Aquatic tests

Moore, M.T., D.B. Huggett, W.B. Gillespie Jr., J.H. Rodgers Jr., and C.M. Cooper. 1998. Comparative toxicity of chlordane, chlorpyrifos, and aldicarb to four aquatic testing organisms. Arch. Environ. Contam. Toxicol. 34 152-157. 

Invertebrate species have been widely used in toxicity studies of pesticides [61]. Zooplankton play a key role in the food chain because they occupy a central position. Therefore, their responses to natural and anthropogenic stresses are intimately linked with other food predator organisms. The most widely accepted bioassays employ species such as Ceriodaphnia dubia, Daphnia magna, Artemia salina, or Thamnocephalus platyurus [62-64]. D. magna has been used for many years as a standard aquatic test species and formally endorsed by the major international organizations such as the EEC, OECD, and ASTM [65-67]. Its choice is mainly because it represents the zooplankton community and is a species of worldwide occurrence. In addition, it has a greater sensitivity to toxicants, particularly pesticides, compared with other aquatic species [61,68] (Table 1). 

Extra effort should be expended, however, to determine that adequate good quality water is available at aquatic testing facilities by more frequent analyses of incoming water. Special arrangements should also be made to handle large volumes of waste water such as pretreatment of the water using charcoal filters before discharging the water from the facility. 

Acute aquatic tests normally last 2 to 4 days depending on the test organisms. Chronic tests for invertebrates, like daphnia, last for 21 to 28 days and may involve several generations of offspring. We are always looking for test organisms that will reach maturity faster so we can evaluate the effect of the test substance on multiple generations in a shorter period of time. 

Acute aquatic tests duration, 133 species selection, 133 Advisory function of QAU, 114 Agricultural chemicals residue field trials program, quality assurance, 99-106... 

Blinova, I. (2000) Comparison of the sensitivity of aquatic test species for toxicity evaluation of various environmental samples, in G. Persoone, C. Janssen and W.M. De Coen (eds.), New Microbiotests for Routine Toxicity Screening and Biomonitoring, Kluwer Academic/Plenum Publishers, New York, pp. 217-220. 

Maltby et al. (2002) and Van den Brink et al. (2006a) compared SSDs based on acute and chronic laboratory toxicity data for aquatic test species exposed to pesticides. The SSDs were constructed with toxicity data for the most sensitive taxonomic group, because of the specific toxic mode of action of the pesticides selected. The SSDs were used to calculate the hazardous concentration to 5% of the species (HC5) by means of a log-normal distribution model, and comparisons were performed for 2 insecticides and 7 herbicides (Table 6.4). The log-normal model did not fit the diuron (herbicide) short-term L(E)C50 data or the atrazine (herbicide) long-term NOEC data. Consequently, the L(E)C50 HC5 value for diuron and the NOEC HC5 value for atrazine should be interpreted with caution, as well as their acute HC5-chronic... 

Van Veld PA, Spain JC. 1983. Degradation of selected xenobiotic compounds in three types of aquatic test systems. Chemosphere 12 1291-1305. 

Besides the complexity of the biological system and the length of the test, there are more practical aspects to toxicity tests. In aquatic test systems the tests may be classified as static, static renewal, recirculating, or flow-through. 

In aquatic test systems, exposure is usually a whole-body exposure. That means that the toxicant can enter the organism through the skin, cell wall, respiratory system (gills, stomata), and ingestion. Occasionally, a toxicant is injected into an aquatic organism, but that is not usually the case in toxicity tests to screen for effects. Whole-body exposures are less common when dealing with terrestrial species. Often an amount of xenobiotic is injected into the musculature (intramuscular), peritoneum (intraperitoneal), or into a vein... 

What is whole-body aquatic test systems exposure ... 

Kenaga, E.E. (1977) Aquatic test organisms and methods useful for assessment of chronic toxicity of chemicals. In Analyzing the Hazard Evaluation Process, Dickson, K.L., Maki, A.W. and Cairns Jr., J. (eds), pp. 101-111. American Fisheries Society, Bethesda, MD. 

The OECD Daphnia spp acute immobilisation and reproduction tests. A mainstay in aquatic toxicity testing, Daphnia tests have been used also to evaluate the toxicity of contaminated groundwaters and leachates (Kross and Cherryholmes, 1992). As with any of the aquatic tests, the principal problem with the Daphnia test is the need to extract a suitable aqueous sample. This problem is illustrated by Kross and Cherryholmes (1992), who compared D. magna and Microtox assay results in leachates but found a poor correlation between the two methods. 

Scaled results from all the tests were collated in the Triad matrix (Table 9.5). For the reference sample of field A the values were set to zero (local reference), except for the Microtox result. The reference sample already demonstrated inhibition compared with the blank, and it was decided to use this value. Calculation of effects using pore water ( bioavailable ) concentrations of contaminants and toxicity data from aquatic tests did not result in notably lower values for the toxic pressure compared with total concentrations. However, it might be questionable to use aquatic toxicity data for the calculation of effects from pore water concentrations of contaminants. 

Aqueous extracts. Various bioassay protocols are available for testing soil elutriates or leachates. Historically these have previously been available for aquatic tests. However, it may be inappropriate to project effects generated with aquatic species to soil organisms or ecosystems. With the development of whole soil bioassays, the use of elutriate or leachate tests focuses now on the prediction of threats to groundwater (leaching of toxicants) or surface water (contaminant run-off). Tests using aqueous extracts address pollutants soluble in water, and therefore are a measure of mobile toxicants. 

Aquatic tests to be carried out with freshwater species... 

Step 3 Determination of the material disintegration under relevant conditions (same as for Step 2) with a batch size of at least 2 litres (liquid) or 20 kg (solid) artificial or natural sediments should be included in aquatic test systems. 

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