYP1A1 in common guillemots.

Development of an immunoassay for the determination of polyaromatic hydrocarbons in plasma samples from oiled seabirds

External exposure assessment of oiled seabirds is undertaken by assessment of the percentage oil coverage of the plumage. Nondestructive monitoring of the toxic fraction of petroleum oils and diesels (polyaromatic hydrocarbons, PAHs) which enters the general circulation (internal exposure burden) of oiled seabirds is rarely undertaken. This is because the traditionally used chromatographic methods for plasma PAH analysis require larger sample volumes than those that can be safely collected from smaller species, such as guillemots (Uria aalge). Furthermore, these methods are not a cost-effective or practical approach for analysis of large numbers of birds in a short time period as part of an oil spill response in wildlife rehabilitation centers. This study describes the modification and validation of a commercially available PAH immunoassay (cRaPID PAH) to enable high-throughput, cost-effective, simple, and rapid determination of total PAH concentrations in 50 microL volumes of plasma. The limit of detection of the assay was 0.1 ng/mL as benzo-apyrene (BaP) equivalents with a working range of 0.120 ng/mL. As further validation of the immunoassay, PAHs were determined by GC-MS. GC-MS data were significantly positively correlated with corresponding immunoassay data for the same birds (r2 = 0.976, p < 0.001). The plasma PAH concentrations of 40 oiled guillemots stranded on U.K. shores were determined using the assay to demonstrate its usefulness for biomonitoring studies. The mean ,PAH concentration observed was 1.05 +/- 0.67 ppm (range 0.02-2.40 ppm as BaP equivalents). The modifications to the cRaPID PAH kit in this study enable nondestructive, high-throughput, semiquantitative determination of PAH concentrations in plasma samples suitable for exposure assessment of oiled seabirds during oil spill response and rehabilitation.

Ranking terrestrial vertebrate species for utility in biomonitoring and vulnerability to environmental contaminants

The measurement of contaminant tissue concentrations or exposure-related effects in biota has been used extensively to monitor pollution and environmental health. Terrestrial vertebrates have historically been an important group of species in such evaluations, not only because many are excellent sentinels of environmental contamination, but also because they are valued natural resources in their own right that may be adversely affected by toxicant exposure. Selection of appropriate vertebrates for biomonitoring studies frequently relies on expert opinion, although a few rigorous schemes are in use for predicting vulnerability of birds to the adverse effects of petroleum crude oil. A Utility Index that ranks terrestrial vertebrate species as potential sentinels of contaminants in a region, and a Vulnerability Index that assesses the threat of specific groups of contaminants to these species, have been developed to assist decision makers in risk assessments of persistent organic pollutants, cholinesterase-inhibiting pesticides, petroleum crude oil, mercury, and lead shot. Twenty-five terrestrial vertebrate species commonly found in Atlantic Coast estuarine habitat (Rattner et al. 2001a) were ranked for their utility as biomonitors of contamination and their vulnerability to pollutants in this region. No single species, taxa, or class of vertebrates was found to be an ideal sentinel for all groups of contaminants. Although birds have overwhelmingly been used to monitor contaminants compared to other terrestrial vertebrate classes, the nonmigratory nature and dietary habits of the snapping turtle and mink consistently resulted in ranking these species as excellent sentinels as well. Vulnerability of Atlantic Coast populations of these species varied considerably among groups of contaminants. Usually a particular species was found to be at high risk to only one or two groups of contaminants, although a noteworthy exception is the bald eagle, which is highly vulnerable to all five of the contaminant groups examined. This index could be further enhanced by generation of additional comparative toxicity data to facilitate interspecific extrapolations. The Utility and Vulnerability Indices have application to many types of habitats in addition to estuaries and are of value to natural resource and risk managers that routinely conduct local, regional, or national environmental quality assessments.

