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At least 1,567 records · Page 87Linked to original sources
USGS2018

Paleolimnological records of nitrogen deposition in shallow, high-elevation lakes of Grand Teton National Park, Wyoming, USA

Reactive nitrogen (Nr) from anthropogenic sources has been altering ecosystem function in lakes of the Rocky Mountains, other regions of western North America, and the Arctic over recent decades. The response of biota in shallow lakes to atmospheric deposition of Nr, however, has not been considered. Benthic algae are dominant in shallow, high-elevation lakes and are less sensitive to nutrient inputs than planktonic algae. Because the benthos is typically more nutrient rich than the water column, shallow lakes are not expected to show evidence of anthropogenic Nr. In this study, we assessed sedimentary evidence for regional Nr deposition, sediment chronology, and the nature of algal community response in five shallow, high-elevation lakes in Grand Teton National Park (GRTE). Over 140 diatom taxa were identified from the sediments, with a relatively high species richness of taxa characteristic of oligotrophic conditions. The diatom assemblages were dominated by benthic taxa, especially motile taxa. The GRTE lakes demonstrate assemblage-wide shifts in diatoms, including 1) synchronous and significant assemblage changes centered on ~1960 AD; 2) pre-1960 assemblages differed significantly from post-1960 assemblages; 3) pre-1960 diatom assemblages fluctuated randomly, whereas post- 1960 assemblages showed directional change; 4) changes in δ15N signatures were correlated with diatom community composition. These results demonstrate recent changes in shallow high18 elevation lakes that are most correlated with anthropogenic Nr. It is also possible, however, that the combined effect of Nr deposition and warming is accelerating species shifts in benthic diatoms. While uncertainties remain about the potential synergy of Nr deposition and warming, this study adds shallow lakes to the growing list of impacted high-elevation localities in western North America.

Wyoming↗
USGS2010

Low prevalence of chytrid fungus ( Batrachochytrium dendrobatidis ) in amphibians of U.S. headwater streams

Many declines of amphibian populations have been associated with chytridiomycosis, a disease caused by the aquatic fungus Batrachochytrium dendrobatidis (Bd). Despite the relatively high prevalence of chytridiomycosis in stream amphibians globally, most surveys in North America have focused primarily on wetland-associated species, which are frequently infected. To better understand the distribution and prevalence of Bd in headwater amphibian communities, we sampled 452 tailed frogs ( Ascaphus truei and Ascaphus montanus ) and 304 stream salamanders (seven species in the Dicamptodontidae and Plethodontidae) for Bd in 38, first- to third-order streams in five montane areas across the United States. We tested for presence of Bd by using PCR on skin swabs from salamanders and metamorphosed tailed frogs or the oral disc of frog larvae. We detected Bd on only seven individuals (0.93%) in four streams. Based on our study and results from five other studies that have sampled headwater- or seep-associated amphibians in the United States, Bd has been detected on only 3% of 1,322 individuals from 21 species. These results differ strongly from surveys in Central America and Australia, where Bd is more prevalent on stream-breeding species, as well as results from wetland-associated anurans in the same regions of the United States that we sampled. Differences in the prevalence of Bd between stream- and wetland-associated amphibians in the United States may be related to species-specific variation in susceptibility to chytridiomycosis or habitat differences.

California, Idaho, Montana, New Hampshire, Oregon,↗
USGS2007

Velafrons coahuilensis , a new labeosaurine haddrosaurid (Dinosauria: Ornithopoda) from the Late Campanian Cerro del Pueblo formation, Coahuila, Mexico

