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An sample label containing the following information is affixed to the sample container: site name, site ID number, sampling reach, sample ID number, date, time, type of sample, type of microhabitat, surface area of collection, and the name of the person who collected the sample. After labeling, all preserved periphyton samples are stored and transported in boxes or containers that prevent exposure of the samples to sunlight.

Preparation of Subsamples

If other periphyton measurements are required in addition to the ID sample, it will be necessary to divide the quantitative periphyton sample into three representative subsamples, preserve the ID subsample, and process the remaining subsamples for (1) CHL and (2) DM and AFDM determinations. In some circumstances, the quantitative periphyton sample will need to be homogenized (or subdivided by other means) to ensure representative subsamples for each type of periphyton measurement. Periphyton are subdivided in the field by cutting algal filaments into smaller pieces with scissors, or by using a battery-powered tissue homogenizer. The periphyton sample is shaken vigorously (approximately 40 to 50 times) prior to withdrawing subsamples for ID, CHL, and AF DM determinations. Because subsampling of filamentous periphyton assemblages can produce considerable error among the resulting replicate subsamples, it is desirable to collect separate quantitative samples for each periphyton measurement when the algal community contains appreciable amounts of macroalgae.

If all periphyton measurements are required for an ecological study, first prepare the ID subsample by withdrawing 15 mL of algae-water suspension from the quantitative periphyton sample into a 20-mL scintillation vial, using a volumetric hand pipettor. Preserve the ID subsample with 0.5 to 0.75 mL (5 to 8 drops) of concentrated, buffered formalin solution, attach a sample label to the vial, and enter the appropriate information on the field data sheet. If the ID subsample contains only small amounts of periphyton (less than a 2-mm accumulation of biomass at the bottom of the scintillation vial), prepare one or more additional 15-mL ID subsamples until sufficient biomass has been obtained. Indicate the number of containers submitted for the ID sample on the sample labels and on the field data sheet.

After the ID subsample has been withdrawn from the quantitative periphyton sample, vigorously shake the remainder of the sample and pour approximately one half of the sample volume into an unused sample container. Designate one of the two subsample containers as the CHL subsample and the other container as the AFDM subsample. Record the volume of each subsample on the field data sheet. Periphyton biomass from each subsample is filtered onto a glass-fiber filter, and the filter is submitted to the National Water-Quality Laboratory (NWQL), Arvada, Colorado, for determination of CHL and AFDM.