Geology topics

M. C. Doyle

Publications and source records attributed to M. C. Doyle.

3 recordsLinked to original sources

USGS2007

Multiple stressors in amphibian communities: Effects of chemical contamination, bullfrogs, and fish

A leading hypothesis of amphibian population declines is that combinations of multiple stressors contribute to declines. We examined the role that chemical contamination, competition, and predation play singly and in combination in aquatic amphibian communities. We exposed larvae of American toads (Bufo americanus), southern leopard frogs (Rana sphenocephala), and spotted salamanders (Ambystoma maculatum) to overwintered bullfrog tadpoles (R. catesbeiana), bluegill sunfish (Lepomis macrochirus), the insecticide carbaryl, and ammonium nitrate fertilizer in 1000-L mesocosms. Most significantly, our study demonstrated that the presence of multiple factors reduced survival of B. americanus and A. maculatum and lengthened larval periods of R. sphenocephala. The presence of bluegill had the largest impact on the community; it eliminated B. americanus and A. maculatum and reduced the abundance of R. sphenocephala. Chemical contaminants had the second strongest effect on the community with the insecticide, reducing A. maculatum abundance by 50% and increasing the mass of anurans (frogs and toads) at metamorphosis; the fertilizer positively influenced time and mass at metamorphosis for both anurans and A. maculatum. Presence of overwintered bullfrogs reduced mass and increased time to metamorphosis of anurans. While both bluegill and overwintered bullfrog tadpoles had negative effects on the amphibian community, they performed better in the presence of one another and in contaminated habitats. Our results indicate that predicting deleterious combinations from single-factor effects may not be straightforward. Our research supports the hypothesis that combinations of factors can negatively impact some amphibian species and could contribute to population declines. ?? 2007 by the Ecological Society of America.

Ecological Applications↗

USGS1997

Sediment oxygen demand in the Tualatin River basin, Oregon, 1992-96

Sediment oxygen demand (SOD) rates were measured by U.S. Geological Survey (USGS) personnel at 20 stream sites in the Tualatin River Basin from 1992 through 1996 as part of an investigation into the sources and sinks of dissolved oxygen in the Tualatin River. During the low-flow summer periods of 1992 through 1994, 97 measurements were collected at 9 sites on the main stem of the river between river miles (RMs) 5.5 and 43.2. During the low-flow summer periods of 1995 and 1996, 28 measurements of SOD were collected at 11 sites on 8 tributaries of the Tualatin River. All SOD rates were measured with in-situ benthic chambers designed to monitor the loss of dissolved oxygen in a known volume of water circulating above a known area of minimally disturbed stream sediment. For main-stem Tualatin River sites, the observed SOD rate ranged from 0.6 to 4.4 grams of oxygen per square meter per day (g/m 2 d) with a median of 2.3 g/m 2 d. In the tributaries, the measured SOD rate ranged from 0.2 to 10.9 with a median of 3.6 g/m 2 d. These rates are in the range of those reported for other sites in Oregon and across the United States. Most of the variation in the measured SOD rates was likely due to heterogeneities in the bed sediment. Statistical comparisons show that the rates measured at the tributary sites are significantly larger than those measured in the main stem. Within the main stem, the rates measured at sites in the meander reach of the river were not significantly different from those measured in the reservoir reach. Similarly, no difference was found when the sites affected by the cycle of phytoplankton bloom and die-off were compared to those unaffected by phytoplankton. Only one site on the main stem, RM 5.5, was found to have an SOD rate that was significantly higher than that found at the other main-stem sites. Algal detritus may contribute to the elevated rate at that site, but other factors such as the rate of sediment accumulation could also account for the increased rate.

Water-Resources Investigations Report↗

USGS1996

Water-quality, streamflow, and meteorological data for the Tualatin River Basin, Oregon, 1991-93

Surface-water-quality data, ground-water-quality data, streamflow data, field measurements, aquatic-biology data, meteorological data, and quality-assurance data were collected in the Tualatin River Basin from 1991 to 1993 by the U.S. Geological Survey (USGS) and the Unified Sewerage Agency of Washington County, Oregon (USA). The data from that study, which are part of this report, are presented in American Standard Code for Information Interchange (ASCII) format in subject-specific data files on a Compact Disk-Read Only Memory (CD-ROM). The text of this report describes the objectives of the study, the location of sampling sites, sample-collection and processing techniques, equipment used, laboratory analytical methods, and quality-assurance procedures. The data files on CD-ROM contain the analytical results of water samples collected in the Tualatin River Basin, streamflow measurements of the main-stem Tualatin River and its major tributaries, flow data from the USA wastewater-treatment plants, flow data from stations that divert water from the main-stem Tualatin River, aquatic-biology data, and meteorological data from the Tualatin Valley Irrigation District (TVID) Agrimet Weather Station located in Verboort, Oregon. Specific information regarding the contents of each data file is given in the text. The data files use a series of letter codes that distinguish each line of data. These codes are defined in data tables accompanying the text. Presenting data on CD-ROM offers several advantages: (1) the data can be accessed easily and manipulated by computers, (2) the data can be distributed readily over computer networks, and (3) the data may be more easily transported and stored than a large printed report. These data have been used by the USGS to (1) identify the sources, transport, and fate of nutrients in the Tualatin River Basin, (2) quantify relations among nutrient loads, algal growth, low dissolved-oxygen concentrations, and high pH, and (3) develop and calibrate a water- quality model that allows managers to test options for alleviating water-quality problems.

Oregon↗