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<p>²²⁶Ra is a radionuclide of much concern since it poses a high risk of radio-toxicity when ingested and is well known for its invariably long half life of 1600 years. As such ²²⁶Ra concentrations were measured in whole body tissue of fathead minnows (Pimephales promelas) in an experimental set up. Fathead minnows obtained were about two months old and fed on a Radium-226 spiked diet until 115 days. A simple and direct method to determine ²²⁶Ra ingested by fish using a homogeneous liquid scintillation counting was developed. The study consisted of three groups; a sham, Radium treatment and acid treatment. Fathead minnows were sampled 75 and 115 days after feeding, and the following end points; mass (w/w), length, specific growth rate, condition factor and radionuclide measurements obtained. Mean end point results were (0.24 ± 0.03 g), (2.78 ± 0.1 cm), (1.75 ± 0.13 % day^-1), (1.10 ± 0.06 g cm^-3) and (577.06 ± 572.13 mBq g^-1) respectively. Also mean total ²²⁶Ra level was calculated as (1911.43 ± 868.64 mBq g^-1) while the activity in sham and acid treatment resulted in levels below the Minimum Detectable Activity of 7.46 mBq g^-1. The mean rate of ²²⁶Ra accumulation, known as the concentration factor, by the fathead minnows was determined as 0.35 ± 0.19. Assuming that the ²²⁶Ra Isotope is evenly distributed in the fish whole body, the derived dose rate was found to be 5.26 μGy h^-1.</p> / Master of Science (MSc)

In this research a test system was developed that is designed as a tool to evaluate the potential hazard of chemicals to aquatic ecosystems. The system developed is a linear three-trophic level food chain consisting of an alga (Ch/ore/la vulgaris), rotifer (Brachionus calyciflorus), and fish (Pimephales promelas). The chemostat design used for the lower two trophic levels was crucial in being able to supply the top trophic level with sufficient food on a continuous basis. The system was initially evaluated using copper (Cu) and selenium (Se) as toxicants. In the copper experiments, results of a 7 day three-trophic level toxicity test were compared with a series of single species tests. The LOEC was 31.5 µg/L based on a temporary impairment of the algal population growth, with a corresponding NOEC of 16.2 µg/L. The algal population at all initially impaired treatment levels demonstrated recovery to control levels by the end of the test. Single species tests with the same species showed impairment at treatment concentrations lower than the corresponding value from the three-trophic level test. The difference in sensitivity is attributable to the fact that most of the Cu in the single species tests was in the dissolved form (approximately 80 %), whereas in the trophic level test most of the Cu was not ( < 15 % dissolved Cu). The three-trophic level Se experiment lasted for 25 days, with both short-term and long-term impacts evident. At the algal trophic level, growth was not impaired on a daily basis at any of the exposure levels (110.3, 207.7, and 396.1 µg/L Se). However, algal densities were slightly reduced at the 207. 7 and 396.1 µg Sell treatments, although not significantly different when the data was pooled across days. Rotifer populations were impaired at these same levels by day 4, and succumbed to the Se by day 7. Fathead minnow growth was also impaired at these two concentrations by day 7. In addition, sub lethal impairment of rotifer and fish growth was evident at the 110.3 pg/L level after day 20 indicating a more subtle trophic impact. Bioconcentration factors ranged between 100 and 1000 µg/L and were found to be dependent on the species, treatment, and day. / Ph. D.

Chronic toxicity of zinc to Pimephales promelas was estimated by conducting replicate static and static-renewal short-term embryo-larval tests and static-renewal seven-day larval tests. The two test methods were highly reproducible. Daily renewal of test solutions had little effect on the toxicity of zinc, however, the stage of development at which exposure was initiated affected the sensitivity of the toxic endpoints measured. The most sensitive and reproducible endpoint in the embryo-larval tests was survival of viable (non-deformed) larvae and in the seven-day larval test was growth of the larvae, which was slightly more sensitive than the embryo-larval test endpoint. The estimated MATC of 0.18 and 0.15 mg/L mean total and mean soluble zinc, respectively, compared well with published results. Because of its advantages and similar sensitivity, the short-term embryo-larval test was recommended for estimating chronic toxicity.

Vitellogenin in Pimephales promelas was used to assess estrogenicity of a local municipal effluent. Vitellogenin induction in male P. promelas increased in frequency and magnitude with increased exposure duration and was greater ("=0.05) than controls after 2 and 3 weeks of exposure. The level of vitellogenesis induced by effluent exposure was high compared to similar studies. A spring season evaluation followed. Biomarkers in P. promelas were used to assess the efficacy of a treatment wetland to remove toxicity and estrogenicity in final treated wastewater effluent. Comparisons were made with an effluent dominated stream and laboratory controls. Vitellogenin, GSIs (gonado-somatic indices), HSIs (hepato-somatic indices) and secondary sexual characteristics were biomarkers used in P. promelas models to assess aqueous estrogenicity. Biological indicators used to assess general fish health included hematocrit and condition factors. The estrogenic nature of the effluent was screened, concurrent with fish exposure, with GC/MS analysis for target estrogenic compounds including: 17-b estradiol, estrone, ethynylestradiol, Bisphenol A, nonylphenolic compounds, phthalates, and DDT. Plasma vitellogenin measured in P. promelas was significantly elevated (p < 0.0001) at the inflow site of the wetland and stream sites. GSIs for these exposures were less (a=0.001) at the wetland inflow site. At wetland sites closest to the inflow, secondary sexual charateristics, tubercle numbers and fat pad thickness, were less (a=0.0001). Hematocrit and condition factors were less (a=0.001) at sites closer to the wetland inflow. Seasonal variation was examined by repeating the effluent characterization in summer. Additionally, summer testing included exposure to an effluent dilution series. Fish condition heavily influenced interpretation of the results. Pre-acclimation exposure to spawning stresses may have altered many of the biological markers measured. Results are discussed relative to fish health and pre-exposure environment. Toxicity assessed with P. promelas biomarkers was compared with Ceriodaphnia dubia and Vibrio fischeri toxicty tests on this effluent. Biomarkers of fish health were somewhat less sensitive than C. dubia test endpoints, but more sensitive than V. fisheri.