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USGS2001

Mortality and kidney histopathology of Chinook salmon Oncorhynchus tshawytscha exposed to virulent and attenuated Renibacterium salmoninarum strains

An isolate of Renibacterium salmoninarum (strain MT 239) exhibiting reduced virulence in rainbow trout Oncorhynchus mykiss was tested for its ability to cause bacterial kidney disease (BKD) in chinook salmon Oncorhynchus tshawytscha, a salmonid species more susceptible to BKD. Juvenile chinook salmon were exposed to either 33209, the American Type Culture Collection type strain of R. salmoninarum, or to MT 239, by an intraperitoneal injection of 1 x 10(3) or 1 x 10(6) bacteria fish(-1), or by a 24 h immersion in 1 x 10(5) or 1 x 10(7) bacteria ml(-1). For 22 wk fish were held in 12 degrees C water and monitored for mortality. Fish were sampled periodically for histological examination of kidney tissues. In contrast to fish exposed to the high dose of strain 33209 by either injection or immersion, none of the fish exposed to strain MT 239 by either route exhibited gross clinical signs or histopathological changes indicative of BKD. However, the MT 239 strain was detected by the direct fluorescent antibody technique in 4 fish that died up to 11 wk after the injection challenge and in 5 fish that died up to 20 wk after the immersion challenge. Viable MT 239 was isolated in culture from 3 fish that died up to 13 wk after the immersion challenge. Total mortality in groups injected with the high dose of strain MT 239 (12%) was also significantly lower (p < 0.05) than mortality in groups injected with strain 33209 (73 %). These data indicate that the attenuated virulence observed with MT 239 in rainbow trout also occurs in a salmonid species highly susceptible to BKD. The reasons for the attenuated virulence of MT 239 were not determined but may be related to the reduced levels of the putative virulence protein p57 associated with this strain.

Diseases of Aquatic Organisms↗

USGS2015

Gross and microscopic lesions in corals from Micronesia

The authors documented gross and microscopic morphology of lesions in corals on 7 islands spanning western, southern, and eastern Micronesia, sampling 76 colonies comprising 30 species of corals among 18 genera, with Acropora , Porites , and Montipora dominating. Tissue loss comprised the majority of gross lesions sampled (41%), followed by discoloration (30%) and growth anomaly (29%). Of 31 cases of tissue loss, most lesions were subacute (48%), followed by acute and chronic (26% each). Of 23 samples with discoloration, most were dark discoloration (40%), with bleaching and other discoloration each constituting 30%. Of 22 growth anomalies, umbonate growth anomalies composed half, with exophytic, nodular, and rugose growth anomalies composing the remainder. On histopathology, for 9 cases of dark discoloration, fungal infections predominated (77%); for 7 bleached corals, depletion of zooxanthellae from the gastrodermis made up a majority of microscopic diagnoses (57%); and for growth anomalies other than umbonate, hyperplasia of the basal body wall was the most common microscopic finding (63%). For the remainder of the gross lesions, no single microscopic finding constituted >50% of the total. Host response varied with the agent present on histology. Fragmentation of tissues was most often associated with algae (60%), whereas necrosis dominated (53%) for fungi. Two newly documented potentially symbiotic tissue-associated metazoans were seen in Porites and Montipora . Findings of multiple potential etiologies for a given gross lesion highlight the importance of incorporating histopathology in coral disease surveys. This study also expands the range of corals infected with cell-associated microbial aggregates.

Veterinary Pathology↗

USGS1985

Survival, growth, and histopathological effects of paraquat ingestion in nestling American kestrels (Falco sparverius)

The use of paraquat as a herbicide is becoming more extensive with the increasing popularity of no tillage agriculture, increasing the possibility of exposure for wildlife species. American kestrel (Falco sparverius) nestlings were orally dosed daily with 5 ?l/g of distilled water (controls), 10 mg/kg, 25 mg/kg, or 60 mg/kg of paraquat dichloride (1, 1'-dimethyl-4,4'-bipyridinium) in distilled water from day 1 through day 10. Forty-four percent of the nestlings given 60 mg/kg died after 4 days. Significant differences in growth rates occurred between controls and all paraquat-dosed groups. Reduced skeletal growth occurred in the humerus and femur in the 25 mg/kg and 60 mg/kg groups, and in the radius-ulna and tibiotarsus in the 60 mg/kg group. Skeletons were otherwise normal in appearance. Histopathological examination revealed localized focal necrosis in the liver of one nestling in the 60 mg/kg group and tubular cell degeneration and focal tubular dilation in the kidneys of another. The brain and lungs were unremarkable histologically. These findings suggest that altricial nestling kestrels are more sensitive to paraquat exposure than young or adult birds of precocial species.

