Embryo-Larval Toxicity Tests with Organic Compounds

Abstract

A continuous-flow system was developed for evaluating the effects of insoluble and volatile organics on the developmental stages of fish. A closed test system, devoid of standing air space, was used to minimize volatility as a variable. Insoluble compounds were suspended in influent water by mechanical homogenization, without the use of carrier solvents. Tests were performed with aniline, chlorobenzene, and phenol. Water hardness was maintained at 50 and 200 mg/litre calcium carbonate, and exposure was continuous from fertilization through four to eight days after hatching for largemouth bass, channel catfish, goldfish, and rainbow trout. The results indicated that there was good reproducibility of exposure concentrations down to 1 µg/litte or less. For a calculated concentration of 1 µg/litre phenol, the actual test-water concentrations (mean ± standard error) for four replicates were 0.7 ± 0.2, 1.2 ± 0.3, 1.3 ± 0.3, and 1.5 ± 0.3. When phenol was administered in hard water, the LC1 and LC50 values determined at hatching were 0.2 and 80 µg/litre for trout, and 2.0 and 710 µg/litre for goldfish. Phenol was less toxic in soft water. Chlorobenzene at 0.09 mg/litre produced complete mortality of trout eggs. When bass eggs were exposed through four days after hatching, the LC50s for chlorobenzene ranged from 50 to 60 µg/litre. The aniline LC50 values calculated for catfish, goldfish, and bass eggs treated in soft water were 5.6, 10.2, and 47.3 mg/ litre, respectively. Because of the differential rates of larval mortality for the three species, the LC50 range narrowed considerably when the exposure time was increased beyond hatching. Water hardness exerted no appreciable effects on the toxicity of either chlorobenzene or aniline. All three organic compounds produced significant frequencies of teratic larvae.

Short‐term fish and amphibian embryo‐larval tests for determining the effects of toxicant stress on early life stages and estimating chronic values for single compounds and complex effluents: Complex mixtures

“…For that matter, 7-d LC5Os or TL5Os determined with adult fish have been introduced occasionally in other studies on acute toxicity (221, and the use of this longer period has the advantage of providing a "worst-case" measurement for acute toxic stress. However, if more typical acute data are desired for general comparative purposes, 96-h LC50 values can be determined easily for the initial 4 d of exposure (7,231. As initial sample size can be set at 100 to 150 eggs [13,23], it may also prove feasible to determine separate LC5Os for the larval portion of the test using newly hatched organisms from either exposed or unexposed eggs, or both.…”

“…These tests were performed using 500-ml Pyrex test chambers as described previously [2,7]. Flow rate through the test chamber was maintained at 200 ml/h, giving a replacement time of 2.5 h. Dilution water was pumped from a 50-liter Nalgene container that was continuously aerated.…”

“…Solutions from the two pump channels were mixed by mechanical stirring and delivered from the mixing unit to the test chamber under moderate positive pressure. The exposure concentration was regulated by adjusting the mixing ratio between cadmium and dilution water and/or by varying the concentration of cadmium delivered from the syringe pump [7]. Flow rates were determined using timed volumetric measurements taken once or twice daily for both syringe and peristaltic pump lines.…”

“…No direct aeration was supplied to the exposure chambers. Further details concerning this continuous-flow system have been given in earlier publications [2,7,8].…”

Pollutants as developmental toxicants in aquatic organisms.

“…In these tests, organisms are exposed from the time of fertilization until some weeks after hatching. The data gathered are generally total hatching success and survival and growth of the larvae (2). These are parameters that are easy to screen in large-scale operations and do not require special experitse.…”