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1.1 This guide covers procedures for obtaining laboratory data concerning the adverse effects of potentially contaminated sediment, or of a test material added experimentally to contaminated or uncontaminated sediment, on marine or estuarine infaunal polychaetes during 10-day or 20 to 28-day exposures. These procedures are useful for testing the effects of various geochemical characteristics of sediments on marine and estuarine polychaetes and could be used to assess sediment toxicity to other infaunal taxa, although modifications of the procedures appropriate to the test species might be necessary. Procedures for the 10-day static test are described for Neanthes arenaceodentata and Alitta virens 2 (formerly Nereis virens and Neanthes virens) and for the 20 to 28-day static-renewal sediment toxicity for N. arenaceodentata.

1.2 Modifications of these procedures might be appropriate for other sediment toxicity test procedures, such as flow-through or partial life-cycle tests. The methods outlined in this guide should also be useful for conducting sediment toxicity tests with other aquatic taxa, although modifications might be necessary. Other test organisms might include other species of polychaetes, crustaceans, and bivalves.

1.3 Other modifications of these procedures might be appropriate for 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 the results obtained using modified and unmodified versions of these procedures might provide useful information concerning new concepts and procedures for conducting sediment tests with infaunal organisms.

1.4 These procedures are applicable to sediments contaminated with most chemicals, either individually or in formulations, commercial products, and known or unknown mixtures. These procedures can be used with appropriate modifications to conduct sediment toxicity tests on factors such as temperature, salinity, dissolved oxygen (DO), and natural sediment characteristics (for example, particle size distribution, organic carbon content, and total solids). These procedures can also be used to conduct bioconcentration tests and in situ tests, and to assess the toxicity of potentially contaminated field sediments, or of materials such as sewage sludge, oils, particulate matter, and solutions of toxicants added to sediments. A median lethal concentration (LC50) or median sublethal effect concentration (EC50) of toxicants or of highly contaminated sediment mixed into uncontaminated sediment can be determined. Materials adhering to sediment particles or dissolved in interstitial water can be tested.

1.5 The results of 10-day toxicity tests with contaminated sediments can be reported as a LC50 if a series of concentrations is tested or as a percent mortality relative to a control or reference sediment. The results of 20 to 28-day toxicity tests with contaminated sediments can be reported as a LC50 if a series of concentrations is tested or as a percent mortality or growth relative to a control or reference sediment.

1.6 This guide is arranged as follows:

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

1.8 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific hazards statements are given in Section 8.

1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.1 The test procedure covered in this guide is not intended to simulate exactly the exposure of benthic polychaetes to chemicals under natural conditions, but rather to provide a conveniently rapid, standard toxicity test procedure yielding a reasonably sensitive indication of the toxicity of materials in marine and estuarine sediments.

5.2 The protection of a community of organisms requires averting detrimental contaminant-related effects on the number and health of individuals and species within that population. Sediment toxicity tests provide information on the toxicity of test materials in sediments. Theoretically, projection of the most sensitive species within a community will protect the community as a whole.

5.3 Polychaetes are an important component of the benthic community. They are preyed upon by many species of fish, birds, and larger invertebrate species, and they are predators of smaller invertebrates, larval stages of invertebrates, and, in some cases, algae, as well as organic material associated with sediment. Polychaetes are sensitive to both organic and inorganic chemicals (1, 2).5 The ecological importance of polychaetes, their wide geographical distribution and ability to be cultured in the laboratory, and sensitivity to chemicals, make them appropriate toxicity test organisms.

5.4 An acute or 10-day toxicity test is conducted to obtain information concerning the immediate effects to a test material on a test organism under specified experimental conditions for a short period of time. An acute toxicity test does not necessarily provide information concerning whether delayed effects will occur, although a post-exposure observation period, with appropriate feeding, if necessary, could provide such information.

5.5 The results of acute sediment toxicity tests can be used to predict acute effects likely to occur on aquatic organisms in field situations as a result of exposure under comparable conditions, except that (1) motile organisms might avoid exposure when possible and (2) toxicity to benthic organisms can be dependent on sediment characteristics, the dynamics of equilibrium partitioning, and the route of exposure to the benthic organisms.

5.6 The polychaete sediment toxicity test might be used to determine the temporal or spatial distribution of sediment toxicity. Test methods can be used to detect horizontal and vertical gradients to toxicity. Mortality data can be used to indicate the relative toxicity of field-collected sediments.

5.7 The results of acute tests with toxicants added experimentally to sediments can be used to compare the acute sensitivities of different species and acute toxicities of different test materials, and to define the effects of various environmental factors on the results of such tests.

5.8 The results of acute sediment toxicity tests are useful for studying the biological availability of, and structure-activity relationships between, test materials in sediment.

5.9 The results of acute sediment toxicity tests might be an important consideration when assessing the hazards of materials to aquatic organisms (see Guide E1023) or when deriving the sediment quality for aquatic organisms (3). Sediment toxicity tests might be useful for making decisions regarding the extent of remedial action necessary for contaminated sites.

5.10 A 10-day test provides data on the short-term effects that are useful for comparisons to other species but does not provide information on delayed effects. Results of the 20-day to 28-day sediment toxicity test, which measures growth in addition to survival, can be useful indicators of the effects of contaminated sediments over a longer time period.