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Nancy C. Nelson

Publications and source records attributed to Nancy C. Nelson.

5 recordsLinked to original sources
USGS1979

Potentials and limits for the use of ozone as a fish disease control agent

Ozone and chlorine inactivation curves were determined in three types of freshwater at 20 C for the destruction of the fish pathogens Aeromonas salmonicida the etiologic agent of furunculosis, and Yersinia ruckeri the enteric redmouth bacterium (ERM). Ozone and chlorine inactivation curves were also obtained in the same water types at 10 C for the fish pathogenic viruses infectious hematopoietic necrosis (IHNV), and infectious pancreatic necrosis (IPNV). Acute toxicity tests using the rainbow trout as a representative salmonid revealed that ozone was highly toxic at the dose levels used. Partial chronic (3. mo.) testing revealed that ozone exposure at 2 μg/L causes only minimal physiological changes, none of which would be expected to compromise biological function.

Ozone: Science and Engineering↗
USGS1979

Physiological and biochemical aspects of ozone toxicity to rainbow trout ( Salmo gairdneri )

An acute toxicity curve for dissolved ozone (O 3 ) in soft water at 10 °C, using 10–13-cm rainbow trout ( Salmo gairdneri ) as the test species was calculated. The 96-h LC50 (95%, confidence interval) was 9.3 (8.1–10.6) μg/L. The lethal threshold level was about 8 μg/L mandating that a conservative margin of safety be used if ozone is employed as a fish disease control agent. Death apparently results from massive destruction of the gill lamellar epithelium together with a severe hydromineral imbalance. In partial chronic (3-mo) testing, 2 μg/L caused no significant biological damage while 5 μg/L caused some gill pathological changes and reduced feeding behavior. Accordingly, 2 μg/L is suggested as a provisional maximum safe exposure level, pending completion of life cycle studies. Thus, if ozone-treated water is discharged into the environment, dissolved O 3 should be reduced to at least the 2 μg/L level to minimize adverse impacts on salmonids in receiving waters.

Journal of the Fisheries Research Board of Canada↗
USGS1978

Survival of the salmonid viruses infectious hematopoietic necrosis (IHNV) and infectious pancreatic necrosis (IPNV) in ozonated, chlorinated, and Untreated waters

Ozone and chlorine inactivation curves were determined in three water types at 10 °C for the fish pathogenic viruses infectious hematopoietic necrosis (IHNV) and infectious pancreatic necrosis (IPNV). In phosphate-buffered, distilled water (PBDW) an ozone dose of 0.01 mg/L for 30 or 60 s inactivated IHNV or IPNV, respectively, suspended at a tissue culture 50% infective dose (TCID50) of 10 4 –10 5 /mL. In hard (120 mg/L as CaCO 3 ) and soft water (30 mg/L) lake waters, an ozone application rate of 70 mg∙h −1 ∙L −1 for 10 min destroyed IHNV. IPNV inactivation in hard water required 90 mg∙O 3 ∙h −1 ∙L −1 for 10 min but only a 30-s contact time in soft water. The IPNV was also somewhat more resistant to chlorine. In PBDW, a residual of 0.1 mg/L with contact times of 30 and 60 s, respectively, destroyed IHNV and IPNV. In soft lake water IHNV was destroyed within 5 min at 0.5 mg/L, while in hard water a 10-min contact time was required. For IPNV disinfection in soft water, 0.2 mg/L for 10 min was sufficient but this chlorine residual had essentially no effect on IPNV in hard water. Increasing this dose to 0.7 mg/L destroyed IPNV in hard water within 2 min. In untreated waters, IPNV was stable for at least 8 wk in either distilled, soft, or hard lake waters. However, IHNV survived only about 2 wk in distilled and 7 wk in the soft or hard lake waters. We suggest the serious consideration of ozone as a fish disease control agent. Key words : ozone, chlorine disinfection, fish pathogens, viruses

Journal of the Fisheries Research Board of Canada↗
USGS1977

Survival of two bacterial fish pathogens (Aeromonas salmonicida and the Enteric Redmouth Bacterium) in ozonated, chlorinated, and untreated waters

Ozone and chlorine inactivation curves were determined in three water types at 20 °C for the destruction of the fish pathogens Aeromonas salmonicida , the etiologic agent of furunculosis, and the enteric redmouth bacterium (ERM). In phosphate-buffered distilled water, 0.01 mg/ℓ ozone inactivated 10 3 cells/ml of ERM and A . salmonicida in 1/2 and 10 min, respectively. Chlorine at this concentration had little effect on either pathogen and a residual of at least 0.05 mg/ℓ was needed to achieve a complete kill within a 10-min contact time. In soft lake water (30 mg/ℓ as CaCO 3 ) a chlorine residual of 0.1 mg/ℓ rapidly inactivated A . salmonicida and ERM but in hard water (120 mg/ℓ) A . salmonicida was more resistant and 0.2 mg/ℓ chlorine was required. Ozonation of the two lake waters at 90 mg O 3 ∙h −1 ∙ℓ −1 (equivalent to a 0.01 mg/ℓ residual in ozone demand-free water) was required to destroy both pathogens within 10 min.In untreated soft lake water 10 3 cells/ml of A . salmonicida survived only 2 days, while the ERM bacterium (10 3 cells/ml) survived even after 20 day s in soft and hard untreated lake waters.

Journal of the Fisheries Research Board of Canada↗
USGS1975

Statistical methods for estimating normal blood chemistry ranges and variance in rainbow trout (Salmo gairdneri), Shasta Strain

Gaussian and nonparametric (percentile estimate and tolerance interval) statistical methods were used to estimate normal ranges for blood chemistry (bicarbonate, bilirubin, calcium, hematocrit, hemoglobin, magnesium, mean cell hemoglobin concentration, osmolality, inorganic phosphorus, and pH for juvenile rainbow ( Salmo gairdneri , Shasta strain) trout held under defined environmental conditions. The percentile estimate and Gaussian methods gave similar normal ranges, whereas the tolerance interval method gave consistently wider ranges for all blood variables except hemoglobin. If the underlying frequency distribution is unknown, the percentile estimate procedure would be the method of choice.

Journal of the Fisheries Research Board of Canada↗