Robert V. Thurston

Acute Toxicity of Ammonia and Nitrite to Cutthroat Trout Fry

Abstract The toxicity of ammonia and of nitrite was tested on cutthroat trout (Salmo clarki) fry (1-3 g) for periods up to a month in eight laboratory flow-through bioassays. Median lethal concentration (LC50) values for ammonia (mg/liter un-ionized NH3) were 0.5-0.8 for 96 hours, and 0.3-0.6 for 36 days. Nitrite LC50 values (mg/liter NO2-N) were 0.5-0.6 for 96 hours, and 0.4 for 36 days. Tissues of fish exposed for 29 days to 0.34 mg/liter un-ionized ammonia evidenced degenerative changes in gills, kidneys, and livers. Cutthroat trout fry are comparable to rainbow trout (Salmo gairdneri) fry in their susceptibility to acute toxicity from aqueous ammonia and nitrite.

Chronic Toxicity of Ammonia to Rainbow Trout

Abstract The chronic effects of ammonia to rainbow trout Salmo gairdneri were studied in a laboratory test conducted over a 5-year period. Fish were tested at five concentrations over the range 0.01–0.07 mg/liter un-ionized ammonia; the mean pH of the test water was 7.7, and the mean temperature was 9.3 C. Parental fish were exposed for 11 months, the first filial generation (F1) for 4 years, and the second filial generation (F2) for 5 months. The parental fish spawned of their own volition at all ammonia concentrations tested; baskets containing crushed rock served as the spawning substrate. The F1 fish did not spawn voluntarily at either 3 or 4 years of age, although manual spawning of 4-year-old F1 fish produced viable eggs. There was no significant correlation between ammonia concentration and numbers of egg lots spawned, total numbers of eggs produced, numbers of viable eggs, growth of progeny, or mortality of parents or progeny in any of the generations tested. Blood ammonia concentrations were meas...

Acute Toxicity of Ammonia to Rainbow Trout

Abstract The acute toxicity of ammonia to hatchery-reared rainbow trout Salmo gairdneri was measured in 86 flow-through tests, 96 hours to 35 days long. Fish ranged in age from 1-day-old fry (<0.1 g) to 4-year-old adults (2.6 kg). The 96-hour median lethal concentrations (96-hour LC50) ranged from 0.16 to 1.1 mg/liter un-ionized ammonia (11 to 48 mg/liter total ammonia-nitrogen). Susceptibility to ammonia decreased as the fish developed from sac fry to juveniles, and increased thereafter. Acute toxicity decreased as temperature increased over the range 12 to 19 C. No significant differences in toxicity were observed in tests with different ammonium salts. The LC50 values obtained for 12- and 35-day tests were not appreciably different from those for tests of shorter time periods. Received July 12, 1982 Accepted June 20, 1983

Comparative toxicity of ten organic chemicals to ten common aquatic species

Abstract The susceptibilities of 10 aquatic organisms to 10 organic chemicals were determined using lethality tests. The species included six fishes, two crustaceans, a chironomid and an amphibian. The chemicals were selected to span the toxicity range from 26 g l−1 to 1 μg l−1 and include chemicals which were lethal by four modes of toxic action. There was no consistent relative susceptibility among the test species because the sensitivity to specific modes of toxic action varied among the chemicals. Nonetheless, the toxicities of the chemicals to any given species were highly correlated to the toxicities to other species, particularly among fishes. The 96-h median lethal concentration (LC50) of the chemicals to rainbow trout (Salmo gairdneri) could be estimated from the 96-h LC50 with fathead minnows (Pimephales promelas) with a correlation coefficient greater than 0.99. Equations for estimating the lethal concentration of chemicals with each species from the 96-h LC50 for fathead minnows are presented.

Effect of fluctuating exposures on the acute toxicity of ammonia to rainbow trout (Salmo gairdneri) and cutthroat trout (S. clarki)

Abstract Acute toxicity bioassays in which fish were exposed to short-term cyclic fluctuations of ammonia were conducted on rainbow trout (Salmo gairdneri) and on cutthroat trout (S. clarki). Companion tests were also conducted in which test fish were subjected to ammonia at constant concentrations. The tests ranged in duration from 96 h to 4 weeks. Median lethal concentration (LC 50) values in terms of both average and peak concentrations of ammonia for the fluctuating concentration tests were compared with LC 50 values for the constant concentration (conventional) tests. Based on comparisons of total dose exposure, results showed that fish were more tolerant of constant concentrations of ammonia than of fluctuating concentrations. Fish subjected to fluctuating concentrations of ammonia at levels below those acutely toxic were subsequently better able to withstand exposure to higher fluctuating concentrations than fish not previously so acclimated.

Acute Toxicity of Ammonia to Fathead Minnows

Abstract The acute toxicity of ammonia to fathead minnows Pimephales promelas was measured in 35, 96-hour, flow-through tests. The fish were from both wild and hatchery-reared stocks, and ranged in size from 0.1 to 2.3 g. The 96-hour median lethal concentrations (LC50) ranged from 0.75 to 3.4 mg/liter un-ionized ammonia (34 to 108 mg/liter total ammonia-nitrogen). The toxicity of ammonia decreased as temperature increased over the range 12 to 22 C. There was no significant relationship between ammonia toxicity and dissolved oxygen concentration, over the range of the latter from 3 to 9 mg/liter. Toxicity was not related to the size or the source of test fish. Received July 12, 1982 Accepted June 20, 1983

Chronic Toxicity of Ammonia to Fathead Minnows

Abstract Chronic effects of ammonia on the fathead minnow Pimephales promelas were studied in the laboratory in two flow-through tests, each test lasting approximately 1 year. Fish were exposed to five test concentrations over the range 0.07–0.96 mg/L un-ionized ammonia (NH3); the mean pH of the test water was 8.0, and the mean temperature was 24.2°C. The tests started with 3- to 5-d-old larvae that were reared to sexual maturity; progeny of these fish (F1 were reared until they were 60 d old. The 5% probability level was chosen to indicate significance. No effects were observed on growth or survival of parental fish at 0.44 mg/L NH3, or on egg production or viability at 0.37 mg/L, but effects on all of these were observed at 0.91 mg/L. Growth and survival of F1 larvae were not affected at 0.36 mg/L NH3, which was the highest concentration at which these were tested. Egg hatching success was not affected at 0.19 mg/L NH3, but was at 0.37 mg/L. Brain lesions were common in parental fish at all stages of de...

Acute Toxicity of Thiocyanate to Trout

Abstract Acutely toxic effects of thiocyanate (SCN−) were studied in brook trout Salvelinus fontinalis and rainbow trout Salmo gairdneri exposed to concentrations of up to 518 mg/L SCN−. These fishes were capable of accumulating thiocyanate against its concentration gradient and at relatively rapid rates dependent upon the exposure SCN− concentration, fish size, and anionic composition of the exposure water. Uptake of thiocyanate was inhibited by external chloride, was accompanied by a decline in the plasma Cl− concentration, and, therefore, presumably involved substitution of SCN− for Cl− at the HCO 3−/Cl− exchange sites of the gill. Endogenous conversion of thiocyanate to cyanide was detected in exposed trout; the molar equilibrium ratio of SCN− to HCN in blood was approximately 664:1. Determinations of 96-h median lethal concentrations were of limited value in assessing the toxicity of thiocyanate because of anomalous deaths of exposed fish. These deaths were characterized by convulsions, gasping, loss...