Algae - Botany 330
SUMMARY OF WRITTEN LAB EXERCISE REPORTS
These exercises were designed to provide 1) instruction in some important techniques
useful in studying algae (and other organisms), 2) experience in technical writing, 3) and
numeracy practice. You might encounter similar assignments in your future occupation
if you are asked to prepare technical reports or grant proposals. Due dates to be
announced.
Exercise 1. Use of the Sedgewick-Rafter Cell and Inverted Microscope/Settling
Chamber (Utermöhl) Techniques for Counting Algae in Mixed Samples.
Follow the instructions in I A and I B of "Quantitative Determination of Algal Density and
Growth" (with modifications and additional advice supplied in class) to count the algae in
the mixed assemblage provided, by two methods. You will have to take turns using the
two inverted microscopes available. You can work in pairs, sharing the counting effort,
and reporting results as a team.
Turn in a written statement of at least a page in length, with counts, and a statement of
your perception of the pros/cons of using the Sedgewick-Rafter vs the inverted
microscope method for counting algae in mixed assemblages. 40 points.
Exercise 2. Comparison of the Use of the Hemacytometer vs Coulter Counter
Method for Counting Algal Cells in Unialgal Cultures.
Use the instructions in II B in "Quantitative Determination of Algal Density and Growth"
to make a hemacytometer count of the algae in a cultured sample that we will provide. You will have to take turns, because we do not have enough chambers for everyone to do this exercise at the same time. Be sure to mix the sample well before removing an aliquot! Do at least 5 replicate counts.
Now, with the aid of the instructor, count the same sample, on the same day, with the
Coulter Counter--the whole class can use the same 5 replicate counts. Pairs of students
may share the counting efforts and preparation of the report. Turn in a statement at
least one page in length of the comparative counts (are they significantly different?),
and your perception of the pros/cons and potential sources of error for the two methods.
40 points.
Exercise 3. Algal Collections from Lake Mendota and Nothern WI humic lakes
Turn in 5 separate sheets of drawing paper, each with a single large (i.e. fill the whole page) drawing of an identified algal genus from samples from Northern WI humic lakes. Instructors will help with identifications, on request. Label distinguishing characteristics such as chloroplast(s), flagella, trichocysts, mucilaginous sheaths, or heterocysts. The point of this exercise is to foster observational powers and an appreciation of diversity differences in eutrophic and dystrophic waterbodies. Put your name on each sheet and staple the sheets together. Compare with your collection from L. Mendota. Write at least half a page on your impressions of diversity in the two waterbodies. Were any of the genera you found in other collections also present in L. Mendota and vice versa? 40 points.
Exercise 4. Diatoms of Lake Wingra.
Read "Sample Preparation, Methods, and Literature for Diatoms." The most effective
method for assaying many diatoms from natural collections requires cleaning, because
distinctive frustule markings are obscured by cell contents (chloroplast, etc.). The most
effective methods for making permanent mounts of diatoms require use of strong acids,
which we prefer not to attempt in this course, because of safety considerations.
Therefore, we have assembled a collection of permanent slides made from L. Wingra
collection for your use.
First, examine a fresh collection of L. Wingra diatoms (mostly members of the
periphyton associated with water milfoil). Make a list of the genera that you can
confidently identify on the basis of cell or colony shape, or presence of stalks (as with
Cymbella.). Use the Prescott key to start. Consult other references as needed.
Now, examine the prepared slides, and make a list of all the species that you can confidently identify on the basis of frustule shape or ornamentation. You will want to use the notebooks of photos of identified L. Wingra diatoms. The photos were made from the same cleaned preparations that you are using.
This exercise should be done individually. Turn in the two lists, together with a brief statement of a page or so comparing the lists and explaining why they might be different. 40 points.
Exercise 5. Algal Isolation & Culture Techniques.
Read "Isolation and Culture of Algae," and watch demonstrations for: 1) pulling
micropipettes, 2) spraying plates, 3) streaking plates, 4) single cell/colony/filament
isolation, 5) making algal culture media & use of the autoclave, & 6) function of the algal
growth room/chambers. Make sure that you have heard all 6 demonstrations.
Now, from one of your field collections (preferably the one from Grass Lake because
various algal taxa are big enough to micropipette easily, but other collections are ok),
use the media provided to make several single-alga isolations. You can choose to
isolate desmids, chrysophytes, cryptomonads, diatoms, or blue-greens. You will need to
make a supply of micropipettes. These don't need to be autoclaved because the heat of
pulling them sterilizes them, but use a separate pipette for each organism. Also try the
spraying technique. You will need to check your isolates for growth and contamination
at various points in the semester; you may need to subculture isolates.
Turn in at least one unialgal culture, identified to genus, with information on origin, date
isolated, and isolator (you) written on the tube/dish with Sharpie. Each individual should
turn in at least one culture. The culture should be accompanied by a single page
description of the isolation process and interesting aspects of the organism. 40 points.