Science of Water : Concepts and Applications

Water Ecology 157
The environment includes everything important to the organism in its surroundings. The
organism’s environment can be divided into four parts:
1. Habitat and distribution—its place to live
2. Other organisms—whether friendly or hostile
3. Food
4. Weather—light, moisture, temperature, soil, etc.
There are two major subdivisions of ecology: autecology and synecology. Autecology is the
study of the individual organism or a species, for example, when a biologist spends his/her entire
lifetime studying the ecology of the salmon. It emphasizes life history, adaptations, and behavior.
It is the study of communities, ecosystems, and the biosphere. Synecology, on the other hand, is the
study of groups of organisms associated together as a unit. It deals with the environmental problems
caused by humankind. For example, the effects of discharging phosphorus-laden effl uent into
a stream or lake involve several organisms. The activities of human beings have become a major
component of many natural areas. As a result, it is important to realize that the study of ecology
must involve people.
KEY DEFINITIONS
Each division of ecology has its own set of terms that are essential for communication between
ecologists and those who are studying running and standing water ecological systems. For this reason,
along with basic ecological terms, key terms that specifi cally pertain to this chapter are defi ned
and presented in the following section.
Abiotic factor The nonliving part of the environment composed of sunlight, soil, mineral
elements, moisture, temperature, and topography.
Aeration A process whereby water and air or oxygen are mixed.
Bacteria Among the most common microorganisms in water. Bacteria are primitive, singlecelled
organisms with a variety of shapes and nutritional needs.
Biochemical oxygen demand (BOD) A widely used parameter of organic pollution applied to
both wastewater and surface water … involving the measurement of the dissolved oxygen
used by microorganisms in the biochemical oxidation of organic matter.
Biotic factor (community) The living part of the environment composed of organisms that
share the same area; are mutually sustaining and interdependent; and constantly fi xing,
utilizing, and dissipating energy.
Biotic index The diversity of species in an ecosystem is often a good indicator of the presence
of pollution. The greater the diversity, the lower the degree of pollution. The biotic index
is a systematic survey of invertebrate aquatic organism used to correlate with river
quality.
Climax community The terminal stage of an ecological succession in an area.
Community In an ecological sense, community includes all the populations occupying a given
area.
Competition A critical factor for organisms in any community. Animals and plants must
compete successfully in the community to stay alive.
Decomposition The breakdown of complex material into simple substances by chemical or biological
processes.
Dissolved oxygen (DO) The amount of oxygen dissolved in a stream is an indication of the
degree of health of the stream and its ability to support a balanced aquatic ecosystem.
Ecosystem The community and the nonliving environment functioning together as an ecological
system.