A new lambeosaurine hadrosaurid, Velafrons coahuilensis , is described as the first lambeosaurine from the Cerro del Pueblo Formation of Coahuila, Mexico, and the first lambeosaurine genus to be named from North America in more than 70 years. Although the holotype specimen is a juvenile individual—as evidenced by its incomplete crest development and relative size compared to other North American lambeosaurines—ontogeny independent autapomor-phies have been identified including quadrate with narrow quadratojugal notch and a postorbital with well developed, dorsally positioned squamosal process. Additionally, this taxon is unique in that the prefrontal is not dorsally deflected and anteroposteriorly expanded as in other lambeosaurine taxa of its size, but rather retains the frontal-prefrontal “clamp” present in smaller individuals of other taxa. Phylogenetic analysis places Velafrons in a polytomy with numerous other fan-crested lambeosaurines. The crest structure of Velafrons more closely resembles that of Corythosaurus and Hypacrosaurus because it possesses an anteriorly projecting nasal process over the dorsal premaxilla process. Biogeo-graphically, Velafrons is one of three distinct hadrosaurids known from approximately 73.5 Ma—two lambeosaurines and one hadrosaurine—all restricted to the southern region of the Western Interior Basin of North America.

Coahuila↗
USGS2004

Characterization of the habitat of Lythrum salicaria L. in floodplain forests in western Turkey—Effects on stem height and seed production

Lythrum salicaria (purple loosestrife) is an invasive wetland perennial in North America native to Eurasia. Because light environment may limit the species’ distribution, information on the relationship of forest canopy coverage to relative height and seed set in its native environment could give insight into its control in North America. This study examined the effect of various light environments related to forest canopy structure on seed set and stem height in L. salicaria in three biogeographical regions of Turkey spanning latitudes from 36 to 39° N. In Turkey, Lythrum salicaria grows in discrete patches in the canopy gaps of riverine forests, which often are dominated by Populus alba . The mean number of seeds per individual and stem height increased with decreasing canopy coverage (10437±284 to 20652±664 seeds individual −1 and 116±2 to 173±2 cm, respectively). A number of insect seed herbivores were noted on these Turkish populations, most notably a seed predator ( Nanophyes marmoratus ), which destroyed all seeds in infested capsules. Our study suggested that the light characteristics associated with canopy gaps influenced the seed set and height of L. salicaria . Other factors likely played a role, such as insect herbivores, soil fertility, and competition with other species, which may also be affected by the light levels provided at various levels of canopy coverage.

Wetlands↗
USGS2005

Observations of Interspecific amplexus between western North American ranid frogs and the introduced American bullfrog (Rana catesbeiana) and an hypothesis concerning breeding interference

Introduced American bullfrogs ( Rana catesbeiana ) come in contact with native amphibians on four continents and are well established in lowlands of western North America. To date, research on the effects of introduced bullfrogs on native frogs has focused on competition and predation, and is based largely on larval interactions. We present observations of interspecific amplexus between bullfrogs and two native ranid frogs ( R. aurora and R. pretiosa ) from six sites across the Pacific Northwest that imply that this interaction is more widespread than currently recognized. Our observations indicate that R. catesbeiana juveniles and subadults in this region are of appropriate size to elicit marked amplectic responses from males of both native species. Our literature review suggests that greater opportunity may exist for pairings between R. catesbeiana and native R. aurora or R. pretiosa than among syntopic native ranids in western North America. We hypothesize that interspecific amplexus with introduced R. catesbeiana could result in reproductive interference with negative demographic consequences in native ranid populations that have been reduced or altered by other stressors.

American Midland Naturalist↗
USGS2006

Extirpation of freshwater mussels (Bivalvia: Unionidae) following the invasion of dreissenid mussels in an interconnecting river of the Laurentian Great Lakes

Previous (1992–1994) surveys for native freshwater mussels (Unionidae) along main channels of the Detroit River showed that unionids had been extirpated from all but four sites in the upper reaches of the river due to impacts of dreissenid mussels ( Dreissena polymorpha and D. bugensis ). These four sites were surveyed again in 1998 using the same sampling method (timed-random searches) to determine if they may serve as “refugia” where unionids and dreissenids co-exist. Two additional sites were sampled using additional methods (excavated-quadrat and line-transect searches) for comparison with unpublished data collected in 1987 and 1990. A total of four individuals of four species ( Actinonaias ligamentina , Cyclonaias tuberculata , Lasmigona complanata and Pleurobema sintoxia ) were found by timed-random searches at four sites in 1998 compared to 720 individuals of 24 species in 1992 and 39 individuals of 13 species in 1994. Excavated-quadrat and line-transect searches at the two additional sites yielded only one live specimen of Ptychobranchus fasciolaris compared to 288 individuals of 18 species in 1987 and 1990. Results of this study suggest that remaining densities of unionids in channels of the Detroit River are too low to support viable reproducing populations of any species. Therefore, we conclude that unionids have been extirpated from main channels of the Detroit River due to dreissenid infestation. As the Detroit River was one of the first water bodies in North America to be invaded by dreissenids, it is likely that unionids will also be extirpated from many other rivers and lakes across eastern North America over the next few decades. Resource agencies should be encouraged to implement active management programs to protect remaining unionid populations from zebra mussels.

