Geology topics

Miguel A. Mora

Publications and source records attributed to Miguel A. Mora.

12 recordsLinked to original sources

USGS2012

Modelling effects of chemical exposure on birds wintering in agricultural landscapes: The western burrowing owl ( Athene cunicularia hypugaea ) as a case study

We describe an ecotoxicological model that simulates the sublethal and lethal effects of chronic, low-level, chemical exposure on birds wintering in agricultural landscapes. Previous models estimating the impact on wildlife of chemicals used in agro-ecosystems typically have not included the variety of pathways, including both dermal and oral, by which individuals are exposed. The present model contains four submodels simulating (1) foraging behavior of individual birds, (2) chemical applications to crops, (3) transfers of chemicals among soil, insects, and small mammals, and (4) transfers of chemicals to birds via ingestion and dermal exposure. We demonstrate use of the model by simulating the impacts of a variety of commonly used herbicides, insecticides, growth regulators, and defoliants on western burrowing owls ( Athene cunicularia hypugaea ) that winter in agricultural landscapes in southern Texas, United States. The model generated reasonable movement patterns for each chemical through soil, water, insects, and rodents, as well as into the owl via consumption and dermal absorption. Sensitivity analysis suggested model predictions were sensitive to uncertainty associated with estimates of chemical half-lives in birds, soil, and prey, sensitive to parameters associated with estimating dermal exposure, and relatively insensitive to uncertainty associated with details of chemical application procedures (timing of application, amount of drift). Nonetheless, the general trends in chemical accumulations and the relative impacts of the various chemicals were robust to these parameter changes. Simulation results suggested that insecticides posed a greater potential risk to owls of both sublethal and lethal effects than do herbicides, defoliants, and growth regulators under crop scenarios typical of southern Texas, and that use of multiple indicators, or endpoints provided a more accurate assessment of risk due to agricultural chemical exposure. The model should prove useful in helping prioritize the chemicals and transfer pathways targeted in future studies and also, as these new data become available, in assessing the relative danger to other birds of exposure to different types of agricultural chemicals.

Texas↗

USGS2009

Metal exposure and effects in voles and small birds near a mining haul road in Cape Krusenstern National Monument, Alaska

Voles and small passerine birds were live-captured near the Delong Mountain Regional Transportation System (DMTS) haul road in Cape Krusenstern National Monument in northwest Alaska to assess metals exposure and sub-lethal biological effects. Similar numbers of animals were captured from a reference site in southern Cape Krusenstern National Monument for comparison. Histopathological examination of selected organs, and analysis of cadmium, lead, and zinc concentrations in liver and blood samples were performed. Voles and small birds captured from near the haul road had about 20 times greater blood and liver lead concentrations and about three times greater cadmium concentrations when compared to those from the reference site, but there were no differences in zinc tissue concentrations. One vole had moderate metastatic mineralization of kidney tissue, otherwise we observed no abnormalities in internal organs or DNA damage in the blood of any of the animals. The affected vole also had the greatest liver and blood Cd concentration, indicating that the lesion might have been caused by Cd exposure. Blood and liver lead concentrations in animals captured near the haul road were below concentrations that have been associated with adverse biological effects in other studies; however, subtle effects resulting from lead exposure, such as the suppression of the activity of certain enzymes, cannot be ruled out for some individual animals. Results from our 2006 reconnaissance-level study indicate that overall, voles and small birds obtained from near the DMTS road in Cape Krusenstern National Monument were not adversely affected by metals exposure; however, because of the small sample size and other uncertainties, continued monitoring of lead and cadmium in terrestrial habitats near the DMTS road is advised.

