The City of Denton Pecan Creek Wastewater Treatment Facility has periodically failed effluent toxicity testing. A Toxicity Identification Evaluation has determined that Diazinon in the effluent is contributing to the observed toxicity. Chlorpyrifos is also implicated as a factor. The City of Denton constructed a half acre experimental wetland to remove Diazinon related toxicity. Results from spiking and microcosm experiments indicate that the wetland can reduce the Diazinon.

In the southwestern United States there is a delicate balance between the existing grasslands and the rodent fauna. The purpose of this investigation was to determine the influence of secondary succession of native grasslands upon the ecology and distribution of small rodents. Two methods of determining the rodent species were plot quadrates and trap lines using Sherman live traps.

Two years before impoundment, the trophic status of Lake Ray Roberts was predicted by applying the total phosphorus input into the Organization for Economic Cooperation and Development (OECD) eutrophication model. Predicted mean summer epilimnetic (MSE) chlorophyll a of Elm Fork arm, Isle duBois arm and Main Body were in the eutrophic category of the OECD model. Observed MSE chlorophyll a two years after impoundment of Elm Fork arm, Isle duBois and Main Body had not reached their predicted means and were at the mesotrophic-eutrophic boundary of the OECD model. Six years after impoundment, observed MSE chlorophyll a for Main Body, was closer to its predicted mean and in the eutrophic category of the OECD model. Six years after impoundment, Elm Fork arm was the most productive area of Lake Ray Roberts. Observed means of chlorophyll a, total phosphates, suspended solids and turbidity were often highest in the Elm Fork arm. Wastewater effluent from Gainesville and Valley View, TX, had an impact on productivity in Elm Fork arm.

The problem of using a state adopted textbook written to apply to a large body of students with varying interests and needs was overcome by using a detailed syllabus that arranged course content in a meaningful sequence that appealed to student interest. The outlined syllabus prepared a two semester life science curriculum to be used by the teacher to guide lesson planning. Both semesters were divided into three units each. Materials included in the syllabus were given to actual student groups in real classroom settings. Since hands on learning was an important part of classroom instruction, two laboratory sections were included in the appendices to be used with the syllabus.

A large, multi-basin, reservoir (Garza-Little Elm Reservoir) in north central Texas was studied to determine the relative effects of various parameters on primary productivity. The basins were impounded several years apart,thus allowing the influence of age on water chemistry and biota to be considered. Another principal influence on water quality was secondary sewage effluent that entered one basin from a nearby source.

The underwater optical climate of Lake Texoma was measured at eleven fixed stations from August 1996 to August 1997. Secchi transparency and submarine photometry characterized seasonal and spatial values of secchi depth (SD), vertical attenuation coefficient (η''), and depth of euphotic zone (Zeu). Indices of Zeu:SD and η'' × SD were compared with universally applied values derived from inland and coastal waters. Turbidity explained 76% of the variation (p = 0.0001) of η'' among water quality parameters, including chlorophyll-α. Using a spectroradiometer, spectral signatures of chlorophyll-α and turbidity were located. Stations with low turbidity exhibited a distinct green reflectance peak around 590-610 nanometers, indicating presence of chlorophyll-α. Stations with high turbidity exhibited a reflectance peak shift towards the red spectrum, making it difficult to detect the chlorophyll signature. Derivative analysis of the reflectance signal at 590-610, and 720-780 nanometers allowed discrimination of this chlorophyll signature from those of turbidity (0.66 ≤ r^2 ≤ 0.99).

A toxicological study was initiated because of concerns about allegations that the Texas Water Commission that effluent from the Dallas Central Wastewater Treatment Plant, which discharges into the Trinity River, was affecting downstream water quality. Monthly, flow-weighted composite effluent samples were collected. Grab samples were also collected upstream and downstream from the effluent from April 1989 to August 1991. Toxicity tests were conducted on these samples using Ceriodaphnia dubia as the test organism. Samples were collected four times during this study in which rainfall occurred prior to sampling. In every instance, this "first flush" of the watershed during a rising hydrograph was toxic to C. dubia upstream. Analyzing toxicity by season resulted in a statistically significantly lower neonate production in the effluent than in the river samples during the months of June, July, and August. This impact on neonate production was suspected of being caused by organic pesticides which are used for insect control on lawns. The effluent was never acutely toxic to C. dubia. Primarily, toxic occurrences in either the effluent or the river samples were primarily of a chronic nature. Overall, survival of C. dubia was affected more frequently at the upstream site than in the effluent or …

The life history and case-building behavior of Molanna tryphena from two spring-fed tributaries in East Texas were studied from January 1997 to May 1998.

