SUMMARY: Three urban stream samples were collected during both dry and rainy seasons in Brazil. Ciliates were classified and identified in each stream. The relationships between the ciliates, abiotic factors, and biotic factors are discussed in the last section of the paper. Some abiotic factors include: turbidity of the water, temperature, oxygen levels, and pH. Biotic factors include: bacteria growth, coliform formation, and algae growth. The study concluded that these abiotic and biotic factors affect ciliate growth more than the seasonal changes did.
LESSON COMMENTS: This study is a good one to try to replicate for both middle and high school students. Taking a day to go out and collect samples from bodies of water near the school (in this study, samples were collected from urban streams, but for a school field trip any fresh body of water will work). Students can identify and classify the organisms during different seasons, using the chart in this paper. This is a great way for students to see changes in ciliate population and observe other ciliate behaviors such as asexual and sexual reproduction, predation, decomposition, etc. To add another layer to this long-term lab, teachers can also do water quality testing on the samples to show levels of pollutants and abiotic factors such as oxygen, nitrogen, and phosphorus. Finally, combining results from the ciliate population observations and water quality tests should give students a better idea of how organisms and abiotic factors influence each other in an ecosystem.
Debastiani, C., Meira, B. R., Lansac-Tôha, F. M., Velho, L. F., & Lansac-Tôha, F. A. (2016). Protozoa ciliates community structure in urban streams and their environmental use as indicators. Brazilian Journal of Biology,76(4), 1043-1053. doi:10.1590/1519-6984.08615