Archives of Environmental Contamination and Toxico↗

USGS1956

Histopathology of fish. II. The salmon-poisoning fluk

THE SALMON-POISONING FLUKE is misnamed as far as the fish culturist is concerned, for the disease affects dogs, not fish. There is considerable evidence, however, that fish may also suffer from the complex chain of events leading from snail to dying dog. Histological studies indicate that young salmon and trout may be severely damaged by the encysted stage of the fluke.

Progressive Fish-Culturist↗

USGS2003

Epizootiology and histopathology of Parvicapsula sp. in coho salmon Oncorhynchus kisutch

The epizootiology and histopathology of the myxosporean Parvicapsula sp. was studied during monthly health surveys of 4 groups of coho salmon Oncorhynchus kisutch at a commercial farm in Puget Sound, Washington, USA, from 1984 to 1986. No Parvicapsula sp. was detected in histological samples taken from juvenile fish in fresh water, but the parasite was detected in fish from all groups 2 to 8 mo after transfer to seawater net pens. Groups placed in seawater net pens in November and December had a higher prevalence of infection, and a longer period of continuous detected infection, than those introduced into net pens in May. For the groups transferred to seawater in November and December, the highest infection prevalence (45 to 90%) was detected during the following March and April. Among 13 tissues examined histologically, only the pseudobranch and kidney were positive for Parvicapsula sp., with 26 (62%) of 42 positive fish showing infections only in the pseudobranch, 5 (12%) showing infections only in the kidney, and 11 (26%) showing infections in both organs. Both the pseudobranch and kidney were apparent primary infection sites, but pseudobranch infections appeared to persist longer in a population. Pseudobranch infections were frequently heavy and associated with extensive inflammation and necrosis of filament and lamellar tissues. The kidney had been the only infection site reported for Parvicapsula sp. in previous studies of coho salmon.

Diseases of Aquatic Organisms↗

USGS2003

Effects of ammonium perchlorate on the reproductive performance and thyroid follicle histology of zebrafish

Adult zebrafish were reared up to eight weeks in control water or in water containing ammonium perchlorate (AP) at measured perchlorate concentrations of 18 (environmentally relevant, high) and 677 ppm. Groups of eight females were paired with four males on a weekly basis to assess AP effects on spawned egg volume, an index of reproductive performance. All treatments were applied to four to five spawning replicates. At 677 ppm, spawn volume was reduced within one week and became negligible after four weeks. At 18 ppm, spawn volume was unaffected even after eight weeks. Also, perchlorate at 18 ppm did not affect percentage egg fertilization. Fish were collected at the end of the exposures (677 ppm, four weeks; control and 18 ppm, eight weeks) for whole-body perchlorate content and thyroid histopathological analysis. Fish perchlorate levels were about one-hundredth of those of treatment water levels, indicating that waterborne perchlorate does not accumulate in whole fish. At 677 ppm for four weeks, perchlorate caused thyroid follicle cell (nuclear) hypertrophy and angiogenesis, whereas at 18 ppm for eight weeks, its effects were more pronounced and included hypertrophy, angiogenesis, hyperplasia, and colloid depletion. In conclusion, an eight-week exposure of adult zebrafish to 18 ppm perchlorate (high environmentally relevant concentrations) affected the histological condition of their thyroid follicles but not their reproductive performance. The effect of 677 ppm perchlorate on reproduction may be due to extrathyroidal toxicity. Further research is needed to determine if AP at lower environmentally relevant concentrations also affects the thyroid follicles of zebrafish.

