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1.1 This guide covers procedures for obtaining laboratory data concerning the adverse effects of a test material added to dilution water on sexual reproduction by seaweeds. The exposure duration is species dependent and is followed by a period of development to allow the evidence of sexual reproduction to appear. There is no exposure to toxicants during the development period. This restricts the tests primarily to the events surrounding egg fertilization, and it minimizes any timelag effects on development that might interfere with correct enumeration of the number of sexual events that occurred. These procedures will probably be useful for conducting sexual reproduction toxicity tests with a variety of species of seaweeds, although modifications might be necessary.

1.2 Other 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. Comparison of the results obtained using modified and unmodified versions of these procedures might provide useful information concerning new concepts and procedures for conducting sexual reproduction tests with seaweeds.

1.3 These procedures are applicable to most chemicals, either individually or in formulations, commercial products, and known mixtures or whole effluents, as well as for use in testing surface waters. With appropriate modifications, these procedures can be used to study the effects of temperature, dissolved oxygen, pH, and such materials as leachates, oils, particulate matter, and sediments.

1.4 The values stated in SI units are to be regarded as the standard.

1.5 This guide is arranged as follows:

1.6 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. For specific hazards statements, see 6.4 and Section 7.

5.1 Seaweeds have historically been considered less useful for toxicity testing than microalgae (1) ,⁴ and microalgae are often considered less sensitive than aquatic animals (2). Such conclusions concerning seaweed insensitivity were based on data for only a few hardy species and based generally on vegetative growth of adult stages as the primary endpoint. The sensitivity of seaweeds increases when effects on sexual reproduction are assessed. This has been shown for Champia parvula(3), as well as for the brown seaweeds, Fucus edentatus, Laminaria saccharina, and Macrocystis pyrifera (4).

5.2 The results of sexual reproduction tests with seaweeds might be useful for predicting the long-term effects likely to occur on seaweeds in field situations due to exposure under comparable conditions.

5.3 The results of sexual reproduction tests with seaweeds might be used to compare the chronic toxicities of different materials, and also to study the effects of various environmental factors on the results of such tests.

5.4 The results of sexual reproduction tests with seaweeds might be an important consideration when assessing the hazards of materials to aquatic organisms or when deriving water quality criteria for saltwater organisms (5).

5.5 The results of sexual reproduction tests with seaweeds will depend on the temperature, composition of dilution water, condition of test organisms, and other factors such as light and media.