The Estuary Biome: Where Freshwater Meets Saltwater — Reading Comprehension

Grades

Standards

MS-LS1-2

About This Reader

This middle school science reading passage explains the estuary biome, a unique ecosystem where freshwater and saltwater meet to form brackish water. Aligned with NGSS standard MS-LS2-1, this passage teaches students about the importance of estuaries in supporting biodiversity, nutrient cycling, and coastal protection. It includes examples of animals and plants found in estuaries, like crabs, oysters, and mangrove trees. The passage also connects the biome to human activity by describing how cities are often located near estuaries for trade and storm protection. With clear scientific vocabulary, real-world examples, and links to ecosystem functions, this reading comprehension activity helps students understand how living and nonliving things interact in an environment. It supports learning about ecosystems, biodiversity, and the interdependence of organisms.

CONTENT PREVIEW

An estuary is a unique biome where freshwater from rivers and streams meets and mixes with saltwater from the ocean. This mixing creates brackish water, which has a salt level between freshwater and seawater. Estuaries are found along coastlines all over the world and are considered one of the most productive ecosystems on Earth. They provide a habitat for a wide variety of plants and animals, making them vital to both marine and land environments.

Estuaries support many species by offering food, shelter, and breeding grounds. For example, fish like salmon and striped bass use estuaries as nurseries where their young can grow safely. Birds such as herons and egrets feed in the shallow waters, while crabs, oysters, and shrimp thrive in the muddy bottoms. Mangrove trees and salt marsh grasses grow along the edges, helping to filter pollutants from the water and prevent erosion.

One reason estuaries are so productive is because of nutrient cycling. As rivers bring nutrients from inland and tides bring in minerals from the sea, these mix in the estuary and create rich soil and water conditions. This supports plankton, which are tiny organisms that form the base of the food chain.

In real life, estuaries are important for humans too. Many large cities, like New York City and San Francisco, are built near estuaries because of their access to water for transportation and trade. Estuaries also help protect coastal areas from storm surges and flooding by acting as natural buffers.

Estuaries show how freshwater and saltwater can come together to create a rich and balanced ecosystem. They are essential not only for wildlife but also for the health of our planet and human communities.

Fun Fact: The largest estuary in the United States is the Chesapeake Bay, home to more than 3,600 species of plants and animals!

What type of water is found in estuaries?

Pure saltwaterFreshwater onlyBrackish waterPolluted water

Which two types of water mix in an estuary?

Groundwater and rainwaterLake water and pond waterFreshwater and saltwaterOcean water and glacier melt

Why are estuaries considered productive ecosystems?

They are always coldThey have little plant lifeThey support many speciesThey do not allow human activity

Which of the following lives in an estuary?

CamelsPolar bearsCrabsScorpions

What is one role of mangrove trees in estuaries?

Raise water temperatureFilter pollutantsEat fishLower oxygen

How do estuaries protect coastal areas?

By drying outBy attracting touristsBy acting as natural buffersBy building dams

What is the main idea of the passage?

All rivers lead to oceansEstuaries are where freshwater and saltwater mix and support lifeOceans are deeper than lakesFreshwater is cleaner than saltwater

If a new city is being planned near an estuary, what benefit might it gain?

More mountain airEasy access to desert sandTransportation and storm protectionLess rainfall