Alaska↗

USGS2008

Organochlorine pollutants and stable isotopes in resident and migrant passerine birds from northwest Michoacán, Mexico

Although concentrations of organochlorine compounds (OCs) in birds from most of the United States and Canada have decreased over the last 30 years, there is still concern that migrant birds might be exposed to elevated concentrations of OCs during migration in Latin America. The Lerma-Chapala Basin in west-central Mexico is an important migration corridor and wintering area for many species. The objectives of this study were to assess if resident and migrant birds wintering in western Michoacán, Mexico accumulated elevated concentrations of OCs during fall and spring and to determine if the stable isotopes δ 15 N, δ 13 C, and δD could be used to predict burdens and origins of DDE accumulation. Resident and migrant passerine insectivorous birds were collected during fall and spring (2001–2002) in northwest Michoacán, near Chapala Lake, Mexico. The carcasses were analyzed for OCs and tail feathers were analyzed for stable isotopes δ 15 N, δ 13 C, and δD. The OCs detected in more than 50% of the samples were: oxychlordane (79%), p,p ’-DDE (100%), p ,p′-DDT (57%), and total PCBs (100%). p,p ′-DDE was the OC detected at the highest concentrations, whereas residues of other OCs were near or below detection limits. Overall, there were no significant differences in concentrations of OCs between seasons or between resident and migrant birds. Concentrations of DDE and oxychlordane were somewhat higher in migrant and resident birds during spring than in fall; however, concentrations were significantly different only for oxychlordane. Two resident birds collected in fall and spring had DDE residues >10 μg/g wet weight in carcass. There were no significant differences in δ 13 C and δ 15 N values among species, between seasons, or between migrant and resident birds. However, δD values were clearly different between species and helped differentiate migrant from resident birds. δD values also were negatively and significantly correlated with DDE concentrations in carcass. Birds with more depleted δD values in feathers tended to have higher DDE concentrations than those with less depleted δD values, suggesting a potential latitudinal accumulation of DDE. Overall, our results suggest that during fall and spring, there is not a significant buildup of persistent OCs in migrant and resident passerine insectivorous birds in northwest Michoacán, Mexico.

Michoacán↗

USGS2008

Assessment of metals exposure and sub-lethal effects in voles and small birds captured near the DeLong Mountain Regional Transportation System Road, Cape Krusenstern National Monument, Alaska, 2006

Voles (n=6) and small ground-nesting birds (n=12) were live-captured near the DeLong Mountain Regional Transportation System haul road in Cape Krusenstern National Monument in northwest Alaska in 2006 to assess metals exposure and sub-lethal biological effects. Similar numbers of animals were captured from a reference site in southern Cape Krusenstern National Monument for comparison. Histopathological examination of selected organs, blood analysis, and analysis for aluminum, barium, cadmium, lead, and zinc concentrations in liver and blood samples were performed. Voles and small birds captured from near the haul road had about 20 times greater blood and liver lead concentrations and about 3 times greater cadmium concentrations when compared to those from the reference site. Barium and zinc tissue concentrations of animals collected from different sites were not remarkably different, and aluminum concentrations were below the reporting limits in most samples. There was no clear evidence of serious sub-lethal biological effects such as lesions in internal organs or DNA damage in blood in any of the animals. Accordingly, blood and liver lead concentrations in animals captured near the haul road generally were less than tissue concentration thresholds associated with serious biological effects reported from other studies; however, subtle effects resulting from lead exposure, such as the suppression of the activity of certain enzymes, cannot be ruled out for those animals nearest the haul road. Notably, liver lead concentrations of voles and small birds at the reference location were considerably less than those previously reported for similar animals at reference sites in other parts of the United States, Canada, and Europe. Results from this reconnaissance-level study indicate that voles and small birds inhabiting this area are not suffering serious biological effects as a result of metals exposure; however, continued monitoring of lead and other metals is recommended because of uncertainties noted and because biological effects thresholds might be approached if exposure levels were to increase.

