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Sample Processing
Sample processing can range from a cursory examination and documentation of presence/absence to a quantitative measurement of abundance and distribution among the samples and will likely include subsampling, particularly for algae and macroinvertebrates. The level of subsampling and process for subsampling should be tested to ensure that the sample is representative of the waterbody segment being assessed. At the more rigorous levels, the number of organisms needed for an adequate subsample is specified (Cao et al. 2002; Hughes et al. 2002). A systematic treatment of samples is needed, regardless of the level of subsampling to ensure the greatest extent of accuracy and precision. The ultimate determination of biological condition is dependent upon the appropriateness of sample processing. As in the field, a strong QA/QC program is desired to ensure that (1) sample sorting procedures are being followed and no organisms are missed in the sample, and (2) the taxonomy is consistent and accurate. This is done by performing QC checks on both the sample sorting and organism identification steps, and retaining a voucher collection of the samples and reference collection of the taxa found in the samples.
Visit EPA's Rapid Bioassessment Protocol discussion on sample processing for benthic macroinvertebrates, as well as the EPA Wadeable Streams Assessment Field and Laboratory Methods. Also, please visit Sampling Protocols in Lessons Learned for Bioassessment .
Cao, Y., D.P. Larsen, R.M. Hughes, P.L. Angermeier, and T.M. Patton. 2002. Sampling effort affects multivariate comparisons of stream assemblages. Journal of the North American Benthological Society 21:701-714.
Hughes, R.M., P.R. Kaufmann, A.T. Herlihy, S.S. Intelmann, S.C. Corbett, M.C. Arbogast, and R.C. Hjort. 2002. Electrofishing distance needed to estimate fish species richness in raftable Oregon rivers. North American Journal of Fisheries Management 22:529-540.