Evidence that variability in ambient fathead minnow short‐term chronic tests is due to pathogenic infection

165

The general status of whole effluent toxicity (WET) tests is assessed relative to their generally accepted purpose of identifying, characterizing, and eliminating toxic effects of effluents on aquatic resources. Although WET tests are useful, they are not perfect tools (no perfect tools exist). Imperfections include the innate variability of these tests, due both to biotic and anthropogenic factors; the reality of species differences both between the laboratory and the field and within the field; and differences between the laboratory and the receiving environment. Whole effluent toxicity tests may be overprotective (because of their conservative nature, the absence of environmental and ecological processes that could ameliorate exposure, and sensitivity to noncontaminant effects), underprotective (because the most sensitive species cannot be tested, multiple stresses tend to be present in the receiving environment, and failure to account for food chain effects or all possible endpoints), or offer an uncertain level of protection (intermittent doses and mixtures in the environment, adaptations, and hormesis). The implication of hormesis and inverted U‐shaped dose responses for WET testing are reviewed in particular detail. Comparisons to field conditions indicate that WET tests are not reliable predictors of effects or lack of effects in the receiving environment. Whole effluent toxicity tests are only the first stage in a risk assessment and as such identify hazard, not risk. Identification of risk requires discarding the concept of independent applicability. The appropriate use of WET tests is identified in the context of their advantages and disadvantages.

Section: Usefulnessmentioning

confidence: 99%

Whole effluent toxicity testing—usefulness, level of protection, and risk assessment

Chapman¹

2000

165

“…Survival of fathead minnows in all river water samples was significantly less in August than in May or October ( p lt; 0.05). The suggestion has been made that excessive mortality of larval minnows during ambient toxicity tests may be caused by bacteria, which cause infections and mortality during the tests [31]. The average temperature of the samples collected in August was approximately 22°C, compared to temperatures of 2 to 5°C in May and 6 to 8°C in October.…”

Section: Discussionmentioning

confidence: 99%

Geochemistry and toxicity of aluminum in the saguenay river, québec, Canada, in relation to discharges from an aluminum smelter

Campbell

Prémont

Labrie³

2000

The transformation of bauxite to alumina, the first step in the production of metallic aluminum (Al), generates Al‐rich effluents. One installation is located near Jonquière (QC, Canada), with the effluents being discharged into the Saguenay River. We undertook an integrated geochemical and ecotoxicological study to determine if these Al discharges affected the receiving water. In the spring, summer, and autumn of 1997, samples of river water were collected from stations upstream and downstream of the effluent outfalls and from a regional reference site. Samples were analyzed for Al (e.g., particulate and dissolved Al, total monomeric and organic monomeric Al, dissolved polymeric Al) and for parameters known to affect Al speciation (pH, SO4, fluoride, dissolved organic carbon). Parallel samples were used for ambient toxicity tests with fathead minnow and Ceriodaphnia dubia. Concentrations of total Al (231‐596 μg/L) and dissolved Al (112‐344 μg/L) at downstream stations were 1.1 to 3.7 times higher than those at the station immediately upstream. Average levels of total and dissolved Al exceeded the Québec provincial criterion of 87 (μ acid‐recoverable Al/L, even at sites upstream of the plant. Inorganic monomeric Al at downstream stations ranged from 22 to 88 (μ/L. With the exception of a single elevated value observed at one downstream site, inorganic monomeric Al levels were> 75 μg/L. Other studies in soft neutral‐pH waters have shown that no toxic effects occur at this concentration of inorganic monomeric Al. None of the river water samples from stations 300 m downstream from the outfalls caused significant toxicity to C. dubia or fathead minnows. We suggest that expressing guidelines as monomeric inorganic Al would offer a more useful basis for comparison with ambient Al concentrations.

“…Test interference attributed to pathogenic organisms has been reported when conducting chronic P. promelas WET tests per standard methodology [1,2]. One study [3] reported a mean survival of ≤60% in P. promelas chronic toxicity tests on ambient water. High among‐replicate variability for survival also was noted in the study.…”

Section: Introductionmentioning

confidence: 99%

“…Survival of P. promelas was substantially increased when the samples were exposed to UV light and when the larva were evaluated individually as opposed to the standard 10 per replicate. The authors concluded that their results were best explained by naturally occurring pathogens present in the ambient waters [3]. Other investigators also reported anomalous test results using P. promelas that were believed to be due to a naturally occurring biological interference characterized by filamentous growths on the larvae.…”

Section: Introductionmentioning

confidence: 99%

“…In data compiled by the Wisconsin Department of Natural Department of Natural Resources, Madison, Wisconsin, USA, 26% of chronic P. promelas WET tests ( n = 1,496 tests) showed unacceptable survival (<80%) in receiving water controls as compared with laboratory‐water controls (2.9%). Receiving water control problems noted by Kszos et al [3] and indicated by the Wisconsin data have the following characteristics in common: low survival in receiving water controls using P. promelas but not in concurrent tests using the cla‐doceran Ceriodaphnia dubia , high variability for survival among replicates (it is not uncommon for mortality in the receiving water and lower effluent dilutions to range from 0 to 100% among replicates), nonmonotonic dose response (i.e., mortality is not always highest in the highest effluent concentrations), mortality typically noted first in receiving water controls and lower effluent dilutions on day 4 of the test, and fungal growth on the head and gills of dying fish.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Sporadic mortality in chronic toxicity tests using Pimephales promelas (rafinesque): Cases of characterization and control

Downey¹,

Fleming

Guinn

et al. 2000

Abstract-In whole effluent toxicity tests, organisms are exposed to various effluent concentrations for a specific time period to estimate the potential effects of an effluent on a receiving stream. Laboratories typically have good success performing valid chronic toxicity tests. However, some difficulty in conducting valid chronic whole effluent toxicity tests with Pimephales promelas (fathead minnow) has been encountered as a result of sporadic control mortality. Some investigators report an interference that causes anomalous patterns of survival in chronic fathead minnow tests. This interference has been termed sporadic mortality phenomenon. Characteristics of sporadic mortality phenomenon include high variability among replicates, nonmonotonic dose responses, mortality beginning on or about day 4 of the test, and fungal growths often observed on the larvae. Histopathologic examinations often indicate bacterial and/or fungal infections on fish exhibiting symptoms of sporadic mortality phenomenon. The most plausible explanation of sporadic mortality phenomenon is a naturally occurring pathogen or pathogens that interfere with the test method. This interference may invalidate tests or falsely indicate toxicity. Sporadic mortality phenomenon can be reduced or eliminated by sample treatments intended to inactivate (heating, antibiotics, or ultraviolet light) or remove (filtration) pathogenic microorganisms. These methods must be used with forethought because of their potential to alter the toxicity of a sample.