METHODS OF ANALYSIS BY THE U.S. GEOLOGICAL SURVEY NATIONAL WATER QUALITY LABORATORY — PROCESSING, TAXONOMY, AND QUALITY CONTROL OF BENTHIC MACROINVERTEBRATE SAMPLES By Stephen R. Moulton II, James L. Carter, Scott A. Grotheer, Thomas F. Cuffney, and Terry M. Short U.S. GEOLOGICAL SURVEY Open-File Report 00-212 Denver, Colorado 2000 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director The use of firm, trade, or brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey For additional information, write to: Copies of this report can be purchased from: U.S. Geological Survey U.S. Geological Survey Chief, National Water Quality Laboratory Information Services Box 25406, Mail Stop 407 Box 25286, Mail Stop 417 Denver Federal Center Denver Federal Center Denver, CO 80255-0425 Denver, CO 80225-0286 CONTENTS ABSTRACT.................................................................................................................................1 INTRODUCTION.........................................................................................................................1 ANALYTICAL METHOD ..............................................................................................................3 1. Chemicals, Equipment, and Supplies Necessary to Process Benthic Macroinvertebrate Samples......................................................................................................................... 3 1.1. Chemicals ............................................................................................................ 3 1.2. Equipment............................................................................................................ 3 1.3. Supplies ............................................................................................................... 4 1.4. Construction of Subsampling Equipment............................................................... 4 2. Sample Preparation ....................................................................................................... 8 2.1. Safety Issues........................................................................................................ 8 2.2. Obtaining Chemicals, Equipment, and Supplies .................................................... 8 2.3. Washing, Sieving, and Elutriating Samples ........................................................... 8 3. Qualitative Visual Sort Method for Processing Benthic Macroinvertebrate Samples ........ 9 3.1. Application............................................................................................................ 9 3.2. Summary of Method ............................................................................................. 9 3.3. Interferences ........................................................................................................ 9 3.4. Procedure............................................................................................................. 9 3.5. Qualitative Selection of Chironomidae Larvae for Slide Mounting.........................12 3.6. Quality Control of Sorting Effectiveness ...............................................................12 4. Quantitative Fixed-Count Method for Processing Benthic Macroinvertebrate Samples...12 4.1. Application...........................................................................................................12 4.2. Summary of Method ............................................................................................13 4.3. Interferences .......................................................................................................16 4.4. Procedure............................................................................................................17 4.5. Quality Control.....................................................................................................20 5. Slide Preparations.........................................................................................................21 5.1. Application...........................................................................................................21 5.2. Summary of Method ............................................................................................21 5.3. Interferences .......................................................................................................21 5.4. Procedure............................................................................................................21 6. Taxonomic Identification of Benthic Macroinvertebrates.................................................21 6.1. Application...........................................................................................................21 6.2. Interferences .......................................................................................................22 6.3. Taxonomic Information Resources.......................................................................22 6.4. Taxonomic Procedures........................................................................................25 6.5. Quality Control.....................................................................................................28 7. Data Management ........................................................................................................29 SUMMARY................................................................................................................................31 REFERENCES CITED ..............................................................................................................31 APPENDIXES ...........................................................................................................................33 Appendix 1.—Benthic macroinvertebrate sample qualifiers..................................................33 Main-body component...................................................................................................33 Large-rare component...................................................................................................33 Elutriate component ......................................................................................................33 Split component ............................................................................................................33 Appendix 2.—List of taxonomic references by major taxonomic groupings...........................34 General Macroinvertebrate References .........................................................................34 Mollusca: Bivalvia and Gastropoda................................................................................34 Annelida: Hirudinea, Oligochaeta, and Polychaeta ........................................................34 Arthropoda: Amphipoda, Decapoda, and Isopoda..........................................................35 CONTENTS III Arthropoda: Insecta (general references).......................................................................35 Insecta: Ephemeroptera................................................................................................36 Insecta: Odonata...........................................................................................................37 Insecta: Plecoptera .......................................................................................................38 Insecta: Heteroptera......................................................................................................39 Insecta: Megaloptera, Neuroptera .................................................................................40 Insecta: Trichoptera ......................................................................................................41 Insecta: Coleoptera.......................................................................................................43 Insecta: Diptera (excluding Chironomidae) ....................................................................47 Diptera: Chironomidae ..................................................................................................47 TABLES 1. Dimensions of subsampling equipment used in the quantitative processing of benthic macroinvertebrate samples ........................................................................................ 8 2. Taxonomic categories used for benthic macroinvertebrate sorting ............................ 12 3. Morphological characters used to select larvae qualitatively for slide preparations from Chironomidae subfamilies ........................................................................................ 13 4. Index of dispersion summary statistics used to determine the distribution of benthic macroinvertebrate organisms in samples spread across subsampling frames........... 14 5. Suggested stage-1 subsampling frame sizes used for various sample volumes ........ 16 6. Processing procedures used to reach 300- or 100-organism fixed-count targets ....... 18 7. Calculation of the laboratory subsampling correction factor....................................... 20 8. Standardized notes used to justify benthic macroinvertebrate identifications where the prescribed taxonomic level is not achieved............................................................... 23 9. Notes of taxonomic interest that convey additional information about benthic macroinvertebrate identifications .............................................................................