294
Exercise 22
The 14C method also has been applied following undisturbed incubation in chambers
of natural substrata [e.g., Wetzel (1964), and Burkholder and Wetzel (1989)].
LITTORAL ZOOPLANKTON AND PHYTOPLANKTON
The zooplankton of the littoral zone of lakes generally are quite distinct from those of
the open water. Many are adapted to living in close association with aquatic
macrophytes. Some, such as Chydorus, attain maximum population density in the
spring and decline to low numbers in the summer [e.g., Keen (1973)]. Other species are
aestival, overwinter as ephippial eggs, and attain maximum densities in late summer
and autumn (Goulden, 1971; Keen, 1973; Whiteside, 1974). High mortality in the
summer has been associated with predation by other invertebrates and by small fish.
The close association oflittoral zooplankton with the macrophytes makes quantitative sampling difficult. A long tube can be lowered into the water, stoppered tightly at
the upper end, and the composite vertical sample withdrawn [cf., also Pennak (1962)
and Exercise 15]. The sample then is passed through sieves to filter the zooplankton
from the water. Fast-swimming zooplankton may avoid collection by this method.
The activity of littoral zooplankton apparently is greater at night (Whiteside and
Williams, 1975), when presumably predation pressure is reduced. Many littoral
zooplankton migrate upward at night, away from vegetation. This migration has been
used to advantage in sampling, by placing a series of inverted funnels, connected to jars
by tubing, over the vegetation (Szlauer, 1963; Whiteside and Williams, 1975; Brakke,
1976). Zooplankton swim into these traps, and few can find their way out. The samplers
are left in place overnight, and zooplankton are collected in the early morning.
Efficiency is especially good for chydorid cladocerans.
LITTORAL BENTHIC FAUNA
The diversity and productivity of benthic animals can be particularly great in the
littoral zone. The presence of macrovegetation makes sampling difficult. A number of
specialized devices has been developed to sample the vegetation and associated fauna
quantitatively [see review of Kajak (1971) and Downing (1984)]. Once the plants and
sediments of a known area of the littoral zone are sampled, it is necessary to separate
the organisms from the extraneous materials collected. No simple method has been
devised, and most are tedious. All of the criteria discussed earlier (Exercise 13) for
quantitative sampling apply here as well, and certain of the sorting aides, such as
staining, can make easier the task of separating the organisms from the plant material.
EXERCISES
OPTION 1. FIELD ANALYSES ALONG A TRANSECT GRADIENT
Divide into five teams; each team will analyze different components of the littoral zone.
1. Establish a transect perpendicular to the shore line in the littoral zone of a representative lake
or reservoir. Extend the ends of the transect from the lower depth limit of submersed
Exercise 22
The 14C method also has been applied following undisturbed incubation in chambers
of natural substrata [e.g., Wetzel (1964), and Burkholder and Wetzel (1989)].
LITTORAL ZOOPLANKTON AND PHYTOPLANKTON
The zooplankton of the littoral zone of lakes generally are quite distinct from those of
the open water. Many are adapted to living in close association with aquatic
macrophytes. Some, such as Chydorus, attain maximum population density in the
spring and decline to low numbers in the summer [e.g., Keen (1973)]. Other species are
aestival, overwinter as ephippial eggs, and attain maximum densities in late summer
and autumn (Goulden, 1971; Keen, 1973; Whiteside, 1974). High mortality in the
summer has been associated with predation by other invertebrates and by small fish.
The close association oflittoral zooplankton with the macrophytes makes quantitative sampling difficult. A long tube can be lowered into the water, stoppered tightly at
the upper end, and the composite vertical sample withdrawn [cf., also Pennak (1962)
and Exercise 15]. The sample then is passed through sieves to filter the zooplankton
from the water. Fast-swimming zooplankton may avoid collection by this method.
The activity of littoral zooplankton apparently is greater at night (Whiteside and
Williams, 1975), when presumably predation pressure is reduced. Many littoral
zooplankton migrate upward at night, away from vegetation. This migration has been
used to advantage in sampling, by placing a series of inverted funnels, connected to jars
by tubing, over the vegetation (Szlauer, 1963; Whiteside and Williams, 1975; Brakke,
1976). Zooplankton swim into these traps, and few can find their way out. The samplers
are left in place overnight, and zooplankton are collected in the early morning.
Efficiency is especially good for chydorid cladocerans.
LITTORAL BENTHIC FAUNA
The diversity and productivity of benthic animals can be particularly great in the
littoral zone. The presence of macrovegetation makes sampling difficult. A number of
specialized devices has been developed to sample the vegetation and associated fauna
quantitatively [see review of Kajak (1971) and Downing (1984)]. Once the plants and
sediments of a known area of the littoral zone are sampled, it is necessary to separate
the organisms from the extraneous materials collected. No simple method has been
devised, and most are tedious. All of the criteria discussed earlier (Exercise 13) for
quantitative sampling apply here as well, and certain of the sorting aides, such as
staining, can make easier the task of separating the organisms from the plant material.
EXERCISES
OPTION 1. FIELD ANALYSES ALONG A TRANSECT GRADIENT
Divide into five teams; each team will analyze different components of the littoral zone.
1. Establish a transect perpendicular to the shore line in the littoral zone of a representative lake
or reservoir. Extend the ends of the transect from the lower depth limit of submersed