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apparatus and hand vacuum pump, and (3) wrapping the filter in aluminum foil, placing the foil into a pre-labeled container, and transporting the container to the laboratory on dry ice. Specific details of the filtration procedure are discussed in the co llection procedures for microalgae.

Obtaining representative chlorophyll subsamples from samples of macroalgae can be a challenge, particularly for filamentous taxa such as Cladophora glomerata. The recommended sample-processing method used will depend in part on the capabilities of the analytical laboratory and on recommendations from the regional biologist. Several sample-processing methods are suggested below. The analytical laboratory should be contacted p rior to the collection of quantitative macroalgal samples for CHL determinations, particularly if sample-processing methods (2) or (3) are selected.

Depositional-Targeted Habitats

Although depositional habitats may support fewer algal species than erosional habitats, algal species diversity, biomass, and primary production can be large in epipelic and epipsammic periphyton microhabitats (Hickman and Round, 1970). Photosynthesis by benthic algae in depositional habitats can contribute to oxygenation of streambed sediments (Antoine and Benson-Evans, 1985; Baillie, 1986), potentially influencing trace-element partitioning between the sediment and water (Horowitz, 1991). Benthic algal communities in depositional habitats also are likely to be exposed to sediment-borne contaminants for extended periods of time.

DTH's are typically dominated by epipelic or epipsammic periphyton microhabitats. Although epipelic and epipsammic microhabitats are relatively easy to sample