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What Is Ocean Acidification

Interactive passage with audio narration, comprehension questions, and printable PDF.

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Format: Interactive (Online), Printable (PDF)
Grades: 5678
Subjects: science
Standards: MS-ESS3-5
Languages: English, Spanish

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Reading passage

Reading comprehension

Audio narration

With word word highlighting

Comprehension quiz

Auto-graded

Writing activity

Open-ended response

Glossary & flashcards

Vocabulary practice

Differentiated version

Adapted for varied levels

Spanish translation

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About this reader

This comprehensive middle school science reading passage explores ocean acidification, often called climate change's evil twin. Students discover how carbon dioxide emissions dissolve into seawater, creating carbonic acid that lowers ocean pH levels. The passage explains the chemical process of acidification and its devastating effects on marine organisms that depend on calcium carbonate structures, including corals, clams, oysters, and plankton. Through clear explanations and real-world examples, students understand how ocean acidification threatens marine food webs and ecosystems. The content aligns with NGSS standard MS-ESS3-5, helping students clarify evidence of factors causing global environmental changes. Audio-integrated features support diverse learners, while differentiated versions ensure accessibility for all students. Activities include comprehension questions, writing prompts, and graphic organizers that reinforce understanding of cause-and-effect relationships in Earth systems.

Written by Workybooks TeamPublished by Workybooks

Sample passage and quiz content

CONTENT PREVIEW

CO2 enters ocean, lowers pH, harms coral reefs and shell-building marine life.

Ocean acidification is a process that happens when the ocean absorbs carbon dioxide from the atmosphere. When carbon dioxide dissolves in seawater, it reacts chemically to form carbonic acid. This weak acid slowly changes the ocean's chemistry. Scientists have measured that ocean water is becoming more acidic than it was in the past.

The chemical process begins when carbon dioxide gas enters the ocean surface. The carbon dioxide reacts with water molecules to create carbonic acid. This acid releases hydrogen ions into the seawater. The extra hydrogen ions lower the ocean's pH level, making it more acidic. Evidence shows that ocean pH has dropped by about 0.1 units since the Industrial Revolution began. This change may seem small, but it represents a 30 percent increase in acidity.

Ocean acidification creates serious problems for marine life that builds shells and skeletons. Corals, clams, oysters, sea snails, and tiny plankton all use calcium carbonate to construct their protective structures. More acidic water makes it harder for these organisms to form calcium carbonate. The acid can even dissolve existing shells and skeletons. Scientists compare this to trying to build with bricks that keep dissolving. These creatures struggle to grow and maintain their structures in increasingly acidic conditions.

The effects reach beyond individual organisms. Many shell-building creatures form the base of ocean food webs. Tiny plankton feed small fish, which feed larger fish. When acidification harms plankton populations, it can affect the entire marine ecosystem. In the Pacific Northwest, oyster hatcheries have experienced massive die-offs of young oysters. Scientists linked these deaths directly to more acidic ocean water upwelling from the deep ocean.

Ocean acidification connects directly to human activities. When we burn fossil fuels, we release carbon dioxide into the atmosphere. The ocean absorbs about one-quarter of this extra carbon dioxide. While this absorption helps slow climate change by removing carbon dioxide from the air, it causes acidification in the ocean. The more carbon dioxide we add to the atmosphere, the more the ocean absorbs, and the more acidic it becomes.

Interesting Fact: Scientists sometimes call ocean acidification climate change's evil twin because both problems stem from the same source: excess carbon dioxide in the atmosphere from burning fossil fuels.

What happens when carbon dioxide dissolves in seawater?

It forms carbonic acid that makes the ocean more acidicIt creates oxygen that marine life needs to breatheIt cools the water temperature throughout the oceanIt produces nutrients that help plankton grow faster

How much has ocean pH dropped since the Industrial Revolution?

About 0.01 unitsAbout 0.1 unitsAbout 1.0 unitsAbout 10 units

What does the term 'pH level' mean in the passage?

The temperature of ocean waterThe amount of salt in seawaterA measurement of how acidic or basic a substance isThe depth of the ocean floor

Which statement best describes what 'calcium carbonate' means in the passage?

A type of plankton that floats in the oceanA chemical compound used to build shells and skeletonsA form of carbon dioxide found in the atmosphereAn acid that dissolves in ocean water

Why does ocean acidification threaten entire marine food webs?

It makes the ocean water too cold for fish to surviveIt removes all the oxygen that marine animals needIt harms shell-building creatures at the base of food websIt causes the ocean to evaporate more quickly

What real-world example does the passage provide about ocean acidification?

Coral reefs in the Caribbean turning whiteOyster hatcheries in the Pacific Northwest experiencing die-offsFish populations declining in the Atlantic OceanWhales migrating to different feeding areas

If ocean acidification continues, what would most likely happen to coral reefs?

They would grow larger and stronger structuresThey would struggle to build and maintain their calcium carbonate structuresThey would move to deeper parts of the oceanThey would develop immunity to acidic water

How does reducing fossil fuel use help address ocean acidification?

It cools down the ocean temperature directlyIt adds more oxygen to the atmosphereIt decreases the amount of carbon dioxide released into the atmosphereIt increases the pH level of rivers flowing into the ocean

True or False: The ocean absorbs about one-quarter of the extra carbon dioxide that humans release into the atmosphere.

TrueFalse

True or False: Ocean acidification only affects large marine animals like whales and sharks.

TrueFalse