306
Exercise 23
medium will consist of filtered (0.45-.um pore size Millipore filter) water augmented
by autoclaved water from the same source.
During the first session of the second week, add enough nitrogen, phosphorus,
or both to one of the reservoirs (containing sterile water) to create an excess
concentration of these elements over that already present in the water. This enriched
medium will be pumped into one of the culture chambers for the next one to two
weeks.
A number of parameters will be measured by each laboratory section or group
during the three-week period. The following is a chronology of the sampling and
analysis requirements. Analytical techniques are discussed elsewhere in the appropriate exercises. Because of the limited amount of water delivered from the chemostat,
some parameters can be measured only on one water sample during a day. For.these
samples, it will be necessary to work as a group and to share the data.
First Week
1. Obtain nutrient-poor pond water, filter it through a 50-.um mesh net to remove
larger zooplankton, and add 81 to the chamber of each chemostat. Start the
chemostats. The chemostats (both culture chamber and medium reservoirs) should
be labeled "control" or "enriched," as appropriate.
2. As a group, collect two separate 40-ml samples from the net-filtered water. Analyze
immediately for N, P, and K concentrations (see Exercise 7) or freeze for analysis at a
later time.
3. As a group, collect a 2-1 sample for phytoplankton from the filtered water. Add
Lugol's preservative and mix well. Distribute into 50- to 200-ml settling-counting
chambers and label. Place the chambers in an area of the laboratory where they will
remain undisturbed for one week.
4. Count phytoplankton in a sample of the filtered water (see Exercise 10).
5. Measure the pH of the filtered water.
Sections e, C, and 0 (Days 2, 4, and 6)
1. Form two groups; each group collects a 40-ml water sample from the outflow tube
from one of the chemos tats. Analyze these samples for N, P, and K content or freeze.
Label all samples with the following information: collection date, time, chemostat
type, your section, and your initials.
2. Each group collects a 200-ml phytoplankton sample from the outflow tube of one of
the chemostats and processes it according to the directions given in Exercise 10.
3. Each group measures the pH and temperature of water sample from the outflow
(about 30 ml). Record the temperature as the water is being collected to get a more
reliable measurement.
4. Each group checks the "culture medium reservoir" and refills it as required with
autoclaved water (about 81 removed every 50 h).
Second Week
Section A (Day 8)
1. Each group collects and chemically analyzes (or freezes) two separate 40-ml water
samples from one of the chemostats. Collect the water from the outflow tube and
label it carefully.
Exercise 23
medium will consist of filtered (0.45-.um pore size Millipore filter) water augmented
by autoclaved water from the same source.
During the first session of the second week, add enough nitrogen, phosphorus,
or both to one of the reservoirs (containing sterile water) to create an excess
concentration of these elements over that already present in the water. This enriched
medium will be pumped into one of the culture chambers for the next one to two
weeks.
A number of parameters will be measured by each laboratory section or group
during the three-week period. The following is a chronology of the sampling and
analysis requirements. Analytical techniques are discussed elsewhere in the appropriate exercises. Because of the limited amount of water delivered from the chemostat,
some parameters can be measured only on one water sample during a day. For.these
samples, it will be necessary to work as a group and to share the data.
First Week
1. Obtain nutrient-poor pond water, filter it through a 50-.um mesh net to remove
larger zooplankton, and add 81 to the chamber of each chemostat. Start the
chemostats. The chemostats (both culture chamber and medium reservoirs) should
be labeled "control" or "enriched," as appropriate.
2. As a group, collect two separate 40-ml samples from the net-filtered water. Analyze
immediately for N, P, and K concentrations (see Exercise 7) or freeze for analysis at a
later time.
3. As a group, collect a 2-1 sample for phytoplankton from the filtered water. Add
Lugol's preservative and mix well. Distribute into 50- to 200-ml settling-counting
chambers and label. Place the chambers in an area of the laboratory where they will
remain undisturbed for one week.
4. Count phytoplankton in a sample of the filtered water (see Exercise 10).
5. Measure the pH of the filtered water.
Sections e, C, and 0 (Days 2, 4, and 6)
1. Form two groups; each group collects a 40-ml water sample from the outflow tube
from one of the chemos tats. Analyze these samples for N, P, and K content or freeze.
Label all samples with the following information: collection date, time, chemostat
type, your section, and your initials.
2. Each group collects a 200-ml phytoplankton sample from the outflow tube of one of
the chemostats and processes it according to the directions given in Exercise 10.
3. Each group measures the pH and temperature of water sample from the outflow
(about 30 ml). Record the temperature as the water is being collected to get a more
reliable measurement.
4. Each group checks the "culture medium reservoir" and refills it as required with
autoclaved water (about 81 removed every 50 h).
Second Week
Section A (Day 8)
1. Each group collects and chemically analyzes (or freezes) two separate 40-ml water
samples from one of the chemostats. Collect the water from the outflow tube and
label it carefully.