Specifications include, but are not limited to: SAMPLE SORTING PROCEDURE/ DESCRIPTION OF MATERIAL 1. Benthic samples will be collected using either artificial substrates (rock baskets) according to the NHDES Protocols for Macroinvertebrate Collection, Identification, and Enumeration or kick-nets according to the VT protocols found in the VTDEC Watershed Management Division Field Methods Manual. It is anticipated that for any given year, more than 85% of the samples submitted with be collected using artificial substrates (rock baskets). 2. Samples are prepared in the field by separating the collected organisms, detritus and sediment from the artificial substrates or kick net and transferring separated material (organisms, detritus and sediment) to a 1-liter, plastic bottle. Samples include organisms, detritus and sediment. 3. Samples will be preserved in 70% or greater ethanol. 4. Samples will require sorting by the primary contractor to remove invertebrate organisms from detritus/sediment in ¼ sample increments. 5. Samples will be processed by sub-sampling using the Caton grid method outlined in the US EPA’s Rapid Bioassessment Protocols, 2nd Edition (Barbour et al. 1999) with some modification as noted in the below paragraph: NHDES requires that the entire sample be homogenized and spread evenly over a gridded mesh bottom (300–600-micron) tray. The number of grids must be evenly divisible by four. A minimum of one-quarter (¼) of the tray’s grids must be randomly selected for sorting. All material contained within the selected grids must then be transferred to a separate sorting tray. From this subsample, all invertebrate organisms are then removed for identification. If after processing the entire subsample, the subsample is found to have the required number of organisms (at least 100 or 300, as specified) for identification, then sorting is complete. If the minimum organism target is not achieved, an additional subsample equal to a quarter (¼) of the grids must be randomly selected and processed entirely, regardless of the total number of organisms contained within the grid. The ¼ incremental random grid selection process is continued until the minimum organism target is reached or the entire sample has been processed.
