Biota of Rivers and Streams - Hydro-Environmental Analysis: Freshwater Environments - page 167

described an intensity study and a model application of periphyton growth on the Jackson River,
Virginia, and also investigated the use of pulsed lows for periphyton management (Flinders and Hart
2009). Chapra et al. (2007) describe a water quality model that includes periphyton.
Periphyton surveys are used to determine periphyton composition or biomass. Methods for sam-
pling vary from scraping or using other techniques to remove periphyton from substrates for analy-
sis, to providing artiicial substrates on which they would grow, and other techniques. USEPA SESD
(2007) describe the methods for periphyton surveys in wadeable streams. Barry and Kilroy (1994)
describe the sampling techniques used in New Zealand. Barbour et al. (1999) describe the periphy-
ton sampling techniques for Rapid Bioassessment Protocols (RBPs), which will be described in
more detail in Chapter 8 and are used as an indicator of aquatic health.
As with other aquatic plants, excess periphyton can be an environmental problem, and the pres-
ence of some forms is an indication of pollution, while the presence of a diverse and viable com-
munity is an indication of aquatic health, as will be discussed in Chapter 8. For example, diatoms
are particularly useful indicators of biological conditions because they are ubiquitous and found in
all lotic systems (Barbour et al. 1999). Conversely, Cyanobacteria are often an indication of pol-
lution and are generally an undesirable form of algae. As such, the determination of the composi-
tion and biomass of the periphyton is often a critical component of stream or nutrient assessment
studies.

6.2.2 p HytopLankton
Phytoplankton are loating plants, carried along with the currents. Like the periphyton, these are not
true plants but consist of algae and Cyanobacteria. According to the RCC, phytoplankton dominate
in higher-order streams, where velocities are less and the storage is greater. Phytoplankton types
are in abundance and will be discussed in more detail in a subsequent chapter on the biota of lakes
and reservoirs.

6.2.3 M acropHyteS
Macrophytes (from makros meaning large and phyton , plant) are, as their name implies, large
plants, either as an assemblage or individual, large enough to be seen without the aid of a micro-
scope. Macrophytes may be:

• Macrophytic algae (such as some green algae, members of the Protista kingdom, such as

Chara )

• Mosses (such as sphagnum, a member of the Bryophyte division of true plants or the

Plantae kingdom)

• Fern allies (such as Salvinia and Iosetes, are also true plants of the Pteridophyta division)

• Angiosperms (true lowering plants of the Anthophyta division)

Of these, the angiosperms make up the majority of aquatic macrophytes. The aquatic angio-
sperms are a diverse group and include species native to the United States and many that are inva-
sive and problematic.
Macrophytes are also commonly classiied based on their growth form, and Westlak (1975, as
given by WOW 2004) identiied four primary forms (Figure 6.5):

1. Emergents (such as cattails) on riverbanks and shoals are typically rooted in soil that is
near or below the waterline and have aerial leaves and reproductive structures. These are
found in the shallowest waters.

2. Floating-leaved species, such as pond lilies, occupy slow-current areas, are rooted in sub-
merged soils, and have aerial or loating leaves and reproductive structures.