7923

• UCREFRP Catalog Number: 7923
• Author: Carter, J. G. and V. A. Lamarra.
• Title: An Ecosystem Approach To Environmental Management, Chapter 17.
• USFW Year: n.d.
• USFW - Doc Type: 261-287
• Copyright Material: YES

the particular environmental conditions present (such as
stream temperature, velocity, oxygen concentration, light
intensity, water hardness or alkalinity). It should also
be noted that within a specific stream reach, a habitat
type (pool or riffle) will also affect the distribution of
macroinvertebrates. Hynes (1970) has extensively
documented the truly unique or specialized
macroinvertebrate adaptations found in riffle or pool
systems. Distributional patterns, within stream systems
of the same size, in terms of occurrence and density, are
influenced by water movement and the nature of the surface
available for colonization (substrate particle size). It
has been previously discussed how velocity and turbulence
limit the ranges of particle size, and thus
macroinvertebrate distribution. Data as to the role of
the above factors on macroinvertebrate distributions and
abundances in the White River are being collected in the
ongoing 1981 environmental program.

Undoubtly, food is the ultimate determinant of
macroinvertebrate distribution and abundance in
non-perturbed running waters. Cummins (1973) has
described the type of community based on food habits. An
analysis of the White River macroinvertebrate data
indicates the presence of the following groups:

1. grazers and scrapers-herbivores
attached algae.

feeding

on

2. shredders-large particle feeding detritivores.

3. collectors-both suspension (filter) and deposit
(surface) fine particle feeding detritivores.

4. predators-carnivores

The role that the primary producers play in the
stream system is related to the previous discussion on
CPOM and FPOM. If the major primary producer is a
micro-algae, its biomass may be reduced by direct
predation (i.e., by macroinvertebrates, functionally
called scrapers) or be sluffed off into the FPOM pool.
However, if it is an aquatic hydrophyte, or a moss, it may
enter the food chain, almost exclusively during die off,
therefore following the same general CPOM pathway as
terrestrial inputs.

There are several important factors that must be
studied in the White River if natural fluctuations in the
primary producers are to be fully understood. Depth and

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