Crude oil exposure affects air-breathing frequency, blood phosphate levels and ion regulation in an air-breathing teleost fish, Hoplosternum littorale

Exposure of a facultative air breather, Hoplosternum littorale, to 12.5, 25, and 37.5% of the water soluble fraction (WSF) of Urucu crude oil, resulted in a rapid increase in air-breathing frequency (ABF) sustained over the 45 min period of exposure. Following 4 h exposure to a graded increase in WSF up to 50%, there was no significant affect on haematocrit, or plasma [Na+] and [K+]. Crude oil ingestion resulted in some degree of ion regulatory impairment, however results were variable. A single oral dose of 3.0 ml/kg of Urucu crude elevated net whole body Na+ efflux and resulted in a 7% reduction in plasma [Na+] 72 h following ingestion. A single oral dose of 3.0 ml/kg resulted in a significant net whole body K+ efflux and a reduction in plasma [K+] 24 h after ingestion. No mortalities were observed in any exposure regime in this study. An oral dose of Urucu crude oil at 3.0 ml/kg also resulted in a 24% reduction in ATP:Hb ratio (from 0.206 to 0.157) and a 31% reduction in GTP:Hb ratio (0.455 to 0.315) 24 h following ingestion indicating that these fish may be hypoxemic. Taken together, these results indicate that exposure of H. littorale to Urucu crude oil affects gas exchange and ion regulation.

Review article: effects of oil pollution, chemically treated oil, and cleaning on thermal balance of birds

The acute effect of oil pollution on birds is on their thermal balance. Oil adheres to the plumage and causes a reduction in water repellant properties of the plumage, causing water to penetrate into the plumage to displace the insulating layer of air. The effect of oil on the plumage insulation is dose-dependent. The effect of oiling is greatly enhanced when the oil is spread in the plumage due to preening. In water, plumage oiling may cause the heat loss to exceed the bird's heat production capacity, resulting in hypothermia. If the oiled bird is ashore, with a dry plumage, it may have a normal thermal insulation. Bird species dependent upon feeding in water (such as diving birds) are therefore much more susceptible to the harmful effects of oil pollution than are semi-aquatic species that can feed ashore. It is possible to restore the water-repelling and insulative properties of the plumage by the process of cleaning if all the oil and soap is removed, and if the plumage is completely dry. Chemical treatment of oil has been suggested as a way to reduce the impact of oil spills on avian life. However, very few reports seem to have addressed the effects of chemically treated oil on the thermal balance of birds, and the results from one study actually indicate that oil treated with dispersants may be more harmful to birds than oil. The urgent need for more information about the effects of chemically treated oil on aquatic birds is therefore stressed.

Effects of ingested crude oil on thyroid hormones and on the mixed function oxidase system in ducks

1. Ingestion of Statfjord A crude oil from the North Sea has no apparent effect on the metabolic rate of ducks (Jenssen, 1989). This may be because this particular oil does not affect plasma concentrations of thyroid hormones and enzyme activities in the mixed function oxidase (MFO) system of ducks. 2. To test this hypothesis, plasma concentrations of thyroid hormones (thyroxine and triiodothyronine), and levels of hepatic cytochrome P-450 and enzyme activities (NADPH cytochrome C reductase and GSH-S-transferase) in the MFO system were measured in domestic ducks (Anas platyrhynchos) which had ingested this crude oil. 3. Daily oral of 5 ml crude oil per kg body weight for 6 consecutive days resulted in a 53% increase in plasma triiodothyronine concentration and a 56% increase in the hepatic cytochrome P-450 level. The changes in these parameters were apparently not sufficient to cause any rise in metabolic heat production. 4. This apparent contradiction is probably because activation of the MFO-system is energetically inexpensive. Also, possible metabolic effects caused by increased plasma-triiodothyronine concentration and activation of the MFO-system may have been masked by an inhibitory effect of the crude oil on mitochondrial electrontransport and coupled phosphorylation.

Review and perspective on the use of mixed-function oxygenase enzymes in biological monitoring

It is often suggested that changes in simple biochemical/physiological responses may be useful for predicting the impacts of pollutants at population and community levels of biological organization. There are serious conceptual constraints to such a thesis and its seems likely that such simple responses can go no further than serving as early warning systems for delineating potential areas of pollutant impact--areas which (if shown to be significant in size) can then be subjected to more detailed population and community type studies. Environmental testing is a prerequisite for any response suggested to have value as a biological monitoring index and the induction of mixed-function oxygenase (MFO) enzymes has now been validated in a large number of field studies worldwide. Investigations have progressed from documenting induction near localized sources of hydrocarbon contamination to more diffuse sources of mixed organic pollution originating from industrial and domestic sources. Studies in the Great Lakes and Europe have demonstrated that the induction of MFO enzymes is a biological response of sufficient sensitivity to discriminate water quality differences over broad geographical areas. We suggest that as an early warning system, the induction of these enzymes can fulfill the requirement of "most sensitive biological response" for assessing a variety of organic pollution conditions. Given the high level of sensitivity of the MFO enzyme response, negative as well as positive field trials can be of value in addressing concerns about the toxicological significance of "high-profile" chemicals (and potent inducers) such as polycyclic aromatic hydrocarbons and organochlorines. MFO enzyme induction can also be an economical tool for environmental managers for reacting to real or perceived concerns about pollution such as effects on commercial fish stocks at sites of petroleum hydrocarbon development in the oceans.

