EXERCISE 24
Diurnal* Changes in a Stream
Ecosystem: An Energy and
Nutrient Budget Approach
Numerous physical, chemical, and biological
processes interact to produce a stream ecosystem.
Small streams tend to reflect the conditions of
the drainage area and usually are chemically and
physically dynamic and biologically rich.
In this exercise we will attempt to observe
various properties of a small stream ecosystem.
By measuring and integrating some of the major
physical and biological components of the energy
and nutrient budgets (energy and mass balances)
during a 24-h period, it will be possible to
evaluate aspects of the functional role of streams
within the landscape as a whole. We will be
interested in the fate of solar radiation as it enters
the ecosystem, how much is used to heat the
water, how much potential energy is lost as water
flows downhill, how much of the solar energy is
utilized by plant photosynthesis in the stream
and converted to stored chemical energy, and
how much of the stored chemical energy is used
by various components of the stream ecosystem.
Some attention also will be given to the flux of
nutrients through the stream ecosystem.
Small steams provide excellent opportunities
for such studies. Sampling can be done relatively
efficiently and inexpensively. In addition to the
techniques and approaches discussed below, see
Odum (1957), Teal (1957), Minckley (1963), Hall
(1972), and Fisher and Likens (1973) for further
information about such studies of stream and
spring ecosystems.
* Diurnal refers to an event that occurs in a day or recurs each day. Diel ( = day) is a more recent
term that refers to events that recur at intervals of 24h or less (Odum, 1971). In studies of
community periodicity, when whole groups of organisms exhibit synchronous activity patterns
in the day-night cycle, diurnal is used sometimes in a more restricted sense, referring to animals
that are active only during the day versus others that are active only during the period of
darkness ( = nocturnal) and still others only during twilight periods (crepuscular).
315
Diurnal* Changes in a Stream
Ecosystem: An Energy and
Nutrient Budget Approach
Numerous physical, chemical, and biological
processes interact to produce a stream ecosystem.
Small streams tend to reflect the conditions of
the drainage area and usually are chemically and
physically dynamic and biologically rich.
In this exercise we will attempt to observe
various properties of a small stream ecosystem.
By measuring and integrating some of the major
physical and biological components of the energy
and nutrient budgets (energy and mass balances)
during a 24-h period, it will be possible to
evaluate aspects of the functional role of streams
within the landscape as a whole. We will be
interested in the fate of solar radiation as it enters
the ecosystem, how much is used to heat the
water, how much potential energy is lost as water
flows downhill, how much of the solar energy is
utilized by plant photosynthesis in the stream
and converted to stored chemical energy, and
how much of the stored chemical energy is used
by various components of the stream ecosystem.
Some attention also will be given to the flux of
nutrients through the stream ecosystem.
Small steams provide excellent opportunities
for such studies. Sampling can be done relatively
efficiently and inexpensively. In addition to the
techniques and approaches discussed below, see
Odum (1957), Teal (1957), Minckley (1963), Hall
(1972), and Fisher and Likens (1973) for further
information about such studies of stream and
spring ecosystems.
* Diurnal refers to an event that occurs in a day or recurs each day. Diel ( = day) is a more recent
term that refers to events that recur at intervals of 24h or less (Odum, 1971). In studies of
community periodicity, when whole groups of organisms exhibit synchronous activity patterns
in the day-night cycle, diurnal is used sometimes in a more restricted sense, referring to animals
that are active only during the day versus others that are active only during the period of
darkness ( = nocturnal) and still others only during twilight periods (crepuscular).
315