5.1 Polychaetes are an important component of the benthic community, in which they generally comprise 30 to 50?% of the macroinvertebrate population. They are preyed upon by many species of fish, birds, and larger invertebrate species. Larger polychaetes feed on small invertebrates, larval stages of invertebrates, and algae. Polychaetes are especially sensitive to inorganic toxicants and, to a lesser extent, to organic toxicants ( 1 ) . ³ The ecological importance of polychaetes and their wide geographical distribution, ability to be cultured in the laboratory, and sensitivity to contaminants make them appropriate acute and chronic toxicity test organisms. Their short life cycle enables the investigator to measure the effect of contaminants on reproduction.

5.2 An acute toxicity or chronic text is conducted to obtain information concerning the immediate effects of an exposure to a test material on a test organism under specified experimental conditions. An acute toxicity test provides data on the short-term effects, which are useful for comparisons to other species but do not provide information on delayed effects. Chronic toxicity tests provide data on long-term effects.

5.3 A life-cycle toxicity test is conducted to determine the effects of the test material on survival, growth, and reproduction of the test species. Additional sublethal endpoints (for example, biochemical, physiological, and histopathological) may be used to determine the health of the species under field conditions.

5.4 The results of acute, chronic, and life-cycle toxicity tests can be used to predict effects likely to occur on marine organisms under field conditions.

5.5 The results of acute, chronic, or life-cycle toxicity tests might be used to compare the sensitivities of different species and the toxicities of different test materials, as well as to study the effects of various environmental factors on the results of such tests.

5.6 The results of acute, chronic, or life-cycle toxicity tests might be an important consideration when assessing the hazards of materials to marine organisms (see Guide E1023 ) or when deriving water quality criteria for aquatic organisms ( 2 ) .

5.7 The results of acute, chronic, or life-cycle toxicity tests might be useful for studying the biological availability of, and structure activity relationships between, test materials.

5.8 The results of acute, chronic, and life-cycle toxicity tests will depend partly on the temperature, quality of food, condition of test organisms, test procedures, and other factors.

1.1 This guide covers procedures for obtaining data concerning the adverse effects of a test material added to marine and estuarine waters on certain species of polychaetes during short- or long-term continuous exposure. The polychaete species used in these tests are taken from laboratory cultures and exposed to varying concentrations of a toxicant in static conditions. These procedures may be useful for conducting toxicity tests with other species of polychaetes, although modifications might be necessary.

1.2 Modifications of these procedures might be justified by special needs or circumstances. Although using appropriate procedures is more important than following prescribed procedures, the results of tests conducted using unusual procedures are not likely to be comparable to those of many other tests. Comparisons of results obtained using modified and unmodified versions of these procedures might provide useful information concerning new concepts and procedures for conducting acute, chronic, or life-cycle tests with other species of polychaetes.

1.3 These procedures are applicable to most chemicals, either individually or in formulations, commercial products, and known or unknown mixtures. With appropriate modifications, these procedures can be used to conduct these tests on factors such as temperature, salinity, and dissolved oxygen. These procedures can also be used to assess the toxicity of potentially toxic discharges such as municipal wastes, oil drilling fluids, produced water from oil well production, and other types of industrial wastes. An LC50 (medial lethal concentration) is calculated from the data generated in each acute and chronic toxicity test. Reproductive success and the number of offspring produced are used to measure the effect of a toxicant on life-cycle tests; data are analyzed statistically to indicate that concentration at which a significant difference occurs between the test solutions and control(s).

1.4 The results of acute or chronic toxicity tests with toxicants added experimentally to salt water should usually be reported in terms of an LC50. The results of life-cycle toxicity tests with toxicants added experimentally to salt water should be reported as that concentration at which a statistically significant difference in the number of offspring is produced with reference to the control(s).

1.5 This guide is arranged as follows:

1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 7 .