CA Waterboards: SWAMP RWB:  SWAMP Reachwide Benthos (Multihabitat) Procedure

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Official Method Name
SWAMP Reachwide Benthos (Multihabitat) Procedure
Current Revision
May 2016
Surface Water  (Waterbody type - Wadeable stream)
Invertebrate Net (w/ handle)
Method Subcategory
Method Source
  CA Waterboards
  Standard Operating Procedures for Collecting Benthic Macroinvertebrate Samples and Associated Physical and Chemical Data for Ambient Bioassessments in California
SWAMP Bioassessment 2016 - SWAMP Bioassessment Procedures 2016
Brief Method Summary
The RWB procedure employs an objective method for selecting subsampling locations that is built upon the 11 transects used for physical habitat measurements. The RWB procedure can be used to sample any wadeable stream reach since it does not target specific habitats. Because sampling locations are defined by the transect layout, the position of individual sub-samples may fall in a variety of erosional or depositional habitats. A 500-micron mesh D-frame net is used.
Scope and Application
The current guidance for macroinvertebrate sampling under the SWAMP program is as follows:
1. For ambient bioassessment monitoring of wadeable streams in California, two methods are to be used at sites with riffle habitats (i.e., one “multihabitat” sample, and one sample that targets the “richest” habitat):
• For sites with sufficient riffle habitat, the two samples shall be: (1) the reachwide benthos (RWB) method (also known as “multihabitat” sampling.); and (2) the targeted-riffle composite (TRC) method.
• For low-gradient sites that do not have sufficient riffle habitat, the RWB method is the standard method, but we also recommend the option of collecting a sample with (2) the “Margin-Center-Margin” (MCM) method until ongoing methods comparisons are completed (see Appendix A).

2. The SWAMP QAMP allows flexibility in sampling methods so that the most appropriate method(s) may be used to address hypothesis tests and project-specific objectives that differ from program objectives. Such situations may include, but are not necessarily limited to, special studies (e.g., evaluation of point source discharges, above/below comparisons where statistical replication is needed), stressor identification investigations, and long-term monitoring projects where consistent data comparability is desired and an alternative method is needed to achieve that comparability. In addition, in some rare cases where funding limitations would make it cost-prohibitive to complete a project in compliance with the protocols listed in #1, above, the project proponent may request to complete laboratory analysis of only one sample, and “archive” one of the macroinvertebrate samples (i.e., the RWB sample in streams with riffles) to reduce lab costs. Deviations from the protocols specified in #1 above may be granted by the SWAMP Bioassessment Coordinator or the full SWAMP Roundtable.
Applicable Concentration Range
Quality Control Requirements
Sample Handling
Once all sub-samples (eight for TRC, 11 for RWB) have been collected, transfer benthos to a 500-mL or 1000-mL wide-mouth plastic sample jar using one of the methods described on pg. 19. Place a completed date/locality label (see Figure 4) on the inside of the jar (use pencil only as most “permanent” inks dissolve in ethanol) and completely fill with 95% ethanol. Place a second label on the outside of the jar. Note that the target concentration of ethanol is 70%, but 95% ethanol is used in the field to account for dilution from water in the sample.
Maximum Holding Time
If jars will be stored for longer than a month prior to processing, jars should not contain more than 50% sample material.
Relative Cost
Sample Preparation Methods