A study of the humus content and the water content of San Saba clay and Denton clay. Studies show that the physical properties of soil are conducive to moisture retention and the availability of moisture to plants.

Baroreflex function and cardiovascular responses to lower body negative pressure during selective autonomic blockade were evaluated in endurance exercise trained (ET) and untrained (UT) men. Baroreflex function was evaluated using a progressive intravenous infusion of phenylephrine HCL (PE) to a maximum of 0.12 mg/min. Heart rate, arterial blood pressure, cardiac output and forearm blood flow were measured at each infusion rate of PE. The reduction in forearm blood flow and concomitant rise in forearm vascular resistance was the same for each subject group. However, the heart rate decreases per unit increase of systolic or mean blood pressure were significantly (P<.05) less in the ET subjects (0.91 ± 0.30 versus 1.62 ± 0.28 for UT). During progressive lower body negative pressure with no drug intervention, the ET subjects had a significantly (P<.05) greater fall in systolic blood pressure (33.8 ± 4.8 torr versus 16.7 ± 3.9 torr). However, the change in forearm blood flow or resistance was not significantly different between groups. Blockade of parasympathetic receptors with atropine (0.04 mg/kg) eliminated the differences in response to lower body negative pressure. Blockade of cardiac sympathetic receptors with metoprolol (0.02 mg/kg) did not affect the differences observed during the control test. It was …

A population of the red-eared slider, Pseudemys scripta, in north central Texas was studied from 1975 to 1980. A life history energy budget was developed for a typical individual in the population and the population dynamics were estimated. A growth model relating growth rate to mean plastron length (PL) was developed from recapture data and used to 1) establish age classes and 2) age individuals. Growth rate was highly variable in both sexes. Females grew more rapidly than males and attained a larger maximum size (230 mm and 195 mm PL in females and males respectively). Females reached sexual maturity in their ninth year at a PL of 185-190 mm. Males matured in their sixth year at a PL of 90-100 mm. Females produced three clutches annually; clutch size ranged from 7 to 14 (X=10.3; N=20). Ova were enlarged in the early spring and ovulation began in late April and early May. Egg laying occurred from mid- May through June. Both egg size and clutch size increased with female body size. Lipid levels were variable within and among seasons. No annual lipid cycling pattern was evident in females. The proportion of assimilated energy devoted to reproduction, a measure of reproductive …

Four species of net-spinning caddisflies, Hydropsyche simulans Ross, Cheumatopsyche lasia Ross, Cheumatopsyche campyla Ross and Chimarra obscura (Walker) are common in the regulated portions of the Brazos River. Hydropsyche simulans spun capture nets with the largest meshdimensions; the two Cheumatopsyche species' nets had the next largest meshes, and Chimarra obscura spun nets with the smallest dimensions. Cheumatopsyche lasia and C. campyla constructed nets with similar sized meshes. The number of individuals m~2 and standing crop biomass were not significantly different among low, medium, and high velocities. Early hydropsychid instars fed on detritus while later instar H. simulans and C. campyla had larger proportions of animal material. Guts of later instar C. lasia individuals had a greater percentage of algae and diatoms.

This thesis presents the results of a three year study devoted to discovering the life and phenomena found in Lake Worth near Fort Worth, Texas.

Presence-absence data for amphibians, chelonians, saurians, ophidians, and the terrestrial and aquatic ecological guilds of reptilians were analyzed using multivariate analyses. Geographically consistant distributional patterns were found for all faunal groupings. The correspondence between analyses of the different taxa and guilds was not perfect, but similarities were found. All analyses agreed on the presence of a distinctive region in east Texas. Most analyses also agreed on the presence of distinctive regions in south Texas, the Trans-Pecos, the Edwards Plateau, and north-west Texas. There is strong correspondence between interpretations of the analyses based on the amphibian, saurian, ophidian, and terrestrial reptilian distributions, and the biotic provinces produced by earlier, subjective analyses. The Edwards Plateau and a region on the western periphery of east Texas were found to be transitional between other, more faunally distinctive areas for most fauna! groups. Detailed examination of these regions suggested they are best described as clinal in nature. The environmental variables which were most effective in explaining patterns in the distribution of the various taxa and guilds were related to precipitation. However, variations in temperature and physiography were also important predictors of distribution for several of the groups. The distributions of soil and vegetation associations were …

