Lab 11 & 12: Phytoplankton and Zooplankton
Introduction
In these lab sessions we will identify and photograph common species of
phytoplankton and zooplankton found in preserved Allen Lake and Lake Erie samples,
and live pond samples. We will examine Lake Erie specimens from May, July, and
August for evidence of seasonal succession in both algae and zooplankton. We will
compare the August sample from Lake Erie to the Allens Lake sample for difference in
community composition between a small glacial lake and a great lake.
Procedures
Samples will be provided from Allen Lake (1 sample), and Lake Erie (3 samples:
May, July, August). Additional live samples from ponds will be provided in order to
observe smaller algae and some live zooplankton. Your goal should be to identify and
photograph at least 10 different algae species and 10 zooplankton species overall.
1. Examine each of the specimens provided. Gently mix each sample and then place a
drop of sample on a microscope slide. Scan slide at low magnification, then use higher
magnification to examine and photograph algae specimens.
2. Rinse and dry slide between samples, disposing of coverslips. Wash and dry slide after
final sample.
3. Use provided guides and the internet to identify algae to the narrowest possible
taxonomic group. TA and instructor will help to confirm your identifications.
4. Use digital camera to record images of specimens and then store images as .jpg files
on your UTAD server space. Note which samples the specimens came from.
5. For each sample, make several transects across your micoscope slide at a lower power.
Note the 2 or 3 most abundant species of phytoplankton and zooplankton in each sample
and rank the species in order of abundance. This information will be used to answer
questions about seasonal succession.
6. For descriptions, use the internet to find information about your specimens.
Report
Results of algae and zooplankton labs will be combined in one report including
the zoobenthos lab (lab 10). For the algae and zooplankton portions, the report should
consist of:
1. Introduction (see above)
2. Methods. Briefly discuss methods (types of microscope, magnifications used,
sources use for identification, etc)
3. Results and Discussion (combined) This will consist of
a. digital images of algae and zooplankton pasted into your report. Each
image should be accompanied by a caption describing the specimen
identification, date and location, and magnification. For example “Figure 1. Asterionella sp. colony (400x), Lake Erie, May 16, 2007”
Note that genus and species names are generally italicized.
b. A brief paragraph describing the habitat of each specimen.
i.
For algae, this description may include whether this species
prefers productive or unproductive lakes (high P or lower P),
prefers spring, winter, or fall. Mixing or stratified conditions,
etc. – and anything interesting you read about this species.
ii. For zooplankton, also describe preferred habitats and whether
the species is a grazer (herbivore), omnivore or a predator.
4. Create a small table to summarize the relative dominance of the most common
zooplankton and phytoplankton species in the 3 Lake Erie and 1 Allens Lake
sample. The table might look something like this:
Taxa
Pediastrum
Fragilaria
Asterionella
Microcystis
Dinobryan
LE (May) LE (July)
1
1
2
3
2
3
Cyclopoid Cop
Calanoid Cop
Daphnia
Bosmina
Diaphanosma
1
2
3
1
2
3
LE (Aug)
1
2
3
Allen (Sept)
3
2
1
2
1
2
3
3
1
5. Answers to questions regarding dominant species, predation, and seasonal
succession.
Questions
1. Did you find any evidence of seasonal succession in Lake Erie between May
and August? Describe how the phytoplankton and zooplankton communities
changed over time. (Graduate Students: Find one online or text source to
support whether your observation is typical or atypical of temperate zone
lakes)
2. How are the phytoplankton zooplankton communities alike and different
between Allens Lake and Lake Erie (August sample)?
a. What do the algal communities suggest about nutrient and mixing
differences between the two lakes? (Graduate Students: Find an
internet or text source to support your answer)
b. What do the zooplankton communities suggest regarding differences
in fish or invertebrate predation between the two lakes? (Graduate
Students: Find an internet or text source to support your answer)
3. Did you find any exotic (non-native) species in your samples? List them and
the possible methods of entry into the lake.
4. Did you find any zooplankton predators in your samples? List them. What
prey species did you find in the same sample with the predator?
5. The Lake Erie and Allens lake samples were collected using a plankton net
with a mesh size of 112 um. How might this method of collection have
created a biased representation of the true plankton community in the lake?