Conference Paper↗

USGS2011

Acute toxicity, histopathology, and coagulopathy in American kestrels (Falco sparverius) following administration of the rodenticie diphacinone

The acute oral toxicity of the anticoagulant rodenticide diphacinone was found to be over 20 times greater in American kestrels (Falco sparverius; median lethal dose 96.8 mg/kg body weight) compared with Northern bobwhite (Colinus virginianus) and mallards (Anas platyrhynchos). Modest evidence of internal bleeding was observed at necropsy, although histological examination of heart, liver, kidney, lung, intestine, and skeletal muscle revealed hemorrhage over a wide range of doses (35.1-675 mg/kg). Residue analysis suggests that the half-life of diphacinone in the liver of kestrels that survived was relatively short, with the majority of the dose cleared within 7 d of exposure. Several precise and sensitive clotting assays (prothrombin time, Russell's viper venom time, thrombin clotting time) were adapted for use in this species, and oral administration of diphacinone at 50 mg/kg increased prothrombin time and Russell?s viper venom time at 48 and 96 h postdose compared with controls. Prolongation of in vitro clotting time reflects impaired coagulation complex activity, and generally corresponded with the onset of overt signs of toxicity and lethality. In view of the toxicity and risk evaluation data derived from American kestrels, the involvement of diphacinone in some raptor mortality events, and the paucity of threshold effects data following short-term dietary exposure for birds of prey, additional feeding trials with captive raptors are warranted to characterize more fully the risk of secondary poisoning.

Environmental Toxicology and Chemistry↗

USGS2012

Histological observations in the Hawaiian reef coral, Porites compressa, affected by Porites bleaching with tissue loss

The scleractinian finger coral Porites compressa is affected by the coral disease Porites bleaching with tissue loss (PBTL). This disease initially manifests as bleaching of the coenenchyme (tissue between polyps) while the polyps remain brown with eventual tissue loss and subsequent algal overgrowth of the bare skeleton. Histopathological investigation showed a loss of symbiont and melanin-containing granular cells which was more pronounced in the coenenchyme than the polyps. Cell counts confirmed a 65% reduction in symbiont density. Tissue loss was due to tissue fragmentation and necrosis in affected areas. In addition, a reduction in putative bacterial aggregate densities was found in diseased samples but no potential pathogens were observed.

Journal of Invertebrate Pathology↗

USGS1979

Histopathology of yearling sockeye salmon (Oncorhynchus nerka) infected with infectious hematopoietic necrosis (IHN)

Infectious hematopoietic necrosis (IHN) is generally believed to be a virus disease of very young salmonids. In recent years there have been increasing numbers of unpublished reports that this disease has been occurring uncharacteristically in fish as old as 7-14 months. Sockeye salmon (Oncorhynchus nerka) of this age the histological changes were not severe. Intestinal tract granular cells thought to be pathognomic in young fish were conspicuously absent. Kidney imprints showed necrobiotic bodies however, and subtle changes were observed in the spleen and kidney hematopoietic tissue.

Fish Pathology↗

USGS1997

Contaminant exposure, biochemical, and histopathological biomarkers in white suckers from contaminated and reference sites in the Sheboygan River, Wisconsin

Fish populations of the lower Sheboygan River, located in east-central Wisconsin, are considered impaired under the Great Lakes Water Quality Agreement between the United States and Canada. Pollutants in the Sheboygan River system include: polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and heavy metals. This study compared general health and biochemical parameters, histology of selected organs, and contaminant residues and metabolites in a population of white suckers ( Catostomus commersoni ) from a contaminated reach of the Sheboygan River and an upstream reference site. Fish from the contaminated site had significantly lower hematocrits, significantly induced ethoxyresorufin-O-deethylase (EROD) activity as a measurement of hepatic mixed-function oxygenase activity, higher biliary metabolites of PAHs, and higher tissue concentrations of PCBs and p,p’-DDE relative to an upstream reference population. Analysis of covariance suggests that both PCB and PAH exposure may be influencing EROD activities. Fish from the contaminated site featured more basophilic clusters and developing nephrons in kidney tissue suggesting the presence of a nephro-toxicant. Also, more fish exhibited hepatic lesions including diffuse cellular vacuolation, multifocal coagulative necrosis, bile ductal hyperplasia, and foci of cellular alteration which may be biomarkers for contaminant impacts. This study demonstrates that white suckers residing in the lower reaches of the Sheboygan River absorbed significant amounts of PAHs and PCBs and also exhibited hematological, biochemical and histological alterations some of which suggest impaired fish condition.