Michigan↗
USGS2014

Historic and contemporary mercury exposure and potential risk to yellow-billed loons ( Gavia adamsii ) breeding in Alaska and Canada

The Yellow-billed Loon (Gavia adamsii) is one of the rarest breeding birds in North America. Because of the small population size and patchy distribution, any stressor to its population is of concern. To determine risks posed by environmental mercury (Hg) loads, we captured 115 Yellow-billed Loons between 2002 and 2012 in the North American Arctic and sampled their blood and/or feather tissues and collected nine eggs. Museum samples from Yellow-billed Loons also were analyzed to examine potential changes in Hg exposure over time. An extensive database of published Hg concentrations and associated adverse effects in Common Loons (G. immer) is highly informative and representative for Yellow-billed Loons. Blood Hg concentrations reflect dietary uptake of methylmercury (MeHg) from breeding areas and are generally considered near background levels if less than 1.0 µg/g wet weight (ww). Feather (grown at wintering sites) and egg Hg concentrations can represent a mix of breeding and wintering dietary uptake of MeHg. Based on Common Loon studies, significant risk of reduced reproductive success generally occurs when adult Hg concentrations exceed 2.0 µg/g ww in blood, 20.0 µg/g fresh weight (fw) in flight feathers and 1.0 µg/g ww in eggs. Contemporary mercury concentrations for 176 total samples (across all study sites for 115 Yellow-billed Loons) ranged from 0.08 to 1.45 µg/g ww in blood, 3.0 to 24.9 µg/g fw in feathers and 0.21 to 1.23 µg/g ww in eggs. Mercury concentrations in blood, feather and egg tissues indicate that some individual Yellow-billed Loons in breeding populations across North America are at risk of lowered productivity resulting from Hg exposure. Most Yellow-billed Loons breeding in Alaska overwinter in marine waters of eastern Asia. Although blood Hg concentrations from most breeding loons in Alaska are within background levels, some individuals exhibit elevated feather and egg Hg concentrations, which likely indicate the uptake of MeHg originating from eastern Asia. Feather Hg concentrations tended to be highest in individuals overwintering farthest west (closer to Asia). A retrospective analysis of museum specimens (n = 25) found a two-fold increase in Yellow-billed Loon feather Hg concentrations from the pre-1920s (as early as 1845) to the present. The projected increase in Hg deposition (approximately four-fold by 2050) along with the uncertainty of Hg being released through the thawing of permafrost and Arctic sea ice suggest that Hg body burdens in Yellow-billed Loons may increase. These findings indicate that Hg is a current and potentially increasing environmental stressor for the Yellow-billed Loon and possibly other Nearctic-Palearctic migrant birds.

Alaska↗
USGS2019

DNA Sequencing confirms Tundra Bean Goose (Anser serrirostris serrirostris) occurrence in the Mississippi Alluvial Valley in Arkansas, USA

—First sighting records of rare occurrences may become increasingly important for recognizing changes in distribution, changes in migratory strategies, or increases in hybridization. We focumented the first record of a Tundra Bean Goose in the Mississippi Alluvial Valley, the outlet and historic floodplain for much of North America and one of the most important waterfowl wintering areas on the continent. We also document the first genetically confirmed record in the contiguous USA. Bean Goose (Anser fabalis and A. serrirostris) occurrences in North America are rare, especially outside of Alaska. On 24 January 2018, a Tundra Bean Goose (A. s. serrirostris) was harvested by a hunter in a winter-flooded rice field in Desha County, Arkansas, USA, near Dumas. The goose was mixed with a flock of 50 Greater White-Fronted Geese (A. albifrons). Because this individual was legally, albeit accidentally shot, we had the rare and exciting opportunity to obtain morphometric measurements and biological samples. As a result, we were able to verify the species and subspecies through genetic and morphological analysis. We determined the goose was an adult female Tundra Bean Goose, and mitochondrial DNA control region sequence data indicated this specimen was the subspecies A. s. serrirostris.

