5th Annual Texas A&M University System Pathways to the Doctorate Student Research Symposium
November 2-3, 2007
Hosted by Tarleton State University

Abstracts of Student Presentations: Environmental Science

WILLIAM HATLER. "Water Use by Saltcedar (Temarix spp.) and Water Savings Due to Control"  *First place award - Environmental Science Masters Degree student*
Faculty Mentor: Dr. Charles Hart, Dr. Carol Thompson

Saltcedar (Tamarix spp.) is a phreatophyte that has invaded many riparian zones and subirrigated pastures in the western United States.  A native of Eurasia, it was introduced into the United States in the early 19th century for use as an ornamental, and is now estimated to cover or have spread over 600, 000 ha of waterways.  Water use by saltcedar through evapotranspiration is a significant concern in the arid to semi-arid regions it favors. Lowered water tables and decreased stream flow are usually noted in areas of saltcedar invasion.  Ground water use by phreatophytes can be estimated by analyzing diurnal groundwater fluctuations in screened wells located within a stand of the target species (White 1932).  This study uses the White method to estimate groundwater use by saltcedar at a study site on the Pecos River near Mentone, TX.  It is a paired plot study, comparing water use on one mile of river with live, untreated saltcedar to an adjacent mile of the river with dead saltcedar that has been sprayed with Arsenal (Imazypyr).  Hays (2003) reported water use at this site for 2001 (pre-treatment), and this study is a continuance and expansion.  This study reports water use for 2001-2006, and estimates potential water savings from saltcedar control.  Preliminary analyses indicate stand-level calculated water loss in 2001 (pre-treatment) ranged from 1.02 m at Site A to 1.31 m at Site B.  Post-treatment water loss at Site A (treated) dropped to 0.19 m in 2002, or 18% of the 2001 calculation, and Site B (untreated) also dropped to 0.40 m, or 30% of 2001.  As vegetation returned to Site A in the form of grasses and saltcedar re-growth, water loss estimates climbed to 0.50 m in 2006 compared with 0.67 m at Site B, but neither site returns to pre-treatment water loss levels throughout the study.  Potential water savings due to saltcedar control are conservatively estimated at 0.06 to 0.12 hectare meters.  Data analyses are ongoing.


MELINA LOPEZ. "An Assessment of Heavy Metal Pollution in Sea Turtles in the Eastern Pacific"
Faculty Mentor: Dr. Carol Thompson

The health of the world’s oceans is a subject of great environmental concern. To assess the impact of these heavy metals on the oceanic environment, direct measurements on ocean water could be performed at specific sites and depths. Single samples of oceanic water will never afford a true picture of water quality because of the temporal fluctuations in concentrations. Instead, assessments of oceanic heavy metal pollution should be carried out through the examination of the presence of metals in affected individuals and species.

Heavy metals can cause detrimental effects to many sensitive marine organisms. Among the species most affected, are the long lived, highly migratory marine turtles who for this reason serve as excellent bioindicators of the general marine ecosystem health. The endangered status of these species has often limited their utilization in research studies to specimens accidentally captured in commercial fishing ventures. The recent discovery that the yolks of sea turtle eggs accurately represent the mother’s level of heavy metal contamination, however, has eliminated the need to kill sexually mature individuals to study heavy metal contamination in the marine environment. Five of the seven existing species are known to inhabit in Las Perlas Archipelago, Panama, making this site an exceptional location for the study of heavy metal pollution variation among marine turtle species.

This study is being designed to answer the following questions. First, is there significant heavy metal concentration variability between yolks of clutchmates collected from the Las Perlas Archipelago’s nesting populations? Second, are heavy metal concentrations variable among individuals of the same species? Third, do heavy metal concentrations vary significantly by species? And finally, if variability does occur between species, is this variability due to factors such as trophic levels or diet?

In this study, collection of the eggs will be done during turtle nesting season which typically occurs mid summer and early fall. These turtles lay anywhere from 100 to 200 eggs per clutch of which I will be collecting 10 eggs. One collection has already occurred in October 2006 for preliminary results and a refinement of our analytical technique. Extraction of egg yolks and lyophilization of samples will take place at the Smithsonian Tropical Research Institute and samples will be sent to Tarleton University, Stephenville, TX. Metals will be analyzed using ICP-AES following EPA method # 200.7.  An appropriate multi-element standard will be prepared for calibration curves. ICP-AES samples will be analyzed for Pb, Fe, Ni, Cu, Zn, Mn, Cd. Mercury analysis will be performed in a direct mercury analyzer DMA-80 at Texas Christian University. Appropriate QA/QC procedures will be followed throughout the project and will include reference and duplicate analysis every 10 samples. Knowledge gained from the data collected during this study will provide important clues to the health of turtles nesting in Las Perlas and the Eastern Pacific as a whole.


BONNIE TERRY. "Probability Sampling Methods of Soil Phosphorus at Erath County Dairies"
Faculty Mentor: Dr. Keith Emmert

Extensive research in the area of nutrient contamination of the Bosque River and other area waterways has been motivated by environmental concerns associated with downstream communities.  Many of these research projects require the extraction and analysis of soil samples from area dairies which is a time and cost intensive procedure.  This thesis project will employ probability sampling methods to predict phosphorous levels and identify areas which exceed the environmental threshold for Texas to a desired degree of confidence.
    We begin with a population of data obtained from soil analysis of samples taken from three Erath County Dairies.  These dairies were divided into 0.1 ha. squares and a sample was extracted from each point.  Four samples were then composed into one sample to represent an area of 0.4 ha.  Each dairy provided a population of almost 300 data points.  The first task at hand, which is the emphasis of this symposium, is to identify those soil properties which are the most meaningful when predicting phosphorous levels.  A multiple linear regression model applied to the data population identifies those soil components which appear to be of the greatest importance for our predictions.  This data analysis will lead us into further investigations of probability sampling methods which could increase the efficiency of soil research by decreasing the number of needed samples for accurate predictions.