Observing Microscopic Life

• To prepare the pond scum for close examination with a microscope, students must collect a sample of pond scum and deposit it on a clear slide and cover it with a slide cover. Quickly place it under a microscope and observe the organisms. Put the back light on low, if possible, to avoid frying the protozoa.
  
  

Identifying Pond Scum Life

• Paramecia are one of the most recognizable organisms; they appear as oblong cells floating in the pond scum. Actinopods are rarer; however, they are also very recognizable. They are omnivorous creatures covered with spines and may contain the undigested remnants of their former prey (apparent as dark spots). Vortacella are singled-celled organisms with tiny hair-like appendages called "cilia," which they use to absorb food.
  
  

Culturing Pond Life

• To culture algae for experimentation, one must provide a suitable growing environment. A simple jar of garden soil, distilled water and plant food provides this environment. Sterilize the jar in a pressure cooker to make sure that foreign bacteria does not enter the culture. Then scrape a small bit of green pond scum with a cotton swab and put it in the jar.
  
  

Isolating Algae Specimens

• Initially, the culturing jar will be home to many species of algae. To isolate individual species of algae, take a swab of cells and spread them on a petri dish with agar implanted. Agar is a sterile, gelatinous growth medium. After a few days, the small collection of cells will grow. Students can then further isolate the cells by taking a new swab and implanting it on a new petri dish. It will take between two and five generations for a unique strain of algae to emerge; when it does, place it in a new culture jar for use in experiments.
  
  

Pond Scum Experiments

• Once the students have isolated species of algae, they can begin experiments to see how individual chemicals affect algae growth. Using tall, thin containers like test tubes or shot glasses, prepare different solutions of the chemical, ranging in concentration from almost pure water to pure chemical. Add the solutions into isolated culture jars with a sample of algae and wait a week for the results. Students can record the clarity of the water and algae count under a microscope.