Scientific Investigations Report↗

USGS2005

Naturally occurring secondary nutritional hyperparathyroidism in cattle egrets ( Bubulcus ibis ) from Central Texas

Naturally occurring secondary nutritional hyperparathyroidism is described in the nestlings of two colonies of cattle egrets ( Bubulcus ibis ) from Central Texas (Bryan and San Antonio, Texas, USA). Nestlings from a third colony (Waco, Texas, USA) were collected in a subsequent year for comparison. Birds from the first two colonies consistently had severe osteopenia and associated curving deformities and folding fractures of their long bones. These birds also had reduced bone ash, increased osteoclasia, a marked decrease in osteoblast activity, variable lengthening and shortening of the hypertrophic zone of the epiphyseal cartilage, decreased and disorganized formation of new bone, and a marked hypertrophy and hyperplasia of the parathyroid glands as compared to birds collected from the third colony. Fibrous osteodystrophy was found in all of the birds from San Antonio and Bryan. Evidence of moderate to severe calcium deficiency was also identified in 33% of the cattle egrets collected from Waco. Gut contents of affected chicks contained predominately grasshoppers and crickets; vertebrate prey items were absent from the Bryan birds. Grasshoppers and crickets collected from fields frequented by the adult egrets in 1994 had 0.12–0.28% calcium and 0.76–0.81% phosphorus. Pooled grasshoppers and crickets collected during a subsequent wet early spring averaged 0.24% calcium and 0.65% phosphorus. Although the phosphorus content of the insect prey was adequate for growth, calcium was approximately one-third the minimum calcium requirement needed for growth for other species of birds. It was postulated that cattle egrets breeding in Central Texas have expanded their range into habitat that contains less vertebrate prey, and as a result, many nestling egrets are being fed diets that contain suboptimal calcium. Therefore, in years where vertebrate prey is scarce and forage for insect prey is reduced in calcium, nestling egrets are at risk for developing secondary nutritional hyperparathyroidism.

Texas↗

USGS2003

Heavy metals and metalloids in egg contents and eggshells of passerine birds from Arizona

Concentrations of inorganic elements were determined in eggs of passerine birds including the endangered southwestern willow flycatcher ( Empidonax traillii extimus ) from four regions in Arizona. The main aim of the study was to determine the distribution of metals in egg contents and eggshells, with emphasis on the deposition of Sr in eggshells. Seventy eggs of 11 passerine species were collected at four nesting locations during 2000. Aluminum, Ba, Cr, Cu, Mn, Se, Sr, and Zn, were detected primarily in egg contents of all bird species. Arsenic, Ni, Pb, and V were detected primarily in eggshells. A proportion of most inorganic elements accumulated in the eggshell. Concentrations of Ba, Cu, Mn, Se, Sr, and Zn in egg contents and As, Ba, Cu, and V in eggshells of yellow-breasted chats ( Icteria virens ) were similar among locations. However, concentrations of Mn, Ni, Sr, and Zn in eggshells were significant different among locations. Except for Cu, Mn, Se, and Zn, concentrations of inorganic elements were 2–35 times greater in eggshells than in eggs. Most concentrations of metals and metalloids in eggs and eggshells of all the bird species were below levels known to affect reproduction or that have other deleterious effects. However, I found somewhat elevated concentrations of Sr in eggshells (highest mean=1505 μg/g dw, n =3) of yellow-breasted chats and willow flycatchers, and in egg contents of yellow warblers ( Dendroica petechia) and song sparrows ( Melospiza melodia ). Whether current observed concentrations of Sr in eggshells are affecting nesting birds in Arizona remains to be determined. Strontium and other metals could be associated with lower hatching success in some areas. This study shows that a proportion of many inorganic elements accumulates in the eggshell and that the potential effects on the proper structure and functioning of the eggshell should not be ignored.

Environmental Pollution↗

USGS2002

Contaminants without borders: A regional assessment of the Colorado River Delta ecosystem

The Colorado River Delta Region (CRDR) is comprised of large agricultural areas in the U.S. (Imperial and Yuma districts) and Mexico (Mexicali and San Luis districts), the Salton Sea, and the Lower Colorado River from southern Arizona to the Gulf of California (Valdés-Casillas et al., 1998). Before agricultural development, the lower delta comprised large riparian and wetland areas (Sykes, 1937; Glenn et al., 1999). Currently, most water from the Colorado River below Imperial Dam is used for irrigation in California and Mexico, and only remnants of the former CRDR wetlands remain. However, the Cienega de Santa Clara and the Rio Hardy wetlands (Figure 111.1) provide important habitat for many resident and migratory birds, including endangered species such as the desert pupfish (scientific names are provided in Table 111.1) and the Yuma clapper rail (Abarca et al., 1993; Mellink et al., 1997). Detailed descriptions of the CRDR and its wetlands are provided elsewhere (Sykes, 1937; Glenn et al., 1995; 1999; Friederici, 1998; Valdés-Casillas et al., 1998).

