How to collect Diatoms in the wild
Objective: obtain a sample of fresh water diatom diversity using a glass slide method
Purpose: sampling a diatom population in fresh water will allow the study of diatom diversity in fresh water systems.
Background: Diatoms may be extremely abundant in both freshwater and marine ecosystems; it is estimated that 20% to 25% of all organic carbon fixation on the planet (transformation of carbon dioxide and water into sugars, using light energy) is carried out by diatoms. This is possible because they contain chlorophyll. Diatoms are thus a major food resource for marine and freshwater microorganisms and animal larvae, and are a major source of atmospheric oxygen.
Diatoms are a major component of plankton, free-floating microorganisms of marine or freshwater environments. Not all diatoms float freely though; many cling to surfaces such as aquatic plants, mollusks, crustaceans, and even turtles. Whales may carry dense growths of diatoms on their skin. Some may even be found in soils or on moist mosses.
Diatoms only construct new walls during cell division. After the cell divides, the epitheca and hypotheca separate, and new valves are laid down between them. Since the frustule cannot grow once it has been laid down, the mean size of a dividing population of diatoms gets smaller and smaller with time. This would be a rather bad state of affairs if diatoms could only reproduce by division! Fortunately, diatoms can also reproduce sexually, producing offspring that secrete a wholly new cell wall from scratch.
Material:
· Glass microscope slide
· Flat piece of Styrofoam approximately 10 cm X 10cm
· Razor blade or other thin cutting device
· Rubber band or tape
· Permanent marker
Procedure:
1. Cut a 10 X 10 piece of Styrofoam
2. Cut a slit in the middle of the Styrofoam large enough for the slide to fit through snugly.
3. Wrap a rubber band on one end of the glass slide
4. Slide glass slide though hole cut in the Styrofoam so that the rubber band rests against the foam, keeping it from slipping through.
5. The foam piece should float with the slide looking like a keel on the bottom of a sail boat.
6. Place the constructed diatom collector on the pond’s surface for 3- 5 days.
7. Collect the slide and observe under a microscope.
Data & Results
Using the online source: http://researcharchive.calacademy.org/research/diatoms/genera/ , identify several diatoms in the slides.
Data Collection:
1. Sketch 10 different diatoms as seen through the microscope.
2. Describe their detail movement and all visible structures.
3. Estimate the total number of Diatoms on your slide. This is a visual population count for the given area of a slide.
Results:
1. Research record the Ecology of freshwater Diatoms.
2. What are some key physiological features of all Diatoms?
3. Compare Marine Diatoms with Freshwater Diatoms.