Journal of Great Lakes Research↗

USGS2013

Macroscopic, histologic, and ultrastructural lesions associated with avian keratin disorder in Black-capped Chickadees (Poecile atricapillus)

An epizootic of beak abnormalities (avian keratin disorder) was recently detected among wild birds in Alaska. Here we describe the gross, histologic, and ultrastructural features of the disease in 30 affected adult black-capped chickadees (Poecile atricapillus). Grossly, there was elongation of the rhamphotheca, with varying degrees of lateral deviation, crossing, and gapping between the upper and lower beak. Not uncommonly, the claws were overgrown, and there was alopecia, scaling, and crusting of the skin. The most prominent histopathologic features in the beak included epidermal hyperplasia, hyperkeratosis, and core-like intrusions of necrotic debris. In affected birds, particularly those with moderate to severe beak overgrowth, there was remodeling of premaxillary and mandibular bones and various dermal lesions. Lesions analogous to those found in beaks were present in affected claws, indicating that this disorder may target both of these similar tissues. Mild to moderate hyperkeratosis occurred in other keratinized tissues, including skin, feather follicles, and, occasionally, sinus epithelium, but typically only in the presence of microbes. We did not find consistent evidence of a bacterial, fungal, or viral etiology for the beak lesions. The changes observed in affected birds did not correspond with any known avian diseases, suggesting a potentially novel hyperkeratotic disorder in wild birds.

Alaska↗

USGS2010

Pathology and virus detection in tissues of nestling house sparrows naturally infected with Buggy Creek virus (Togaviridae).

Alphaviruses ( Togaviridae ) infect wild birds, but clinical illness and death attributable to virus in naturally infected birds is rarely reported, particularly for small passerine species or nestlings. Buggy Creek virus is a unique alphavirus in the Western equine encephalomyelitis virus (WEEV) complex that is vectored by the cimicid swallow bug ( Oeciacus vicarius ), an ectoparasite of the colonially nesting Cliff Swallow ( Petrochelidon pyrrhonota ) and the introduced House Sparrow ( Passer domesticus ). While sampling birds for Buggy Creek virus (BCRV) during the summers of 2007 and 2008, we discovered large numbers of clinically ill or dead House Sparrow nestlings. Ill nestlings exhibited ataxia, torticollis, paresis, and lethargy. Histologic examination revealed that encephalitis was the most common finding, followed by myositis, myocarditis, and hepatic changes, but pathology was highly variable. We isolated BCRV from brain tissue in most of the ill or dead nestlings, and from blood, liver, kidney, spleen, lung, feather pulp, and skin in some birds. To our knowledge, this is the first report of clinical illness, gross pathology, and histopathology for a WEEV-complex alphavirus in a field-collected passerine species.

Journal of Wildlife Diseases↗

USGS2003

Morphometric and histopathological parameters of gonadal development in adult common carp from contaminated and reference sites in Lake Mead, Nevada

This study examined the hypothesis that exposure to sublethal concentrations of contaminants alters the gonadal condition of feral common carp Cyprinus carpio . Adult common carp in Lake Mead, Nevada, were collected from a contaminated site (Las Vegas Bay) that receives municipal and industrial effluent and from a reference site (Overton Arm) with a relatively low level of contamination. Fish were sampled seven times over a 1-year period extending over two separate spawning seasons. Morphometric and histopathological parameters of gonadal and germ cell development were determined. In males, the pattern of seasonal changes in the gonadosomatic index (GSI) was similar between the sites and showed no clear association with site-specific seasonal temperature profiles. However, Las Vegas Bay males had consistently lower GSI values and, on one of the sampling dates, a lower proportion of sperm relative to other germ cell stages (determined histologically). Further, Las Vegas Bay males had a higher incidence of gonadal macrophage aggregates, which are putative tissue biomarkers of contaminant exposure in fishes. In females, seasonal GSI profiles, the frequency of fish with postovulatory follicles (an index of spawning activity), and the timing of new follicle recruitment all showed differences between sites, but these differences generally matched differences in water temperature profile. Also, the peak size-frequency of full-grown follicles did not differ between sites, and estimates of fecundity for the second spawning season indicated that females from the reference site unexpectedly produced a lower number of gametes. Overall, site differences in gonadal condition were observed in carp of both sexes but they seemed to be associated with site differences in contaminant levels only in males. The apparent lack of association between contaminant level and gonadal condition in female carp from mildly mesotrophic Lake Mead may indicate a lack of contaminant effects in females or a confounding effect of the higher nutrient loads in the Las Vegas Bay environment.