California↗

USGS2001

A comparative assessment of contaminants in fish from four resacas of the Texas, USA-Tamaulipas, Mexico border region

A recent survey of contaminant information for the Lower Rio Grande Valley (LRGV), Texas, has shown that little is known about contaminants and their impacts on biota of resacas (oxbows) along the US-Mexico border. In 1996, fish were collected from four resacas in the Texas- Tamaulipas border region to assess contaminant loadings and their impacts on fish and birds. Tissue residue concentrations in fish were analyzed and also compared to two histopathological bioindicators of unhealthy environmental conditions. Of the organochlorine insecticides measured, DDE was the most common and was present at relatively high concentrations (10 ??g/g w/w) at some sites. DDE concentrations were nearly 20 times greater in fish from resacas in Texas than from resacas in Tamaulipas, although the limited sample sizes obtained precluded statistical comparisons. DDE concentrations in fish from the two Texas resacas were also greater than those reported in fish from nearby areas during the 1980s and 1990s. Most trace element concentrations were similar among resacas from Texas and Tamaulipas. Arsenic, however, was two to six times greater in fish from a downtown resaca in Matamoros than in fish from other resacas in Tamaulipas and Texas. The bioindicators, pigment accumulation, and macrophage aggregates (MAs), in general, reflected the contamination indicated by the tissue residues for each site. Overall, it appears that some resacas of the US-Mexico border region are contaminant sinks and could pose potential health or reproductive problems for fish and wildlife, and humans that consume fish from those sites. Published by Elsevier Science Ltd.

Environment International↗

USGS1997

Transboundary pollution: Persistent organochlorine pesticides in migrant birds of the Southwestern United States and Mexico

The hypothesis that migratory birds accumulate persistent organochlorine pesticides (POPs) during the winter in Latin America has been prevalent for many years, particularly since 1,1,1-trichloro-2,2–bis(p-chlorophenyl)ethane (DDT) was banned in the United States in 1972. It has been suggested that peregrine falcons ( Falco peregrinus ), black-crowned night herons ( Nycticorax nycticorax ), white-faced ibises ( Plegadis chihi ), various migratory waterfowl and shorebirds, and other avian species accumulate higher concentrations of POPs while on migration or on their wintering grounds in Latin America. Nonetheless, the data obtained thus far are limited, and there is no clear pattern to suggest that such accumulation occurs on a widespread basis. In this review wildlife contaminant studies conducted along the U.S.-Mexico border and throughout Mexico are discussed. The results for the most part seem to indicate that no major accumulation of 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene) (DDE), the most persistent organochlorine compound, has occurred or been reported for most parts of Mexico. The majority of the DDE values in birds from Mexico were similar to those reported in birds from the southwestern United States during the same years. More work needs to be done, particularly in those cotton-producing areas of Mexico where DDT was applied heavily in the past (e.g., Chiapas and Michoacan). Because DDT is still used for malaria control and may still be used in agriculture in Chiapas, this state is probably the one where most migrant species would still be at a significant risk of increased accumulation of DDE and DDT.