Arkansas↗
USGS2005

Causes of mortality in sea ducks (Mergini) necropsied at the USGS-National Wildlife Health Center

A number of factors were identified as causes of mortality in 254 (59%) of 431 sea ducks submitted for necropsy at the USGS-National Wildlife Health Center, Madison, Wisconsin from 1975 until 2003. Bacteria causing large outbreaks of mortality were Pasteurella multocida and Clostridium botulinum Type E. Starvation was responsible for large mortality events as well as sporadic deaths of individuals. Lead toxicity, gunshot and exposure to petroleum were important anthropogenic factors. Other factors that caused mortality were avian pox virus, bacteria ( Clostridium botulinum Type C, Riemerella anatipestifer and Clostridium perfringens ), fungi ( Aspergillus fumigatus and an unidentified fungus), protozoans (unidentified coccidia), nematodes ( Eustrongylides spp.), trematodes ( Sphaeridiotrema globulus and Schistosoma spp.), acanthocephalans ( Polymorphus spp.), predation, cyanide and trauma (probably due to collisions). There were also a number of novel infectious organisms in free-living sea ducks in North America, which were incidental to the death, including avipoxvirus and reovirus, bacteria Mycobacterium avium , protozoans Sarcocystis sp. and nematodes Streptocara sp. Apart from anthropogenic factors, the other important mortality factors listed here have not been studied as possible causes for the decline of sea ducks in North America.

Waterbirds↗
USGS2002

Timing and magnitude of Broad-winged Hawk migration at Montclair Hawk Lookout, New Jersey, and Hawk Mountain Sanctuary, Pennsylvania

The Broad-winged Hawk ( Buteo platypterus ) breeds in eastern and central Canada and the United States, and winters in Central America and northern and central South America. Birders and ornithologists count migrating Broad-winged Hawks at dozens of traditional watch sites throughout the northeastern United States. We modeled counts of migrating Broad-winged Hawks from two raptor migration watch sites: Montclair Hawk Lookout, New Jersey, and Hawk Mountain Sanctuary, Pennsylvania, to determine whether annual abundance and trend estimates from individual sites within the mid-Atlantic states are representative of the region as a whole. We restricted ourselves to counts made between 10:00 and 16:00 EST during September to standardize count effort between sites. We created one model set for annual counts and another model set for daily counts. When modeling daily counts we incorporated weather and identity of individual observers. Akaike’s Information Criteria were used to select the best model from an initial set of competing models. Annual counts declined at both sites during 1979–1998. Broad-winged Hawk migration began, peaked, and ended later at Montclair than at Hawk Mountain, even though Hawk Mountain is 155 km west-southwest of Montclair. Mean annual counts of hawks at Montclair were more than twice those at Hawk Mountain, but were not correlated. Broad-winged Hawks counted at Montclair may not be the same birds as those counted at Hawk Mountain. Rather, the two sites may be monitoring different regional subpopulations. Broad-winged Hawks counted at the two sites may use different migration tactics, with those counted at Hawk Mountain being more likely to slope soar, and those at Montclair more likely to use thermal soaring. A system of multiple watch sites is needed to monitor various breeding populations of this widely dispersed migrant.

