Science of Water : Concepts and Applications

Environmental Biomonitoring, Sampling, and Testing 233
sloping banks and are, therefore, considered to have erosion potential. Signs of erosion
include crumbling, unvegetated banks, exposed tree roots, and exposed soil.
J. The riparian vegetative zone is defi ned as the width of natural vegetation from the
edge of the stream bank. The riparian vegetative zone is a buffer zone to pollutants
entering a stream from runoff. It also controls erosion and provides stream habitat and
nutrient input into the stream.
√ Note: A wide, relatively undisturbed riparian vegetative zone refl ects a healthy stream system;
narrow, far less useful riparian zones occur when roads, parking lots, fi elds, lawns, and other
artifi cially cultivated areas, bare soil, rock, or buildings are near the stream bank. The presence
of “old fi elds” (i.e., previously developed agricultural fi elds allowed to revert to natural conditions)
should rate higher than fi elds in continuous or periodic use. In arid areas, the riparian
vegetative zone can be measured by observing the width of the area dominated by riparian or
water-loving plants, such as willows, marsh grasses, and cottonwood trees.
MACROINVERTEBRATE SAMPLING: MUDDY-BOTTOM STREAMS
In muddy-bottom streams, as in rocky-bottom streams, the goal is to sample the most productive
habitat available and look for the widest variety of organisms. The most productive habitat is the
one that harbors a diverse population of pollution-sensitive macroinvertebrates. Samples should be
collected using a D-frame net (see Figure 8.5) to jab at the habitat and scoop up the organisms that
are dislodged. The idea is to collect a total sample that consists of 20 jabs taken from a variety of
habitats.
FIGURE 8.5 D-frame aquatic net.