Implement this Lesson:
This unit can be used in conjunction with a carbon cycle lesson, microscope unit, or ocean unit.
Learning Objective:
- Observe changes in algal growth in response to nutrient levels.
- Explain changes in water quality due to algal growth.
- Assess the potential affects of water quality on a water ecosystem.
Texas Essential Knowledge and Skills (TEKS)
6.11(A) research and describe why resource management is important in reducing global energy poverty, malnutrition, and air and water pollution
6.11(B) explain how conservation, increased efficiency, and technology can help manage air, water, soil, and energy resources
6.12(A)* investigate how organisms and populations in an ecosystem depend on and may compete for biotic factors such as food and abiotic factors such as availability of light and water, range of temperatures, or soil composition
6.12(B) describe and give examples of predatory, competitive, and symbiotic relationships between organisms, including mutualism, parasitism, and commensalism
6.12(C) describe the hierarchical organization of organism, population, and community within an ecosystem
6.13(A) describe the historical development of cell theory and explain how organisms are composed of one or more cells, which come from pre‐existing cells and are the basic unit of structure and function
6.13(B) identify and compare the basic characteristics of organisms, including prokaryotic and eukaryotic, unicellular and multicellular, and autotrophic and heterotrophic 6.13(C) describe how variations within a population can be an advantage or disadvantage to the survival of a population as environments change
7.10(A)* describe the evidence that supports that Earth has changed over time, including fossil evidence, plate tectonics, and superposition 7.10(B)* describe how plate tectonics causes ocean basin formation, earthquakes, mountain building, and volcanic eruptions, including super volcanoes and hot spots
7.11(A)* analyze the beneficial and harmful influences of human activity on groundwater and surface water in a watershed
7.11(B)* describe human dependence and influence on ocean systems and explain how human activities impact these systems
7.12(A)* diagram the flow of energy within trophic levels and describe how the available energy decreases in successive trophic levels in energy pyramids
7.13(A)* identify and model the main functions of the systems of the human organism, including the circulatory, respiratory, skeletal, muscular, digestive, urinary, reproductive, integumentary, nervous, immune, and endocrine systems
7.13(C)* compare the results of asexual and sexual reproduction of plants and animals in relation to the diversity of offspring and the changes in the population over time
7.13(D)*describe and give examples of how natural and artificial selection change the occurrence of traits in a population over generations
7.14(A) describe the taxonomic system that categorizes organisms based on similarities and differences shared among groups
8.10(A) describe how energy from the Sun, hydrosphere, and atmosphere interact and influence weather
8.10(B) identify global patterns of atmospheric movement and how they influence local weather
8.10(C) describe the interactions between ocean currents and air masses that produce tropical cyclones, including typhoons and hurricanes
8.12(B) describe how primary and secondary ecological succession affect populations and species diversity after ecosystems are disrupted by natural events or human activity
8.12(C) describe how biodiversity contributes to the stability and sustainability of an ecosystem and the health of the organisms within the ecosystem
8.13(A) identify the function of the cell membrane, cell wall, nucleus, ribosomes, cytoplasm, mitochondria, chloroplasts, and vacuoles in plant or animal cells 8.13(C) describe how variations of traits within a population lead to structural, behavioral, and physiological adaptations that influence the likelihood of survival and reproductive success of a species over generations
8.13(B) describe the function of genes within chromosomes in determining inherited traits of offspring
Red Tides — When the Ocean Turns Red
Sometimes the ocean water along the coast turns reddish-brown, orange, or even green.
That’s called a red tide — but it’s not really made of blood or paint!
A red tide happens when tiny algae in the water grow too fast and too many. This sudden growth is called a “bloom.”
What Causes Red Tides?
The ocean is full of microscopic algae, also known as phytoplankton — tiny plant-like organisms that float near the surface.
Most of the time, these plankton are good because they:
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Make oxygen
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Feed fish and other sea animals
But sometimes, certain kinds of algae multiply too quickly, especially when:
Warm water- Algae grow faster in warm, sunny weather
Nutrients in the water- Runoff from farms, cities, or rivers add fertilizer-like nutrients
Calm seas- Still water helps the algae stay near the surface
When this happens, the water becomes cloudy and discolored — that’s a red tide!
What Makes the Tide “Red”?
Not all red tides are the same color.
