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EVALUATION OF TWO MACROINVERTEBRATE SAMPLING METHODS FOR NON-WADEABLE STREAMS
Citation:
Klemm, D J., K A. Blocksom, AND W T. Thoeny. EVALUATION OF TWO MACROINVERTEBRATE SAMPLING METHODS FOR NON-WADEABLE STREAMS. Presented at North American Benthological Society, Keystone, CO, May 29-June 2, 2000.
Description:
Two macroinvertebrate sampling protocols for non-wadeable streams were evaluated during the summer of 1997 and 1998 as part of the USEPA's Environmental Monitoring and Assessment Program (EMAP), Mid-Atlantic Integrated Assessment (MAIA). Macroinvertebrates were collected by kick net and drift net methods to determine if these methods would adequately collect 300 organisms (or within 10% of 300) that could be used for bioassessment of a non-wadeable stream segment. Eleven transects were marked off equidistant in proportion to stream size, and the benthic macroinvertebrate assemblages collected on one side of the stream. In 1997, one kick net sample was collected from each of 11 transects and all samples composited, but in 1998 two kick net samples were collected from each of 11 transects. For both years, two drift net samples were collected and composited per site. In 1997 and 1998, kick net samples and drift net samples were collected from 13 and 34 non-wadeable stream sites, respectively. Using EMAP laboratory protocols for processing of benthic invertebrate samples, the kick net samples were split into thirds, and the random split sub-samples were randomly sorted using a tray containing 40, 5 cm by 5 cm squares until 300 organisms were picked, and all sub-samples sorted if necessary. The drift net samples were not split, and the entire sample was randomly picked. The number of individuals collected with the drift net and kick net were compared across years and within each year. In 1997, neither sampling device collected 300 or more organisms (the performance criteria), while in 1998, 27% of kick net samples (9 of 34) and 3% of drift net samples (1 of 34) collected 300 or more organisms. As expected, the median number of taxa and individuals for kick net samples in 1998 (47 and 279, respectively) were much higher than for 1997 (23 and 62, respectively). In addition, the drift nets collected consistently much fewer taxa and individuals than kick nets in both years (medians 18 and 44, respectively). It is recommended that three kick net samples be collected at each transect and that split sub-samples be continually picked until the number of organisms picked from the splits are within 10% of 300. It is also reocmmended that the drift net sampling method be dropped from the EMAP non-wadeable stream protocols because the results indicate poor sampling power to collect benthic macroinvertebrates during the time of day the drift nets are employed.