USGS-NAWQA: BS0332: Benthic Macroinvertebrates: Qualitative Visual-Sort Method for Processing Samples
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Official Method Name
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Qualitative Visual-Sort Method for Processing Benthic Macroinvertebrates Samples |
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Current Revision
| 2011 |
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Media
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Biological (Waterbody type - Wadeable stream) |
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Instrumentation
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Standard metal sieve |
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Method Subcategory
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Population/Community |
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Method Source
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Citation
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Protocol
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USGS NAWQA 2002 Eco Protocols - Revised Protocols for Sampling Algal, Invertebrate, and Fish Communities as Part of the National Water-Quality Assessment Program |
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Brief Method Summary
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The goal of this method is to standardize procedures used for the taxonomic identification of benthic macroinvertebrates (BMIs). These procedures can be applied to any BMI sample submitted to the National Water Quality Laboratory (NWQL) for analysis. Taxonomic identification of BMIs requires experienced personnel trained in zoological taxonomic principles and possessing a broad knowledge of all aquatic macroinvertebrate groups. Refer to the method document for steps on how to sort the sample. |
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Scope and Application
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Summary of Procedure—The goal of the qualitative visual sort processing method is to produce a comprehensive list of benthic macroinvertebrate (BMI) taxa present in a sample. This method can be applied to any BMI sample collected in the field. Samples are visually sorted by a taxonomist for up to 2 hours. Samples are first size-fractionated to separate coarse and fine organic debris to increase sorting effectiveness. The coarse size fraction is sorted for about 0.25 hour; the fine size fraction for up to 1.75 hours. Sorting targets mature, undamaged organisms that contributes to success of genus- or species-level taxonomic resolution if requested. Immature or damaged specimens are sorted from the sample only if they are to likely represent new taxa. The objective of sorting is to find as many distinct taxa as practical within the 2-hour time limit. Taxa are reported only as present; individual abundances of each taxon are not determined. |
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Applicable Concentration Range
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Interferences
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1.5.1. Sorting effectiveness varies with the type and amount of sample detritus. An excessive amount of organic detritus makes it difficult to observe and remove organisms (especially small, cryptic organisms) from the sample matrix adequately. 1.5.2. Clumps of algal filaments are difficult to sort; they must be carefully separated and delicate organisms (for example, mayfly larvae) handled gently to minimize damage or loss of taxonomically valuable body parts such as gills and legs. |
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Quality Control Requirements
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Sample Handling
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Refer to NWQL SOP No. BS0331.0. for sample preparation. |
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Maximum Holding Time
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Relative Cost
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Unknown |
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Sample Preparation Methods
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see method documentation PDF |