New Jersey, Pennsylvania↗
USGS2014

Age-Ratios and Condition of En Route Migrant Blackpoll Warblers in the British Virgin Islands

The en route migration ecology of Blackpoll Warblers ( Setophaga striata ) is poorly understood, yet intriguing. Blackpoll Warblers undertake the longest open water migration of any wood warbler species, traveling from northeastern North America to South America, with the first potential landfall being the West Indies. This migration requires substantial energy reserves and subjects Blackpoll Warblers to unpredictable weather events, which may influence survival. Few studies have examined age ratios or condition of Blackpoll Warblers while the warblers are en route through the Caribbean region. I captured and banded Blackpoll Warblers in the British Virgin Islands over 10 consecutive autumn migrations. Ratios of hatch-year to adult Blackpoll Warblers were variable but averaged lower than the ratios reported at continental departure locations. Average mass of Blackpoll Warblers was less than that reported at continental departure locations, with 26% of adults and 40% of hatch-year birds below the estimated fat free mass; hatch-year birds were consistently in poorer condition than adults. Blackpoll Warblers captured in the British Virgin Islands were also in poorer condition than those reported from the Dominican Republic and Barbados; this may be because of the British Virgin Islands being the first landfall after the transatlantic crossing, whereas Blackpoll Warblers arriving at the other Caribbean study locations may have had opportunities for stopover prior to arrival or have departed from farther south on the continent. However, this suggests that the British Virgin Islands likely provide important stopover habitat as a first landfall location for Blackpoll Warblers arriving from the transatlantic migration route.

Guana Island↗
USGS2016

Observations of seismicity and ground motion in the northeast U.S. Atlantic margin from ocean bottom seismometer data

Earthquake data from two short-period ocean-bottom seismometer (OBS) networks deployed for over a year on the continental slope off New York and southern New England were used to evaluate seismicity and ground motions along the continental margin. Our OBS networks located only one earthquake of M c ∼1.5 near the shelf edge during six months of recording, suggesting that seismic activity (M Lg >3.0) of the margin as far as 150–200 km offshore is probably successfully monitored by land stations without the need for OBS deployments. The spectral acceleration from two local earthquakes recorded by the OBS was found to be generally similar to the acceleration from these earthquakes recorded at several seismic stations on land and to hybrid empirical acceleration relationships for eastern North America. Therefore, the seismic attenuation used for eastern North America can be extended in this region at least to the continental slope. However, additional offshore studies are needed to verify these preliminary conclusions.

Seismological Research Letters↗
USGS2025

Reflections on a trio of North American earthquakes in 1925

In 1925, three moderately large damaging earthquakes occurred in North America over four months: the 28 February (local time; LT) M 6.2 Charlevoix, 27 June (LT) M 6.6 Montana, and 29 June M 6.5 Santa Barbara earthquakes. The centennial anniversaries of these events motivated this retrospective consideration focused on the ground motions generated by the three events, including a reconsideration of early intensity assignments for the Montana earthquake. At the time, these three earthquakes appeared to support the arguments of some geologists who downplayed the severity of seismic hazard in southern California relative to other parts of the country. Some of the arguments advanced at that time, for example that Los Angeles “has the least to fear from ‘Acts of God’ of any city under the American flag,” ( Hill, 1928 ) sound naïve if not laughable now, but a comparison of well‐constrained shaking distributions for the three earthquakes reveals the dramatic difference in wave propagation efficiency in western versus eastern North America (ENAM), which leads to moderate ENAM events being felt to much larger distances. At M 6.2, the 1925 Charlevoix earthquake was a notably large event in ENAM. This earthquake was the largest event in eastern Canada since 1870 and caused damage in the epicentral region in addition to towns as far away as 200 km, with felt shaking extending over 1000 km. In contrast, felt shaking from the Santa Barbara earthquake barely extended beyond ∼200 km. Compiling published intensity distributions for larger ENAM earthquakes, we show that perceptible earthquake shaking is not uncommon in ENAM over century time scales, but experience with weakly felt shaking may incline people to downplay potential earthquake risk.