Clinical, gross, and histological findings in herring gulls and Atlantic puffins that ingested Prudhoe Bay crude oil

Oral doses of 0, 1, 4, 5, 10, or 20 ml of Prudhoe Bay crude oil/kg body weight/day were given to herring gull and Atlantic puffin nestlings for 5 to 7 consecutive days. Gulls defecated substantial amounts of oil within 10 to 15 minutes after receiving a dose. Clinical signs and lesions occurred only in birds given greater than or equal to 10 ml oil/kg body weight/day. Gulls consumed less food and lost weight. Two categories of lesions were observed: those considered secondary to a primary toxic hemolytic disease, and those considered nonspecific reactions to stress. The former included phagocytosis of degenerate erythrocytes in the liver and spleen, hemoglobin resorption droplets in renal proximal tubule cells, and erythroid hyperplasia in the bone marrow; the latter included lymphocyte depletion in primary lymphoid tissues, an increase in heterophil: lymphocyte ratio in peripheral blood, lipid depletion and necrosis in adrenal steroidogenic cells, and an increased prevalence and severity of lesions in the bursa of Fabricius. These findings indicated that the primary target of oil toxicity was the peripheral red blood cell, but that significant stress-related lesions were also associated with ingestion of oil.

Differential viability of phosphoglucose isomerase allozyme genotypes of marine snails in nonionic detergent and crude oil-surfactant mixtures

The effects of a nonionic detergent and of crude oil-detergent mixtures in aqueous solutions on the allozyme frequencies of phosphoglucose isomerase (Pgi) genotypes were tested in the Mediterranean marine gastropods Monodonta turbinata and M. turbiformis. Our results indicate differential survivorship of electrophoretical Pgi allozyme genotypes for both detergent alone and for crude oil-detergent mixtures. These results reflect the adaptive nature of some Pgi genotypes in these marine gastropods and seem inconsistent with the neutral theory of allozyme polymorphisms. Furthermore, these findings suggest that allozyme variants demonstrate a differential tolerance to these organic pollutants and can, therefore, be used as detectors of organic pollutants in the sea.

Heinz-body hemolytic anemia from the ingestion of crude oil: a primary toxic effect in marine birds

Hemolytic anemia developed in young herring gulls and Atlantic puffins given daily oral doses of a Prudhoe Bay crude oil. Anemia developed 4 to 5 days after the initiation of oil ingestion and was accompanied by Heinz-body formation and a strong regenerative response. The data evince a toxic effect on circulating red blood cells involving an oxidative biochemical mechanism and the first clear evidence of a primary mechanism of toxicity from the ingestion of crude oil by birds.

Liver hypertrophy in winter flounder following exposure to experimentally oiled sediments

1. Male winter flounder were exposed to sediments contaminated with Venezuelan crude oil in 3 laboratory experiments of 4-5 months duration. 2. Oil exposure resulted in significant increases in liver weight. This was particularly evident in fish weighing less than 400 g. 3. The enlarged livers of the oil-exposed flounder had reduced concentrations of DNA, protein, Na+ and Zn2+, and increased concentrations of lipid and phospholipid. 4. The reduced DNA and Na+ concentrations suggested liver hypertrophy rather than hyperplasia. 5. The increased phospholipid concentrations suggested growth of membrane structures such as endoplasmic reticulum.

