Geology topics

C.A. Caldwell

Publications and source records attributed to C.A. Caldwell.

4 recordsLinked to original sources

USGS2005

Effects of depleted uranium on survival, growth, and metamorphosis in the african clawed frog (Xenopus laevis)

Embryos (stage 8-47, Nieuwkoop and Faber) of the African clawed frog (Xenopus laevis) were subjected to water-borne depleted uranium (DU) concentrations that ranged from 4.8 to 77.7 mg/Lusing an acute 96-h frog embryo teratogenesis assay-Xenopus (FETAX). In a chronic 64-d assay, X. laevis (from embryo through metamorphosis; stages 8-66) were subjected to concentrations of DU that ranged from 6.2 to 54.3 mg/L Our results indicate DU is a non teratogenic metal. No effects on mortality, malformations, or growth were observed in the 96-h FETAX with concentrations of DU that ranged from 4.8 to 77.7 mg/L From stage 8 to stage 47, X. laevis tadpoles do not actively feed and the gills are not well developed. Thus, uptake of DU was reduced despite exposure to elevated concentrations. The 64-d assay resulted in no concentration response for either mortality or malformations; however, a delay in metamorphosis was observed in tadpoles subjected to elevated DU concentrations (from 13.1 to 54.3 mg/L) compared to tadpoles in both the well-water control and reference. The delay in metamorphosis was likely due to increasing body burden of DU that ranged from 0.98 to 2.82 mg/kg. Copyright?? Taylor & Francis Inc.

Conference Paper↗

USGS2002

Effects of depleted uranium on the health and survival of Ceriodaphnia dubia and Hyalella azteca

Depleted uranium (DU) has been used as a substitute for the fissionable enriched uranium component of atomic weapons tested at Los Alamos National Laboratory (LANL) (Los Alamos, NM, USA) since the early 1950s, resulting in considerable concentrations of DU in the soils within the test sites. Although the movement of DU into major aquatic systems has been shown to be minimal, there are many small-order ephemeral streams and areas of standing water in canyons throughout LANL that may be affected by inputs of DU via runoff, erosion, and leaching. Ninety-six-hour acute and 7-d chronic toxicity assays were conducted to measure the toxicity of DU on survival and reproduction of Ceriodaphnia dubia. A 14-d water-only assay was conducted to measure survival and growth of Hyalella azteca. The estimated median lethal concentration (LC50) to produce 50% mortality of the test population for the 96-h Ceriodaphnia dubia assay was 10.50 mg/L. Reproductive effects occurred at a lowest-observable-effect concentration ≥ 3.91 mg/L with a no-observable-effect concentration of 1.97 mg/L. The estimated 14-d LC50 for the Hyalella azteca assay was 1.52 mg/L No significant relationship was detected between growth and DU concentrations. Concentrations at which toxicity effects were observed in this study for both invertebrates exceeded concentrations of total uranium observed in runoff from LANL lands. Thus, it is likely that current runoff levels of uranium do not pose a threat to these types of aquatic invertebrates.

New Mexico↗

USGS2000

Observations of health indices used to monitor a tailwater trout fishery

Health of the population of rainbow trout Oncorhynchus mykiss in the San Juan River tailwater was monitored to determine the effects of potential crowding from a reduced winter flow test at Navajo Dam, northwestern New Mexico. A systematic necropsy-based health profile provided a rapid method to detect gross changes in the health of the fish population. The health assessment index (HAI) was calculated to quantify the necropsy system and allow statistical comparisons of data sets. Other suborganismic indices were selected to encompass a range of responses specific to the stress of environmental alterations: physiology assessment using total protein and percent muscle lipids, an immune assessment using serum lysozyme, and a cellular-based evaluation using histology. The HAI values showed no clear trend in fish health, although significant differences occurred among fish samples during the test. Significant declines in condition factors and percent muscle lipids throughout the study suggested a seasonal effect. Total protein and lysozyme levels were variable, showing no discernible patterns. Most histological observations appeared to be incidental during the study. Although there was no clear demonstrable effect of altered flow on fish health, this study revealed the sensitivities of various health indicators, which may help in designing future studies and supporting or interpreting results using these approaches.

New Mexico↗

USGS1997

Aromatic hydrocarbon pathology in fish following a large spill into the Nemadji River, Wisconsin, USA

On June 30, 1992, a train accident resulted in a rail car releasing 114,000 L of a complex mixture of aromatic hydrocarbons into the Nemadji River, a tributary of Lake Superior near Superior, Wisconsin (Table 1). Although the majority of the spilled material evaporated, damage to aquatic life was extensive. Several thousand fishes were killed and an inestimable number were exposed to low concentrations (< 5 mg/L) of the chemical concentrate for several weeks (Allen 1993). Fishes that survived the spill were examined within 7 days of exposure to determine the extent of injury when compared to fishes collected from the reference site. The liver, spleen, gill, and head kidney were examined for histopathology. Blood was collected to determine the severity of liver damage reflected by the presence of the serum enzymes (aspartate aminotransferase, alanine aminotransferase, and d - glutamyl transferase).

Bulletin of Environmental Contamination and Toxico↗