California, Montana, Quebec↗
USGS1995

Source parameters and crustal Q for four earthquakes in South Carolina

Two three-component seismometers (one surface and one borehole) were re-installed on the Savannah River Site (SRS), South Carolina in July 1992 to determine attenuation in the Coastal Plain sediment wedge and source parameters of local earthquakes. Four earthquakes M ∼ 1.8 to 3.6 were recorded during the next 6 months. The largest event was located near Summerville within the meizoseismal area for the 1886 Charleston earthquake. Two shocks were located 50 km to the east near Neeses, and one was located 20 km north of the SRS near Aiken. Although source parameters have been determined from strong motion data and short-period regional networks for east coast earthquakes, such as the Saguenay, Nahanni, and Mt. Laurier earthquakes (e.g., Atkinson, 1993 ), these are some of the first source parameters determined from broad-band digital recorders. Seismograms for the Summerville event are also available from Chapel Hill, North Carolina and Blacksburg, Virginia, providing estimates of t * beyond 200 km. Here we determine source parameters such as moment, stress drop, and the attenuation parameter t * using a non-linear least-squares algorithm. We do not correct for site response because the deepest borehole is not below the Coastal Plain sediments (about 300m thick at this site) and because only one station is available for most of the data. Values of t* are marginally higher from seismograms recorded at the surface when compared to records from the 91m depth borehole seismograph. A value of 170-200 bars was determined for the Brune stress drop of the Summerville event using the borehole data, which is high compared to a value of 50 bars usually specified for modeling strong motion in western North America, but similar to other estimates for eastern North America. A higher stress drop leads to a higher seismic risk because peak acceleration is approximately proportional to stress drop. Moreover, mid- to upper-crustal Qs are in the range of 2,000 to 3,000, which would permit the propagation of high frequency seismic waves. A comparison of the surface records from the SRS with a record from the USGS dense array at Parkfield, CA for an event at about the same distance range and moment as the Summerville event-SRS case shows that the peak acceleration of the Summerville event is 16 times higher than that for the event from California (stress drop of 21 bars).

South Carolina↗
USGS1997

Boundary separating the seismically active reelfoot rift from the sparsely seismic Rough Creek graben, Kentucky and Illinois

The Reelfoot rift is the most active of six Iapetan rifts and grabens in central and eastern North America. In contrast, the Rough Creek graben is one of the least active, being seismically indistinguishable from the central craton of North America. Yet the rift and graben adjoin. Hazard assessment in the rift and graben would be aided by identification of a boundary between them. Changes in the strikes of single large faults, the location of a Cambrian transfer zone, and the geographic extent of alkaline igneous rocks provide three independent estimates of the location of a structural boundary between the rift and the graben. The boundary trends north-northwest through the northeastern part of the Fluorspar Area Fault Complex of Kentucky and Illinois, and has no obvious surface expression. The boundary involves the largest faults, which are the most likely to penetrate to hypocentral depths, and the boundary coincides with the geographic change from abundant seismicity in the rift to sparse seismicity in the graben. Because the structural boundary was defined by geologic variables that are expected to be causally associated with seismicity, it may continue to bound the Reelfoot rift seismicity in the future.

Illinois, Kentucky↗
USGS2006

Response of Everglades tree islands to environmental change

Tree islands are centers of biodiversity within the Florida Everglades, USA, but the factors controlling their distribution, formation, and development are poorly understood. We use pollen assemblages from tree islands throughout the greater Everglades ecosystem to reconstruct the timing of tree island formation, patterns of development, and response to specific climatic and environmental stressors. These data indicate that fixed (teardrop-shaped) and strand tree islands developed well before substantial human alteration of the system, with initial tree island vegetation in place between 3500 and 500 calibrated years before present (cal yr BP), depending on the location in the Everglades wetland. Tree island development appears to have been triggered by regional- to global-scale climatic events at 2800 cal yr BP, 1600–1500 cal yr BP, 1200–1000 cal yr BP (early Medieval Warm Period), and 500–200 cal yr BP (Little Ice Age). These periods correspond to drought intervals documented in Central and South America and periods of southward displacement of the Intertropical Convergence Zone. The records indicate a coherence of climate patterns in both subtropical North America and the Northern Hemisphere Neotropics. Water management practices of the 20th century altered plant communities and size of tree islands throughout the Everglades. Responses range from loss of tree islands due to artificially long hydroperiods and deep water to expansion of tree islands after flow reductions. These data provide evidence for the rapidity of tree island response to specific hydrologic change and facilitate prediction of the response to future changes associated with Everglades restoration plans.

