10.16 cm (4 in.) or more. A rubber seal is affixed to one end of the pipe. The pipe sampler is used in the same manner as described for the SG-92 sampler; a long-handled bottle brush is used to brush periphyton contained within the sampling area, and the algae-water mixture is removed by aspiration (for example, with a poultry baster). The diameter of the sampling area and the total number of areas sampled are included on the sample label and on the field data sheet.
Collections of quantitative epidendric samples from natural substrates represent a special challenge because the surfaces of submerged tree limbs, trunks, and roots are generally irregular and can rarely be removed from the water without significant loss of algal biomass. In cases where the epidendric surface is relatively flat, the SG-92 periphyton sampler may be used as described for sampling of epilithic periphyton. Alternatively, a section of submerged tree root or limb can be wrapped with aluminum foil and the section severed with pruning shears or by sawing. The foil-covered section is then placed into a plastic bag and removed from the water. Periphyton biomass is brushed or scraped from the surface of the section into a sample container, and periphyton remaining on the foil or plastic bag is rinsed into the container. The surface area of algal colonization is determined by the foil-template method, as described previously. Sampling inform ation is recorded on the field data sheet (fig. 5).
Artificial substrates may be considered for obtaining quantitative periphyton samples in reaches where neither the SG-92 nor the foil-replicate method can be used. Although artificial substrates, such as glass slides or clay tiles, may be used for this purpose, the use of weathered wood-substrates more accurately represents the availability and abundance of epidendric algal food resources for aquatic herbivores in the sampling reach.
Quantitative periphyton samples are collected from submerged leaves and stems of aquatic vascular plants (macrophytes) by gently excising submerged sections of macrophytes (leaves, leaf sections, or stems) with scissors, placing the sections into a submer ged plastic bag, and removing the bag from the water. Periphyton is brushed or scraped from the macrophyte surface, and the area of colonization is determined by the foil-template method or by direct measurement of leaf dimensions. To obtain an epiphytic sample from linear-shaped macrophyte leaves (for example, Vallisneria ), submerged sections may be gently cut with scissors, placed into submerged plastic bags, and processed as described previously. The surface area is determined by measuring the dimensions of the leaf sections and calculating the total area of periphyton colonization represented in the sample. Sampling information is recorded on the field data sheet (fig. 5).
Epiphytic samples from macrophytes with small or finely dissected leaves (for example, Elodea or Ceratophyllum ) are difficult to quantify because the surface area of periphyton colonization cannot be reliably determined in the field. Althou gh quantitative samples should be collected from these macrophytes if the epiphytic periphyton microhabitat is predominant in the RTH of the sampling reach, the regional biologist should be consulted in relation to site-specific methods of sample collection, processing, and preservation.