Influence of ingested petroleum on the reproductive performance and pituitary-gonadal axis of domestic ducks (Anas platyrhynchols)

1. The chronic ingestion of a sublethal dose (5%) of dietary North Sea crude oil delayed the onset of lay in adult Khaki Campbell ducks transferred from a short (8L:16D) to long day (16L:8D) photoperiod and greatly reduced the rate of oviposition and quality (weight and shell thickness) of the eggs subsequently laid. 2. Refeeding the oil-fed birds with the uncontaminated control diet stimulated the rate of egg production and improved egg quality, but in both cases not to the level in the controls. 3. Food intake and the plasma calcium level in the petroleum-fed birds were reduced, but these effects are unlikely to be causally responsible for the adverse effects of petroleum on avian reproduction. 4. Gonadotrophic (luteinizing hormone, LH) hormone secretion in the oil fed birds was not suppressed and the impairment of reproductive performance was not due to low plasma LH levels. 5. The reduced rate of lay in the oil-fed birds was accompanied by low gonadal steroid (progesterone) levels. The detrimental effects of oil and reproduction may be due to direct or indirect effects on the ovary or shell gland.

Accumulation of 14C-Naphthalene in the tissues of redhead ducks fed oil-contaminated crayfish

Crayfish, artificially contaminated with 14C-naphthalene-5% water-soluble fraction of No. 2 fuel oil, were force-fed to one-year-old redhead ducks to determine the accumulation of petroleum hydrocarbons. The relative distribution of carbon-14 activity in the gall bladder containing bile, and fat were similar, and significantly greater (P less than 0.05) than the activity in the blood, brain, liver, and kidney. There was a significant increase (P less than 0.05) in the disintegrations per minute per gram (dpm/g) in the blood, brain, kidney, and liver between days 1 and 3 of feeding, indicating a progressive accumulation of carbon-14 activity (naphthalene and presumably its metabolites). There was no significant effect of sex or the interaction of the duration of feeding and sex on carbon-14 activity in any of the tissues. The low daily dose of petroleum hydrocarbons (a total of approximately 1.25 mg/day) received by the ducks from the crayfish and the relatively short feeding regimen did not cause any overt signs of toxicity in the ducks.

Effects of petroleum on adrenocortical activity and on hepatic naphthalene-metabolizing activity in mallard ducks

Unstressed mallard ducks (anas platyrhychos), given uncontaminated food and maintained on a short photoperiod, show two daily maxima in plasma corticosterone concentration ([B]) on occurring early in the light phase and a second just before the onset of darkness. After one week of exposure to food containing 3% (v/w) South Louisiana crude oil, plasma [B] were significantly lowered throughout the day. Similar abrupt declines in plasma [B] also occurred during the first 10 days of exposure to food containing 1% and 0.5% crude oil. Although the plasma [B] in birds consuming food contaminated with 0.5% crude oil increased between 10 and 50 days of exposure, the concentration after 50 days was still lower than normal. During the same interval, normal plasma [B] were restored in birds consuming food containing 1% and 3% crude oil. Significant increases occurred in the naphthalene-metabolizing properties of hepatic microsomes prepared from birds acutely exposed to all levels of petroleum-contaminated food and elevated levels were sustained throughout the first 50 days of exposure. Birds given food containing 3% crude oil for more than 50 days, however, showed steady declines in hepatic naphthalene-metabolizing activity. After 500 days, the activity was similar to that found in contemporaneous controls. During the same interval the plasma [B] increased until the levels were higher than normal after 500 days of exposure; at this time, an inverse relationship, similar to that seen during the first week of exposure to contaminated food, was once more established between plasma [B] and the concomitant hepatic naphthalene-metabolizing activity.

Effects of chronic ingestion of No. 2 fuel oil on mallard ducklings

No. 2 fuel oil was fed to mallard (Anas platyrhynchos) ducklings in concentrations of 0.5 and 5.0% of the diet from hatching to 18 wk of age to assess the effects of chronic oil ingestion during early development. Five growth parameters (body weight, wing length, ninth primary length, tarsal length, and bill length) were depressed in birds receiving a diet containing 5% fuel oil. There was no oil-related mortality. The 5% fuel oil diet impaired avoidance behavior of 9-d-old mallard ducklings compared with controls or ducklings fed 0.5% oil. Open-field activity was greatly increased in 16-wk-old ducklings fed 5.0% oil. Liver hypertrophy and splenic atrophy were gross evidences of pathological effects in birds on the 5.0% oil diet. More subtle effects included biochemical lesions that resulted in the elevation of plasma alanine aminotransferase and ornithine carbamoyltransferase activity.