Acclimation
(1) Acclimation means the physiological compensation by test organisms to new environmental conditions (e.g., temperature, hardness, pH). (2) Acute toxicity test means a method used to determine the concentration of a substance that produces a toxic effect on a specified percentage of test organisms in a short period of time (e.g., 96 hours). In this guideline, death is used as the measure of toxicity. (3) Carrier means a solvent used to dissolve a test substance prior to delivery to the test chamber. (4) Conditioning means the exposure of construction materials, test chambers, and testing apparatus to dilution water or to test solutions prior to the start of a test in order to minimize the sorption of the test substance onto the test facilities or the leaching of substances from the test facilities into the dilution water or test solution. (5) Death means the lack of opercular movement by a test fish. (6) Flow-through means a continuous or an intermittent passage of test solution or dilution water through a test chamber, or a holding or acclimation tank with no recycling. (7) Incipient LC50 means that test substance concentration, calculated from experimentally-derived mortality data, that is lethal to 50 percent of a test population when exposure to the test substance is continued until the mean increase in mortality does not exceed 10 percent in any concentration over a 24-hour period. (8) LC50 means that test substance concentration, calculated from experimentally-derived mortality data, that is lethal to 50 percent of a test population during continuous exposure over a specified period of time. (9) Loading means the ratio of fish biomass (grams, wet weight) to the volume (liters) of test solution in a test chamber or passing through it in a 24-hour period. (10) Static means the test solution is not renewed during the period of the test. (11) Test solution means the test substance and the dilution water in which the test substance is dissolved or suspended.