Nevada↗

USGS2018

Biomarker responses of Peromyscus leucopus exposed to lead and cadmium in the Southeast Missouri Lead Mining District

Biomarker responses and histopathological lesions have been documented in laboratory mammals exposed to elevated concentrations of lead and cadmium. The exposure of white-footed mice ( Peromyscus leucopus ) to these metals and the potential associated toxic effects were examined at three contaminated sites in the Southeast Missouri Lead Mining District and at a reference site in MO, USA. Mice from the contaminated sites showed evidence of oxidative stress and reduced activity of red blood cell δ-aminolevulinic acid dehydratase (ALAD). Histological examinations of the liver and kidney, cytologic examination of blood smears, and biomarkers of lipid peroxidation and DNA damage failed to show indications of toxic effects from lead. The biomagnification factor of cadmium (hepatic concentration/soil concentration) at a site with a strongly acid soil was 44 times the average of the biomagnification factors at two sites with slightly alkaline soils. The elevated concentrations of cadmium in the mice did not cause observable toxicity, but were associated with about a 50% decrease in expected tissue lead concentrations and greater ALAD activity compared to the activity at the reference site. Lead was associated with a decrease in concentrations of hepatic glutathione and thiols, whereas cadmium was associated with an increase. In addition, to support risk assessment efforts, we developed linear regression models relating both tissue lead dosages (based on a previously published a laboratory study) and tissue lead concentrations in Peromyscus to soil lead concentrations.

Missouri↗

USGS2013

Histopathological analysis of fish from Acorn Fork Creek, Kentucky exposed to hydraulic fracturing fluid releases

Fracking fluids were released into Acorn Fork, KY, a designated Outstanding State Resource Water, and habitat for the threatened Chrosomus cumberlandensis (Blackside Dace). As a result, stream pH dropped to 5.6 and stream conductivity increased to 35,000 μS/cm, and aquatic invertebrates and fish were killed or distressed. The objective of this study was to describe post-fracking water quality in Acorn Fork and evaluate if the changes in water quality could have extirpated Blackside Dace populations. Semotilus atromaculatus (Creek Chub) and Lepomis cyanellus (Green Sunfish) were collected from Acorn Fork a month after fracking in lieu of unavailable Blackside Dace. Tissues were histologically analyzed for indicators of stress and percent of fish with lesions. Fish exposed to affected Acorn Fork waters showed general signs of stress and had a higher incidence of gill lesions than unexposed reference fish. Gill lesions observed were consistent with exposure to low pH and toxic concentrations of heavy metals. Gill uptake of aluminum and iron was demonstrated at sites with correspondingly high concentrations of these metals. The abrupt and persistent changes in post-fracking water quality resulted in toxic conditions that could have been deleterious to Blackside Dace health and survival.

Southeastern Naturalist↗

USGS1999

Biosafety of parenteral Brucella abortus RB51 vaccine in bison calves

Vaccination is considered among the primary management tools for reducing brucellosis prevalence in Greater Yellowstone Area (GYA) ungulates. Before their use, however, vaccine safety and efficacy must be demonstrated. Twenty-seven female bison (Bison bison) calves (approx 5 months old) were vaccinated with Brucella abortus Strain RB51 (1.5 × 1010 colony forming units [CFU], subcutaneously) as part of routine management. We assessed the persistence, pathology, shedding, and transmission associated with RB51 by serial necropsy, bacteriology, histopathology, and serology of 20 of these 27 vaccinated calves, and RB51 serology of 10 nonvaccinated, commingling adult females. With the exception of 1 calf, RB51 dot-blot titers at necropsy were <1:80. Strain RB51 was cultured from lymph nodes in 4 of 4 calves at 14 weeks postvaccination (PV), 4 of 4 calves at 18 weeks PV, 1 of 4 calves at 22 weeks PV, 3 of 4 at 26 weeks PV, and 0 of 4 calves at 30 weeks PV. No gross lesions were observed. Mild histologic changes occurred only in a few draining lymph nodes early in sampling. Adverse clinical effects were not observed in vaccinates. Swabs from nasopharynx, conjunctiva, rectum, and vagina were uniformly culture negative for RB51. Strain RB51 dot-blot assays of bison cows were negative at a 1:20 dilution at 26 weeks PV. Our results suggest that RB51 persists longer in bison calves than in domestic cattle and is systemically distributed within lymphatic tissues. However, bison apparently clear the RB51 vaccine strain without shedding, transmission, or significant adverse reactions.

