4.1 The significance of measuring algal growth potential in water samples is that differentiation can be made between the nutrients of a sample determined by chemical analysis and the nutrients that are actually available for algal growth. The addition of nutrients (usually nitrogen and phosphorus singly or in combination) to the sample can give an indication of which nutrient(s) is (are) limiting for algal growth (1,10,11,12,13,14).

1.1 This practice measures by Pseudokirchnereilla subcapitata growth response, the biological availability of nutrients, as contrasted with chemical analysis of the components of the sample. This practice is useful for assessing the impact of nutrients, and changes in their loading, upon freshwater algal productivity. Other laboratory or indigenous algae can be used with this practice. However, Pseudokirchnereilla subcapitata must be cultured as a reference alga along with the alternative algal species.

1.2 This standard does not purport to address all of the safety problems, 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 a specific precautionary statement, see Section 15.