296
Exercise 22
750nm and cell differences; ODa = optical density at 665 nm after acidification,
corrected for turbidity at 750 nm and cell differences; v = volume (ml) of solvent used
to extract the sample; 1 = path length (cm) of spectrophotometric cell; and
Ilgphaeopigment per sample = [11.9(v/l)] [(1.70Da) - Chi a]
b. Collect the attached algae from the surfaces of representative macrophytes for which the
surface area can be estimated [e.g., submersed portion of a bulrush (Scirpus) plant where
the area (A) can be estimated as the convex surface of the frustum of a cone: A = h/2 (c + c'),
where c 'and c' are circumferences (c = 2nr) of the bases and h is the slant height].
Determine the pigment concentrations per unit area and compare to those determined
from artificial substrata located within the same area.
c. Take cores (ca. 2 cm 2 in area) of the sediments and extract the pigments from the upper
2 cm, correcting for phaeopigment degradation products. Compare these concentrations
with those found in algae attached to substrata "incubated" near the sediments.
d. If possible, determine the in situ rates of primary productivity of algae attached to the
stems and leaves of underwater portions of emergent macrophytes by modification of
the oxygen difference or 14C-uptake methods as outlined in Exercise 14.
i. Place segments ofthe stems into light and dark bottles (inject 14C) and incubate at the
depth from which the plants were taken. Care must be taken not to disturb the
epiphytic microflora.
ii. Simultaneously, incubate control bottles containing only the littoral water. Why?
111. At the end of the incubation, fix the oxygen chemically or, when the 14C-uptake
method is used, remove the attached algae by scraping and filter onto membrane filters
along with the water content of the bottles.
iv. Determine the surface area of the macrophyte segment (see above).
v. Evaluate the rate of primary productivity of the attached algae, correcting for that of
littoral phytoplankton of the control bottles.
vi. Calculate the primary productivity of the epiphytic algae per unit area per unit time
(see Exercise 14). Using the data of other teams, estimate the productivity per square
meter of the littoral zone.
5. A fourth team should collect phytoplankton and zooplankton samples in the littoral zone
and make qualitative and quantitative comparisons of these communities to those found
at a similar depth in the open water of the pelagial zone.
a. Using a tube sampler, take composite vertical samples of a known volume along transects
through the littoral zone and different vegetation.
b. Put the sample into a large container, mix well, and withdraw a small sample for
phytoplankton analysis. Preserve with Lugol's solution (see Exercise 10).
c. Filter the whole sample through Nitex mesh screens of a mesh size of ca. 45 pm.
Concentrate by washing and preserve in a sample bottle (see Exercise II).
d. Proceed to the open water of the lake and take several samples of the pelagial water to
analogous depths by the same methods.
e. In the laboratory, identify the dominant species of littoral phytoplankton and zooplankton. By the methods outlined in Exercise 10 and 11, enumerate the organisms and
calculate the numbers per liter or cubic meter. Compare to those species and abundances
found in the open water of the lake.
6. A fifth team should sample the littoral zone for benthic fauna.
a. Because of the difficulties associated with the separation of the benthic fauna from the
vegetation and sediments, it is suggested that three areas be sampled: one among the
emergent vegetation with some standing water and two sites among submersed vegetation,
one in shallow and one in deeper water.
b. Using the large plastic cylinder (see "Apparatus and Supplies"), carefully but quickly
lower the cylinder through the vegetation and work in into the sediments to a depth of
ca. 10cm. With several persons holding the cylinder rigid, work a sharpened metal or
plastic plate under the end penetrating the sediments. With the end sealed, bring the
entire sample to the surface and deposit it into a large pail (see Exercise 5).
Exercise 22
750nm and cell differences; ODa = optical density at 665 nm after acidification,
corrected for turbidity at 750 nm and cell differences; v = volume (ml) of solvent used
to extract the sample; 1 = path length (cm) of spectrophotometric cell; and
Ilgphaeopigment per sample = [11.9(v/l)] [(1.70Da) - Chi a]
b. Collect the attached algae from the surfaces of representative macrophytes for which the
surface area can be estimated [e.g., submersed portion of a bulrush (Scirpus) plant where
the area (A) can be estimated as the convex surface of the frustum of a cone: A = h/2 (c + c'),
where c 'and c' are circumferences (c = 2nr) of the bases and h is the slant height].
Determine the pigment concentrations per unit area and compare to those determined
from artificial substrata located within the same area.
c. Take cores (ca. 2 cm 2 in area) of the sediments and extract the pigments from the upper
2 cm, correcting for phaeopigment degradation products. Compare these concentrations
with those found in algae attached to substrata "incubated" near the sediments.
d. If possible, determine the in situ rates of primary productivity of algae attached to the
stems and leaves of underwater portions of emergent macrophytes by modification of
the oxygen difference or 14C-uptake methods as outlined in Exercise 14.
i. Place segments ofthe stems into light and dark bottles (inject 14C) and incubate at the
depth from which the plants were taken. Care must be taken not to disturb the
epiphytic microflora.
ii. Simultaneously, incubate control bottles containing only the littoral water. Why?
111. At the end of the incubation, fix the oxygen chemically or, when the 14C-uptake
method is used, remove the attached algae by scraping and filter onto membrane filters
along with the water content of the bottles.
iv. Determine the surface area of the macrophyte segment (see above).
v. Evaluate the rate of primary productivity of the attached algae, correcting for that of
littoral phytoplankton of the control bottles.
vi. Calculate the primary productivity of the epiphytic algae per unit area per unit time
(see Exercise 14). Using the data of other teams, estimate the productivity per square
meter of the littoral zone.
5. A fourth team should collect phytoplankton and zooplankton samples in the littoral zone
and make qualitative and quantitative comparisons of these communities to those found
at a similar depth in the open water of the pelagial zone.
a. Using a tube sampler, take composite vertical samples of a known volume along transects
through the littoral zone and different vegetation.
b. Put the sample into a large container, mix well, and withdraw a small sample for
phytoplankton analysis. Preserve with Lugol's solution (see Exercise 10).
c. Filter the whole sample through Nitex mesh screens of a mesh size of ca. 45 pm.
Concentrate by washing and preserve in a sample bottle (see Exercise II).
d. Proceed to the open water of the lake and take several samples of the pelagial water to
analogous depths by the same methods.
e. In the laboratory, identify the dominant species of littoral phytoplankton and zooplankton. By the methods outlined in Exercise 10 and 11, enumerate the organisms and
calculate the numbers per liter or cubic meter. Compare to those species and abundances
found in the open water of the lake.
6. A fifth team should sample the littoral zone for benthic fauna.
a. Because of the difficulties associated with the separation of the benthic fauna from the
vegetation and sediments, it is suggested that three areas be sampled: one among the
emergent vegetation with some standing water and two sites among submersed vegetation,
one in shallow and one in deeper water.
b. Using the large plastic cylinder (see "Apparatus and Supplies"), carefully but quickly
lower the cylinder through the vegetation and work in into the sediments to a depth of
ca. 10cm. With several persons holding the cylinder rigid, work a sharpened metal or
plastic plate under the end penetrating the sediments. With the end sealed, bring the
entire sample to the surface and deposit it into a large pail (see Exercise 5).