Environmental Toxicology and Chemistry↗

USGS1995

Organochlorine residues in bat guano from nine Mexican caves, 1991

Samples of bat guano, primarily from Mexican free-tailed bats ( Tadarida brasiliensis ), were collected at nine bat roosts in caves in northern and eastern Mexico and analysed for organochlorine residues. DDE, the most abundant residue found in each cave, was highest (0.99 p.p.m. dry weight) at Ojuela Cave, Durango. Other studies of DDE in bat guano indicate that this concentration is too low to reflect harmful concentrations in the bats themselves. The DDE at Ojuela may represent either lingering residues from use of DDT years ago in the Ojuela area of perhaps depuration loss from migrant bats with summer maternity roost(s) in a DDE-contaminated area such as Carlsbad Cavern, New Mexico. Presence of o,p′ -DDT at Tio Bartolo Cave, Nuevo Leon, indicates recent use of DDT, but the concentration of this contaminant was low. Possible impacts on bat colonies of the organophosphorus and carbamate insecticides now in extensive use are unknown.

Ecotoxicology↗

USGS1995

Concentrations of dissolved and particulate Polychlorinated Biphenyls in water from the Saginaw River, Michigan

The Saginaw River receives water from a major drainage basin in the east-central portion of the lower peninsula of Michigan. Historically the river has been contaminated with polychlorinated biphenyls (PCBs) from several sources. The present study was conducted to determine the concentrations of PCBs in both the dissolved and particulate phases of water in the lower Saginaw River, as well as the relative contribution of PCBs from the lower portion of the river relative to more upstream locations. Water samples were collected in 1990–1991, during a range of discharge conditions. Suspended particulates were collected from water onto glass-fiber filters by use of a “Penta-plate” filtration apparatus. Filtered water was subsequently passed through XAD-2 macroreticular resin to collect the “dissolved” PCBs. Concentrations of PCBs in both phases were determined by congener specific gas chromatography with electron capture detection. Total concentrations of PCBs ranged from 11 to 31 ng/L. The concentrations of PCBs in the dissolved phase ranged from 1.9 to 16 ng/L. The ratio of total PCBs bound to suspended particulates, relative to dissolved PCBs, was 2:1 and remained fairly constant for discharges less than approximately 400 M 3 /sec. The loading of total PCBs to Saginaw Bay was estimated to be 225 kg/yr, of which approximately 60% was found to be contributed by the lower 8 km of the Saginaw River.

Michigan↗

USGS1995

Residues and trends of organochlorine pesticide and polychlorinated biphenyls in birds from Texas, 1965-88

Concentrations of DDE (a metabolite of DDT) in birds decreased during recent years in most areas of the continental United States. Organochlorine pesticides were widely used in agriculture in Texas from the early 1950s to the 1970s. I used previously published data to determine whether concentrations of DDE and polychlorinated biphenyls (PCBs) in birds from Texas have followed a decreasing trend similar to that in birds from other areas in the United States. A total of 2,669 bird samples was collected between 1965 and 1988 from diverse locations in Texas and was analyzed for organochlorines and other environmental contaminants. The brown pelican ( Pelecanus occidentalis ), peregrine falcon ( Falco peregrinus ), laughing gull ( Larus atricilla ), black skimmer ( Rynchops niger ), and European starling ( Sturnus vulgaris ) were the most frequently studied species. DDE and PCBs were the most commonly detected organochlorines in bird tissues. Mean DDE concentrations ranged from 0.4 to 61.00 parts per million (ppm) wet weight (ww) and PCBs from 0.02 to 32.00 ppm ww. Concentrations of DDE in eggs and carcasses of black skimmers decreased significantly during 1970-84 and dropped from approximately 10 to nearly 3 ppm ww. PCBs decreased from approximately 7 ppm ww to 1 ppm ww in eggs and carcasses. DDE concentrations in eggs of brown pelicans varied from more than 3 ppm ww in 1970 to approximately 1 ppm ww in 1983; and PCB concentrations diminished from about 10 to 1 ppm ww. Decreasing trends in concentrations of DDE and PBCs were observed in most species, although in some cases, the estimated trends were not significantly different from zero. Concentrations of DDE in birds from the Texas coast decreased from more than 6.0 ppm in 1978 to below 0.5 ppm in 1985. The decreasing ratios in selected species varied from approximately 2.0 to 12.0 (DDE) and from 4.5 to 9.0 (PCBs). The results indicate that in general from 1965 to 1988, DDE and PCBs declined in birds from Texas.

Texas↗