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Remove the funnel from the base of the filtration assembly, place a glass-fiber filter on the base of the assembly, and replace the funnel. Wet the surface of the glass-fiber filter with de-ionized water (or filtered stream water) and apply a partial vac uum of approximately 69 kPa (10 pounds per square inch) to the assembly. Record the volume of the subsample on the field data sheet, pour the subsample into the filter funnel, and maintain a vacuum not greater than 69 kPa until all periphyton biomass in the subsample is retained on the filter, periodically rinsing down the sides of the funnel. Gently remove the funnel from the filtration assembly, remove the glass-fiber filter from the assembly base with forceps, fold the filter twice, and wrap the filter with aluminum foil. Insert the foil-wrapped filter into a pre-labeled sample container, such as a scintillation vial, and place the sample containers into a plastic bag with a label that identifies the samples and the sampling reach. Place the plastic bag in a cooler, and place a small block of dry ice on top of the plastic bags that hold the sample containers. The procedure is identical for CHL and AFDM subsamples. Do not filter the samples in direct sunlight, and protect the filters from exposure to light. Ship the filters to the laboratory for analyses as soon as possible.


Processing, enumeration, and taxonomic identifications of algal samples are performed by contract laboratories under the direction of the USGS Quality Management Group's Biological Quality-Assurance Unit (BQAU) located at the National Water-Quality Labora tory, Arvada, Colorado. The BQAU oversees and coordinates all contracts for the processing and identification of algal samples according to standardized qualification, processing, and quality-assurance/quality-control criteria analogous to those used for processing invertebrate samples (Cuffney and others, 1993). The BQAU is responsible for overseeing the quality of sample processing by contract laboratories, in terms of the accuracy of enumeration and taxonomic identifications, and for resolving taxonomic issues within and among study units. The BQAU also oversees the entry of contractor data into the National Water Information System-II (NWIS-II) data base, maintains reference collections, and deposits voucher specimens in outside museums.

Study-unit personnel send sample components to the contract laboratory and the BQAU (split-sample components) as soon as possible, preferably directly from the field. This procedure helps to minimize storage of formalin-containing samples and reduces the damage or loss of specimens and samples during shipment and storage. The study-unit biologist contacts the BQAU prior to collection of the samples to determine which contract laboratory will receive the samples. The contract laboratory is not apprised of the existence or identity of quality-assurance samples.

The buffered formalin used as a preservative for algal samples is a hazardous material; therefore, specific Federal guidelines govern the shipment of these samples. In addition, individual shipping companies could have more stringent requirements for the packaging and labeling of preserved samples. It is important to consult the shipping company regarding its requirements prior to collecting any samples. Make sure that the shipping company understands that the samples contain a solution of 3- to 5-perc ent formalin (not 3- to 5-percent formaldehyde) and be prepared to provide information on the maximum amount of preservative in each container and the total in each package. Packaging and labeling standards require special boxes, packing materials, and labels that need to be