Between February 1986 and October 1988, 863 amphibians and reptiles were collected in northcentral Texas and examined for coccidial parasites. Thirteen percent of amphibians <26% salamanders, 11% frogs and toads) and 28% of reptiles (54% turtles, 25% snakes) harbored 20 previously described and 16 new species of coccidia; overall prevalence of infection was 176/863 < 20%). Sixteen Ambvstoma texanum were infected with Eimeria ambystomae which represents new host and geographic locality records for the coccidium. Forty anurans were found to be passing coccidia, including Pseudacris streckeri. Bufo valliceos and Gastrophryne olivacea. Four new species of coccidia were described from anurans and include Eimeria flexuosa. E. streckeri. Isospora dellcatus and I_. fraaosum. However, oocysts found in B. v.. valliceps were determined experimentally to represent pseudoparasites. Sixty-eight turtles were infected with coccidia, including Chelvdra serpentina, Kinoeternon flavescens. Pseudemvs texana. Terrapeng ornata and Trachemvs scripta eleoans. Fourteen eimerians (5 of which are described as new species) were found in turtles. The new species from turtles include Eimeria cooteri, E. ornata, E. Btvlosa. E. texana and E. trachemvdis. Interestingly, all 96 lizards examined were negative for coccidia. Fifty-three snakes including 11 colubrids and 1 viperld harbored coccidia of the genera Caryospora. Cryptosporidium. Eimeria and …

Sediments in the Trinity River were chemically, physically and biologically characterized and assessed for toxicity. Laboratory bioassays were conducted to identify sediments which induced toxic responses in test organisms and to document these responses through time. Metal and organic contaminant concentrations in bottom sediments were measured. Relationships between these concentrations and biological responses observed in laboratory bioassays were determined. Toxicity identification / reduction methods were used to characterize sediment toxicants. Sediment oxygen demand was also measured in resuspended and undisturbed bottom sediments through time. The Background Sediment Chemistry Approach and the Sediment Bioassay Approach were used to assess sediment quality. Sediment toxicity was observed in whole sediment bioassays using Chironomus tentans as the test species. A relationship between sediment contaminant concentration and toxicity was observed in approximately sixty percent of the sediments. Oxygen demand of resuspended sediments was elevated in sediments at two locations on the river. Oxygen demand of undisturbed sediments was elevated at one location on the river. Characterization of sediment toxicants was conducted using EDTA, pH, and carbon treatments and manipulations of the sediments. Aeration tests were also used to evaluate the contribution of volatile organic contaminants to observed toxicity.

This study is an attempt to determine the relationship between humus and the water found in it and how both effect soil in Denton county, Texas.

This thesis presents the results of an examination conducted to determine the status of mourning doves in Throckmorton County, Texas.

This thesis explores the feeding habits of sunfish and bluegill in Texas lakes. Data gathered for this study is aimed to aid conservation of these pan fish by making a contribution toward a greater life history understanding of each species.

This study used a geographic information system (GIS) and an empirical pollutant load model to estimate average annual pollutant loads contained in storm water charges from the City of Carrollton, Texas. The Geographic Resource Analyses Support System (GRASS) was used to create a number of spatial data layers as input variables to a model that estimates loads in Kilograms/Hectare/Year, and Kilogram/Basin/Year. Average annual pollutant loads for twelve pollutants were derived from average annual rainfall/runoff volumes, coupled with Local Dallas/Fort Worth Metroplex storm water Event Mean Concentrations.

This thesis describes the vertical distribution, quality, and quantity of the fauna found at the bottom of Lake Worth in Texas.

The average level of sexual knowledge and attitudes about sexual situations among surveyed high school seniors in Gregg County, Texas are presented in this thesis.

This thesis resulted from an examination of Lake Worth plankton in comparison to plankton found in similar bodies of water throughout the United States.

The objectives of this project were to measure changes in frequency of occurrence of submerged macrophytes over the first two growing seasons following stocking with triploid grass carp at two fish per acre and to measure differences in macrophyte biomass between areas excluded from herbivory and adjacent control sites after 16 months following establishment of exclosures. The project also seeks to measure concentrations of fluridone following the herbicide treatment, and to compare two methods of aquatic vegetation sampling.