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The fate of ring-14C labeled triphenyltin hydroxide was studied in a model ecosystem consisting of soiI, water, and channel catfish (Ictalurus punctatus). Two initial levels of triphenyltin hydroxide concentration in soiI, 1.0 and 0.010 ppm, were compared. The soiI showed a gradual loss of 20 to 30% of the total 14C residues. Only about 33% of the remaining soil residues could be extracted and almost all of these were triphenyltin hydroxide. Total residues in the water were very low. Catfish muscle and viscera accumulated 14C residues continually throughout the treatment portion of the experiment. When the catfish were transferred to untreated aquaria the total residues in the catfish remained at a steady plateau. In the catfish muscle, extractable residues accounted for less than 10% of the total residues and essentially all were triphenyltin hydroxide. Approximately 80% of the total residues in the entire model ecosystem remained bound, mainly in the soiI and catfish. Of the extractable residues from the soiI, water, and catfish muscle the greatest percentage was found to be triphenyltin hydroxide.

Lethal toxicity values (96 h LC50; mg Cd/L) for the test species were similar: Lepomis cyanellus, 11.52; Notropis lutrensis, 6.62; Pimephales promelus, 3.58. However the effects of cadmium concentration and exposure time on temperature tolerance varied between species. Neither cadmium concentration nor exposure time had a significant effect on the CTM of green sunfish. Both cadmium concentration and exposure time had a significant effect on the CTMs of red shiners and fathead minnows. By day 10 mean CTMs were 2.3 t- 4.5 C (red shiners) and 4.2 to 5.7 C (fathead minnows) lower than control CTM. These results suggest a potential problem in cadmium contaminated systems for high environmental temperatures to stress or kill fish.

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The trophic level impact of structural changes in Aufwuchs communities resulting from low levels of stress can be assessed through analyses of the nutritive value of the microfloral community in conjunction with measurements of grazer consumption rates and assimilation efficiencies. Artificial streams dosed with either intermittent chlorination (20 minute doses 3 times per day) or continuous treatments of copper (0.05 ppm) or dextrose (1 or 2 ppm) were used to obtain Aufwuchs communities from stressed environments. Aufwuchs communities were also sampled from the New River within and around a chlorinated-thermal, power plant discharge. Food quality analyses included quantification of organic carbon, protein, carbohydrate, and caloric content through gravimetric, Coomassie blue staining, anthrone staining, and wet chemical oxidation procedures, respectively. Snail (Pleuroceridae:Anculosa) utilization of Aufwuchs from the variously perturbed environments was assessed through laboratory feeding studies employing radiolabeled (sulfur-35) Aufwuchs to determine snail feeding rates and assimilation efficiencies. The heterotrophically dominated Aufwuchs communities developing under the dextrose enrichment contained more protein, carbohydrate, and calories compared to reference communities. These increases were attributed to the copious extracellular mucilage associated with the bacteria. There was no significant change in snail consumption of Aufwuchs from the dextrose enriched streams, although this community was consistently assimilated with greater efficiency relative to reference communities. When Aufwuchs developing under the chlorine or copper treatments became dominated by blue-green algae, the protein content of these communities increased as a result of the algal proteinatious sheath. Carbohydrate content was generally less than reference values for Aufwuchs developing under chlorine or copper stress. Aufwuchs from these treated streams were consumed to a less extent than reference communities and assimilated with 2 to 12% less efficiency. These results agree with literature reports that blue-green algae are a less preferred food for aquatic grazers and are assimilated with less efficiency. Aufwuchs sampled from habitats influenced by the power plant discharge were of less nutritive value compared to samples from uninfluenced stations. Snails consumed more of the reference communities and assimilated them with greater efficiency compared to Aufwuchs influenced by the power plant discharge. Both the autotrophic and heterotrophic components of the Aufwuchs community were labeled with sulfur-35, allowing sensitive measurements of the feeding parameters. Snail feeding studies demonstrated that low levels of stress may not alter grazer consumption of Aufwuchs until substantial changes in algal composition occur. Snail assimilation efficiency was generally a sensitive parameter in assessing trophic level effects of changes in Aufwuchs communities resulting from pollutant impacts. Food quality analyses provided useful information regarding changes in Aufwuchs community structure. A lack of correlation among Aufwuchs food quality parameters and snail utilization measurements reflected the opportunistic feeding strategy of the grazer. / Ph. D.

The event which prompted this study was a spill of two hundred thousand gallons of chromium-arsenic-copper solution from a holding pond into an adjacent, first-order stream on January 31, 1981. The holding pond, owned by Culpeper Wood Preservers Company of Culpeper, Virginia, was used to store wastes generated during the wood-preserving process. The stream is a tributary of Jonus Run whose waters eventually empty into the Rappahannock River. A waste-chemical landfill, located on a different first-order stream, but within the same vicinity and watershed, also threatens the water quality of the area. It is known as Lamphier landfill and industrial solvents, paint thinner's and metals were dumped there. The landfill is located on an unnamed tributary which also drains into Jonas Run. Aquatic insects and detritus were collected at all sampling sites. Crayfish and small fish were collected whenever possible. Various water quality parameters were measured at each site. Also, aquatic insect community structure and function, concentration of metals in aquatic insects and the pathway of metals through the aquatic food web was studied at each site. Generally, the concentrations of metals in waters near the spill and landfill areas were higher in chromium and arsenic then would normally be expected. Also, the concentrations of most metals, especially copper, were higher at downstream contaminated waters (rather than at upstream reference sites). The community structure and functional analysis showed that the sampling sites were influenced by various factors (agricultural runoff, road runoff, silt, heavy metal pollution, possible chemical pollution). Unfortunately, it was difficult to distinguish which effects were caused by heavy metal or chemical contaminants. Consequently, the results of the community structure and function analysis were inconclusive. Metals pollution may have contributed to the concentrations of metals found in aquatic insects collected at only one site. However the analysis of the concentration of metals found in aquatic insects from the remaining sites were inconclusive. The concentrations of metals found in detritus and crayfish suggested that metal contamination from the spill site did occur, however biomagnification did not. / M.S.

Estimates of the concentration of cadmium constituting a threat to aquatic ecosystems were derived from laboratory tests conducted at two levels of the biological hierarchy. A population level estimate was derived from single species toxicity tests and a community level estimate was derived from laboratory tests on microbial communities. Estimates were compared to each other and to an ecosystem level estimate derived from reports of ecological health and ambient cadmium levels in rivers, lakes, and streams. Estimates of permissible levels for short term exposures differed by an order of magnitude. Single species toxicity tests indicated that a level of 46.1 ug Cd/L would affect only 5% of taxa. The corresponding estimate from the community level test was 459.4 ug Cd/L. Similar estimates of permissible levels for chronic exposures were not significantly different (1.02 and 0.20 ug Cd/L, single species arid community level tests, respectively). Both of the laboratory derived estimates of permissible levels for chronic exposure fell within a rational range; the minimum level defined by median cadmium levels reported in healthy aquatic systems (0.05 ug Cd/L), and the maximum level defined by median cadmium levels reported in damaged aquatic systems (9.2 ug Cd/L). However, the community level estimate was obtained more efficiently, permitting an estimate of effects on diversity from a single test. Single species level tests, community level tests, and field studies each contributed unique information to hazard evaluation. Using information from all levels will strengthen predictions. / Master of Science