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Reading passage Grade 5 Science

Too Much of a Good Thing: Nutrient Runoff at Windham Creek

A grade 5 informational passage tracing how fertilizer runoff feeds an algae bloom at a creek, lowers oxygen, and affects fish living in the water.

Objectives

  1. Students will identify the sequence of events that led to an algae bloom at Windham Creek.
  2. Students will explain why decomposing algae lowers the amount of oxygen available to fish.

Vocabulary

Dissolved oxygen
Dissolved oxygen is the oxygen gas mixed into water that fish and other underwater animals breathe. Cold, moving water holds more oxygen than warm, still water.

Also: nutrients, algae bloom, decomposer, runoff

Teacher overview

Windham Creek, a fictional creek used for this passage, runs behind a stretch of farmland before joining a larger river. This passage traces what happened one spring when fertilizer washed off nearby fields and into the creek, causing a fast growth of algae that later used up the oxygen fish needed to survive. The passage traces water pollution as a sequence of connected causes and effects, beginning with a spring rainstorm, leading to an algae bloom, and ending with fish struggling to get enough oxygen.

Too Much of a Good Thing: Nutrient Runoff at Windham Creek — Grade 5 Science
Name: ____________________________ Date: ______________

Passage

Windham Creek runs behind a stretch of farmland before it joins a larger river. For most of the year, the creek looks healthy. The water is clear enough to see pebbles on the bottom. Minnows dart between patches of grass.

Every spring, farms near Windham Creek spread fertilizer on their fields. Fertilizer helps crops grow. It contains nutrients, mainly nitrogen and phosphorus, the same nutrients that make lawn grass and garden plants turn green. Crops use some of these nutrients, but not all of the fertilizer gets absorbed by the plants. The rest stays in the soil. A heavy rain can wash it away, carrying it toward the nearest stream.

Last April, heavy rainstorms washed a large amount of fertilizer off the fields near Windham Creek. About two weeks later, the creek's still, slow-moving sections turned cloudy and green. The green color came from algae, tiny plant-like living things that grow in water. Algae multiply fast when they have extra nutrients to feed on. Scientists call this fast growth an algae bloom. The extra nitrogen and phosphorus from the fertilizer gave Windham Creek's algae exactly what they needed to bloom.

At first, the bloom did not seem to bother anyone. But algae die, like all living things. As the bloom died, decomposers began breaking down the dead algae. Most of these decomposers are bacteria. Breaking down dead material uses up oxygen, the same way a fire uses up oxygen as it burns. Fish and other creek animals need oxygen dissolved in the water to breathe through their gills. The more oxygen the decomposers used, the less was left for everything else living in the creek. Warm water holds even less oxygen than cool water. That is why warm summer days after a bloom are especially dangerous for fish.

By early June, a local wildlife group found dozens of dead fish along a stretch of Windham Creek downstream from the farms. The group tested the water. They found very low oxygen levels exactly where the algae bloom had been thickest. The fertilizer that once helped crops on land had traveled downstream and taken away the oxygen that fish needed underwater.

Communities near Windham Creek are now working with local farms to reduce this problem. One idea is planting strips of grass and shrubs along the creek's edge. These buffer strips catch some of the fertilizer-laden runoff before it reaches the water. They give plants along the bank a chance to absorb the nutrients first.

Questions

  1. What do farms near Windham Creek spread on their fields every spring? Name the two nutrients it contains.
  2. What happened to the creek's still, slow-moving sections about two weeks after the heavy rainstorms?
  3. What is an algae bloom? Why did Windham Creek have one last April?
  4. Use details from the passage to explain why decomposing algae lowers the oxygen in the water.
  5. Why are warm summer days especially dangerous for fish after an algae bloom?
  6. What did the local wildlife group find when they tested Windham Creek's water in June?
  7. Explain how a buffer strip of grass and shrubs along a creek could help prevent future algae blooms.
  8. The passage compares decomposing algae to a fire. Explain what this comparison means.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: Fertilizer, containing nitrogen and phosphorus.
    The passage states that farms spread fertilizer every spring and names nitrogen and phosphorus as its main nutrients.
  2. Answer: The still, slow-moving sections turned a cloudy green color.
    The passage states this happened within about two weeks of the heavy rainstorms that washed fertilizer into the creek.
  3. Answer: An algae bloom is a fast, thick growth of algae.
    Windham Creek had one because fertilizer runoff added extra nitrogen and phosphorus that let algae in the creek multiply quickly, as the passage explains.
  4. Answer: Decomposers use up oxygen as they break down the dead algae.
    The passage explains that decomposers, mostly bacteria, break down the dead algae, and that this process uses up oxygen from the water, leaving less oxygen for fish and other creek animals.
  5. Answer: Warm water holds less oxygen, and the bloom had already used up much of the oxygen in the creek.
    Combining warm summer temperatures, which further lower the water's oxygen, with an already reduced oxygen supply from the bloom's decomposition makes conditions especially dangerous for fish, as the passage states.
  6. Answer: Dozens of dead fish and very low oxygen levels.
    The wildlife group found dozens of dead fish and very low oxygen levels in the stretch of creek where the algae bloom had been thickest.
  7. Answer: A buffer strip can absorb runoff before it reaches the creek.
    A buffer strip of grass and shrubs can catch and absorb some of the fertilizer-laden runoff before it reaches the creek, so fewer nutrients wash into the water to feed future algae blooms.
  8. Answer: The comparison means decomposing, like burning, consumes oxygen.
    Understanding that decomposing uses up oxygen the same way a fire does helps explain why the dying algae used up the oxygen that fish in Windham Creek needed to survive.

Differentiation

Support (below grade level)

Provide a simple sequence chart (Fertilizer spread, Rain washes it into creek, Algae bloom grows, Algae dies and decomposes, Oxygen drops, Fish affected) for students to reference while answering the questions, and allow question 4 to be answered as a short spoken response instead of writing.

Extension (above grade level)

Ask students to research, using only the passage and teacher-provided facts rather than outside sources, what other steps besides buffer strips a farm might take to reduce how much fertilizer washes off its fields, and to explain why timing fertilizer application around expected rain might matter.

ELL supports

Pre-teach "nutrients," "algae bloom," "decomposer," and "dissolved oxygen" with simple definitions and a visual sequence (green cloudy water, then dying algae, then a fish gasping) before reading. Allow students to answer literal questions 1, 2, and 6 with short phrases rather than full sentences.