Using Scientific Inquiry to Teach Students about Water Quality
Puche, Helena, Holt, Jame, The American Biology Teacher
Inquiry is a process of interaction between teacher and students whereby the teacher engages students in generating questions and pursuing answers through careful observation and reflection (Llewellyn, 2004). The inquiry cycle begins with a question that has to be comparative, time-wise, simple, and exciting. In this cycle (question [right arrow] action [right arrow] reflection [right arrow] question), students help decide what to compare, what to measure (compare at least two, measure one), and how to measure and collect the data (action). In the reflection
process, students explain their results and deliberate about what to do differently next time, which generates new questions. These are the stepping stones to reaching a global understanding of the inquiry process and involving students in doing science, both of which are conducive to more sophisticated comparisons later on.
One way to help students understand the scientific inquiry process is by encouraging them to investigate the quality of different types of water samples. This is important because the water quality in streams and rivers had been declining since the 1960s, becoming a serious concern (Feminella & Flynn, 1999). Because of the release of harmful pollutants in the water, such as heavy metals, sewage, and other chemical wastes, the Clean Water Act (CWA) was enacted in 1977. The goal of the CWA was to "restore and maintain the chemical, physical and biological integrity of the nation's waters" (CWA, 1977).
In order to identify which water sources were becoming polluted, a water-quality monitoring approach was needed. The traditional water-quality monitoring approach became a collection of water samples and laboratory analysis for suspended physical and chemical pollutants. However, a biological approach to water-quality monitoring was less costly and incorporated water organisms as a basis for pollution detection. The basis of biomonitoring is that certain types of water animals, such as macroinvertebrates, occur or thrive only under certain water-quality conditions (Lenat, 1988). When conditions change, such as when a stream receives a significant chemical run-off, the abundance and distribution of invertebrates in the affected site change as well (Feminella & Flynn, 1999).
To introduce students to the cycle of inquiry and how to conduct real-world science, the ideal situation would be to bring students outdoors to stimulate their curiosity. However, when this is not possible, an alternative is to bring the outside world into the classroom. This is the case with water samples taken from rivers and ponds that are filled with macro-invertebrates and microscopic organisms. They are easily identified and categorized using magnifying glasses, portable scopes, ID books, and pictures.
Macroinvertebrates are small animals, usually >1 mm long, that do not have backbones and live on the bottom of a pond, lake, stream, or river for at least part of their lives (Feminella & Flynn, 1999). They can be found in crevices between submerged stones, in organic debris, on aquatic vegetation, or within sediments. Most of the species are aquatic insects, represented by immature stages of mayflies, dragonflies, damselflies, stoneflies, caddisflies, flies, and beetles. However, other types of organisms can be commonly found in the water, such as crustaceans (side swimmers, crayfish, scuds), oligochaetes (earthworms, leeches), mollusks (snails, mussels, clams), and arachnids (aquatic mites).
We developed a semi-guided inquiry-based activity in the classroom to compare abundances of macroinvertebrate faunas from water samples that were assumed to have different pollution levels. Students related these macroinvertebrate abundances to pollution levels using macroinvertebrate tolerance levels and a key. The students processed the samples, analyzed and interpreted the data, and discussed the effects of pollution on macroinvertebrate populations. …