Florida↗
USGS2007

Satellite telemetry and prey sampling reveal contaminant sources to pacific northwest ospreys

Migratory behavior can be an important factor in determining contaminant exposure in avian populations. Accumulation of organochlorine (OC) pesticides while birds are wintering in tropical regions has been cited often as the reason for high concentrations in migrant populations. To explore this issue, we satellite tracked 16 Ospreys (Pandion haliaetus) over the period 1996-2003 from breeding sites in British Columbia, Canada, and integrated the results into a database on 15 Ospreys that were satellite tracked over the period 1995-1999, from breeding locations in Washington and Oregon, USA. Data on wintering sites of 31 Ospreys in Mexico and Central America were used for spatially targeted sampling of prey fish. Concentrations of the main organochlorine contaminant, p,p???-dichloro-diphenyl-dichloroethylene (DDE), in fish composites from Mexico ranged from 0.005 to 0.115 ??g/g wet mass. Significant differences existed among fish families in p,p???-DDE, total dichloro- diphenyltrichloroethane (??DDT), ??chlordanes, and total polychlorinated biphenyls (??PCBs). Catfish (family Ariidae) generally had significantly higher levels of DDT metabolites and other organochlorine contaminants compared to other fish families collected. Differences in prey contaminant levels were detected among the collection sites around coastal Mexico, with fish from Veracruz State generally having higher levels of DDT metabolites, ??chlordanes, ??PCBs, and hexachlorobenzene. Eggs collected from 16 nests throughout the Pacific Northwest (nine from British Columbia, seven from Oregon and Washington) where Ospreys had been satellite tagged, showed marked variation in levels of DDT metabolites (p,p???-DDE; range 0.02-10.14 ??g/g). Wintering site had no significant effect on contaminant concentrations in sample eggs from those specific Ospreys; rather concentrations of p,p???-DDE, were predicted by breeding sites with highest levels in eggs of Ospreys breeding in the lower Columbia River, consistent with published reports of continued high concentrations of DDT and related compounds in that system. ?? 2007 by the Ecological Society of America.

Ecological Applications↗
USGS2010

Are inland wolf-ungulate systems influenced by marine subsidies of Pacific salmon?

Wolves ( Canis lupus ) in North America are considered obligate predators of ungulates with other food resources playing little role in wolf population dynamics or wolf–prey relations. However, spawning Pacific salmon (Oncorhyncus spp.) are common throughout wolf range in northwestern North America and may provide a marine subsidy affecting inland wolf–ungulate food webs far from the coast. We conducted stable‐isotope analyses for nitrogen and carbon to evaluate the contribution of salmon to diets of wolves in Denali National Park and Preserve, 1200 river‐km from tidewater in interior Alaska, USA. We analyzed bone collagen from 73 wolves equipped with radio collars during 1986–2002 and evaluated estimates of salmon in their diets relative to the availability of salmon and ungulates within their home ranges. We compared wolf densities and ungulate : wolf ratios among regions with differing salmon and ungulate availability to assess subsidizing effects of salmon on these wolf–ungulate systems. Wolves in the northwestern flats of the study area had access to spawning salmon but low ungulate availability and consumed more salmon (17% ± 7% [mean ± SD]) than in upland regions, where ungulates were sixfold more abundant and wolves did or did not have salmon spawning areas within their home ranges (8% ± 6% and 3% ± 3%, respectively). Wolves were only 17% less abundant on the northwestern flats compared to the remainder of the study area, even though ungulate densities were 78% lower. We estimated that biomass from fall runs of chum (O. keta) and coho (O. kisutch) salmon on the northwestern flats was comparable to the ungulate biomass there, and the contribution of salmon to wolf diets was similar to estimates reported for coastal wolves in southeast Alaska. Given the ubiquitous consumption of salmon by wolves on the northwestern flats and the abundance of salmon there, we conclude that wolf numbers in this region were enhanced by the allochthonous subsidy provided by salmon and discuss implications for wolf–ungulate relations.

Ecological Applications↗