Skip Navigation


Author(s): Nancy Moreno, PhD, and Barbara Tharp, MS.

Can Nutrient in Water Cause Harm?

In general, two types of sources contribute to water pollution in the United States. Point sources, such as factories, sewage treatment plants, abandoned mines and oil tankers, introduce pollutants into waterways at single places. This type of pollution is not always significant in terms of volume, but it is the major point of entry for toxic chemicals into water supplies. In most cases, point sources of pollution can be identified and monitored by government agencies. 

Non-point source pollution occurs across large areas of land that drain into underground and surface water sources. Pollutants are collected and deposited by water as it travels over land and through layers of soil. Major contributors to non-point source pollution include agricultural activities (which can add chemical fertilizers, pesticides, manure and soil to water), logging and other activities that leave the soil surface bare (allowing soil to be washed into waterways), urban and suburban areas (where lawn chemicals, household chemicals, motor oil and gasoline can enter water supplies), and septic systems (which can contaminate underground water supplies with disease-causing bacteria). Non-point sources of water pollution are difficult to control because they are spread over large areas, and often result from the actions of many individuals. 

fertilizers lead to murky water and overgrowth of plants, green algae and some microorganisms in the marsh, threatening the marsh animals and their habitat. Riff and Rosie (characters in the story) are able to connect development of the park to changes that they have observed in the marsh.In the story, Mystery of the Muddled Marsh, which accompanies this unit, runoff from a new park development introduces soil and fertilizers into a marsh and stream ecosystem. Excess soil and 

In this activity, students investigate, on a small scale, the changes that occur when fertilizers are added to pond water cultures.

The water and plants in Dyke Marsh are not only adversely affected by contaminants already in the fresh water and salt water, but also by shoreline erosion and surface runoff.

Session 1: Setup pond water cultures

  1. Begin by asking students if they remember what happened to Marigold Marsh in the story, Mystery of the Muddled Marsh. Allow time for everyone to share his or her ideas. Then, tell students that they will be able to see some of the tiny plants and animals that lived in the muddled marsh while they conduct an investigation of what happens when fertilizer is added to a water ecosystem. 

  2. Have one or two students label the three bottles “NF” (no fertilizer, or control), “N” (natural fertilizer), and “C” (chemical fertilizer). In bilingual classrooms, label the containers “SF” (sin fertilizante), “N” (fertilizante natural), and “Q” (fertilizante químico). 

  3. Show students the prepared (or pond) water. If possible, put a few drops of the water under a microscope for students to observe. Explain that they will be growing similar living things in the bottles. Add about 250–500 mL of the hay infusion or pond water, along with some hay/dried grass, to each bottle. 

  4. Set the soft drink bottles in a bright window or under bright fluorescent lights for 1–2 days to allow the culture to develop. (In conditions with low light, hay infusions will tend to develop mold and/or foul smelling bacteria within 2–3 days.) Note. If using pond water that already has plenty of green algae and other growth, proceed directly to the next step without resting the cultures. 

Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

My Health My World: National Dissemination
Grant Number: 5R25ES009259
The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698, R25ES06932

Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education