The color depends on the type of algae causing the bloom.
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Some are red or brown (like Karenia brevis, common in the Gulf of Mexico).
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Others can look green or yellow depending on the species.
Even though it looks pretty, it can be dangerous to animals and people.
Why Red Tides Can Be Harmful
Some red tides produce toxins, or poisons, that can harm marine life.
Fish- The toxins can damage their gills, making it hard to breathe.
Dolphins and manatees- can get sick from eating fish that have the toxins
Shellfish (like oysters and clams)- Store toxins in their bodies, making them unsafe to eat
Seabirds- Can get poisoned from eating fish during a red tide
People can also feel sick if they eat shellfish caught during a red tide or if they breathe in ocean air near a bloom — it can irritate the eyes, throat, and lungs.
Red Tides on the Texas Coast
Red tides sometimes happen along the Texas Gulf Coast, especially in late summer and fall when the water is warm.
Scientists from the Texas Parks and Wildlife Department and other groups monitor red tides by testing the water.
If a bloom is detected, they post warnings to keep people safe from swimming or fishing in affected areas.
Can Red Tides Be Stopped?
It’s hard to stop a red tide once it starts, but we can help prevent them!
Reduce pollution- Less fertilizer and waste means fewer nutrients for algae to grow
Keep waterways clean- Picking up trash keeps harmful materials out of the ocean
Learn and share- Understanding red tides helps communities stay safe.
Scientists are also studying how winds, currents, and weather affect red tides to better predict when they might happen.
Fun Facts!
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“Red tide” is also called a harmful algal bloom (HAB).
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The algae that cause red tides are as small as dust, but together they can color miles of water!
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Dolphins and sea turtles sometimes move away from red tide areas to find clean water.
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The Gulf of Mexico is one of the most studied places for red tides in the world.
Why It’s Important to Know About Red Tides
Even though red tides can be harmful, learning about them helps us protect our oceans, animals, and ourselves — keeping the Gulf of Mexico healthy and full of life!
Possible Books:
- What is Red Tide
- The Mystery of Red Tide
- Red Tide Alert
Materials Needed:
- Water samples containing algae
- Clear containers for holding samples (5 one quart jars)
- Plant fertilizer such as Peters or Rapid-Gro
- Measuring spoons in either metric or standard measure
- Spoon
- Paper for labels
- Markers for labeling
Lesson Plan:
Advanced Prep:
- Water containing algae must be obtained prior to the set-up day.
- Pond water or water from another natural source works best if it is available.
- Aged tap water (let it sit for about 48 hours) or tap water seeded with gravel from an aquarium will also work if pond water is not available.
Engage:
- Explain to students that they are setting up model water environments to be used in a later experiment.
- Have students fill the jars with the water containing algae.
- Have students add one teaspoon of plant fertilizer to each jar.
- Have students stir the water thoroughly.
- Have students put jars in an area with good indirect light. (Make sure that the area is not too cold.)
- Project Oceanography 39 Spring 2001 Unit Three Red Tide and Harmful Algal Bloom
- Explain that the plant food acting as a nutrient will help the algae to grow to a point where it can be seen.
- Allow the algae to grow for about two weeks or until algal growth is evident.
- Note: Duplicate jars could be set-up and a discussion of replicates and statistically valid data could be added.
Explore:
- Discuss with students the various water parameters that affect algal growth rate such as temperature, sunlight, pH, and nutrient levels.
- Discuss sources of nutrients and what type of activities would affect nutrient levels in water.
- Explain that in this experiment only the affects of one variable, nutrient level, will be observed.
- Have students observe the water in the jars that were previously set-up and record their findings.
- Have students label one jar as a control. Explain that no additional nutrients will be added to this jar. It will be used for comparison purposes only.
- Have students label each of the other four jars.
- Have students add increasing amounts of plant fertilizer to each jar. For instance, jar one could have an additional teaspoon of fertilizer; jar two could have two additional teaspoons, etc. (Be sure labels include nutrient level amounts.)
- Have students observe the jars over the next two weeks (or longer period) and record their observations.
- Discuss how nutrient concentration affected growth rate. Was there a point at which the nutrient level did not seem to affect growth rate? How is this like what happens in nature? Where would those extra nutrients come from? At what point does a nutrient become a pollutant?