Journal of Wildlife Management↗

USGS2014

Gross and microscopic pathology of lesions in Pocillopora spp. from the subtropical eastern Pacific

Coral reefs are threatened by a variety of factors including diseases that have caused significant damage in some regions such as in the Caribbean. At present, no data are available on coral diseases in the Mexican Pacific where Pocillopora spp. is a dominant component of coral communities. Here, we describe gross and microscopic morphology of lesions found in pocilloporids at four sites in the Mexican Pacific. Corals were identified and their lesions photographed and quantified in the field. Tissue samples were collected from healthy and affected colonies for histopathology. We recorded seven species of pocilloporids at the study sites with Isla Isabel being the location with the highest coral diversity ( H ′ = 1.27). Lesions were present in 42% of the colonies and included discoloration (32%), predation-induced tissue loss (30%), unexplained tissue loss (3%) and overgrowth by sponges or algae (35%). The most affected species, P . damicornis (50%), was also one of the most common in the region. No species was more prone to a particular lesion, but there was a significant association between location and the presence of lesions. Northern Islas Marietas (61%) and Isla Isabel (41%) had the highest prevalence of lesions, followed by Manzanillo (37%) and Bahías de Huatulco (23%). Histological changes included atrophy of the surface body wall with depletion of zooxanthellae (91%) in corals with discoloration (bleaching). Ablation of tissue from mesoglea (18%) was also observed. Colonies with unexplained tissue loss showed atrophy and thinning of the epidermis (89%), characterized by cuboidal instead of pseudocolumnar cells normally found in healthy pseudocolumnar ciliated epithelium. Bacterial aggregates between the mesoglea and gastrodermis (11%) were very conspicuous in healthy and diseased corals. Lesions produced by fish bites and gastropods were associated with tissue atrophy (40%) and, in some cases, algal overgrowth near the lesion (20%). No infectious agents associated with cell pathology were detected microscopically. Bleaching and overgrowth by algae and sponges, as well as unexplained tissue loss, are common in Pocillopora . These lesions and anatomical changes warrant further study since their incidence is potentially indicative of reef degradation.

Mexican Pacific↗

USGS2014

Synthesis of nearshore recovery following the 1989 Exxon Valdez oil spill: sea otter liver pathology and survival in Western Prince William Sound, 2001 – 2008

We examined livers and liver biopsies collected from captured sea otters in WPWS, 2001–2008, to determine whether indicators of liver health correlated with history of oil contamination from the 1989 Exxon Valdez oil spill. Sea otters captured in oiled areas had a significantly higher proportion of livers with gross pathological change, based on visual inspection at the time of capture, than those from unoiled areas. Of the 10 histopathology variables scored on liver biopsies, only two (vacuolar change and pigment) differed between animals from oiled and unoiled areas, and neither correlated with gross pathology scores. Vacuolar change indicates physiological disturbance, which is consistent with potential effects from oil exposure but also could be influenced by a number of other factors. We concluded that, as of 2008, some differences in liver health were evident between sea otters from oiled and unoiled areas; these differences were consistent with, but not specific to, effects that might be expected with sublethal exposure to lingering Exxon Valdez oil. We also quantified variation in survival of radiomarked sea otters within oiled areas of WPWS in relation to age, sex, body condition, selected blood serum chemistry variables, and histological scores indicative of liver health. Of the variables considered, only the serum enzyme aspartate aminotransferase (AST) and the ratio of serum proteins albumin and globulin (A/G) were correlated with survival, with higher levels of AST and lower levels of A/G associated with increased likelihood of mortality. High AST and low A/G both may be indicative of liver disease. Taken together, results reported here suggest that liver health of sea otters in oiled areas was slightly poorer than those from unoiled areas and, ifurther, that this may have translated to poorer survival through 2008, nearly 2 decades after the spill. More recently collected information indicated that mortality patterns and abundance had returned to pre-spill conditions between 2010 and 2013, suggesting that the effects that we detected through 2008 may have represented the end of effects related to exposure to lingering oil.

Alaska↗