WATER QUALITY--Measurement and Use of Diversity Indices for Biological Samples In Reply Refer To: April 16, 1985 WGS-Mail Stop 412 QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM NO. 85.10 Subject: WATER QUALITY--Measurement and Use of Diversity Indices for Biological Samples Enclosed for your information is a restatement of Quality of Water Branch Technical Memorandum No. 82.07. Please note especially equation 4, (page 5) for the calculation of Hmax. This equation was in error in memorandum 82.07 and has now been corrected. We thank Jurate Landwehr, Northeastern Region Research, for bringing this problem to our attention. Changes in biological communities caused by natural or anthropogenic stress are often of interest in water-quality studies. Diversity indices have been among the most widely used methods for identifying changes in aquatic community structure. The use of indices to summarize large amounts of species-abundance information is still undergoing development, but the content of Quality of Water Branch Technical Memorandum No. 82.07 (February 10, 1982) remains relevant. A recent review (Washington, H. G., 1984, Diversity, biotic and similarity indices: A review with special relevance to aquatic ecosystems: Water Research, v. 18, no. 6, p. 653-694) provides a state-of-the-art discussion of the subject; a number of different diversity indices as well as biotic and similarity indices are examined for their applicability to aquatic ecosystems. David A. Rickert Acting Chief, Quality of Water Branch Attachment WRD Distribution: A, B, FO-LS, PO This memorandum supersedes Quality of Water Branch Technical Memorandum No. 82.07